THE
CONTROL OF QUALITY
IN
MANUFACTURING
By
G. S. RADFORD
/(
Consulting Engineer; Member, American Society of
Mechanical Engineers; Society of Naval Architects and
Marine Engineers; American Society of Naval Engineers
NEW YORK
THE RONALD PRESS COMPANY
1922
Copyright, 1922, by
THE RONALD PRESS COMPANY
All Rights Reserved
c/
To MY PARENTS
520411
PREFACE
There is an erroneous but wide-spread belief that quality
and high cost go hand in hand. The existence of this
feeling is readily explained, because it is the general prac-
tice to advertise quality as something worth paying for.
From the purchaser's standpoint this is very true, but it
does not follow by any means that quality is costly to pro-
duce. Very high-grade ''quality" products are often high
priced, but lower grade and less expensive articles also
possess their own quality standards.
In the factory, quality is a costly thing to neglect, yet it
is the usual experience to find a disproportionate emphasis
being placed upon quantity of output, in the effort to effect
economies. Often this is not so much due to lack of proper
intent as it is to the failure to realize what the quality ap-
proach means. To establish and maintain definite and
sensible standards of quality requires care and thorough-
ness. These are the very things which remove obstacles
to production and thus decrease costs — quite independently
of whether the product is high grade or low grade, high
priced or low priced.
In the following pages, presenting the results of an inten-
sive study of quality in manufacturing, it has been the
intention to show that the control of quality is the correct
starting point for economy (as well as to obtain higher
standards for their own sake), since if quality is under
positive and continuous control, increase of output follows
as a by-product advantage. Hence one of the central
thoughts of the book is that increased output and decreased
costs are more certainly attained when manufacturing
vi PREFACE
problems are approached with quality, instead of quan-
tity, as the primary guide and objective.
It is well-nigh impossible to pass a store window, or to
ride in a street car, or to glance at the pages of a magazine
without encountering the word "quality." Yet there is
no formal literature about quality in manufacturing—
nearly all of our attention having been devoted to quantity.
Therefore, in constructing this book the introductory
chapters, I and II, discuss the general relationships of
quality to manufacturing.
When it comes to controlling quality, inspection plays
a large part. Chapters III to XI, accordingly, are intended
to insure a clear understanding of the various forms of
inspection. In sketching the relationship of inspection to
the control of the flow of work in process, the idea of plan-
ning with material in physical form is advanced as an
advantageous extension of the usual planning systems.
With this earlier portion of the book as a foundation,
Chapter XII, et seq., takes up definitely the relation of
measurement to quality and the development of quality
standards in the various types of manufacturing, using the
methods for controlling dimensional quality as the principal
example. Dimensional work has been reduced to very pre-
cise regulation in the industrial arts and thus permits of
exhaustive treatment. Hence most of the illustrations
throughout the book are drawn from that source as best
typifying the principles involved in quality control generally.
Among the important characteristics of manufactured
articles there are many other qualities which as yet have
not been brought to the same perfection of control as dimen-
sion. Color, the control of which is just now beginning to
receive close attention in many industries, is discussed as
typical of these other qualities.
The concluding chapters present the author's idea of the
PREFACE vii
best method of attack for approaching, and bringing under
control, any quality problem whatever, regardless of the
particular industry or the particular product which may
happen to be involved.
Throughout the text a careful effort has been made to
give credit to the many firms and individuals who have
supplied technical information and illustrative matter.
Probably this book would not have been written if Mr. L. P.
Alford, Editor of Management Engineering, had not re-
quested me to do so, and then assisted in its preparation
with his usual thoughtful and competent advice. It only
remains to be said that doubtless many of the conclusions
presented in the subject matter were influenced by profes-
sional conversations with several former associates. It is a
pleasant duty in this connection, to express my obligation
especially to Messrs. William B. Ferguson, H. H. Pinney,
D. G. Seagrave, Brigadier-General John T. Thompson,
U. S. A., retired, and Captain R. M. Watt (C. C.) U. S. N.,
formerly Chief Constructor and Chief of the Bureau of
Construction and Repair.
G. S. RADFORD
New York City,
September i, 1922
CONTENTS
CHAPTER PAGE
I INTRODUCTION 3
The Changed Industrial Demand
Quality a Distinguishing Characteristic of Goods
Uniformity the Essence of Quality
Standardization Does Not Bring Quality
^jy-niformity Requires Continuous and Positive Control
Instances of Failure in Quality Control
^Advantages of Considering Quality at Outset
cLmproved Labor Relationships
Testimony
^"increase of Output and Decrease of Costs
Carnegie's Maxim
Experience of War Time Manufacturing
-^J&ontrol of Quality Basic
The Quality Bonus
Experience of The Shelton Looms
Experience of the Armstrong Cork Company
Decreased Selling Costs with Quality Goods
II THE APPROACH TO QUALITY CONTROL 25
The Starting Point — Determining Nature of Product
The Commercial Factors — Requirements of the Consumer
The Design — Securing Consumer's Requirements
Provision for Improving Design
Materials
Processes
Workmanship
Operating Organization and Records
Inspection an Essential
III INSPECTION — THE NEED FOR INDEPENDENT SCRUTINY 35
Maintaining Standards — Measurement and Control
The Instrument for Measuring and Controlling
Convincing the Management
<^Growing Importance of Inspection
*-Jnspection Often a Necessity, Always an Economy
*-Need of Intensive Study of Inspection
Sfudy of Theory Needed
) *T unctions and Limits of Inspection
'IV THE TYPES OF INSPECTION 46
Conformity with Special Factory Situation
-"Material Inspection
"Office Inspection
Inspection
x CONTENTS
CHAPTER PAGE
IV THE TYPES OF INSPECTION — Continued
^/Process Inspection
yCdvantages of Centralized Inspection
/Inspection Combined with Remedy of Defects
Use of Special Mechanical Devices
The Amount or Quantity of Inspection
The Danger of Becoming "Fussy"
Unnecessary Inspection
Jhe Percentage of Inspection
impling — The Theory
Safeguards for Sampling
Bother Economies in Inspection
— V^a
t V THE INSPECTION DEPARTMENT IN THE ORGANIZATION. . 63
^vital Importance of Inspection
The Engineering Department
The Production Department
The Inspection Department
A Parallel with Governmental Organization
ixfhspection's Relation to Engineering and Production
Purpose Help — Not Mere Criticism
^The Real versus the Apparent Organization
S Engineering and Inspection
-'Production and Inspection
VI INSPECTION'S CONTRIBUTION TO GENERAL SERVICE ... 74
The Collection of Useful Information
Trouble Reports
The Inspector's Sense of Responsibility
A Typical Instance
Reception of Trouble Reports
Inspection and the Assembling Department
Benefits to Entire Factory
An Example of Selective Assembly
The Custody of Work in Process
Stimulus to Order and Cleanliness
The Analysis of Work in Process — "Good" and "Bad"
Handling Rejected Parts
Quality as an Incentive to Production
The Individual Worker's Interest
J Interest in the Work Itself
Expert Knowledge — Causes and Results
Interest in Quality versus Fatigue
A Phase of a Major Problem
VII INSPECTION'S RELATION TO PLANNING 95
The Flow of Work in Process
Uneven Flow — Disadvantages
Effects on Piece Work
Supply of Raw Materials
Material in Process
CONTENTS xi
CHAPTER PAGE
VII INSPECTION'S RELATION TO PLANNING — Continued
Insuring a Continuous Flow
Planning with the Material Itself
Master Planning
The Operation Mark or Symbol
Operation Mark to Remain Unchanged
The Operation Data Sheet
Route Tags
The Manufacturing Schedule
Allowance for Losses in Process
Determining Quantities of Work in Flow
The Design of Space Assignments for Planning with Material
Inspection and Dispatching
VIII CENTRAL INSPECTION 115
The Most Advanced Form of Inspection
Not Restricted to One Form
Value of Self-Counting Trays
The Two-Bin System Extended
Systematic Layout for Material in Process
Layout of Central Inspection Crib
Construction of Central Inspection Cribs
An Adaptation to Rough Work
The Resulting House Cleaning
An Adaptation to Close Work in Metal
I Aisle Arrangement
/ Advantages of Several Centralized Inspection Spaces
/ Standard Arrangement Desirable
v Summary of Advantages
y
IX THE ORGANIZATION OF THE INSPECTION DEPARTMENT 139
-designing the Instrument for Controlling Quality
""The Development of Organization
-The Chief Inspector ^
J-hities of the Inspection Department
Work Related to Process Inspection
The Line Organization
Special Value of Understudies
Duties of Inspectors
The Chief Inspector's Staff
The Inspection Department Personnel
The Bench Inspector
The Floor-Inspector
Salvaging Native Ability
A Case in Point
Study the Individual
MANAGEMENT OF THE INSPECTION DEPARTMENT .... 156
The Task
Co-ordination
The Use of Conferences
xil CONTENTS
CHAPTER PAGE
X MANAGEMENT OF THE INSPECTION DEPARTMENT — Continued
Letters of Instructions and Advice
Reduction of Turnover of Inspection Force
Provision for Promotion
Wages
Piece Work in Inspection
Working Hours
The Cost of Inspection
Teaching Inspectors
Combine Instructions with Staff Supervision
Unskilled Help in Inspection
Female Labor for Inspection Work
Women Inspectors on Heavy Work
Morale
XI INSPECTION IN PRACTICE 172
Type Varies with Individual Factory
When to Use Extensive Inspection
Inspection in Automobile Plants
The Packard Inspection Service
An Example of Former Practice
Machine Tool Industry
Small Precision Work
General Machine Shop and Foundry Practice
Special Qases
Ratio of Inspectors to Workers
XII QUALITY CONTROL IN PRACTICE ..':.. 187
Complexity of the Problem of Quality
The Shell Contracts of the American Locomotive Company
Beginning the Work
No Rejections After Delivery
Shells
Bullets
Time Fuses
Quality First — Then Quantity Follows
Liberty Motors at the Lincoln Motor Company
Remington Arms Company — Springfield-Enfield Rifle Production
Quality Is the Road to Production
/ XIII MEASUREMENT AND ERRORS . . . , , . . 210
The Evolution of Measuring
The Selection of Characteristic Qualities for Measurement
Standard Samples
Dangers of Standard Samples
Measurement by Comparison with a Standard Scale
The Measuring Instrument
Danger of Overgraduation
The Need of a Final Check
The Choice of Instruments
The Precision of Measurement
Precision of Workmanship
CONTENTS xiii
CHAPTER PAGE
XIII MEASUREMENT AND ERRORS — Continued
The Theory of Errors
When Theory and Practice Differ
The Chain of Inaccuracy
The Chain of Wear
The Cure for Errors
XIV QUALITY DEFINED — THE IDEAL STANDARD 233
Characteristic Qualities of Product Must Be Known
Quality Varies Continually
Development of the Design
The Theoretical Standard
The Ideal Standard
Progress Toward More Exact Designs
Changes in Design Must Be Avoided
When Improvement Changes Should Be Made
Every Cause Has Several Effects
Precautions to Avoid Changes
XV THE WORKING STANDARDS 264
The Compromise in Setting Tolerances
Raw Material Standards
Conditioning Standards
Standards of Finish
Standards of Dimension and Form
Allowed Variations Denned
Necessary Precautions
Dimensional Working Standards
Assembling Standards
Final Tests
Recapitulation
XVI REPETITION MANUFACTURING 264
Uniformity for Economy
Uniformity of Product Means Uniformity Throughout Production
Interchangeable Manufacturing
The Industrial Revolution
The Mechanical Revolution
Economy in Assembling
The Work of Simeon North and Eli Whitney
Continuous Standardized Production
Vital Importance of Uniform Quality in Raw Materials
Continuous Processing
Duplicate Manufacturing
Partial Interchangeability
Production of Machine Tools
The General Prniciple
XVII THE DIMENSIONAL CONTROL LABORATORY 281
Practical Value of Precision
The Laboratory Proper
xiv CONTENTS
CHAPTER PAGE
XVII THE DIMENSIONAL CONTROL LABORATORY — Continued
The Surface Plate
The Dimensional "Court of Highest Appeal"
The Brown and Sharpe Measuring Machine
The Pratt and Whitney Standard Measuring Machine
The Johansson or Swedish Block Gages
The Pratt and Whitney Precision Gages
Comparators
Miscellaneous Equipment
Personnel
XVIII GAGES AND GAGE-CHECKING 303
When Should Fixed Dimension Gages Be Used?
Fixed-Dimension Limit Gages
Adjustable Limit Gages
Multiplying Gages
Special Gages
Gage Tolerances
The Application of Gages
Gage-Checking
The Slip in Transferring Size
XIX THREAD-GAGING 317
Evolution of Thread-Gaging
Inter-relation of Thread Elements
Working Thread Gages
The Hartness Comparator
Other Equipment for Measuring Threads
Thread Gage Tolerances
Precision Depends upon Service Requirements
XX THE PRECISE CONTROL OF PROCESSES 330
What Dimensional Precision Is Practicable?
Automobile Experience
Tables of Tolerances
Precautions for Obtaining Precise Work
The Principle of Balance
The Effect of Finish on Accuracy
Quick Checks on Precision
XXI THE CONTROL OF COLOR 346
Application of Measurement to Other Qualities
Appearance and Color
Standard Samples
The Standard Color Card
Dangers of Standard Samples
What Is Color?
The Illuminant
The Subject
The Eye
The Color Constants
CONTENTS xv
CHAPTER PAGE
XXI THE CONTROL OF COLOR — Continued
Color Vision
Methods of Analyzing Color
Analysis By Primary Colors
Instruments for Measuring Color
The Spectrophotometer
The Monochromatic Colorimeter
Auxiliary Instruments
Reduction of Errors in Color Work
Standards of Appearance
XXII THE SCIENTIFIC ATTITUDE OF MIND AND ITS METHODS 368
Science and the Arts
Science and the Practical Man
Theory or Theorists
The Engineer as Co-ordinator
The Scientific Attitude
The Scientific Method
The Place of the Engineer
XXIII THE METHOD OF ATTACK TO CONTROL QUALITY .... 377
The Approach to the Problem
Uniformity within Limits
Getting the Facts
Analysis
Tripartition or Tripartite Analysis
Quality Records
Using the Facts — Synthesis and Adjustment
The Order of Procedure
Begin with the Product
Written Descriptions of Processes
The Assemblage of Processes
Organization and System
Conclusion
LIST OF ILLUSTRATIONS
FIGURE PAGE
1 . Full Set of Johansson Gage Blocks 1 1
2. Time Fuse Manufacture of the American Locomotive Company . . 18
3. An Object Lesson in Quality 22
4. A Common Method of Holding a Micrometer Caliper 28
5. Measuring a Turned Piece in Lathe 31
6. A Centralized Inspection Point in the Lincoln Motor Company's
Plant 37
7. Tool and Gage Inspection at the Packard Motor Car Company's
Factory 42
8. Some of the Special Equipment of the Tool and Gage-Checking
Room — Lincoln Motor Company 48
9. Inspection of 9.2-Inch Shells — American Locomotive Company . . 51
10. Rough Stock Inspection — Packard Motor Car Company 58
11. Sample Checking Room — Packard Motor Car Company 65
12. Inspection Room — Lincoln Motor Company 71
13. Trouble Report 76
14. Inspection Form — American International Corporation, Hog Island 80
15. Gear Inspection — Lincoln Motor Company 88
1 6. The Flow of Work in Process — Shell Work of American Locomotive
Company 96
17. Operation Study Sheet as Used at the Bridgeport Armory of the
Remington Arms Company 105
18. Operation Data Sheet . .106,107
19. Route Tag — Remington Arms Company 108
20. From Forging to Finished Crank-Shaft 118
21. A Wood Frame Truck 119
22. An "A" Frame Wood Truck for Connecting Rods 120
23. Standard Steel Tote Boxes 121
24. Diagram of Line of Flow of Work 123
25. Diagrammatic Shop Arrangement 124
26. Diagram of Relative Size of Space Assignments 125
27. Transporting Rack for Rifles — Remington Armory, Bridgeport . . 126
28. Type Section of Central Inspection Crib 127
29. Floor Plan of Central Inspection Crib <. . . 128
30. Floor Plan of Canvas Shop 129
31. Typical Modern SJiop Floor Plan 132
32. Modern Shop Floor Arranged for Central Inspection 133
33. Type Floor Plan of Central Inspection Crib . . 135
34. Type Arrangement of Material Storage Point in Central Inspection
Crib 137
35. Organization Chart — Inspection Department 145
36. Various Sorts of Special Manufacturing Gages 15°
37- Curve of Output and Number of Men 163
38. Prestwich Fluid Gage as Used to Inspect Piston Pins 167
39. Inspection Organization Chart — Packard Motor Car Company . . 174
40. Inspector's Tag Disposing of Work — Packard Motor Car Company . 1 76
41. Piston Ring Inspection — -Packard Motor Car Company 179
42. Inspection of Time Fuse Parts 183
43. Perch for Inspecting Textile Fabrics — The Shelton Looms .... 185
44. Typical Pages from Shop Instruction Book 192-196
xvi
LIST OF ILLUSTRATIONS xvii
FIGURE PAGE
45. Work Table Layout and Operation List for Time Fuses 198
46. Fuse Body Inspection Layout 199
47. Special Gages for Bottom Rings of Time Fuses 202
48. Typical Operation Sheet — Lincoln Motor Company 204
49. Typical Instructions for Inspection — Lincoln Motor Company . . . 205
50. Standards of Weight and Length for the United States 216
51. Method of Using Hub Micrometer Caliper No. 241 — Brown and
Sharpe Manufacturing Company 218
52. Setting a Johansson Adjustable Limit Snap Gage by Means of
Johansson Gage Blocks 222
53. Probability Curve, Showing the Frequency of Occurrence of an Error 228
54. Checking Johansson Adjustable Limit Plug Gage with Gage Blocks
Mounted in Holder 235
55. Use of Johansson Gage Blocks and Sine Bar to Check Taper of a
Milling Cutter Shank 239
56. Set-Up of Johansson Blocks for Checking Taper of a Special Plug
Gage 241
57. Order for Change in Drawing 246
58. Measuring Diameter of Automobile Piston 253
59. Reading Inside Micrometers After Measuring Inside of Cylinder . 257
60. Measuring Large Diameter of Piece in Grinder 260
61. Height Gage Used with Johansson Blocks 268
62. Set-Up of Johansson Blocks to Check Drill Jig 273
63. Special Milling Fixture Using Johansson Gage Blocks for Locating
Purposes 276
64. An Excellent Dimensional Control Center 282
65. Brown and Sharpe Measuring Machine 288
66. Pratt and Whitney Measuring Machine 290
67. Details of Measuring Head — Pratt and Whitney Measuring Machine 292
68. Special Set of Johansson Block Gages 297
69. American Amplifying Gage Used with Swedish Gage Blocks . . . 299
70. Group of Brown and Sharpe Gages 305
71. Adjustable Limit Snap Gages — Pratt and Whitney Type 307
72. Adjustable Limit Plug Gages with Reversible Ends — Pratt and
Whitney Type 308
73. Pratt and Whitney Taper Gages 315
74. An Exaggerated Form of Stud 320
75. Typical Thread Gages — Pratt and Whitney Company 322
76. Typical Thread Gage — Pratt and Whitney Company 323
77. General View of Hartness Screw Thread Comparator 324
78. Another General View of Hartness Screw Thread Comparator . . . 324
79. The Work Holder and Projection Lens of Hartness Screw Thread
Comparator 325
80. Sketch of Drill Showing Various Fits — Johansson 334
81. Diagram of Limit System — Shaft Basis — Johansson 335
82. Tolerance System (Table) with the Shaft as Basis — Johansson . . . 336
83. Diagram of Limit System — Hole Basis — Johansson 337
84. Tolerance System (Table) with the Hole as Basis — Johansson . . . 338
85. Chart for Spectral Analysis of Color Showing Relative Visibility
Curve 352
86. Chart for Spectral Analysis of Color Showing Typical Color Analyses
Plotted as Curves 357
87. Sketch of Prism and Spectrum 359
88. Diagram of Spectrophotometer 363
89. Precision Torsion Balance — Roller-Smith 386
THE CONTROL OF QUALITY
IN MANUFACTURING
CHAPTER I
•
INTRODUCTION
The Changed Industrial Demand
The years 1919 and 1920 marked definitely the end of a
period in manufacturing and industry. It was characterized
by the demand for "maximum production," for quantity or
volume of manufactured goods. The means and agencies
of production — material, equipment, and labor — were
planned and directed to satisfy this end. But with the
close of this period has come a great change which will
vitally affect industry and manufacturing of the present
and immediate future.
The new demand is for effective unit production, that is,
a maximum useful and marketable output per machine, per
hour, per man. ' ' Useful, marketable ' ' production implies a
different characteristic from that associated with mere
quantity. This characteristic is quality. It is destined to
distinguish the great purpose in present and future manu-
facturing, in' the same way that quantity demand distin-
guishes the period which has closed.
At the outset it must be recognized that both quantity
and quality are general or "universal" characteristics in
that they apply to all manufactured goods. The horizon of
quality is just as broad as the horizon of quantity. This is
their similarity — they both belong to all kinds of goods and
articles. Quality belongs to those articles which are in-
expensive no less than to those which are costly. It is
closely associated^ with usefulness and marketable possibili-
ties. It is a characteristic emphasized again and again in
advertising and sales literature, but has no direct connection
C&N-tROL OF QUALITY
with cost or selling price. A point to note is that whether
the article costs much or little, quality and the reputation
for quality establish the market which will make possible
quantity production and its attendant advantages.
Quality a Distinguishing Characteristic of Goods
The term "quality," as applied to the products turned
out by industry, means the characteristic or group or com-
bination of characteristics which distinguishes one article
from another, or the goods of one manufacturer from those
of his competitors, or one grade of product from a certain
factory from another grade turned out by the same factory.
Quality serves to identify an article. It is the character-
istic which measures the evenness of a specific grade. Qual-
ity is used in this sense whenever we say that the same
factory produces the same article in several different qual-
ities, or that the output of certain factories is graded
according to quality.
It is evident that the group or combination of charac-
teristics which form the quality of an article includes such
elements as design, size, materials, workmanship, and finish.
To consider some of these elements — so far as size is in-
volved, quality is concerned with precise adherence to size.
For instance, one pair of shoes of a specified length and
width must be like another pair of shoes of the same length
and width. In this case quality depends upon adherence to
a particular characteristic. The same requirement holds in
regard to the raw materials from which the article is made
and to the workmanship applied in the manufacturing. A
manufacturer to secure and maintain quality attains uni-
formity or evenness in the raw materials which enter his
product and in the workmanship applied. This adherence
to established requirements is a major responsibility of the
manufacturer.
INTRODUCTION 5
Uniformity the Essence of Quality
The purchaser's principal interest in quality is that
evenness or uniformity which results when the manufac-
turer adheres to his established requirements. No matter
when or where the purchaser buys an article he expects the
same definite and proper return for his money, not only at
the time of purchase but through a reasonable period of use.
He is justified, no doubt, in expecting a gradual improve-
ment from time to time in the quality of all the articles which
he buys, but at any one time his chief expectation, as re-
gards quality, is that it shall be the same for like articles.
No shoe must be either better or worse than its mate. The
quality of two pairs of the same grade of shoes, or of ten or a
thousand pairs for that matter, must be practically identical.
The manufacturer himself as a purchaser of raw ma-
terials, supplies, and equipment, views the matter in the
same light, perhaps with even greater insistence upon uni-
formity and evenness of grade. Thus he requires that all
lots of a given kind of steel shall have the same characteris-
tics from lot to lot; and, as just indicated, the evenness of
characteristics and the degree of precision with which they
are attained are what determines quality. As a matter of
fact, the manufacturer is often more concerned with obtain-
ing uniformity in raw material than he is in getting an im-
proved quality, because it is easier to produce uniform
results from material which is uniform to begin with, and
uniformity of product is what he is after.
Standardization Does Not Bring Quality
At this point it is important to realize that standardiza-
tion of products or articles does not of itself influence
quality. Unfortunately, these two terms are frequently
confused in use, but they are not synonyms. One signifies a
characteristic, the other a process.
6 THE CONTROL OF QUALITY
Standardization in American industry has been applied
in general to the proportions of articles and is frequently
referred to as ' ' standardization of proportionality. ' ' An ex-
cellent example is the United States standard screw thread.
This was adopted many years ago and is generally used
throughout American industry. However, it is possible to
make United States standard threads of poor quality, good
quality, or of any intermediate quality. If the proportions
are the same throughout this range of quality, all of the
screws would be "U. S. S." Another example, appreciated
by everyone, is presented by our railroads. A standard rail-
road gage is almost universally used throughout the United
States, yet everyone has discovered that there is no stand-
ard in the quality of these standard-gage roadbeds. That
is, while the gage is standard, the quality of the roadbeds
varies. The distance between the rails is only one of a
number of elements which make up the quality of the road-
bed itself. So far as the gage is concerned, the requirement
of quality is attained when the rails are maintained at the
standard distance apart. But the smoothness of the road-
bed depends upon many other things, which grouped to-
gether give characteristics or quality.
The quality of an article, therefore, is made up of a large
number of characteristics or attributes, some of which may
be standardized for convenience or economy. It is quite
possible to have two articles, both standard, which appear
alike, but whose quality differs essentially. In the case of
raw materials, ordinary city water undoubtedly is handled
in greater bulk than any other standard commodity. When
collection and filtration are completed, the water is said to
be distributed in standard form ; but even then its quality
differs widely from place to place and from time to time.
Although alike to all outward appearances, the water supply
in two cities may be far different in essential quality, be-
INTRODUCTION 7
cause the ingredients which cause a quality difference are
usually incapable of detection by human senses. In this
instance also, quality depends on the consumers' require-
ments. Thus water may be satisfactory for cooking but
not at all satisfactory for many industrial and technical
purposes.
In the case of manufactured articles the same difference
must be recognized between standards and quality. Re-
ferring again to shoes as an example, the purchasing public
requires footwear in a great variety of sizes and kinds, and
exact satisfaction of each individual's wants would result in
almost as many kinds of shoes as there are persons. To
avoid making such an indefinite number of varieties and
sizes it is necessary to standardize some of the elements
through striking a compromise. The effect of this process
is to create a sufficient volume of like work to permit of using
the method of quantity production. This compromise for
the purpose of securing the economy of repetition manu-
facturing takes place when shoes are classified in a stand-
ardized series of styles, sizes, and widths. A little reflection
will show that this process of compromise or standardiza-
tion is quite different from the establishing of quality or
qualities which define the character of any particular make
and grade of shoe regardless of size and of style.
Uniformity Requires Continuous and Positive Control
In meeting and satisfying the purchaser's expectations,
the manufacturer's problem would be very simple indeed if
quality were some definite thing which could be easily and
accurately measured out so much to an article — but it is
not. On the contrary, quality tends to slip away, to change
and, in fact, be almost everything except what it should be.
The perversity of inanimate things and the fallibility of
animate persons are always at work to render quality fugi-
8 THE CONTROL OF QUALITY
tive. In this respect quality differs markedly from quan-
tity. It is comparatively easy to say that we will make a
thousand articles and to proceed to make them. The prob-
lem becomes difficult only when we are required to make
them alike within precise commercial limits and with mini-
mum variations from standard.
This difficulty in attaining uniform standards of quality
in manufacturing makes the control of quality so vitally
important. The advertised claim of quality is one thing but
the positive and continuous control of quality to definite
standards in the factory is something altogether different—
as many people have discovered in recent years. By "posi-
tive control of quality" is meant that form of manage-
ment or direction which establishes the quality requirements
and then sets up the organization and selects the personnel
capable of securing that quality. By " continuous control
of quality" is meant the vigilant maintenance and direction
of the organization and personnel set-up to make the control
positive.
The resulting and final quality of a manufactured article
is created and influenced by a great number of things. In
fact each element of the business plays some part in the
final result. Consequently the control of quality must be
positive in action in order that all the factors and agencies
involved may be co-ordinated. If one factor gets out of
control, the entire system is thrown out of adjustment, errors
accumulate, and quality suffers.
The control must be continuous because quality is not
one of those things which once established stays put for all
time. Its tendency to slip away is incessant. But a single
serious slip in quality may result, in some businesses — for
example in the manufacture of foodstuffs — in the destruc-
tion overnight of a good-will which has required years to
build up.
INTRODUCTION 9
Instance of Failure in Quality Control
In most successful and long-established industries it has
become a fixed habit to consider quality as basically neces-
sary and thus to take it for granted. Most of these people
sincerely believe that they have quality under control, and
that once having attained a certain standard nothing more
is necessary to perpetuate it indefinitely. Not long ago an
engineer happened to spy a small sewing machine in the
window of a Fifth Avenue store. It was of a standard make
and therefore presumably of standard quality. It hap-
pened that he had a place where such a machine might be
used advantageously so he purchased one, which was handed
to him in the original container. Upon trial, however, the
machine proved to be very stiff and jerky in its action. So
he personally took it back to the store and was informed
that such a thing could not be.
"Every one of our machines is inspected before it leaves
the factory, but you may take it to Miss X at the repair
desk in the rear. " Miss X took one look at the machine and
said, " Yes, the looper shaft is not straight. We get a good
many that way. I'll give you another one."
The second machine proved to foe only a little better than
the first. By this time the engineer was interested in the
problem as an engineer, so he proceeded to take the ma-
chine apart and discovered that the shaft had nothing to do
with the trouble but that a slight filing and fitting of three
other parts remedied the difficulty, so that his machine
finally "ran like a sewing machine." He was especially in-
terested to note, however — and this is the point of the story
—that all of these difficulties should have been corrected
and could easily have been corrected in the manufacturing
of the parts, with a probable reduction in cost of assembly.
This, it may be noted, is quite aside from the question of the
reflection on this particular manufacturer's reputation for
10 THE CONTROL OF QUALITY
quality, for it is obvious that the engineer referred to is not
going to buy a life-sized machine of that particular make
until he has made sure that other manufacturers do not mar-
ket a more uniformly satisfactory product.
The experience just recited is significant of what happens
with many concerns. The manufacturer in question has
had a long-established reputation for a satisfactory product
and it would be an extremely difficult and painful under-
taking to make him believe that his control of quality had
slipped badly in this instance. He probably believes that
he has always had quality and consequently that he always
will have it. He regards it as a part of his fixed assets.
In order to get quality under proper control it is necessary
to note that every phase of the business from designing to
shipping is involved and requires critical examination. It
is not merely a matter for the inspection department to take
care of. For example, here is a factory which sets up a
very high standard of dimensional accuracy on paper. The
plans call for splitting thousandths of an inch in the manu-
facturing processes. It has an elaborate and expensive
inspection department, but it lacks the modern mechanical
methods for checking the accuracy of its measuring instru-
ments. It cannot possibly attain the dimensional precision
called for by the plans, because of the failure to provide a
comparatively inexpensive bit of apparatus. Yet the people
in the factory think that they are doing remarkably fine
work, while as a matter of fact they are only fooling them-
selves. Their measuring instruments read to the precision
required but they do not measure to that precision — which
is something entirely different — and there is no positive way
of checking them when they wear. In this instance, as a
matter of interest, the management was not even aware of
the fact that their dimensional checking arrangements were
deficient and antiquated.
INTRODUCTION
I I
Here is another factory which is in nearly the same situa-
tion but for a different reason. It has all of the apparatus
and all of the provisions for inspection that are necessary,
but the work in process is under such unsystematic regula-
tion that the inspectors are frequently unable to tell you
with certainty what parts have been rejected for minor
defects and what parts are satisfactory and up to standard.
Disorder in the shops has been carried over into the quality
of the output.
These are by no means isolated examples, nor are they
exceptional cases.
Figure I. Full Set of Johansson Gage Blocks
Set No. i, consisting of 81 blocks; 300,000 different dimensions are possible with this set.
There are other sets, but this is the one most used in America. Millimeter sets are also to be had.
All blocks are accurate to within one-hundred-thousandth of an inch per inch of dimension.
12 THE CONTROL OF QUALITY
Advantages of Considering Quality at Outset
The idea seems to prevail that, because quantity produc-
tion has been desired, quantity itself is the proper starting
point in attacking production problems. This idea is seem-
ingly supported by the honest belief in many industries,
both large and small, that everything which should be done
in regard to quality is being done. As a result, quality con-
trol has been disregarded and the demand for quantity has
been kept in the forefront.
Now the fact of the matter is that in concentrating di-
rectly on quantity production and hence taking quality
very much for granted or treating it as a secondary consid-
eration, we have been overlooking an opportunity; and the
oversight is costly in more ways than one. This is proved
at once if we stop to consider the advantages which accrue
from approaching management problems with quality in-
stead of quantity as the primary criterion. There are
immense and as yet largely undeveloped economies to be
found when management is critically scrutinized from the
quality standpoint. These resulting advantages are quite
apart from the direct advantage of quality for its own sake,
since they result in better labor relationships, increased out-
put, and decreased costs.
Improved Labor Relationships
Let us consider the point of labor relationships. These
present an ever and most pressing factory problem. The
moment you endeavor to get an increase in output (which
is attacking the problem from the standpoint of quantity)
the question of bargaining enters and provides an occasion
for dispute. On the other hand, if the workman is taught
to better his product, and is urged to be more careful, and
to be sure that his work is performed correctly, a common
meeting ground is provided. It is a poor mechanic indeed
INTRODUCTION 13
who does not take sufficient interest in his work to join you
in improving the results of his craftsmanship.
Suppose now for the moment that this greater attention
to quality, requiring thoroughness and attention to detail as
it does, will result in an actual increase in output for the
same effort. I say " suppose" that it does, although as a
matter of fact it will be proved presently that there is no
supposition about it. But assuming for the moment that
more attention on the part of the workman to quality will
bring about an increase in output, have we not secured that
increase in a much pleasanter, more effective, and more
permanent way than if we had made a direct request for in-
creased production? It is in every way more satisfactory
to discuss a factory problem on a basis in which both sides
are mutually interested and moving in a common direction
which brings them closer together.
In order to carry out such quality discussions intelli-
gently, the management must be informed, and very
thoroughly informed at that, about the technical side of the
business. Certainly this alone is a desirable thing. This
method of approach is bound to lead into a study of the
technical details of the business, to the mutual edification
of both management and men. Failures to attain quality
standards take the form of variations in the characteristic
qualities. These errors in manufacturing must be listed
and evaluated, and the basic causes of the errors located and
cured, all of which is bound to be both stimulating and in-
tensely interesting. It is about the only sure basis for off-
setting the well-recognized danger of the modern industrial
system. Men cease to be mere automatons when they
think in this way about their work.
It is a fact that the manager who strives to interest his
organization in improving the quality of the work done will
find that the process will work out to be a wonderfully effec-
14 THE CONTROL OF QUALITY
tive co-ordinator. When the men are trying for better and
more careful workmanship, there is small chance of those
disputes and arguments which so frequently arise when
pressure is applied for more output. There is a world of
difference between bargaining and appealing to the pride of
craftsmanship. By the very reason of his being an artisan
the worker is interested in improving his work.
Testimony
In 1912, a report was submitted to the American Society
of Mechanical Engineers on "The Present State of the Art
of Industrial Management," which quoted an earlier paper
by L. P. Alford and A. Hamilton Church on "The Princi-
ples of Management,"1 setting forth the latter as:
1. The systematic use of experience,
2. The economic control of effort, and
3. The promotion of personal effectiveness.
Both of these papers dwelt upon "the conscious trans-
ference of skill" (which necessitates that the management
must first have the skill to transfer) as a vital step in pro-
moting the personal effectiveness of the worker. There
thus begins to appear an attitude toward management,
which, when translated into general practice, is bound to
have a profound influence on the labor situation. The
evidence is strong that managers are leaning more and more
towards this point of view, accentuated by a stronger and
growing realization of the value of stressing quality.
At the annual meeting of the American Society of Me-
chanical Engineers in December of 1919, Robert B. Wolf
(then manager of the Spanish River Pulp and Paper Mills,
Ltd., of Sault Ste. Marie, Ontario) presented a paper on
'The Use of Non-Financial Incentives in Industry," which
was recognized at once as containing many original and
American Machinist, May 30, 1912, Vol. XXXVI, p. 857.
INTRODUCTION 15
thought-provoking ideas that were widely discussed. The
following is taken from Mr. Wolf's paper:
Such records can be grouped under three main headings: quan-
tity records, quality records and economy or cost records. Quality
records which occupy the middle position, are, perhaps of the great-
est importance, for they bring the individual's intelligence to bear
upon the problem, and as a consequence, by removing the obstacles
to uniformity of quality, remove at the same time the obstruction to
increased output. The creative power of the human mind is, how-
ever, not content simply to produce the best quality under existing
conditions of plant operation. The desire to create new conditions
for the more highly specialized working out of the natural laws of
the process demands expression, and this expression at once takes
the form of suggestions for improvements in mechanical devices.
Only recently a paper was presented by W. N. Polakov
entitled, " Making Work Fascinating as the First Step
Toward Reduction of Waste."2 This paper is carefully
worked out and will repay reading with the general attitude
of mind which recognizes the great desirability of organizing
work "so that the worker's intelligence and his creative or
imitative instincts will be brought into play. This requires :
(i) analysis of jobs and processes to bring out the interrela-
tion of causes and effects, and (2) the education of operators
in conscious control of these forces and relations so that they
can at will influence the results." This quotation is indic-
ative of Mr. Polakov's attitude, but the reader is referred
to the original text for a more thorough presentation of the
subject.
Increase of Output and Decrease of Costs
Let us now consider the effect which the control of
quality produces in increasing output and decreasing costs
of manufacturing. The statement has already been made
that such an increase in the volume of production does result
2 Mechanical Engineering, Nov. 1921.
16 THE CONTROL OF QUALITY
from the establishment of adequate quality control, and
that it further results in a decrease in the cost of production
as well. This idea was advanced in brief form in a paper
by the author, published in October, iQiy.3 Time and a
subsequent study of a number of manufacturing enterprises
have only served to strengthen these significant conclusions.
Before exploring the basis of these conclusions, it is wise
to remember that quality of itself is not a costly thing. For
example, one buys a Ford car, not necessarily because it is
cheap, but because it is built to a rather definite standard of
quality and the purchaser has every reasonable assurance of
obtaining a known return for his investment without refer-
ence to price or time. Although the Ford car is compara-
tively inexpensive, it has definite quality.
The misapprehension that quality is costly doubtless
arises from the fact that it is used as the chief inducement
to make people spend money. In current use, moreover,
the phrase "quality production" as distinguished from
"quantity production" does not imply the idea of manu-
facturing to certain predetermined standards of quality so
much as it does that the quality of material and workman-
ship is of unusually high grade.
From this latter mode of thinking has arisen a wide-
spread belief that quality is expensive and that it is always
cheaper to make things to a lower standard. So it is, if we
are working intentionally to a lower grade and definite
standard ; but usually a lower grade article implies indefinite
and inaccurate standards, poor material and slipshod work-
manship, and little, if any, inspection. In such case the
outputs lower and the work more expensive than if the
thing were done correctly and well in the first place. It is
axiomatic that it is always cheaper to make things right at
the start.
"The Control of Quality," by G. S. Radford, Engineering Magazine, Oct. 1917.
INTRODUCTION 17
Carnegie's Maxim
One of our greatest manufacturers clearly understood
that quality by itself is not necessarily costly, but it is always
expensive to ignore; as the following quotation indicates.
Almost everyone knows that the success of Andrew Carnegie
was founded in meeting the " impossible" requirements of
the United States Navy Department for a much higher
grade of steel ; so it is interesting at this point to note what
he has to say relative to quality in his "Autobiography" :
We were as proud of our bridges as Carlyle was of the bridge his
father built across the Annan, — "An honest brig" as the great son
rightly said.
This policy is the true secret of success. Uphill work it will be
for a few years until your work is proven, but after that it is smooth
sailing. Instead of objecting to inspectors, they should be wel-
comed by all manufacturing establishments. .A high standard of
excellence is easily maintained and men are educated in their effort
to reach excellence. I have never known a concern to make a de-
cided success that did not do good, honest work, and even in these
days of the fiercest competition, when everything would seem to be
a matter of price, there lies still at the root of great business success
the very much more important factor of quality. The effect of at-
tention to quality, upon every man in the service, from the presi-
dent of the concern down to the humblest laborer, cannot be
overestimated. And bearing on the same question, clean, fine work-
shops and tools, well kept yards and surroundings, are of much
greater importance than is usually supposed. " Somebody appears
to belong to these works" remarked one of a party who passed
through the works. He put his finger there upon one of the secrets
of success.
The surest foundation of a manufacturing concern, is Quality.
After that, and a long way after, comes Cost.
Experience of War Time Manufacturing
The analysis of enterprises which were intensified by
war conditions illustrates the point vividly. It is now more
generally realized that the specifications furnished for war
18
THE CONTROL OF QUALITY
INTRODUCTION 19
material (unfortunately for the manufacturer) were inexact
in many cases, so that great latitude existed for the applica-
tion of judgment by inspectors, this being specially true in
the case of the earlier contracts for foreign material. When
the contractor failed to clear up all doubtful points affecting
quality at the start, and plunged boldly into large-scale
manufacturing, the resulting failure of the good old methods
of quantity production came as a distinct shock to both
engineers and manufacturers.
The lessons to be drawn from these experiences are mani-
fold, but close examination will reveal the fact that the
manufacturers who were more careful in all matters deter-
mining and affecting quality, reaped a greater harvest in the
end, although they usually took longer to get started. The
most clearly marked contrast between those who achieved
results and those who did not do so well is to be found, in
every case, in more exact definitions of quality backed up by
an inspection service and general control of quality adequate
for safeguarding the standards established. It is undoubt-
edly true, moreover, that when the precautions just stated
were taken and when, in addition, a very high grade of di-
mensional accuracy was adhered to, the quantity of output
was astonishing.1 The fact that these enterprises dealt
with large-scale interchangeable manufacturing in no way
weakens the general applicability and truth of the principles
involved ; which serves to show that the method of planning
for large output at low cost with quality as the basic and
primary guide is more than vindicated by the results.
Control of Quality Basic
The facts demonstrate that when manufacturing ar-
rangements are made first and primarily with the intention
of controlling manufacturing to definite and uniform stand-
4 Typical examples of war time production successes are set forth in Chapter XII.
20 THE CONTROL OF QUALITY
ards of quality, quantity of output will follow. Briefly, if
we first take care of quality, quantity will take care of itself.
This does not mean that there is no need of the various
modern devices for increasing and controlling production,
because all of these things have their place. What it does
mean, however, is that quality should be the basic guide and
that, like quantity, it is an integral part of all the manufac-
turing operations and demands recognition accordingly.
In this connection the effect of losses of work in process
on quantity of output alone is all too frequently overlooked.
These losses seriously affect production in a direct way, but
they still more seriously slow down production, reduce out-
put, and increase cost in certain indirect ways which are
much less apparent and hence, by reason of this obscurity,
more difficult to detect and to remedy. A piece that is
wholly spoiled represents a loss of all the work expended in
its manufacture up to the point of spoilage; yet, even so, its
outright loss is frequently cheaper than a partial injury
which requires the attention of the best men in the shop to
repair the defect, while their regular work meanwhile is at a
standstill. In other words, the generalization that it is
always easier to do a thing right in the first place, holds
equally well in the factory.
The Quality Bonus
As further indications of the trend toward recognizing
the value of the quality approach, a few cases may be cited
where managers have had the courage to go so far as to
establish a wage payment based definitely upon quality.
Even when a quality bonus is superimposed upon a piece
work system which contemplates payment for good work
only, the results obtained by a separate payment for quality
have been astonishingly satisfactory. In two instances
which were merely isolated mechanical operations, where
INTRODUCTION 21
the rejections were exceedingly numerous, shifting the piece
work rate to a reward for quality reduced rejections to a
negligible amount almost overnight. The following exam-
ples, however, deal with quality bonus payments which are
in effect on a much greater scale, and which represent a radi-
cal departure from currently accepted practice.
Experience of The Shelton Looms
Some time ago The Shelton Looms, under the progressive
control and guidance of Sidney Blumenthal, established a
quality bonus for weaving. This mill is engaged in making
high-grade, deep-pile silk and woolen fabrics and of course
a great deal of attention is paid to quality. At a certain
stage of development the manufacturing problem was ap-
proached from a new angle, and the quality bonus for weav-
ing was adopted. The improvement in both quality and
quantity is indicated by contrasting the following figures 5
(which are for the first quarters of the years stated) :
1917 1920
Number of men 1,784 1,645
Hours per week 50^ 47^
Yardage 107 154
Quality 73i% 90+ %
Mr. Blumenthal has been quick to take advantage of
suggestions for improving management methods and to
follow them up with care. Consequently, it is interesting
to note that he summarizes the experience of his company
in the matter of paying for quality by saying, "Attention
to quality demands thoroughness, and thoroughness removes
the obstacles to production."
Experience of the Armstrong Cork Company
As a further example in the field of wage payment based
primarily upon quality, the experience of the linoleum divi-
5 Furnished through the courtesy of L. DeK. Hubbard, Operating Vice-President, and
F. Stolzenberg, Mill Manager of The Shelton Looms.
22
THE CONTROL OF QUALITY
WILL IT
HIT
6- JALES
N A STACK
ARC MAP6
TO SMO
THE OOOP.S
TbTWEr 8£ST
AOVAMTACE.
— TUB FMlSHRP
PAOOUCT
ery
A/NO SCMKOOI.es
^OST&E QEV
TO TAKS TM
TMB
EVERY .BOOV ELSE
OR.
GO I UT V
ARE "L-AiD of=P
Figure 3. An Object Lesson in Quality
Drawn by an employee of The Shelton Looms.
INTRODUCTION 23
sion of the Armstrong Cork Company, Lancaster, Pennsyl-
vania, is equally interesting.6 As everyone knows, "battle-
ship linoleum" is a standard product of established quality,
and it is natural that its makers should view the matter of
production with quality as a guide.
The bonus system for quality production was conceived
and installed in 1914, and has been in successful operation
ever since. The primary object of the plan was to decrease
the quantity of seconds produced and at the same time to
guard against a decreased production per man. The result
has been a consistent increase in quality each year, so that
from the early part of 1914 to date the increase in output
of first-quality goods is 30 per cent greater than when the
quality bonus was started.
During this period the production per man increased
slightly, but this was not one of the motives for installing
the system. Since production in this industry is deter-
mined almost exclusively by the speed of given machinery,
the special aim was to see that the production governed
by the speed of the machines was not reduced by the efforts
of the men to turn out perfect goods. This has been suc-
cessfully accomplished. In fact, during the war period
when the man-efficiency in industry generally reached a very
low ebb, the experience of this plant was the exact opposite,
for the efficiency per man throughout the various depart-
ments increased perceptibly. This experience under the
trying conditions of the period in question is a further vin-
dication of the managerial judgment which makes quality
the basic criterion for attacking production problems.
Decreased Selling Costs with Quality Goods
The results obtained by The Shelton Looms and by the
Armstrong Cork Company certainly warrant a wider study
6 From information supplied through the courtesy of John J. Evans, General Manager.
24 THE CONTROL OF QUALITY
and application of quality payment ; for, in addition to im-
proved quality itself, the resulting increase in production
means decreased costs — both directly and through the elimi-
nation of various sorts of losses.
There is, moreover, another phase of lowered cost when
quality receives attention, which should not be overlooked,
and that is the lessened selling expense which is a direct
result of supplying goods of standard quality. Such arti-
cles sell themselves at the factory.
There is evidence on every hand that the purchasing-
public is applying much finer and more intelligent discrimi-
nation in its buying. Even the non-technical press is full of
advertising matter setting forth in detail the reasons why
the goods advertised possess the characteristics claimed for
them. In other words, the average purchaser is becoming
a better inspector. Consequently, work which is held to
standard is being more and more appreciated and the sale of
such merchandise is immensely simplified.
The element of quality enters into a number of things
which are not a part of production. When the buyer realizes
that nobody else's goods come to him as well packed or in
such an economical form for him to handle, it is easier to
sell to him. So quality enters into packing. And it is not
a far extension of this idea to say that quality enters into
shipping as well ; because prompt deliveries by the cheapest
routes are certainly factors which are influential in the repu-
tation of your goods almost as much as the satisfactory
quality of the goods. Also, quality in "service" generates
reliance in the firm which really stands behind its goods.
In fact, anything that tends to control quality to more
definite and satisfactory standards, whether in the goods
themselves or in service connected therewith, increases
selling power just that much. Thus the statement that
quality goods are sold at the factory becomes a reality.
CHAPTER II
THE APPROACH TO QUALITY CONTROL
The Starting Point — Determining Nature of Product
Quality, being a characteristic or group of characteristics
of a product, is intimately a part of the product. There-
fore, the only safe and orderly starting point for any en-
deavor to bring quality under exact control is the product
itself. We may be sure of successful results if we begin at
this point. This procedure differs radically from the usual
approach when quantity production is sought directly. In
the latter method of attack on the problems of manufactur-
ing there is an ever-present tendency to begin with the sta-
tistics of the business. Records of past production, esti-
mates of future production, and calculations as to what
equipment, tools, materials, and labor are necessary to se-
cure an increased quantity are brought to the forefront. It
is only later that consideration is given, if time permits, to
matters affecting routing, processing, inspection, and others.
Now the product is a final result of the orderly and co-
ordinative working-out of all these things. Each makes a
plus or minus contribution to quality. So the control of
quality demands that the quality standards be determined
first, and then that all the arrangements for creating the
product be so made as to insure the realization of these
standards. This means nothing less than shaping the means
to produce the desired end, instead of permitting manufac-
turing system, methods, and what-not to determine the
character of the factory output.
As L. P. Alford l has frequently stated in his excellent
1 Editor of Management Engineering.
25
26 THE CONTROL OF QUALITY
analyses of management problems: "The end of manufac-
turing is the production of goods." Let us select what we
intend to make first, and then take up the processes, work-
ing arrangements, organization, and system necessary to
achieve that result; for it is by the results and not by the
means that our work is judged.
This procedure distinctly stresses the fundamental im-
portance of establishing definitely the standards of quality
which are to be followed, before we can know exactly what
we are trying to make; for if there has been found any vir-
tue in preplanning for production, it has been demonstrated
that the more completely we know what we are trying to do,
before we actually start doing it, the more easily and swiftly
will the work be carried out. It is this wider idea of quality
which exactly describes the features of a design with which
we are chiefly concerned.
The Commercial Factors — Requirements of the Consumer
Quality, therefore, as referred to here, involves a very
definite specification of the important characteristics of the
product which enable it to fulfil the needs and demands of
the customer in a satisfactory manner. The customer re-
quires that the article be suitable for his purpose. That is,
it must be reliable, it must be durable over a period of time,
it must be economical both in first cost and in operation,
and usually it must be pleasing to the senses as well.
The Design — Securing Consumer's Requirements
From the standpoint of the designer each of the com-
mercial factors is created by the various features of materials
of construction, shape, dimension, finish, and so on; and the
quality of the final result is determined by these as well as by
the degree of precision with which the design standards
are realized. This involves processes and workmanship.
THE APPROACH TO QUALITY CONTROL 27
Needless to say, the product should be designed to meet the
commercial requirements as nearly as may be consistent
with economical manufacture; and in doing so the manu-
facturer is faced with the necessity for compromising in
almost every instance. To solve the problem intelligently
requires a knowledge of what we are trying to produce and
why. The quality may be anything we choose, but as a
starting point a clear idea of what we seek to accomplish is
fundamental.
As an example of this process, what is so simple as an
alarm clock? Like all other clocks an alarm clock may be
expected to keep reasonably good time over a period of
time. That is part of its job as a clock. But beyond that
it has a very unpleasant duty to perform. It should begin
with as gentle a tone as possible and still accomplish its pur-
pose with certainty. Having attracted attention, the more
pleasing its appearance the less likelihood of trouble. The
least the manufacturer can do for an alarm clock is to pre-
pare it for this part of its job, so he gives it a fine finish in
nickel plate.
Now a certain manufacturer took great pride in the fact
that he was making the cases of his clocks out of a high
grade of brass, but he overlooked for the time being that the
quality of the brass in the case was of no interest to the pur-
chaser whatever. His real job as manufacturer was to
provide a nickel-plated surface which would stand ordinary
alarm clock service. When he investigated the matter from
this point of view he discovered that a cheaper grade of
brass would take a better nickel plate and hold it longer
than the higher priced material he was using. Thus you
will observe that the manufacturer, having first studied his
product from the standpoint of the commercial factors in-
volved, learned what he was trying to produce and why.
This led him at once to the conclusion that he should carry
28
THE CONTROL OF QUALITY
the problem to the manufacturer of raw materials, who might
reasonably be supposed to know more about such materials
than anyone else, with the direct result of an improvement
Figure 4. A Common Method of Holding a Micrometer Calipcr
Courtesy of Brown and Sharpe Manufacturing Company.
in quality accompanied by an actual economy in produc-
tion.
We are pretty sure to be on safe ground if we understand
that quality requires accuracy and care, and that these
things are less expensive than their opposites — inaccuracy
THE APPROACH TO QUALITY CONTROL 29
and carelessness. Consequently, if it has been decided that
the commercial requirements of the case call for a low-grade
product, let us proceed on that basis but with the determina-
tion that the lower standards of quality are just as delib-
erately and intentionally selected as if they were of higher
grade.
Provision for Improving Design
As has been pointed out, economy of manufacture and
uniformity of quality standards go hand in hand ; but there
is no reason why the standards should not be raised from
time to time without conflicting with the requirement of
uniform standards during any one period or season of manu-
facturing. One of the desirable advantages of paying
special attention to quality is that this method constantly
reveals chances for improving quality without increasing
costs. The stage is not likely to be reached where further
advances are impracticable.
The manufacturer who is satisfied that his product can-
not be improved is in a dangerous state of mind, because
progress has not stopped in any art or in any science. If he
thinks that the limit of improvement has been reached with
the means available, then it is time to look for improved
methods, because no business should stand still in any sense.
Ordinarily when an art is not advanced, the reason is to be
found in failure to provide, within the organization, for
systematic and progressive improvement. Further, when
someone says that the thing is impossible, that very thing
provides an opportunity; for "the man who says that a
thing can't be done nowadays, is pushed out of the way by
someone doing it!"
From the design standpoint, the best way to provide for
the systematic advance of quality, is to realize at the start
just what the departures from the highest standard are going
30 THE CONTROL OF QUALITY
to be. Picture a lower grade product from the viewpoint of
a de-graded high-grade article, in which the reductions in
quality are known and have been made deliberately and
with "malice aforethought." Then we are in a position to
know the directions in which improvements can be made,
and in great detail.
The path of future progress is thus made clear, and it
will be found that the process of gradually refining and im-
proving the product, step by step, will bear fruit presently
and quite rapidly.
Materials
After the product has been thoroughly analyzed with
reference to the qualities which it is desired to secure, and
after the design has been carried through the stages of com-
promise made necessary by considerations of economy, the
next step is the selection of materials of construction. Now
the raw material of one manufacturer is the finished product
of another. The manufacturer of the raw material has been
through the same process of analysis and economical com-
promise. Hence it is not reasonable nor even possible to
select materials which are 100 per cent right for our purposes,
and we are faced again with the necessity for making up our
minds. In fact this is just one step in a long series of com-
promises, all flowing from the fact that quality is something
which is peculiarly subject to change and variation.
Since uniformity of result is the thing sought, the most
desirable characteristic of the raw material, other things
being equal, is uniformity. Once more, cost becomes a sec-
ondary issue, within reasonable limits of course. In the
case of brass for alarm clock cases, it was noted that a
cheaper brass took a more permanent and uniform nickel
plating. But the same demand for uniform results, or for
ease and certainty of working up the material may justify
THE APPROACH TO QUALITY CONTROL 31
a higher cost. Thus it is currently reported that the lowest
priced automobile made today contains the highest per-
centage of alloy steels, as a matter of economy.
Processes
With raw materials decided upon, the stage is reached
where processes must be studied with the same mental atti-
tude. Can the processes and their equipment possibly pro-
duce the results which are desired? If not we should cer-
tainly understand just how they should be changed to bring
the work to our predetermined standard, with economy.
It will invariably be found that certain approximations
to the standard are necessary. In other words, the con-
Figure 5. Measuring a Turned Piece in Lathe
Illustrating another correct way of holding micrometer caliper. Courtesy of Brown and Sharpe
Manufacturing Company.
32 THE CONTROL OF QUALITY
sideration of the problem requires another compromise as
soon as the selection of manufacturing processes is made.
This fact holds true no matter how sensibly the processes
are selected or how simple they may be. Quality varies,
and the design must be modified accordingly to suit the
processing, by stating the permissible variations from
standard which will be tolerated. The idea of tolerances
and limits for variations from standard thus enters the man-
ufacturing scheme. Whatever the other conditions may
be, the processes must be chosen to permit reasonable
control of the resulting work to the degree of uniformity
allowed by the tolerances in question.
Workmanship
Intimately associated with the study of processes is the
matter of workmanship, which involves all questions asso-
ciated directly or indirectly with the proper application of
the machinery provided for production. It is not infre-
quently the case that the foreman says his tools are all right
because he has personally used them to make satisfactory
articles. On the other hand, all he has proved by using the
tools himself is that an expert workman can get the results
with the equipment available. But the only labor obtain-
able for using these tools may be quite incapable of attaining
equally satisfactory results without changing the tools or
without very careful instruction, or without change in the
surrounding conditions of inspection or other means in use
to safeguard the production. ' ' Transfer of skill ' ' and ' ' the
promotion of personal effectiveness" at once come into
action.
Operating Organization and Records
Evidently this same process of intensive investigation of
the manufacturer's problem from the standpoint of quality
THE APPROACH TO QUALITY CONTROL 33
will now carry us to the study of the organization for operat-
ing the factory and finally to the system of records of per-
formance, which are used in controlling the organization in
a way to result ultimately in production in accordance with
the quality standards as set. It goes without saying that
each and every factor entering into the production problem
requires sufficient study to insure definite ideas as to how
each of these factors can be positively and separately con-
trolled. When this control goes into effect in the qualita-
tive refinement of the industry, production problems for
the most part will be found to have been solved in the proc-
ess, simply because quality is so fundamental in its nature
that it requires a consideration of all the factors involved in
the business.
Inspection an Essential
If we were starting a new project the preliminary study
of quality which has been outlined in the foregoing pages
would be made before and during the starting of the factory.
Once manufacturing has begun, however, the same continued
investigation must be supplemented and assisted by some
sure method of bringing to the surface information relative
to the errors and failures to attain quality standards.
This is a situation in which every factory finds itself.
The factory is running along under pressure of production,
and quality is always tending to slip away from the stand-
ard and to get out of control. Consequently there is an
urgent need to bring to light immediately, and to evaluate
the deviations from the desired quality, in order that prompt
steps may be taken to limit and correct them.
As an instrument for the prompt and perpetual analysis
of the quality situation, and thus for assisting in the control
of quality, a proper inspection service is necessary. But to
render such service, as well as to carry out its many other
34 THE CONTROL OF QUALITY
important functions, the inspection department must be
placed in a position to act effectively. That is only com-
mon sense. Yet the fact remains that there is a very general
failure to appreciate the possibilities of inspection, although
war experience has helped considerably to dispel this lack
of appreciation for what inspection can do if given a chance.
The subject is one which has received far too little atten-
tion from the standpoint of systematic study. There is
practically no literature or philosophy of inspection. In
view of this situation let us now examine some of the various
characteristic peculiarities of inspection as an introduction
to the further study of quality and of methods for the con-
trol of quality.
CHAPTER III
INSPECTION— THE NEED FOR INDEPENDENT
SCRUTINY
Maintaining Standards — Measurement and Control
To set up standards of quality, no matter how thor-
oughly and carefully it is done, is one thing; but to realize
those standards in the actual work in the factory is quite
another thing, for the mere stating of what is wanted will
not secure the result. Suppose that a design has been
proved out in a thoroughly satisfactory working model or
that an article is found to be acceptable to the market;
that the working standards have been determined with
experience based on the best practice and guided by the
highest mechanical engineering skill ; that the equipment is
adequate and installed in keeping with the requirements of
economical and high-grade manufacturing; and then sup-
pose that the factory is started to operate with nearly all
work on a piece rate or similar basis, with schedules of
desired daily output in the hands of each department
head — in short, with the usual great pressure for quantity
production. Under these circumstances will the product
measure up to the working standards of quality so carefully
determined and clearly described? Certainly not, unless
means are provided for measuring the quality of the work as
it is made, together with the necessary organization for
seeing that the work is held to standard within economical
bounds.
To control quality so as to realize the working standards
as nearly as may be, requires both logical thinking and
masterly management. The seriousness of the task in-
35
36 THE CONTROL OF QUALITY
creases rapidly with the degree of accuracy or grade of
quality required and with the complexity of the product.
It is made still more difficult if the manufacturing opera-
tions are conducted on a large scale, for this is one of the
things which becomes magnified in the large plant in a ratio
that increases much more rapidly than does the size of the
plant itself.1 There are certain problems which are solved
in the small shop with comparative ease, because of the di-
rectness with which they can be seen and the simplicity
and promptness with which they can be handled ; yet these
same problems become serious difficulties in the large
plant.
When we are surrounding the work as it flows through
the factory with an environment that makes for quality
production, someone must exercise the duty of viewing
the work closely and critically so as to ascertain the quality,
detect the errors, and present them to the attention of the
proper persons in such a way as to have the work brought
up to standard. This function of carefully scrutinizing the
work as it progresses through the various stages of manu-
facture, and of pointing out the unsatisfactory work, is the
principal purpose of inspection; and by " inspection " is
meant inspection conducted as a function of the factory
organization, and not by some outside organization em-
ployed by the purchaser.
The Instrument for Measuring and Controlling
One of the first things brought to light by a study of the
problem of measuring the quality of work and establishing
the necessary organization to secure and maintain this
quality is the fact that inspection is, first, the instrument for
quality measurement, and second, that it is a powerful
factor in quality control. It is like the keystone of the arch.
1 "Production as Affected by Size of Plant," by G. S. Radford, Management Engineering,
Aug. 1921.
NEED FOR INDEPENDENT SCRUTINY
37
38 THE CONTROL OF QUALITY
You can get along without it, but the supporting false work
which must be left to take its place is crude, clumsy, less
effective, and more costly.
Its relation to quality is indicated by this thought.
Quality may be likened to a globule of mercury — it is al-
ways tending to slip away. You can hold mercury in a
given position or on a particular line with a certain degree
of success without resorting to control. In the same way it
is possible to secure quality of a certain kind and degree
without inspection, but in the factories which stand as
leaders in their respective lines there is always a well-
developed, scrupulously maintained inspection service.
Convincing the Management
Every chief inspector must first realize, with entire
conviction, that inspection is a necessary step in the great
process of manufacture. Then it becomes his painful duty
to get this idea across to the management. The latter task
is usually difficult. The inspector is responsible for quality
to a very great extent; he is the management's guardian
against spoilage and waste; and when quality slips he is
conveniently at hand to receive the blame. In many plants
where his true relationship to quality is not clearly under-
stood, this latter "duty" of receiving the blame for errors in
work constitutes a large part of his daily job.
That such an attitude toward the inspector is untenable
is proved by a moment's reflection on the fact that the in-
spector never puts his hand to the work except to look it
over or to measure it. The inspector enforces quality by
refusing to accept poor work, but this act of rejection is
passive as regards enforcing the production of good work.
The quality or lack of it must necessarily be worked into the
material by the production department which controls
production processes. How then can we blame the in-
NEED FOR INDEPENDENT SCRUTINY 39
spector for lack of quality? In this regard his duty is com-
plete when he passes upon the quality characteristics of the
goods and reports his findings. It may be noted parenthet-
ically that this very fact is one of the reasons why quality
cannot be placed under control until every department of
the factory has been reviewed from the quality standpoint
and brought into proper alignment and co-ordination.
Growing Importance of Inspection
The kind of inspection, the manner of its application,
and the extent to which it is used are conditioned, of course,
by the circumstances in each case. One must first deter-
mine what it is desired to accomplish by inspection and then
consider the several different ways in which the desired re-
sult may be obtained, always with a view to selecting the
most economical method. There is such a thing as too
much inspection as well as too little, but a proper degree of
inspection is always an economy because it stops leaks by
the early detection of errors and thus prevents unnecessary
loss. From a strictly business standpoint it is justified as an
insurance of that part of "good-will" which is cultivated
and retained by the delivery of goods made to a definite
standard.
The evolution of inspection is both interesting and il-
luminating. In early factory practice (and, for that mat-
ter, in many plants today) inspection involved merely look-
ing at the work. Dimensions were scant or full. Then
through a gradual development, following in step with the
attainment of greater accuracy in the mechanical arts
which was made possible by more accurate measuring de-
vices and better machinery, we began to measure in
hundreths of an inch, then thousandths, then ten- thou-
sandths, and now in hundred-thousandths, if necessary.
Such progress in material ways calls for adequate and
40 THE CONTROL OF QUALITY
similar adjustments in organization; but the development
of an inspection force within the factory organization, and
hence paid for by the manufacturer, has not kept pace with
the technique of manufacturing except in a rather limited
way.
The fact is that inspection in the past has been applied
in many cases by the purchaser, and often, especially in
government work, in a manner to give rise to the feeling in
the manufacturer's mind that inspection should be regarded
as a necessary evil. Without question, a purchaser's in-
spector can cause ruinous conditions in any factory, es-
pecially if there is a lack of practical control, and if the
specifications and other data under which the work is being
performed are inexact or conflicting.
Inspection Often a Necessity, Always an Economy
It is generally recognized that it is a paying proposition
for the large purchaser of materials to provide his own in-
spection force. Yet it is even more to the interest of the
manufacturer to establish an inspection organization for
himself. He gains all the advantages secured by the pur-
chaser and many more besides through his ability to control
and direct the activities of his own inspecting force into the
channels most useful to him.
If you who are neither an architect nor a builder are
about to erect an expensive house or construct a new factory
building, do you inspect it yourself or do you employ some-
one who is competent? Of course you adopt the latter
method and consider the money expended for supervising
the inspection well spent. You do this no matter how
trustworthy or careful or reputable your builder may be.
Now consider carefully why this expenditure is a good
business proposition, and then apply the reasoning to your
own factory. You cannot make everything yourself, nor
NEED FOR INDEPENDENT SCRUTINY 41
even view it in a cursory way; nor can your superintendents
and foremen, for they are occupied with many other things
principally connected with human relations and quantity of
output. The average workman himself is least of all
concerned with safeguarding the quality of your product,
unless you make special provision to keep his work up to
standard. In many cases nowadays, he has not the ability,
of his own motion, to furnish the result you desire. Thus
inspection becomes, oftentimes, a necessity. In any event
an inspection service properly adjusted to the needs of the
case, is an economy as well.
Comparatively few factories had their own inspection
services prior to the war, but many of those operating under
war contracts were forced to provide such service as a mat-
ter of protection and have learned thereby its value. It is
to be hoped that much of the old and prejudiced attitude
toward factory inspection as an expense to be avoided if
possible, has disappeared; and that there will be realized
the large return in both quality progress and decreased
costs which are made possible only through the applica-
tion of a proper system of factory inspection, and not
otherwise.
Need of Intensive Study of Inspection
Inspection, to be sure, is only a part of the control of
quality, but it is an essential part. For quality can be
controlled properly only through a factory inspection serv-
ice— adequately organized and applied with an apprecia-
tive understanding of the philosophy behind it.
Inspection is being more generally used than ever before/
but is its function thoroughly understood? At present
there is evidence that inspection methods in many plants
are being overhauled to meet the oncoming and more critical
demands of commerce. In some cases, inspection depart-
THE CONTROL OF QUALITY
NEED FOR INDEPENDENT SCRUTINY 43
ments as such are being provided for the first time, and
existing inspection is being brought into line with the
best modern practice, for closer acquaintance with a good
inspection service is bound to prove its sound business
value, not only in raising quality but also in lowering costs
and increasing output.
In view of this situation one might expect to find con-
siderable attention being paid to the theory and practice of
inspection, but the engineering profession has been slow to
give it the same serious study that it has shown in other
lines of work. For example, the last ten years have wit-
nessed the intensive development of a literature concerning
itself, from the standpoint of the engineer-executive, with
the business of management in all its details. This litera-
ture is full of references to standards of quantity of output
per man per day, and contains countless methods, schemes,
and devices for increasing output and decreasing cost, all by
the route of laying stress primarily on quantity. Much is
said about how to determine the proper standards for
quantities of output under given conditions. Much more
is said about how to attain these standards of quantity
through all the varied means management engineering has
developed ; for while it is a difficult task to determine just
what the standard quantity of output should be; by the
same token it is much more difficult to put these standards
into effect; just as it is harder to keep trains running on
schedule than it is to lay out the timetable.
Study of Theory Needed
But with all this intensive study of industry, how little
attention is paid to the discussion of how to fix upon and
realize standards of quality in production, and the relation
of inspection to this problem! The Society of Industrial
Engineers recently, and very properly, defined the activities
44 THE CONTROL OF QUALITY
under which candidates for membership shall qualify.2
Some twenty industrial subjects were listed. An examina-
tion of the subjects so set forth indicates that no mention is
made of inspection, and that little if any consideration has
been devoted to quality control in production — certainly
nothing like the attention devoted to questions principally
affecting quantity of output. This, moreover, is merely
typical of the general professional attitude, although this is
not the first time that something has been used practically,
before the underlying theory has been investigated. Plan-
ning was always done in effect, but it was not performed
with the greatest economy until the engineer separated it
out of manufacturing as a whole, for individual and exhaus-
tive inquiry.
Can we afford in this instance, to neglect so important a
matter any longer, especially in the face of existing condi-
tions? The answer would seem to be strongly in the nega-
tive. The size of modern inspection departments alone
would warrant careful investigation of the subject. In
many well-established plants 5 per cent of the entire work-
ing force is employed in the inspection department and fre-
quently the percentage is considerably higher. In many
cases it could be made higher with advantage, until quality
is under such control that the amount of inspection can be
reduced.
Further, the sphere of influence of the inspection service
is far greater than its numerical relationship, for it reaches
into every department and touches all the detailed factory
operations having to do with creating and maintaining
quality standards. These facts alone, it is submitted,
should indicate the need for careful study of the theory and
practice of inspection, by all who have to do with the
management of industry.
2 Industrial Management, Jan. 1920, p. 55.
NEED FOR INDEPENDENT SCRUTINY 45
Functions and Limits of Inspection
If one is going duck-hunting it is just as well to take
along a shot gun, but having the gun does not mean that the
hunter will return with a bag of ducks. Unhappily this
truism holds for many things besides duck-hunting and
leads to frequent misunderstanding of the inspector's
function. It has its limitations like everything else. Its
purpose is to measure quality and in this and in other ways
to assist in quality control ; but it does not create quality.
In this preliminary study of the need of inspection it
should be noted finally that inspection itself is not a fixed
and definite function or process except as regards the prin-
ciples which are involved. In contrast to being fixed, it is
very flexible and may be applied in many different ways.
CHAPTER IV
THE TYPES OF INSPECTION
Conformity with Special Factory Situation
The factory is guided toward production in accordance
with the working standards, by inspection, which measures
quality, applies discriminating judgment in close cases, and
in short forms an environment that continually sorts out
defective work while allowing satisfactory work to proceed.
Naturally the kind of inspection most suitable for a particu-
lar situation depends on the character of the work, the
standards of quality, the skill of the workmen, and similar
matters relating to the given manufacturing conditions and
circumstances. The thoroughness of inspection varies
from a casual viewing of samples taken at random in the
shop, up to the analysis, testing, or careful measurement in
separate inspection rooms, of each part after each mechan-
ical operation. In large plants engaged on high-grade,
interchangeable work, almost every one of the many pos-
sible kinds of inspection will be needed at some stage in the
process of manufacture.
Material Inspection
Little need be said of the inspection of raw materials.
The development of highly standardized material specifica-
tions has been made possible through a previous and pro-
gressive development in applied physics and chemistry.
The methods of the physical and chemical laboratories
which originated the data for the standard specifications in
the first place, are thus available in turn for testing and
analyzing the materials themselves. It is most unusual to
46
THE TYPES OF INSPECTION 47
find a plant of even moderate capacity without some sort of
laboratory in which samples of each lot of raw material
received by the stores department are carefully inspected
before being passed for issue to the factory.
A chemical works with a single product as simple and
cheap as silicate of soda has its own laboratory for inspecting
both raw materials and finished product. A flour mill using
the method of mixtures to secure a definite quality standard,
measures in the laboratory the food values of each lot of
grain, in order to secure data for the proper balancing of its
output. A paper mill makes microscopical examination of
fibers. In a great metal-working plant we find an assem-
blage of thoroughly equipped laboratories — chemical, physi-
cal, and metallurgical. So it goes throughout the great
range of the arts. Even small shops may avail themselves
of facilities for inspection of materials by patronizing the
commercial testing laboratories to be found in every im-
portant manufacturing center.
When the local conditions are such that there seems to be
no method or apparatus already in existence for this im-
portant work, the scientist should be called upon to work
out the problem. There is no reason today why means
should not be developed to meet almost any requirement for
inspecting and grading material.
Office Inspection
It is common practice, also, to provide an inspection
service in the drafting-room, especially in the tool-designing
section, so that the work of the "detailers" and other
subordinate draftsmen is carefully gone over by the
" checkers." It is perhaps not too far from our subject to
note that the application of similar methods has been
carried into large general offices in the form of an inspection
of outgoing mail. When department heads sign outgoing
48
THE CONTROL OF QUALITY
mail originating in their departments, it is not unusual to
find a further checking up, through carbon copies of such
mail being sent to the office of the general manager.
Tool Inspection
Factory inspection first appears in the tool-room. The
value of a careful inspection of all special tools, fixtures,
jigs, and gages, is quite evident, whether they are made in
the factory's tool-room or purchased outside. If the tools
are not correct, nothing is surer than that the work will not
be correct. As an additional check on the tools, even if the
work is simple, it is good practice in quantity production to
make an inspection of the first piece (and the last) produced
by a new machine tool set-up. A theoretically correct tool
Figure 8. Some of the Special Equipment of the Tool- and Gage-Checking
Room — Lincoln Motor Company
West and Dodge lead tester and Shore scleroscope in foreground.
THE TYPES OF INSPECTION 49
may not produce correct work, due to some peculiar interre-
lation between the tool and the way it is applied to the
stock. In many cases this first-piece inspection may be per-
formed by the mechanic who sets up the machine. This
duty sometimes falls to a special inspection service, how-
ever, if such a body exists.
The subsequent periodic inspection of tools, and in fact
of all manufacturing equipment, should be provided for
systematically, so that nothing will be overlooked, special
attention being given to the points where wear is rapid or
likely to cause the most trouble. Where gages are in use, as
in small interchangeable work, or when specially accurate
measuring instruments are used, as on close work of a size
beyond the accuracy of special gages or of too small a
quantity to justify the cost of gages, then, of course, the
greatest attention must be given to verifying gages or instru-
ments. The questions which arise in gage-checking involve
an individual practice, and therefore will be dealt with in a
separate chapter.
Process Inspection
Coming now to the inspection of work in process, the
first question to decide is where the inspection is to be made.
This ordinarily involves either choosing between two types
of inspection which are fairly well known under the respec-
tive names of "floor-inspection" and "central inspection"
or using some combination of the two systems. Floor-
inspection means inspecting work at the machine or near it,
while central inspection is the term used to designate the
system under which the work to be inspected is carried to
special spaces or rooms devoted entirely to inspection
purposes.
Central inspection involves the physical separation of
inspection from production, but it may exist in any one of
50 THE CONTROL OF QUALITY
several forms. Convenience rarely permits all inspection
to be centralized in one place for the entire factory, so that
the ordinary method of using central inspection involves
setting aside a place for it in one or more convenient loca-
tions in each shop.
Floor-inspection may vary from a sort of patrolling
supervision which scans the work at the machines, up to the
taking of very careful measurements and minutely scrutiniz-
ing the work. It begins to merge into central inspection
when the inspector is furnished with a special inspection
bench or similar station located near the machines whose
work he inspects. The inspection point may be located be-
tween machines in the line of flow of the work, just as if it
were a machine itself. If the separation between inspection
and production is clearly denned, we have a distributed form
of central inspection. In its most highly developed form
central inspection implies that all of the work of inspection
in a shop is centralized in a separate place, usually a room or
enclosure, to which the work is brought.
Advantages of Centralized Inspection
The most evident difference between the two types of
inspection is that, in one case the inspector goes to the work,
while in the other case the work is brought to the inspector.
But this apparent difference is by no means the greatest
dissimilarity. Centralized inspection has characteristics
differing markedly in many other and more important ways
from inspection that is scattered by reason of being done on
the site of the work. Central inspection, in general, per-
mits the use of a less degree of experience and skill than floor-
inspection, because the supervision of the work of the
individual inspector is made easier. Frequently division of
the labor of inspection is possible, and economy of inspection
results.
THE TYPES OF INSPECTION
52 THE CONTROL OF QUALITY
Similarly the work of inspecting may be performed
more thoroughly, as there is less likelihood of interferences.
More important still, the inspector and the producer are
not able to "get together" to anything like the extent pos-
sible in floor-inspection. Accordingly it is much easier to
control quality to definite standards, as well as to obtain
a better control of the flow of work by means of central
inspection, as will be indicated in more detail in Chap-
ter VIII.
Highly centralized inspection is the ideal type, for it is
the specialization of inspection carried to the limit. Its use
is not justified when parts are large or relatively few in
number, nor when the production work requires such skilful
mechanics that detailed inspection of their work is not re-
quired. With massive work, of course, the inspection must
be made at the place where the work is performed. As the
size of the component parts of the work decreases, and
transporting them becomes less difficult, a stage is reached
when central inspection in some form is both possible and
desirable. For example, the last or final inspection of large
automotive engine parts would naturally be made in a
separate room or space, through which the parts in question
pass after being finished in the shops where they are made.
In high-grade work of the same class it is good practice to
remove these parts to the inspection room after each of a
few operations in the course of manufacture. In this case
the operations selected for central inspection are those in
which close and complex work is performed, and whose
influence upon succeeding operations may be very serious
in accumulating errors.
When many operations are used in making one part in
quantity it is usually better to reinforce central inspection
by a floor-inspection in sufficient quantity to locate costly
errors more quickly.
THE TYPES OF INSPECTION 53
Inspection Combined with Remedy of Defects
Inspection takes another form in many manufacturing
processes where it is expedient to merge it with production.
Ordinarily this involves an inspection for defects in combi-
nation with the repair of the defects by the inspector. In
the manufacture of fabrics, for example, the work may be
rerolled on perches under the eye of an operator who repairs
broken threads and similar defects as he finds them. A
very simple case of allied nature is to be found in the testing
of tanks, or water-tight compartments in ships. The por-
tion of the structure to be tested is subjected to water pres-
sure, inspected for leaks and "weeps," and the leaking rivets
and seams caulked.
Use of Special Mechanical Devices
Inspection of large quantities of small pieces is some-
times done economically by the use of special machines.
In this kind of inspection, the operation is best considered as
a part of the manufacture of the part. Strictly speaking, of
course, no work is done on the part, inasmuch as the part
is not changed by the process of inspection, although the
quality of the factory output is improved thereby. The
making of rifle balls and small cartridge cases offers examples
of this sort. In one plant rifle bullets were carried on an
endless belt (originally designed as a bean-sorting machine")
before a number of inspectors, so that obviously defective
ones might be detected easily and removed quickly. Simi-
larly, cartridge shells with surface defects are more readily
located by the use of special machines which roll them before
the inspector's eyes in an endless procession. Scrutiny is
made more certain by mirrors suitably placed in the ma-
chine, to show all parts of each shell as it is rolled by. The
opportunity for making an inspection operation more ef-
fective and less costly is often revealed when consideration
54 THE CONTROL OF QUALITY
is given to developing mechanical devices to assist in the
work of inspection.
The Amount or Quantity of Inspection
Intimately associated with the question as to the kind of
inspection to be used, is the determination of how much
inspection — a question that must be settled in the light of
economy, for evidently we should provide the least inspec-
tion which will accomplish the purpose.
The necessary amount will vary, of course, with the prog-
ress that has been made in the particular factory toward a
better control of quality. If special attention is paid to
quality, the amount of inspection can be reduced gradually.
When this has been done, however, the inspection should be
reconstituted before the manufacture of a radically new
model is undertaken, for reasons that would not seem to re-
quire detailing.
In the first place it should be realized that the inspection
department must use judgment — "horse sense" — without
that it is only too possible for the department to tie the
factory up tight. The abuse of inspection through having
too many inspectors represents, of course, a dead loss from
the direct cost of inspection. It is chiefly to be feared,
however, because of the deadening influence on production
of the attempt to get too large a percentage of the work up
to standard. Incidentally this error will illustrate the value
of a clear appreciation of inspection's function in the control
of quality.
Quality, as we have seen, is a variable. It is not practica-
ble, therefore, to conduct manufacturing operations in such
a way as to produce nothing but good work, i.e., work that
is in accordance with the specified standards. Inevitably
there will be some bad work. If inspection is applied with a
view to reducing the amount of bad work to the absolute
THE TYPES OF INSPECTION 55
minimum, the effect will be to slow down the quantity of
production to such an extent as to increase costs out of all
proportion to the value of the few parts that might other-
wise have become scrap. As a matter of economy, to do a
certain amount of unsatisfactory work is practically neces-
sary, paradoxical as this might seem on first thought.
The Danger of Becoming "Fussy"
In many cases where the standard is difficult to set
exactly, and judgment must enter to a large extent, as in the
case of inspecting for finish and surface defects, there is a
fertile field for trouble of this sort. A factory manager, who
was a man of unusually wide experience in many lines of
interchangeable manufacturing and an alert and discerning
observer as well, once said with reference to a case of this
sort, " If you pass a hundred parts through the hands of a
hundred (or even fewer) inspectors, not a single part will
escape rejection. Every piece will be rejected by at least
one inspector."
This point of view was vindicated soon afterward in the
following manner: A large quantity of sword bayonet
blades were rejected for the alleged defect of not being
straight, especially near the pointed end. Perfect straight-
ness was, of course, impossible. The permissible variations
from perfect straightness were purely a matter of judgment.
Inasmuch as the blade was flexible, was of variable thick-
ness, and curved both lengthwise and transversely, it had
not been practicable to design a satisfactory gage, or other
checking instrument. It should be said, by the way, that the
purchaser's chief inspector was very competent, reasonable,
and fair minded. The working inspectors under his super-
vision were unusually well controlled. He had personally
examined several blades and rejected the lot of several
thousand. On the manufacturer's side, however, the same
56 THE CONTROL OF QUALITY
blades had been passed by a carefully trained corps of in-
spectors who were in the factory's employ. Their foreman
had reinspected a quantity of these blades, and passed
them all.
Here was a large plant running under pressure for pro-
duction, with several days output stalled in the middle of
the road because the purchaser said the work was wrong,
while the maker insisted that it was right. The purchaser,
of course, held the whip-hand, and it was of no avail to plead
that there was little military or other practical advantage in
such a degree of straightness as was required for these
blades. The problem was one of finding the quickest way
out of an embarrassing impasse.
The cure for the difficulty, however, was simple. The
purchaser's inspector was told that the factory manage-
ment felt the standard had been stiffened by imperceptible
increments until it had become impracticable. It was re-
quested therefore that he examine 20 blades which were
presented for his inspection, and designate those that he
considered straight.
The 20 blades in question were obtained in this way-
each of five of the company's best blade inspectors were
asked to select, from the rejected lot, 10 blades that he knew
were straight and 10 that he felt equally sure were not quite
straight. In this way there were then accumulated 50
"straight" blades and 50 " crooked" ones. A committee
consisting of three of the factory inspection department's
expert supervisors then agreed upon 10 blades from each
lot of 50, and marked them accordingly with secret marks,
10 as "straight" and 10 as "crooked."
The result was that the purchaser's chief inspector
passed 19 of the blades and rejected the twentieth for a
surface defect not in any way connected with straightness.
Of course, he was promptly told the whole story, and in a
THE TYPES OF INSPECTION 57
fine spirit of fair play he immediately ordered the entire lot
inspected and accepted nearly all.
This episode is related here because it exemplifies so clearly
a number of inspection phenomena of the sort that must be
taken account of, in determining what is to be avoided.
Unnecessary Inspection
Another thing which requires attention is the elimina-
tion of unnecessary inspection. Many operations require
no inspection whatever, or else the inspection of work after
a given operation may cover also the work of several preced-
ing operations. Similarly, and especially in the case of
floor-inspection, if the first several parts inspected are found
to be right, the inspection of the rest of the lot may be
waived. The procedure is safer, however, if a few of the
last parts made are inspected in the same way.
Other parts may be of such minor importance and
slight cost as to make it advisable to drop the inspection in
favor of the more certain test of their use in the assembling
department. This is true of most small screws and similar
minor screw machine products.
The Percentage of Inspection
As to the quantity or amount of inspection that should
be used and when it is to be applied, a safe general rule is
this: Use 100 per cent inspection (i.e., the inspection of
every piece in a lot as regards all essential qualities of the
standard) when the work done largely affects other work
that is to follow, as in the case of drawings, tool-room out-
put, gages, etc., or when any part may unduly affect the
integrity of the entire assembly. Furthermore, apply 100
per cent inspection at points where an operation is subject to
serious errors, or when one operation may control or mark-
edly influence many subsequent operations.
THE CONTROL OF QUALITY
THE TYPES OF INSPECTION 59
Sampling— The Theory
If less than 100 per cent inspection is used, we are
brought to the consideration of sampling. For the most
part, inspection is made possible economically by applying
the theory of this method. This involves the assumption
that a piece selected at random probably is representative
of the rest of the lot, or that a portion of a quantity of some
substance probably is like the remainder. The word
"probably" here is to be noted. It is sound theory to as-
sume that if something happens under given conditions,
exactly the same thing always will happen again under the
identical conditions, which is one way of stating the law of
similarity in nature. In manufacturing, however, we are
not dealing with a theory, but rather with a very practical
condition of things, which is changing and varying all the
time.
Every portion of an ingot of metal, for example, differs
from every other portion. This is so well recognized in the
inspection of raw materials that very exact practices have
been evolved for taking samples or " drillings" of metals
for analysis; also for selecting samples of coal and similar
substances.
No such definite practice is practicable for sampling in
shop inspection. The best we can do is to assume, in the
case of first-part inspection, that if the first part made, after
the tools are set up, is satisfactory, the following parts
probably will be right; or to assume likewise that one part,
taken at random from a lot of the same parts, probably will
exemplify the condition of all of them. This, however, is
not necessarily true. We should remember that one of the
most common fallacies of reasoning, well known to students
of logic, is that of arguing from a special case to a general
conclusion.
In sampling, this fallacy takes a peculiar form. You
60 THE CONTROL OF QUALITY
may say to yourself, for example, " This bolt which I hold in
my hand, is well and correctly made. Therefore all the
bolts in the box from which I took this one are correct."
If, on the other hand, it happens that the bolt is not correct,
you are not nearly so willing or quick to conclude that all
the bolts are not correct, so you select one or two more from
the box; and if they are correct, you promptly assume, as at
first, that all the rest are correct, although you are not quite
so certain.
Such optimism may perhaps show a commendable spirit,
but the plain fact remains that your conclusion may not be
true, although it probably is. It is usually well to give
everyone and everything the benefit of the doubt. It
might be said when a conclusion based upon sampling is not
true, that the case in hand is exceptional and that "the
exception proves the rule," but the inference is wrong.
This is a very old expression in which the word "proves" is
used in its original sense, as in proving a gun. In reality the
exceptional case tests the rule.
Safeguards for Sampling
The use of sampling, especially in important and costly
work, must be surrounded and reinforced with certain in-
dependent safeguards. This makes possible the great
economy which sampling permits, while protecting the
conclusions from most of the probable errors, provided hasty
deductions are avoided.
Among such safeguards are the following:
1. Mention has been made of the desirability of having
the first and last few parts from each machine set-up checked
by the tool-setter or taken to the inspector for checking.
This can be extended by a continuous, random floor-inspec-
tion or patrolling supervision.
2. Parts may be taken at random from current product
THE TYPES OF INSPECTION 6l
and tried by actual assembly, thus discounting the danger
due to the wait in shops and in component stores.
3. Parts in stores may be similarly checked at random
from time to time.
4. The two-bin principle should be applied wherever
work is piled up, either in process, or in stores, in order to
insure an uninterrupted flow of work. (See Chapter VIII.)
5. A sort of blind, double inspection can be tried oc-
casionally, in order to check a doubtful inspection point, by
sending the same parts through the same inspector twice
without notifying the inspector. The practice often gives
a valuable insight as to what is really going on.
6. Each day a good part and a reject may be collected at
random at each inspection point and carried to the central
gage-checking point for independent verifying.
7. One or two pieces may be quickly routed through all
operations, being carried from machine to machine by the
foreman inspector so as to discount the delays between
operations. As each operation requires, roughly, a day for
a lot of parts to pass it, a part requiring fifty operations will
ordinarily take fifty days to pass through the shop. A
"quick routed test part" or "pilot part," which can be put
through in a clay, will be found an excellent device for
detecting trouble under certain circumstances.
Other Economies in Inspection
The cost of inspection may be reduced in a direct way by
combining it with other duties, but any work so added to
the duties of the inspector should preferably be of the sort
that is best separated from actual production. The excep-
tion is in the case of a combination of inspecting and re-
pairing, as referred to earlier in this chapter.
It is not unusual to have the inspector certify as to the
amount of work done by each workman whose work he
62 THE CONTROL OF QUALITY
inspects. It is believed that this combination of duties
should be more extensively used, especially in steel construc-
tion and similar large outside work. The employment of
higher grade men for both purposes is permitted by the
combination of duties.
In a highly developed central-inspection system the
counting of work done is handled by the inspector as a
matter of course. In addition, the collection of useful in-
formation, the custody of work in process, dispatching the
same, and otherwise assisting the shop, are all things in-
spection is specially suited to take charge of. Other serv-
ices, more indirect, which may be allocated to the inspec-
tion department with profit will be mentioned later on.
CHAPTER V
THE INSPECTION DEPARTMENT IN THE
ORGANIZATION
Vital Importance of Inspection
Effective use of inspection necessarily is predicated upon
its recognition and elevation to a point where it is a real
factor in management.
The importance of inspection should be recognized in a
practical and concrete way by assigning to it a place in the
organization commensurate with the vital duty of safe-
guarding the quality of the product, whatever that may
happen to be. When this has been done it is possible to
give quality the attention it deserves. For it seems beyond
question that the most prominent feature in the progress of
factory practice in the future should be the greater and
more general appreciation of the possibilities of quality con-
trol, the development of refinements in its application, and
the consequent attainment of both higher standards of
quality and greater fidelity to such standards, with a de-
cided gain in economy.
The last few years have witnessed the evolution of a
science of management and its translation into an engineer-
ing practice covering planning in its widest sense, the deter-
mination of standards of output, and the methods of
handling a complexity of human relations, rapidly changing
under the reaction of labor to the new situations introduced
into industry. The machinery thus created and developed
will now be used to accelerate the progress of industrial
management, with care for quality more and more as the
guiding principle. It is but in the natural course of events
63
64 THE CONTROL OF QUALITY
that the greater mechanical accuracy made more generally
possible through development under stress of war time, to-
gether with the experience of manufacturers during that
period, will now result in an intensive application of these
new forces in the betterment of the work of the industrial
world. The reaction on labor alone will be worth the
effort. As stated , this attitude on the part of managers leads
toward better inspection, which in turn will have to be pre-
ceded by a deeper understanding of the inspection function.
Every student of industrial management must recognize
that the late Dr. Frederick W. Taylor made a remarkably
clear and powerful analysis of the elements of manufactur-
ing, although he may not entirely accept the Taylor methods
for handling the elements thus disclosed. It is therefore
interesting to note that Dr. Taylor's analysis of the duties
of foremen, even in ordinary machine shop practice, resulted
in the separating out of inspection, as a function calling for
an independent foreman. In other words, he recognized
the necessity for an inspector or quality boss, just as he pro-
vided for a " speed boss" to look out for quantity, and a
planner to do the thinking and prearranging necessary to
co-ordinate subsequent effort. This analysis is evidence of
a realization that someone should attend to inspection, and
that so important a duty is best carried out independently
and therefore with authority.
The Engineering Department
Suppose that we analyze some great manufacturing
enterprise into its most general terms. Our problem is to
make, let us say, a large number of engines, or motors, or
guns, or other articles assembled from component parts
which must be made to rather definite standards of accuracy
and finish. What the industry happens to be makes little
difference, because all involve the application of labor to an
INSPECTION DEPARTMENT IN ORGANIZATION
66 THE CONTROL OF QUALITY
assemblage of raw materials. Perhaps the first large duty
or group of duties that we would segregate in our minds
would be the engineering group, whose duty is to make plans
for something that is to be done in the future, and to con-
centrate on the practical and intensive application of an-
ticipatory imagination.
This work is warranted because it reduces the cost of
production through describing exactly what is to be done
and thus avoiding waste of effort on the shop's part in doing
things that are not wanted. This passion for visualizing
work before it is performed and preparing plans showing
what should be done, is resulting in the transfer of more and
more work from the domain of ''trial and error" in the
actual fabrication of the work, to its more scientific treat-
ment in the engineering department. All doubtful ques-
tions are settled as a part of preparation for production and
before the latter begins, and a sharp line is drawn between
experimental or research work and the business of making
things. Vexatious and costly delays are confined to the
laboratory and the engineering office in order that produc-
tion may flow on without interruption from such things.
Thus the designing engineer works out his plans on paper,
describing in great detail what the shops are to make; the
production engineer makes plans on paper covering the
things to be done to obtain greater productive efficiency,
and so on. None of this effort is expended in doing the
physical work of production, but it does result in a much
greater output from the whole organization. It pays
amazingly. It is cheaper to correct mistakes on paper
before they have been worked into steel.
The Production Department
Continuing the analysis of manufacturing, probably the
next great function that will attract attention, if our minds
INSPECTION DEPARTMENT IN ORGANIZATION 67
are proceeding in an orderly manner, is that of production,
which has the duty of applying human effort to the execu-
tion of the plans made by the engineering group. The
latter's work is now subjected to the acid test — it is con-
vertible into action, or it is not.
The time element, it may be noted, is significant here,
for production is most seriously engaged with meeting the
pressing necessities of the present, just as engineering deals
principally with the future. Production solves its problems
as it meets them in the actual physical performance of man-
ufacturing, while the machinery is running — engineering
solves just as many problems as it can mentally visualize
and work out on paper before any wheels are turned.
The Inspection Department
It would seem that the next logical step in this process
of analysis must reveal inspection, which has the duty of
passing upon the results of production after the latter has
endeavored to carry out the plans of engineering. Inspec-
tion work is retrospective. It is performed after work has
been done.
Each of these three main groups of functions calls for
special experience and for its own characteristic and pecul-
iar attitude of mind. Engineering and inspection are the
primary contributories of production, while all other fac-
tory activities are secondary in the sense of being merely
general service duties.
A Parallel with Governmental Organization
It is not difficult to find a parallel case in a field of admin-
istration much older and wider than the industrial organiza-
tion. The experience of men in evolving governments for
social administration has developed the necessity for
three main functions, which assure stability through mutual
68 THE CONTROL OF QUALITY
independence of authority in action, but with interdepend-
ence and mutual helpfulness through balancing each other,
just as there must be three points of support for stable
equilibrium. The three governmental functions referred to
are, of course, the legislative, executive, and judicial. It is
easy to trace their correspondence with engineering, pro-
duction, and inspection, respectively, which have the same
general relationships. Inspection is judicial because it is
measurement plus judgment. If it were easy to distinguish
between the right and the wrong execution of either laws or
plans, there would be little need of applying independent
judgment, but in very many cases it is not easy. In the one
as in the other, in the factory as in civil procedure, the best
results demand for their attainment that the final applica-
tion of judgment be made with authority subordinate only
to the supreme controller of all three functions.
Inspection's Relation to Engineering and Production
If there is any one thing that the management of a large
industrial enterprise needs in its business, it is the unvar-
nished truth about what is really going on in the plant — not
the reports from an espionage system, but the plain facts
brought frankly into the open as to where errors are most fre-
quently made, the extent to which they occur, and the causes
of production choke-points. It is just as useful to know in
detail what has been done as the work proceeds, as it is to
know what you are going to try to do before you begin. If
an engineer-executive has the facts he usually can cure the
trouble. Yet ordinarily this information is the hardest to
obtain, either promptly or accurately. The chance of get-
ting it is much better, and under good management it is
assured, if there is competent personnel in an unbiased
position to observe, locate, and report the difficulties as they
appear. This is a duty that the inspection department is
INSPECTION DEPARTMENT IN ORGANIZATION 69
best able to perform by reason of its freedom from respon-
sibility for anything except passing upon quality. Here is
another reason why the inspection department should be
subordinate only to the management. There is a great
value in having inspection in what might be termed, to fol-
low the above analogy, a judicial position ; but that value is
seriously abridged if inspection is subordinate to either the
engineering department or the production department.
Failure to obtain both the standard of quality and the
scheduled output will occur from faulty engineering or from
a failure of the production department to carry out properly
the engineering plans. If inspection is subordinate to en-
gineering, the faults of engineering will not come to light
when they should. That is only human — but it is not
scientific. Worse still, if inspection is subordinate to pro-
duction, not only the latter's faults will be concealed but
also there will be a strong tendency to skimp quality.
When once quality is allowed to slip, costly losses will soon
result in fact, although frequently not detected.
Purpose Help — Not Mere Criticism
When, however, inspection is raised to its proper posi-
tion and is assigned the important duty of bringing the
facts to the surface, it should be clearly shown to the other
departments that the purpose is one of mutual helpfulness
and service, and not one of destructive criticism. Facts
are necessary to solve problems. If they are presented in a
spirit of helping to conquer difficulties, surely no one can
take offense.
Quality is a variable. Everyone makes mistakes. It is
immaterial who is to blame for them. It is folly to be forever
in search of a "goat" when things go wrong; the precious
time thus spent should be used more constructively. It is
essential merely that the mistakes be promptly located,
70 THE CONTROL OF QUALITY
recognized, and cured before loss piles up. The group of
workers in the best position to do this are those in the least
prejudiced situation and hence best able to see things as
they really are. There can be but one conclusion, namely
that the inspection department should perform this service.
But it cannot do that efficiently if its hands are tied.
The Real versus the Apparent Organization
In the majority of factories, especially before the war,
factory inspection received little recognition. Even now,
in very few factories indeed is it given a chance to demon-
strate its greatest possibilities for service. In nearly all
plants, however, even those which are comparatively small,
the latent possibilities of inspection can be developed if the
real organization is made more nearly like the apparent
organization. The difference between the two is often
considerable.
What maybe termed the "apparent" organization is that
shown by the assignment of duties in the form of an organi-
zation chart, or perhaps by the titles given to the various
department heads and their assistants. Often, however,
the actual work is not carried out in accordance with the
apparent organization. Certain individuals will be found
to be exerting a far greater influence than their assigned
positions would seem to indicate. If the organization
chart were redrawn to show the true way in which duties are
carried out rather than how they are assigned in theory, and
to indicate clearly a relationship between individuals in
accordance with their proportionate contribution to the
enterprise, then it would indicate the real organization.
If an organization is analyzed with this test in mind, the
discovery will probably be made that the inspection depart-
ment's contribution is greater than the apparent organiza-
tion would seem to indicate. If it is exalted to a position
INSPECTION DEPARTMENT IN ORGANIZATION
72 THE CONTROL OF QUALITY
equal to that of production and engineering, it will give
a still greater return. If it is subordinated, its greatest
potentialities will be lost.
Engineering and Inspection
As has been stated elsewhere, the working or practical
standards of quality are furnished in the main by the en-
gineering department. These standards serve well enough
for work that is plainly seen to be well inside the limits or
well outside the limits. The difficulty in fixing standards of
quality accurately arises from the large proportion of work
which falls close to the limits.
At this point the engineering department must be re-
leased in favor of the inspection department, for in such
cases, in the last analysis, someone must make up his mind
as to whether the work should be passed or rejected. Thus
the element of personal judgment enters, and a specialized
technique must be cultivated and applied. For judgment
varies as between individuals, and in the same individual at
different times. To this fact may be ascribed many of the
phenomena of the inspection of close work, where only a
small percentage of parts are made that cannot be rejected
on some technicality. This is the case with respect to di-
mension, and still more with respect to matters of finish,
because judgment is accentuated so much more in inspect-
ing for finish. Now the value of judgment depends upon
its freedom from influence.
Production and Inspection
The inspection department's relation to the whole or-
ganization is judicial rather than creative. It is responsible
to the management for detecting failures in quality, and in
that sense it bears a very heavy responsibility for the main-
tenance of standards. It does not manufacture, however,
INSPECTION DEPARTMENT IN ORGANIZATION 73
and therefore when poor work is produced the production
department cannot usually shift the blame to the inspection
department. The production department should be made
to realize that it is itself responsible for the quality of its
product — it makes the work right or it makes it wrong. If
the production force is organized by operations, the in-
dividual subforeman, tool-setter, or adjuster in charge of
each operation should be made to feel that he is responsible
for the quality of the work produced under his direction.
In addition to checking the work frequently in person, he
may be required to bring the first two or three pieces made
after each new machine set-up to the inspector for verifying,
but merely as a guide in his own work. Both departments
then bear a definite responsibility to the management for
quality, but independently and in different ways.
It is a well-accepted principle that responsibility should
be re-enforced by adequate authority. Accordingly, if in-
spection is charged with the responsibility of stopping losses
from work not up to standard, it must be given the authority
to stop machines. When this authority is granted, it is
only good judgment to specify an exact procedure for advis-
ing the responsible production executive, also for putting
the machine back into production. It hardly need be added
that such authority is not likely to be used if the inspection
department's freedom is restricted by its subordination to
production.
In fact, if inspection is to develop its greatest possibilities
for service, it requires room to work and a free, fair chance
to solve its problems. If you believe in inspection suffi-
ciently to have an inspection department, why not give it
a chance to show what it can do ?
CHAPTER VI
INSPECTION'S CONTRIBUTION TO GENERAL
SERVICE
The Collection of Useful Information
One of the greatest benefits of the inspection service
comes from its power to bring promptly to the attention of
the management information as to the true state of affairs
in the shops. No tool is so useful to the manager as knowl-
edge of the facts, yet nothing is so hard to obtain. The
foreman-inspector of each shop is very close to what is going
on in that shop, and is likely to be in the most unbiased
state of mind because he is an observer rather than a
producer.
Counting the work done and certifying to it is part of
the inspector's duty as a matter of course. Summarizing
this information for reports to be used for the purposes of
the pay-roll, the cost records, and the production records
may or may not be a part of his duty, depending on the
character of the work. If this warrants a well-developed
inspection system, it is quite likely that the foreman-in-
spector of every sizable department will require clerical
assistance. If so, this clerk may just as well assemble the
count of work performed in his department, before it is
transmitted to the general factory offices. When produc-
tion and cost data are assembled and analyzed by the use of
power-driven tabulating machines, the data may be
collected at the original sources and its accuracy certified
to by the inspectors, with the obvious advantage of securing
competent assistance in gathering the information together
with the resultant saving in clerical expense. The addi-
74
INSPECTION'S CONTRIBUTION TO SERVICE 75
tional burden on the inspector is slight, and the added duty
may even be beneficial because it tends to bring him closer
to his job.
There is another sort of information of equal or of even
greater importance, which the inspector evidently is in the
best position to obtain ; namely, the location of production
troubles, the isolation of their causes, and frequently the
offering of suggestions for their cure. Production difficulties
ordinarily appear in the form of too great losses in spoilage,
or through the slowing down of production at some opera-
tion, thus creating a choke-point or a partial choke-point.
It is essential, of course, to correct the difficulty as soon as
possible, but to do this it is necessary to develop and bring
to light the true causes.
Trouble Reports
A very useful device for the prompt collection of such
data may be secured by providing a printed form of
" trouble report" to be made out and sent by foremen-
inspectors of shops to the chief inspector, who will transmit
such facts as seem worth attention to the department that
should correct the trouble — the management being fur-
nished with a copy. The trouble report should read pref-
erably as shown in Figure 13.
A detailed list of usual soruces of trouble, such as tools,
gages, material, and so on, may be added for convenience,
but the essential idea is to make the foreman-inspector feel
the responsibility for promptly reporting the facts and
nothing but the facts. Hence the requirement that he
must state either that he "knows" or that he merely
"thinks" that the trouble is due to the cause stated in his
report. For the trouble report to be used successfully, the
foreman-inspector must have confidence in the judgment,
fairness, and courage of his chief — he must feel sure that he
76 THE CONTROL OF QUALITY
From Foreman- Inspector
To Chief Inspector
Shop Date
Operation Hour
I report the following trouble
I know think (scratch out one) that the trouble is due to the following
Figure 13. Trouble Report
will be backed up if he is right. Further, the management
should make quite clear that it is looking for facts in order
to cure troubles, and not to find someone to blame. There
is no surer way to put a premium on the concealment of
facts than by trying to fix the blame on an individual, nor
does blaming someone help to cure the trouble. Presum-
ably each executive holds his job because he is the best
available man for the position. If he is not, the manage-
ment will know it much sooner if he and his associates are
not continually placed in the position of being called upon
to make excuses.
The Inspector's Sense of Responsibility
Certain phases of the psychology involved in trouble
reports deserve more detailed consideration at this point.
In the first place, if the device of the trouble report is to be
successfully applied the inspector must be made to feel that
INSPECTION'S CONTRIBUTION TO SERVICE 77
he is exercising a trust, and that the management reposes
unusual confidence in his impartiality and adherence to
accuracy. This feeling on his part has two very practical
results: first, the information will be more truthful; second,
the inspector will perform his other duties with the increased
efficiency that flows from a stronger realization of his value
to the organization. There are very few men who will
not rise, in spirit as well as in act, to meet increased
responsibilities.
At the same time the inspector should be made to know
positively that accuracy will be insisted on. The latter
purpose is accomplished by requiring him to state in each
report whether he knows what he is talking about, or merely
thinks the situation is thus and so. Quite a distinction is
involved, of course, both in the report itself, as well as in the
action likely to be taken. On the other hand, provided the
inspector truthfully states the degree of his belief as to the
facts, it is of comparatively little importance which form
the report takes.
A Typical Instance
Experience with the trouble report as used in a very
large and highly organized inspection department developed
some very interesting reactions. This form of report was
designed to meet a special set of conditions, first, because it
was vitally important to get the best available information
about a complex manufacturing situation as soon as pos-
sible; and second, because stiffening up the morale was
judged to be the most important thing in reorganizing this
particular inspection department. A few days after the
form of report was placed in the hands of the foremen-
inspectors, reports began to come in without either verb
"know" or " think" scratched out. That was to be ex-
pected, as the inspection force had been led to feel that its
78 THE CONTROL OF QUALITY
work might be performed negligently or otherwise without
visible effect on the running of the plant. All such indefi-
nite reports, however, were returned promptly with the re-
quest that they be corrected in this respect. The inference
was clear that the reports were considered of value and were
to be used. Some of those which had been returned never
came back, as was hoped, and the total number of reports
became less. But over QO per cent of those which did come
in read "I know." This is the thing to note especially.
When the management began to take action on the more
important reports, the inspectors' growing feeling of re-
sponsibility was confirmed by seeing things begin to happen,
and the effect on the morale of the entire department was
very marked.
Reception of Trouble Reports
As stated at first, the use of such reports carries with it
the necessity of using them in the spirit in which all scien-
tifically trained minds should work. They should be
received as being presented in a spirit of helpful and con-
structive criticism and as the opinion of an impartial ob-
server reporting things as he views them. The department
whose work is most involved must be made to feel that this
is the way the report is offered, and to accept it in the same
spirit. If the report is not well founded, no one is reflected
upon so much as the inspector. If the report is correct no
one should be so glad to discover, and to correct the trouble
as the department responsible for the trouble. To secure
this co-ordination and, in fact, to require a spirit of mutual
confidence and good-fellowship, is distinctly the duty of the
management. This is apparently a small point, but it is
vital.
The use of some such report will yield just as valuable
returns in many other kinds of work than factory inspection
INSPECTION'S CONTRIBUTION TO SERVICE 79
in its more limited sense. Figure 14 is an example of a
form adapted to use in a great ship assembling plant.1
Inspection and the Assembling Department
After the various component parts have passed inspec-
tion in the respective parts-making shops and have been
placed in the finished-parts stores prior to being issued to
the assembling department, it may be assumed with reason-
able assurance that they can be assembled satisfactorily.
There is an ever-present tendency, however, for work to slip
away from the desired standards of quality, and to do so by
such small daily increments that the changes are difficult of
detection. Measuring devices, whether gages or precision
instruments of more general type, and cutting tools, are
subject to wear like everything else. The fact that the
wear does not take place rapidly or evenly makes the
process all the more subtle and insidious. Then there is al-
ways the chance of a gage being accidentally injured, and
work incorrectly disposed of, in consequence. In close
work, as already noted, these troubles are accentuated by
personal errors and by a multitude of other influences.
The net effect is, that in spite of every reasonable precau-
tion quality will slip, and the errors may not be detected
until the parts are issued for assembling. If the errors are
due to gradual wear or similar cause, the condition will be
manifested first by a slowly increasing difficulty in assem-
bling, which is more dangerous than an absolute failure to
assemble. For example, a part may assemble satisfactorily,
and even pass final tests in the assembled mechanism, and
still be just enough outside the lowest permissible limits to
wear into a non-functioning shape after a short time in ac-
tual service.
1 Furnished through the courtesy of William B. Ferguson, formerly Assistant to the President
and Manager of the Division of Standards, American International Shipbuilding Corporation
(Hog Island).
80 THE CONTROL OF QUALITY
FROM WAY No .
AGREEMENT No. PIECE MARK DRAWING No.
AGREEMENT NAME .... .
LOCATION OF WORK.
1 FAULTY MATERIAL? FAULTY WORKMANSHIP?
2 HAD WORK BEEN COMPLETED ON WAYS
3 COULD FAULT HAVE BEEN CAUGHT BY MORE CAREFUL INSPECTION*!
4 IN YOUR OPINION SHOULD WORK HAVE BEEN PASSED ON WAYS?
5 To WHOM SHOULD THIS BE REPORTED SO THAT IT WILL NOT
OCCUR AGAIN'
JOB STARTED JOB FINISHED,
No. OF MEN ON JOB No. OF MAN HOURS,
DESCRIPTION OF FAULT
SIGNED
Figure 14. Inspection Form — American International Corporation, Hog
Island
INSPECTION'S CONTRIBUTION TO SERVICE 8l
There was a particular make of engine of excellent and
even very advanced design, which nevertheless failed in
certain cases, most unexpectedly, after being used for a
short time. A cursory viewing of the factory's inadequately
controlled inspection system revealed an obvious reason for
the service troubles which were killing future business.
Parts of the mechanism of the engine in question required
very accurate work. Some of these parts, with proper in-
spection lacking, were found to be just good enough to pass
factory tests, but not good enough to stand up long in ac-
tual use.
Benefits to Entire Factory
With a highly organized inspection service in the shops
and extending into the subassembly and final assembly
rooms, a means is provided for avoiding such difficulties.
The direct work of inspecting in the assembling department
is often of less value, however, than the collection of infor-
mation of value to the rest of the factory. The assembling
rooms are a particularly fertile field for revealing errors, and
the inspection department, for the reasons previously stated,
is specially in a position to catch these errors and to pass the
word about them back into the factory for the help and
guidance of all. Time is a vital factor in such matters, and
a well-organized inspection service will be able to send the
warning back along the line with the proper speed. The
possibilities of such a service are so great that it may be the
part of wisdom to place the assembling under the general
control of the head of the inspection department, especially
if such a combination of duties will serve as a further reason
for selecting a man of larger caliber for that important
position.
Curiously enough, if the work is not strictly inter-
changeable there is often a greater reason for increasing the
82 THE CONTROL OF QUALITY
importance of the inspector's position in the assembling
department. In this case, of course, selection of parts be-
comes necessary. Very often it can and should be made a
separate operation from that of putting the parts together.
The work of choosing parts that will mate properly in-
volves measuring the parts and then sorting them out in a
systematic manner into a few groups, each of which is made
up of parts of very nearly the same dimension. The proc-
ess is simpler if the work is of a character to warrant the
use of selective gaging. It is merely an extension of division
of labor to separate this work of sorting from that of as-
sembling, and the sorting is more closely allied to inspection
than it is to production.
An Example of Selective Assembly
An example of this kind is to be found in the manufac-
ture of rifles or pistols which have raised sight-bases integral
with the barrel. The barrel has a milled thread which
screws into a similarly threaded opening in the receiver or
frame. The barrel must screw into the frame so that the
sight-bases are in line with the vertical plane of the frame
(to insure correct alignment of the sights) ; and, in addition,
the barrel and receiver must be drawn together at a given
tension, this "draw" being required to be between given
limits expressed in pounds for a stated lever arm or length of
wrench. Both barrel and frame require many operations
before they are ready for assembling, and several of these
operations are referred back to the location of the milled
threads and sight-bases. Needless to say, it is not always
the simplest matter in the world so to locate and mill the
threads as to fulfil the two conditions of sight alignment and
draw of threaded joint, while still conforming to full inter-
changeability. Therefore, if a proportion of the parts de-
mand selective assembling, a very considerable amount of
INSPECTION'S CONTRIBUTION TO SERVICE 83
work can be saved if the parts are separately gaged, with
gages provided with, say, 10 numbered stages, to indicate
corresponding positions in relation to the draw marks when
the gages are set up with a fixed turning moment of, say,
n pounds at the end of a wrench a inches long. The female
gage applied to the barrel and the male gage applied to the
frame are so calibrated that barrels drawing to point 8 on
the barrel-gage, for example, will properly mate with frames
drawing to point 8 on the frame-gage, and so on; and the
parts will be sorted accordingly before issuing to the as-
semblers.
This method may be applied in principle to many cases
in which economy in making the parts indicates the desir-
ability of selective assembly. It will be noted that what
really happens is that by means of the inspection and sorting
of parts the assembling advantages of true interchangeabil-
ity are secured.
The Custody of Work in Process
Many factories possessing very complete systems for
production control are more concerned with the paper
records of the system than they are with the systematic and
orderly arrangement of the work in process of manufacture
in the shops. The machinery may very likely be arranged
to secure the best possible compromise for straight-line
routing. If the work is large in volume and concentrated on
one product, the machines are arranged in the order of the
operations, so that work flows from machine to machine in
regular sequence. If the work is varied in character, the
machines are arranged by classes, as lathes, planers, millers,
and so forth. In either case it is likely that planning and
routing are well cared for in any modern shop. It is a
common fault, however, for the work in process to be piled
all over the shop. Even if the work flows directly from
84 THE CONTROL OF QUALITY
machine to machine, it is no unusual sight to observe parts
rusting at the bottom of a pile where they have lain for
months, or other parts in like condition under an inspector's
bench.
The first point to be determined is whether this condition
should be corrected. In certain instances, as in a great
shipyard machine shop, the change may not be practicable.
In most cases, however, it is worth while to make the effort ;
nor need it involve much expense, provided there is an
effectively organized and managed inspection department to
which this duty can be turned over. If central inspection is
in use the job is readily taken care of. If not, the inspector
at least can guide the work into a more orderly arrangement
if he is given the authority to have work moved to the next
machine after he has passed it. The placing of work
naturally carries with it the custody of work in process. A
little encouragement of the inspection department will
develop a "fatherly" interest in the work itself, from which
will flow a more orderly shop.
Stimulus to Order and Cleanliness
While considering the advantages obtained by a more
systematic arrangement of the shop as regards work in proc-
ess, the effect of order (and the greater shop cleanliness it
permits) upon the working force should not be overlooked.
An artist's temperament may be suited, perhaps, to doing
good work under messy conditions, but the average man
does better work if his environment is orderly and clean.
It is well recognized that a desk covered with papers is not
desirable. It has come to be regarded as an indication of a
mind in the same condition as the desk. Does not the same
criterion hold in the shop?
The first step in securing order, if a reasonably good shop
arrangement exists, is the prompt sorting out of work as it
INSPECTION'S CONTRIBUTION TO SERVICE 85
leaves the machine, followed, of course, by a systematic
placing of the work after it has been sorted.
The Analysis of Work in Process— "Good" and "Bad"
Sorting out work in process by inspection requires the
guidance of some sort of classification; the matter cannot be
dismissed by merely saying that work is good or bad. The
parts or pieces of work that are passed by the inspector may
be designated as "good parts" or "good work," as this ter-
minology is brief, and the term "good work" is definite and
accurate enough, provided we remember that the work is
probably up to standard. As there is, of course, the men-
tal reservation that the inspector may be wrong, there is a
necessity for applying sampling tests to good parts from
time to time, and for surrounding the inspector's work with
safeguards, as set forth in Chapter IV. Parts obviously
good require no other treatment than to be passed on to
the next stage in their manufacture, assuming that some
definite place is assigned for their temporary storage until
the succeeding operation.
"Rejected work," that is to say, "bad work," calls for
analysis into several classes with appropriate definitions for
each class. As in the case of good work, allowance must
be made for the possibility of error on the inspector's part.
Provision should be made so that work rejected on the first
inspection may have some chance of reinspection. It is
quite the usual thing in the inspection of all kinds of work,
from shipbuilding to small interchangeable and high-grade
parts, to have some of the rejected work really fit for passing.
Handling Rejected Parts
Next comes up the question of how the rejects should be
handled — we are concerned principally with interchangeable
parts because such work furnishes the widest range of ex-
86 THE CONTROL OF QUALITY
amples illustrative of inspection. The first step is to sort
out those which require only a remachining on the machine
from which they just came. Usually too little metal has
been removed, or further polishing is required, and the
work can be made good by the shop itself. Ordinarily this
work should be done by the machine operator who did the
work in the first place, and on his own time. Of like nature
are the instances of parts with certain operations missing;
also those which are best repaired on jigs and fixtures avail-
able only in the shops.
The rejects remaining after taking out the ' 'shop repairs"
should be accumulated at some point in the shop, preferably
in a space set aside as the shop salvage space and under the
care of the inspection department. At this stage, when
sufficient rejects are accumulated to warrant the work, a
reinspection should be made, in which the parts are sepa-
rated into two, or possibly three classes, as follows:
I. Spoiled parts, which should be sent to the factory
salvage room to be kept under lock and key; for if this is not
done, some of them, under stress for production, are apt to
find their way back into process by some path or other. In
the salvage department they will be carefully examined
with a view to their conversion into the most marketable
form, either as scrap or otherwise. Circumstances will indi-
cate whether they should be mutilated to prevent their use
except as scrap, or sold as they are for use in another article.
Springs, for example, rejected as below your own standard of
quality, may be sold to a consumer whose needs are less
exacting. You can afford to supply him at a lower price
than he would otherwise pay, and both of you make money.
A cleverly handled salvage department, which classifies the
scrap from a large factory in this way, and which is alertly
in search of better markets for its goods, is a money-maker
in itself.
INSPECTION'S CONTRIBUTION TO SERVICE 87
2. Rejected parts which require special work to bring
them up to standard but which exist in sufficient quantity to
warrant such repairs should be sent to a separate parts-re-
pairing department or ''hospital, " specially designated as
such, and located clear of the regular production depart-
ments. This is the place for the all-round mechanic with a
taste for improvising and inventing. Supply this little shop
with a few general utility machines, welding outfits, and so
on, and considerable loss will be avoided. Apply the most
rigorous inspection both to its work during the repairs and
to its output.
In the course of repairing some parts, occasions may
arise when it is necessary for the repair department to send
the work out into the factory for some treatment or process
beyond the repair shop capacity. If this occurs, by all
means provide a special routing card of distinguishing color
to go with the work, and return the work to the repair shop
for inspection. Otherwise the repair shop inspector can-
not be held responsible for the quality of repaired work of
this character. In addition, he knows best what defects to
look for by reason of his previous acquaintance with the
parts in question. Finally, the repair department should
keep a follow-up record of all of its work so sent out.
It is suggested that very careful consideration be given
to the matter 'of a separate repair shop for rejected parts.
Too frequently the attempt is made to do such work, or a
large part of it, in the parts-making shops. Then again,
work is often scrapped that otherwise would have been re-
stored to a perfectly satisfactory condition in a special repair
shop, whose working force is skilled in such things and proud
of its ability to accomplish the apparently impossible.
The effect on production of having repairs made in the
local parts-making shops must also be considered. Such
work calls for the more expert workmen, so that the repairs
88
THE CONTROL OF QUALITY
INSPECTION'S CONTRIBUTION TO SERVICE 89
cost not only the direct time of such men, but also the in-
direct cost of lessened output due to their separation from
the regular production work.
One more reason for the separate repair shop: When
a great number of parts are turned loose in a large and com-
plexly equipped shop, strange and curious things happen.
Some parts are likely to run wild unless their fields of move-
ment are carefully restricted. If repair work is superim-
posed on the routine production, some of the repairs are
quite capable of running in circles. They are inspected
and repaired, and inspected again. The same individual
pieces are returned for repairs and then inspected, and so on
indefinitely, until they give way under the strain of so much
activity — the best disposition of them because really the
cheapest. "Circling" is of more frequent occurrence than
might be imagined, because it is exceedingly difficult to
detect, unless the work is of such a character that the in-
spector stamps a mark on the work after each important
inspection, and even stamping may not prove effective.
The danger of circling, however, is obviated by rigorously
excluding repair work from the parts-making shops.
3. Under some conditions it may be compatible with
business policy to consider a third class of rejected work.
This case occurs when some of the rejected work is suitable
for use in a second-grade product. Presumably such a
product will not be marketed under the company label and
the necessary precautions will be taken to insure the pro-
tection of the reputation of the company's standard goods,
as well as to insure that the manufacture of second-grade
goods does not become the factory's principal occupation.
Quality as an Incentive to Production
With work classified by inspection as indicated above, it
is no difficult matter to count the work of each class and
90 THE CONTROL OF QUALITY
tabulate the results. In this way the inspection force pro-
vides the usual production data, as referred to in the preced-
ing chapters. The same information in somewhat modified
form is the basic matter for the all-important quality records.
Certain of this information is of special interest to the
individual workman, and may be used to great advantage
in stimulating better workmanship and thereby greater pro-
duction. In the first place, the output of good parts for the
day, presented in simple form, may be posted on a shop
bulletin board devoted to this purpose only. The results
should be contrasted with the scheduled output desired, and
to this may be added other significant information, such as
the statement, for example, that "Operation No. 23 spoiled
20 per cent of its pieces today. This is a difficult process,
but we will have to hustle tomorrow to meet the schedule."
Workmen are interested in this sort of thing, much more so
than might be supposed. If they are not, the fact is ad-
vance notice to the management to overhaul the things that
affect the good-will of the so-called " human factor."
Bulletin boards, it may be said, can be made much more
useful as an instrument of publicity if attention is given to
taking down notices as well as to posting them. The shop
bulletin board is too often plastered with papers and notices
of ancient vintage. Its effectiveness increases remarkably
if it is kept absolutely cleared except when something is to
be put across quickly. Then post your notice, briefly worded
and clearly printed in large type, and just as soon as it has
served its purpose, have it taken down, and the boards left
clear as before.
The Individual Worker's Interest
Much of the data accumulated by the inspection depart-
ment is of greater interest to individual workers than to the
entire shop working force, considered collectively. Bill
INSPECTION'S CONTRIBUTION TO SERVICE 91
Jones's interest in his work can be stimulated very often by
showing him the effect that his personal endeavors have had
on the output of his shop. The inspection department's
records will provide the excuse for Bill's production boss to
discuss things with him in a friendly way. Good-fellowship
is pretty sure to result and the chances are that both Bill
and the factory will profit as he begins to react to this sort of
encouragement.
I should hesitate to stress this thought, in view of the
feeling of some executives, if I had not seen the results in
practice; for this is not theory, but hard fact. We talk a
great deal about welfare work and carry some of it into effect
with very desirable results, but what can be closer to the
workman's interest than his regular work? You must
answer for yourself whether the opportunities for building
up the worker's interest in what he is doing are utilized to
the full in the plant or plants in which you are personally
interested. I do not refer to creating " bread-and-butter"
interest — that is the usual appeal of incentives for stimulat-
ing production — but rather to the pride of good workman-
ship and the satisfaction of personal achievement which go
to make up the worker's " prof essional pride."
Interest in the Work Itself
The modern industrial system, with its minute division
of labor, has been freely criticized for reducing machine
operators to mere automatons, forced to eke out an exist-
ence of tedious and countless repetition of the same opera-
tion. It is alleged that this endless repetition results in
bodily, mental, and spiritual fatigue. The system of man-
ufacture cannot be abandoned, because the division of labor
results in too great an economy of effort even to think of its
elimination. On the other hand, there is one simple but
very effective corrective measure that we can apply, namely
92 THE CONTROL OF QUALITY
to encourage the operator's interest in, and to excite his
curiosity about, the work he is engaged in doing. Now the
theme that runs through this entire subject is that quality
is variable, hence no two pieces turned out by any machine
operation are alike. The points of difference may be com-
paratively small, but to the eye of the trained expert these
same differences grow to look much larger and to be very
apparent and real. It is a question of relativity and of
degree.
Expert Knowledge — Causes and Results
To the trained eye of an experienced inspector the in-
terior of one rifle barrel is quite different from another,
whereas the greatest difference you or I might note, after
repeated trials, would be a slightly fuzzy spot resembling a
pencil mark. The inspector would tell you that this barely
distinguishable spot indicates a bad drill groove, but we
should not be at all certain as to the degree of the defect, its
location, or even its existence. In the course of time, how-
ever, and with much repetition we could learn to distinguish
these and similar defects or differences. Things that ap-
peared indistinguishably small at first would become of
appreciable size, and finally they would take on individual
characteristics. But the main point I wish to bring out
is that we should never know about them at all, if they
were not first pointed out to us by someone skilled in their
detection.
Now, the same thing occurs with the average machine
operator. He may drift along without noticing the results
of his efforts except quantitatively. Especially is it likely
that he will have very little idea of the fine points in the
work which are subject to his control, nor of the things he is
in a position to influence, nor why and how he can do so.
It is no great trouble, however, for the inspector (or the
INSPECTION'S CONTRIBUTION TO SERVICE 93
production boss, if you prefer) to show him how each part
differs a little from the next one ; also what different kinds of
differences exist and what causes them, so that he can see
for himself what he is doing qualitatively. Thus he will
learn how his failure to clean off the chips, when bedding a
piece, throws out his own work and perhaps the next man's,
and almost certainly makes unnecessary work for the pol-
isher. Or perhaps he will see that forcing the cutting tool
causes him greater personal loss in total output than if he
used less apparent speed. The net effect, however, will be
the widening of his viewpoint, the building up of an interest
in his work, and the consequent and proportionate lessening
of fatigue.
Interest in Quality versus Fatigue
Many men can play golf every day in the week including
Sunday. They seem to enjoy the repetition without expe-
riencing unhealthy fatigue, and the discouraging monotony
of their novitiate is forgotten. The same thing applies in
principle in our daily work, no matter how restricted its
field ; if it is interesting the resulting fatigue is a healthy one.
But the work is only made interesting through an apprecia-
tion of its fine points. It may take years of application to
be able to see for ourselves those fine points and small dis-
tinctions, or some more fortunate person may be kind
enough to point them out to us early in the game.
The modern application of division of labor has brought
with it an acute problem due to extreme limitation of indi-
vidual tasks, but the apparent smallness of the field of work
covered by any one machine operator can be changed into
one of much greater interest and wider scope by suggesting
a different viewpoint to the workman. The employer
might well consider carefully the mutual benefit to be de-
rived from educating the worker in the finer points of his
94 THE CONTROL OF QUALITY
job, and from doing so in a spirit of friendly helpfulness that
will build up a feeling of mutual interest in a common task.
The workman usually is not capable of doing it alone, but
he can be helped to do it by means of the regular factory
organization if the employer will direct the foremen toward
this different attitude in dealing with their men.
A Phase of a Major Problem
It is suggested that this is one way to help correct one
of the major problems confronting engineers, which Herbert
Hoover recently expressed in the following language:2
We have until recently greatly neglected the human factor that
is so large an element in our very productivity. The development
of vast repetition in the process of industry has divorced the em-
ployer and his employees from the contact that carried responsibility
for the human problem.
I am daily impressed with the fact that there is but one way
out, and that is to again re-establish through organized representa-
tion that personal co-operation between employer and employee in
production that was a binding force when our industries were
smaller of unit and of less specialization.
2 From Mr. Hoover's presidential address to the American Institute of Mining and Metal-
lurgical Engineers, Feb. 1920.
CHAPTER VII
INSPECTION'S RELATION TO PLANNING
The Flow of Work in Process
It is quite the usual thing in factory parlance to use the
term "flow of work in process." More frequently it is ab-
breviated to "the flow of work," or just "the flow." This
little expression, which is used so readily and easily, covers a
matter that is intimately interwoven with the whole fabric
of manufacturing ; for the flow of work is of the very essence
of production.
Manufacturing results from the combination of labor,
machinery, and material — remove one of the three and the
process ceases. If we can keep the flow of the material
under control, we are in a position to control manufacturing;
or, as has been said many times, "planning begins and ends
with material." Thus one of the principal aims of planning
is secured by arranging for a continuous supply of material
to each production point, and at a velocity or rate of flow
set to permit the scheduled output for that point.
It would appear also that the economy of manufactur-
ing is greatest when there is an even and uninterrupted flow
of work all along the line throughout the factory. Uni-
formity seems to be generally desirable in manufacturing.
Let us consider some of the reasons for this. In the first
place, there is no advantage gained by pushing one opera-
tion ahead of the average scheduled rate of production.
The average rate at which completelyassembled mechanisms
can be produced, and hence the average output of finished
articles, is fixed by the average output of that component
part which lags most in the manufacture. In fact, the rate
95
96
THE CONTROL OF QUALITY
INSPECTION'S RELATION TO PLANNING 97
of total output is determined by the rate of flow of work
through the single manufacturing operation or process that
is lagging — "The speed of the fleet is the speed of the
slowest ship."
Uneven Flow — Disadvantages
When assembling is permitted to proceed more rapidly
than parts can be produced, it soon eats up the available
reserve of parts and a famine results, with its accompanying
pressure on the parts-producing shops. The first effect of
too great pressure for quantity output is psychological —
it amounts in practice to "getting everybody all worked
up." The same thing happens when the train stops at an
eating place— " twenty minutes for dinner — lots of time."
All of us know what an iron nerve it takes not to hurry
through with the job in half the time, at the expense of both
appetite and digestion. When unusual pressure is placed
on a shop the foremen stand over the men and hurry things
along, with the net result of less output and of poorer qual-
ity. When a factory is run in this manner the cost of in-
spection for maintaining the set standards is much greater
than it need be under more normal conditions. In the same
way other indirect expenses are increased disproportion-
ately. Thus transportation of work in process is much less
expensive if carried on at a uniform rate, instead of being
turned into the movement of many small lots of parts as
soon as they are produced.
The ideal plan is so to protect the flow of work as to have
fixed or schedu'ed quantities passing each production point
during each unit of time. Unless we approximate to this
ideal within reasonable limits, we shall have less production
and at the expense of undue strain of the producers. When
real emergencies occur they should find the organization
fresh and ready to meet them.
98 THE CONTROL OF QUALITY
Effects on Piece Work
Another serious defect resulting from an uneven flow of
work arises from the fact that the continuous use of piece
work is interfered with. Everyone knows that the output
under a straight piece work or other system of payment
based upon paying a man for what he does, is very much
greater than when the man is paid for his time, on a day-
wage basis. But the advantages of piece work cannot be
fully realized unless there is a supply of material waiting at
each machine for that particular operation. If there is a
hitch in the chain of supply, workmen are soon to be seen
standing round waiting for material to work on. It is not
their fault, and they must be paid "day-work" for any
appreciable loss of working time imposed upon them.
Supply of Raw Materials
Approaching the question from a different angle, we may
note a similarity of situation in the supply of raw material.
A prompt and continuous supply is always important, but
during the war the procurement of material and supplies
in the order and in the amounts required for continuous
production assumed serious proportions. In the ship-
building business especially, this matter of procurement
took on a new value, and it is a safe statement that the
speed of building in any yard was determined first and to
a controlling degree by the efficiency of the preplanning for
this purpose.
Even if the size of a factory's raw material storehouses
and storage spaces were not influenced by a desire to be able
to take advantage of favorable market conditions, it still
would be necessary to set aside the space. A stock must be
accumulated against possible failures in delivery, in order
that machines may not have to be shut down for lack of
something to work upon.
INSPECTION'S RELATION TO PLANNING 99
Material in Process
The identical principle applies to providing a supply or
"bank" of material ahead of each manufacturing operation
or production point, although this fact is not so generally
appreciated. A proper flow of work can hardly be main-
tained with less than a half-day's supply ahead of each
operation, although the amount of work in each bank is
governed by local conditions. It is understood that the
French small-arms arsenals were eminently successful in
obtaining large output of high quality under very trying
conditions; also that it was the practice to keep at least a
day's supply of work (and two days' if practicable) ahead of
each operation.
Breakdowns of equipment and other troubles are bound
to develop choke-points from time to time, and an unbroken
flow can only be insured by building up and maintaining
reserves all along the line. These banks of material can
then be drawn upon as needed to keep the machines going
ahead of the choke-point, until the production point that is
in trouble is restored to running condition. Then the re-
serves can be again accumulated by extra shift work.
From this point of view, there is a bank between the
assembling room and the parts-making shops in the form of
a finished component stores, which bears the same relation
to the assembling department that the raw material stores
bears to the parts-fabricating shops.
The quantity of parts to be kept in each bank depends,
of course, on the likelihood of trouble at preceding opera-
tions, or other interruptions to production. For example,
if it is probable that changes in design or method of manu-
facture are to be made, it must be remembered that a change
of any sort means a serious interruption in the flow of work.
To handle the situation, when a change must be made,
requires special treatment in each case, and calls for masterly
100 THE CONTROL OF QUALITY
planning of the highest order. It is economy to take the
time to do this planning before carrying out the change.
Insuring a Continuous Flow
The effect of a breakdown in production can be mini-
mized at times by providing the factory with a chart show-
ing approved alternative routings of the work. It is not
safe, however, to route work more than two ways simul-
taneously, especially if there are many parts in flow. Special
care should be taken when two routes are used to keep dis-
tinct the work sent over each route, and in this effort the
inspection department can be of the greatest assistance.
Similarly, the inspection department, in its regular task
of sorting out the defective parts, makes a large contribu-
tion to promoting a uniform flow of work, for it is essential
from the standpoint of protecting the flow that rejected and
condemned work be disposed of swiftly and promptly re-
moved from the shop.
The control of supplies of material and of banks of work
in process, and therefore the control of the flow of work
throughout the factory, is greatly simplified if there is a
systematic storage of work in process. This result cannot
be secured by planning on paper alone, no matter how com-
pletely and extensively this planning is done. The work
itself should be distributed in such a definite and orderly
manner (and in a shop swept clean of everything not used in
the business) that the condition of the flow can be vizualized
by looking at the work — without reference to paper rec-
ords. This brings us to a matter which deserves special
consideration.
Planning with the Material Itself
In order to treat this matter thoroughly, it is necessary
to trace the steps that must be taken to reach a position
INSPECTION'S RELATION TO PLANNING IOI
where planning with the material in process is possible.
Planning, in the broadest sense in which the term is used,
has developed certain mechanisms in addition to its first
work of preplanning the routing of work. Thus it must be
considered as inclusive of the preparing of schedules of
quantities of work to be produced at given times ; and of the
dispatching of work at rates in conformity with these sched-
ules. To this will now be added the planning of space
assignments for work in process.
Only the high-spots can be touched upon, with reference
to the details involved in such planning, but that is really
all that is necessary, because the other details will readily
suggest themselves when the general scheme is applied to
a concrete case. It should be kept in mind concurrently
that the inspection department can be made the principal
instrument, and a most economical one, in giving life to the
planning department's work, when the time comes to trans-
late plans into action.
Master Planning
Let us assume now that an article has been designed and
is ready for manufacture, and that the planning force is called
upon to preplan for producing and bringing to assembly
given quantities of parts which meet certain stated standards
of quality, and for assembling these parts into the complete
articles. It is assumed at the outset that the management,
in conference with the principal department heads, has
developed and approved a general plan for carrying out the
project; also that this plan has been drawn up by the plan-
ning department in the form of a master control sheet or sheets
for the guidance of all concerned. Among the data shown
thereon would be a list of the things to be done (i.e., the
whole project is analyzed into its parts), the department or
individual responsible for carrying out each part of the
/\H/i Clff'f! ! «v*.I *
102 THE CONTROL OF QUALITY
work, and the time when each part of the work should be
started and completed in order to secure co-ordination of all
the parts.
As the drafting-room takes up the making of working
drawings and special tool designs, the planning department
in co-operation with the drafting-room should make up a
complete list of parts and subassemblies, together with the
tentative outlines of bills of material, which last may later
be entered on the appropriate plans. The first draft of
material requirements is then taken off for the guidance of
the purchasing department and the storeskeeper, so that
they may make their preliminary arrangements.
The Operation Mark or Symbol
With a complete list of component parts and subassem-
blies in hand, it now devolves upon the planning department
to devise and apply a set of symbols, as some such device is
a sine qua non to an orderly and systematic control of the
flow of work. If the factory does not have a satisfactory
symbol system already it is suggested that a combination of
figures and letters may be used to advantage.
In building up such a scheme of symbolization it is im-
portant to distinguish between the symbol for a particular
manufacturing operation, and the number which indicates
the order or sequence in which the operation is to be per-
formed. Such an operation may be defined as meaning any
one application of a mechanical or other process in the
course of making some one part. Drilling is a mechanical
process. Drilling a hole for the hinge-pin in the shackle
of a given model of a lock is an operation. In this case
the mechanical equipment for the operation would be a
light drill press, drills, a drill jig, and a limit plug gage.
The first layout for processing the job of making this lock
shackle might list the drilling of the hole as the fourth opera-
INSPECTION'S RELATION TO PLANNING 103
tion to be performed on the pieces. Later on, the order of
processing might be changed to permit of improvement, or
for some other equally good reason. A way might be found
to eliminate some of the earlier operations, or additional
operations might have to be inserted, so that the operation
of drilling the hole might become perhaps the third, perhaps
the tenth in order of sequence. Now it is of considerable
value to have some one permanent mark or symbol for des-
ignating the operation of drilling this hole, if for no other
reason than cost-keeping. In shops where the attempt is
made to make one symbol do for indicating both the opera-
tion and its sequence, the cost of operation No. 1103 may
cover drilling this month and grinding next month. Con-
sider the effect on the tool storage and supply system alone,
as well as on all quantity and quality records.
Operation Mark to Remain Unchanged
It is to be understood then, that the operation mark
is assigned once and for all to a given operation, and never
changed. If the operation is abandoned, so is the operation
mark. If there are twenty operations in making a part
and it is found necessary to provide another operation, the
new one is marked as the twenty-first, without reference to
the place where it is inserted in the list of operations. This
mark is then used in correspondence, on plans, in marking
tools, tool storage bins, and so on, wherever and whenever it
is necessary to refer to the operation or anything connected
with it. As stated before, no attempt is made to make this
symbol designate the sequence of the operation's application.
The matter of sequence is covered, when necessary, by a
separate number entirely divorced from the operation mark ;
but the sequence number as such is not required to anything
like the extent that the mark is. When the operations are
listed, a separate column should be provided for entering
104 THE CONTROL OF QUALITY
the sequence number for each operation ; and a corrected
list should be furnished for the guidance of the shop when
changes are made in the order of performance of operations.
If route tags are used with each lot of parts, the sequence is
indicated by the order in which the operation marks are
listed, or the sequence numbers may be printed opposite the
corresponding marks. (See Figure 19, page 108.)
This scheme for symbolizing applies to the factory prod-
uct, its component parts, the operations used in manufac-
turing them, and the equipment strictly related to such
operations. It does not apply to the symbol system used
for designating parts of the factory itself, or the machine tool
equipment, which should be provided for separately. If
you have a system in use which is giving reasonable satisfac-
tion, by all means use it in the shops as well as in the office,
the important point being that something of the sort is
necessary to bring order out of chaos and to permit a sys-
tematic and orderly arrangement of work in process.
The Operation Data Sheet
The next step in planning involves the assembling of all
the information the shops should have relative to the proc-
essing that is to be followed in manufacturing the parts and
putting them together. It is suggested that an operation
study sheet of standardized form (see Figure 17) be used in
developing and recording the process information for each
part, and that from this there be compiled an operation data
sheet (Figure 18) for shop use.
It is believed that the preceding discussion, relative to
the distinction between the sequence of an operation and its
distinctive mark or symbol, will make clear the data to be
entered on this sheet. All the machine tool equipment
will be labeled or otherwise suitably numbered and marked
for inventory purposes at any rate, and these individual
INSPECTION'S RELATION TO PLANNING
105
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THE CONTROL OF QUALITY
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INSPECTION'S RELATION TO PLANNING
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THE CONTROL OF QUALITY
machine numbers may be entered on the operation data
sheet, if additional clearness is required.
Special tests should be entered as separate operations.
Inspection points may be mentioned in like manner, or re-
ferred to by some designating mark, or left out altogether,
depending on the character and relative complexity of the
work. Operation data sheets should be made out for each
subassembly, and for the final assembly, just as in the case
of each component part.
A similar sheet showing alternative routings, or sequences
of operations to be followed
in case of emergency, may
be developed for each part ;
but as these will not be used
frequently, it is probably
simpler and better practice
to show this information
in chart form.
Pifces 0 8°BB1
Order No. Lot No.
DATE
EMP.
NO.
OPERATION
OPER.
MARK
Swage Catch Hole
49
Shop £-7-7 I out
in
File T Slot Burr Catch Hole
50
Shop B-2 I out
In
R.Pol.SideEnd&CornerPom.
41
Cut Down Under Pom.
86
Fin.LtSide,Under&Chamfer
158
Shop C-1-1 I out
In
Corner Slot.Mill
87
Corner Slot File
88
Shop £-7-7 1 out
In
Assemble and Fit Catch
51
Shop B-2 1 out
in
Rough Polish Edge Guard
89
Rough and Finish Pol. Pom.
166
Rough and Finish Pol. Guard
167
Pol. for Gage
61
Shop B-7-7 fl out
In
Edge
67
Finish Points
162
Shop c-1 II out
In
Fit to Gage
53
Stamp
66
Brown
56
Shop C-B || out
In
Sand Blast
58
Shop E-1 1 out
in
Wash and Oil Pom.
59
Assemble Grip
60
Straighten Tang
68
SwedgeTSlot
63
Shoo B-3
Figure
19. Route Tag — Remington
Arms Company
Route Tags
From the operation
data sheet it is a simple
matter to work up printed
route tags, if these are re-
quired, to go with each lot
of parts. Under the system
proposed, no mention of the
sequence of operations need
be made, as this will be cov-
ered by the order in which
the operations are listed.
The data taken from the
operation data sheet for in-
corporation in the route tag
INSPECTION'S RELATION TO PLANNING 109
then consists only of the shop symbol or name, and the
operation mark or symbol. (See Figure 19.)
The route tag, and in fact all planning work, will be
simplified if shops are designated by number or letter rather
than by name. A simple but effective plan is to assign a
letter to each building; to number the floors, beginning with
the basement as No. i ; and then add a letter to locate the part
of the floor according to compass direction.
The Manufacturing Schedule
In tracing the steps to be taken by the planning depart-
ment in order to reach a point where planning with material
is possible, it now becomes necessary to work out the daily
or weekly production schedule, upon which the design of
the space assignments for material in process is to be based.
Suppose the production schedule contemplates an output of
1,000 complete articles during each working day. This
means that somewhat more than a thousand of most of the
component parts must be produced daily, for the reason
that a few will be spoiled in the assembling department, or
for some other reason will cease to be available. Then in
the case of each part, this quantity of 1 ,000 +n pieces must be
increased by the estimated losses at each operation as we
trace it back through the various steps in its manufacture,
so that material for perhaps 1,200 pieces of the part in ques-
tion must be started into production at the first operation
each day, in order to maintain the schedule with certainty.
Allowance for Losses in Process
The losses at each operation which are allowed in pre-
planning, should be checked in practice by comparison with
reports supplied to the planning department by the inspec-
tion department. The importance of making an adequate
allowance for loss of work in process should be realized and
110 THE CONTROL OF QUALITY
it may be noted at this place that the percentage of loss for
most economical production at each important operation
may be worked out quantitatively for the planning depart-
ment by the inspection department as the work proceeds.
The inspection department, for example, may tighten up or
loosen up, on such part of the work as it is in a position to in-
fluence by its personal judgment (i.e., work that is question-
ably close to the limits) ; and then report back to the planning
department the total production and totals of rejected work
corresponding to the different degrees of inspection applied
in the tests. It is then up to the planning department to
compute the corresponding total costs, including losses, and
set the standard percentage of loss to which the inspection
department should hold the work in order to recover the
greatest economy in production. This percentage loss
may be reduced later when improvements in workman-
ship and equipment warrant.
The production schedule just referred to is for a uniform
flow and therefore should be supplemented by a gradually
increasing schedule for use in starting into production. A
similar schedule should be used in tapering off production
to prepare for changing models.
Determining Quantities of Work in Flow
The planner is now in a position to prepare a table show-
ing the quantities of work to be provided in the banks of
material at each stage of manufacture in order to insure a
continuous flow of work. In brief but complete form
this will include:
1. The maximum and minimum quantity of raw ma-
terial to be carried in raw-stock stores for each
part.
2. For each operation the minimum quantity of ma-
terial in process waiting for the next operation.
INSPECTION'S RELATION TO PLANNING III
The maximum quantity should be specified, but is
not of great importance.
3. The minimum and maximum quantity of finished
parts to be carried in the finished-parts stores as a
bank between the producing shops and the assem-
bling department, including similar data far sub-
assemblies.
These assumed quantities will be adjusted later to bring
them into accord with the conditions as they develop after
production is under way.
There is no exact rule that can be followed in fixing
upon the maximum and minimum quantities of parts to be
carried in the banks of work in process. Generally speaking,
it is safe to allow a day for any one piece to pass each opera-
tion, and therefore it is well to provide for a minimum supply
of a half-day's work, and a maximum of from one to two
days' work, depending upon the local conditions.
The Design of Space Assignments for Planning with Material
It is now proposed :
1 . That the table of quantities of material required at
each operation, in order to maintain uninterrupted
flow, be used as a guide to compute the space re-
quired to store each maximum quantity.
2. That layout plans be made for each shop, on which
a definite space is assigned to each such bank of
material, in the same way as machines are shown.
3. That the space so assigned be designated in physical
form, if the class of work will permit (and it
usually will), e.g., by boundary lines on the floor.
4. That each space so assigned have the symbol marked
thereon, and that the maximum and minimum
quantities either be shown in figures or at least be
readily accessible for reference.
112 THE CONTROL OF QUALITY
This contemplates, it will be observed, an extension of the
best factory raw-material storeroom practice to the storage of
material in process in the shop. This is for the purpose of
reaping the advantage accruing both to quality and quan-
tity of output by keeping work in process under positive
control at all times and places.
The objection most frequently advanced against such a
plan is that there is not enough room in the shop. As against
this view, it is submitted that there is always more room
when things are systematically arranged. But to carry out
an orderly arrangement of work, it should be borne in mind
that it is idle to try to have everything in its proper place,
unless the proper place in question is clearly indicated.
This last is no difficult matter. It is a common practice to
paint aisle lines on the shop floor, and what is proposed is
merely an extension of this scheme.
For example, if the shop building is wide there probably
is a space in the center which is not well lighted. This space
can be ruled off for the orderly storage of work in process.
Or the best arrangement may be to utilize spaces between
machines, or next to columns, or possibly under the windows.
With the added refinement of having the quantities to
be carried in these storage spaces either marked near them,
or otherwise made readily accessible, it is possible to walk
through the shop and observe the condition of the flow of
work without the necessity of resorting to paper records to
discover how things stand. It is exactly comparable, in
principle, to checking up the stock of a well-arranged store-
room by a simple visual inspection. For practical purposes,
it has the great merit of speed. You do not have to wait to
find out what you need to know.
This is what is meant by " planning with material" — a
term here used to distinguish the method from planning on
paper, which process it extends and supplements. It rep-
INSPECTION'S RELATION TO PLANNING 113
resents indeed a culminating point in the system work of
planning.
Inspection and Dispatching
Let us assume now, that we have an orderly condition of
things in the shop, and that the inspection force is reason-
ably efficient and on the job. No very great additional
burden will be placed on the inspectors if they are given the
added task of the custody of work in process. The inspector
will see that work is moved to the next bank (or operation
storage space) as soon as it has been passed by him. Con-
currently, the inspector will assist in dispatching work in
accordance with the schedules.
When the flow gets out of balance at some point it
devolves upon the inspector to direct the production depart-
ment's attention to the fact if the foreman is not already
aware of the situation. If the condition is a serious one,
and a bad choke-point is resulting therefrom, the produc-
tion department may resort to overtime work, or prefer-
ably to the use of an extra shift. There is nearly always
work for such a balancing shift of all-round, or " handy,"
machine operators to help maintain a uniform flow in a large
factory.
Doubtless there are many other methods for controlling
the flow of work. At one time I visited a factory in which
the flow was controlled by limiting the daily output of the
fastest operators, although the superintendent did not so
designate the process. He stated that on certain operations,
which were indicated, the workmen were through with their
day's work when they had completed a fixed number of
pieces, and that this made it a very simple matter to keep
the slower operations from being swamped. Surely this
is a simple and direct method of insuring a balanced con-
dition of flow, but how about its reaction on the whole
114 THE CONTROL OF QUALITY
matter of production? The inspection force was available,
and could have been utilized, under a properly organized
plan, to keep the shop in balance as well as in a far more
orderly and workmanlike condition, without stopping work
at any process.
CHAPTER VIII
CENTRAL INSPECTION
The Most Advanced Form of Inspection
The greatest possibilities of controlling the flow of work
in process, by planning with the material itself, are realized
when conditions permit that inspection be centralized and
physically separated from the rest of the shop. Further-
more, the control of both production and inspection reaches
its highest development under this system. While central
inspection is the most highly specialized form of inspection,
its use need not be so restricted as might appear. For work
that is done in large volume, central inspection provides by
far the best means for controlling manufacturing conditions.
This statement holds good even if the amount of inspection
to be performed is relatively small, because central inspec-
tion provides, in addition to the inspection feature, a better
chance to issue work and record individual production in an
orderly and accurate way.
Not Restricted to One Form
Central inspection may take many forms, and is not re-
stricted in its application to the business of making small
interchangeable parts in quantity. The basic principle of
widest application is that of physically separating inspec-
tion from production. In the weave shed of a textile plant,
for example, there would natually be some sort of inspection
or patrolling supervision of the work on the looms. Central
inspection would hardly be looked for. Yet the practice of
removing the goods to a separate inspection room after
weaving (where they are rerolled, measured, graded accord -
115
Il6 THE CONTROL OF QUALITY
ing to quality, and the defects indicated by some system of
marking) is nothing if not centralized inspection. (See
Figure 43.) It will be apparent from the following that the
principle can be extended to embrace many different sorts of
work, with all the advantages from the more special use of
central inspection in strictly interchangeable manufacturing.
A natural restriction to the application of central inspec-
tion is encountered when the work is too bulky or too heavy
to warrant moving except from machine to machine. Never-
theless, it should be noted that central inspection can be
used for much larger and heavier work than is ordinarily
supposed to be the case, provided full use is made of modern
handling devices. For example, large military rifle stocks,
which are heavy and bulky in the earlier stages of manu-
facture, have been handled in shops under central inspec-
tion, by transporting them in lots of as many as 40. In this
case, they were carried in a double rack mounted on large
casters. Other large and heavy parts are often carried on
lifting truck platforms, designed to carry a definite number.
Value of Self-Counting Trays
The use of special carrying trays of the self-counting
variety should be extended. They are inexpensively made
of wood, protect the pieces from damage, and save much
time in counting work. For example, suppose the problem
is to provide means for handling in quantity a part approxi-
mating T in shape — a shape which typifies the general form
of many parts. In the earliest operations of its processing,
it may be handled in bulk in ordinary metal tote boxes, hold-
ing, say, 200 pieces. As the processing advances, opera-
tions are encountered that remove metal down to or near
the finished surfaces. It is now an economy to keep the
pieces from injuring each other. Carriers should be made,
preferably of shellacked wood, of rectangular form to sup-
CENTRAL INSPECTION 117
port ioo parts, in, say, 10 rows of 10 pieces each, and ar-
ranged to permit stacking.
The objection to open bottom containers of this type is
that oily work drains onto the floor, but most of this trouble
can be avoided by providing a draining pan under the tray
of work at the machine. As just stated, tote boxes of this
character serve a very useful purpose in assuring a finer fin-
ish by protecting parts from the little scratches, dents, and
cuts that so detract from quality. Their principal value,
however, flows from the self-counting feature, which sim-
plifies the labor of securing an accurate count, and does
away with arguments as to the number of pieces issued to,
or received back from the machine operator. Central in-
spection almost necessitates something of the sort to develop
its greatest possibilities.
In this connection attention is invited to Edward H.
Tingley's article on " Making the Truck an Asset in Man-
agement,"1 from which the following is quoted (see also
Figures 20 to 23 inclusive from the same article) :
SPEEDING UP THE WORK OF OPERATORS, INSPECTOR, AND
STOREKEEPER. The workman expects any system for handling
material to help him increase his productive capacity as well as
decrease his effort. The special trucks illustrated have these ad-
vantages, as they occupy a minimum of floor space and allow the
work to be brought as close as possible to the machine. The trucks
are easily moved by one man, and with work stacked on both sides
they can be turned around to bring the other side to the machine,
thus eliminating useless walking. The construction of the truck in-
sures the separation of the pieces and so prevents damage to any
finished or ground surfaces. It also suggests the idea of order and
care to the workman, and it gives him the satisfaction of seeing his
work progress. He unconsciously sets a goal for himself, endeavor-
ing to complete a row or truck by noon or night. The amount on
the truck is proportioned to what one man can push around and
also what will make a good quantity for piecework operations.
1 Management Engineering, Nov. 1921.
118
THE CONTROL OF QUALITY
CENTRAL INSPECTION
119
The work of the inspector should be as limited as possible, as his
work is indirect labor, an item of overhead expense. In any well-
regulated factory the foreman should be fully responsible for the
Figure 21.
A Wood Frame Truck
handling the armatures when
This type is used in the armature department fo
complete.
quality of work produced, and the inspector should merely check the
foreman. If the truck, box, or rack in which the material is handled
will permit of quick and accurate counting by the inspector, easy
removal and quick replacement after inspection, the time of the
inspector can be reduced to the minimum. Through the use of
120
THE CONTROL OF QUALITY
trucks such as shown by the illustrations in this article, counting is
unnecessary, as the inspector knows from the Production Order
card the total number the truck or box should contain, and only
Figure 22. An "A" Frame Wood Truck for Connecting Rods
The rough forging is placed in the truck in the raw-stock room and the finished
rod is taken off in the finished-stock room.
has to subtract the missing pieces from this total. This counting
of the missing parts can be done at a glance.
The finished parts stockroom is also benefited in several ways by
the special trucks, as the counting of material as received is ex-
pedited and a visual inspection can be made in a short time. If the
CENTRAL INSPECTION
121
122 THE CONTROL OF QUALITY
material is to be stocked in bins, the truck can be pushed to the loca-
tion and emptied as desired. Frequently the material is to be used
in other assembly operations, and if allowed to remain on the truck
it can be sent at once without further work to the assembly depart-
ment. I n preparing material for group assemblies the special trucks
can be loaded in the finished parts stockroom with speed and the
assurance that no damage will result while in transit, and that the
count is correct as to the number of pieces sent out.
Operators working on a piecework basis will not try to claim
pay for the full amount of the order if some parts are missing, as the
evidence of such missing pieces is open to the time clerk and the
foreman at a glance. In the matter of placing the responsibility
for scrap it is very easy for a foreman to check the actual amount of
material coming into his department in order to be sure that the
Production Order shows the amount scrapped on previous opera-
tions. This is a factor frequently overlooked in the design of
equipment to move material.
The Two-Bin System Extended
Consider an application in the shop of what Dr. Fred-
erick W. Taylor, I believe, called the "two-bin" system.
Its application in modern storehouses is generally known.
For each article stored and issued with any frequency, two
storage spaces are provided instead of one, as usual under
the older system. Or perhaps it would be more accurate to
say that the storage bin or other space is divided into two
parts, A and B. Issues of stock are made from A until it
is empty. Meanwhile new stock is accumulated in B, as
it is received in the storehouse. As soon as A is empty
the storekeeper begins to issue from 5, and to accumulate
new stock in A, and so on, alternating the issuing bin,
which is indicated by a tag or movable indicator. In
this way no old stock is permitted to lie in the bottom of
the bin, as is almost certain to be the case when new stock
is piled in on top of old stock in the single-bin system of
storehousing.
CENTRAL INSPECTION 123
Systematic Layout for Material in Process
A continuous flow of work through the shop indicates the
desirability, and perhaps the necessity, of laying out the
storage spaces, for banks of material in process, on the two-
bin system. For example, with banks carrying a day's
supply the two-bin scheme can be worked by issuing from
one end of the pile today, from the other end tomorrow, and
so on, alternating each day or each shift if the flow is rapid.
Under a system of central inspection the storage spaces for
material should be systematically arranged with this object
in view. Needless to say, control of the flow is much sim-
plified under such an application of central inspection.
As a preliminary step to taking up the arrangement of
the shop under central inspection, attention is invited to the
following diagram (Figure 24), which indicates the theo-
retical line of flow of work :
First Operation Second Operation
Figure 24
So represents the stores of raw material for the part in
question, which is daily or hourly issued to replenish the
material waiting for the first manufacturing operation at
the process storage point Si — preferably arranged in two
parts, or piles of work, on the two-bin system, and in self-
counting tote boxes. From Si the work is issued as needed,
one box at a time, to the operator at the production point,
PI. The production point in question may be one machine
or a group of machines, under one or several operators, or
it may be a bench job or some special test. After the oper-
ator at PI finishes the box of work, it is removed to the in-
spection point 1 1, where it may be inspected in whole or in
part (in whole only if 100 per cent inspection is required) or
perhaps merely counted by the inspector. After the inspec-
124 THE CONTROL OF QUALITY
tion, the tray of work is moved to S2, the storage point for
work waiting for the time being for the next manufacturing
operation. When certain parts are rejected and a "broken"
box results, the box should be filled up from the next box of
parts or from a small stock kept for that purpose in the in-
spection room, so that only full boxes are issued from S2
to P2, and so on.
Layout of Central Inspection Crib
In centralizing the inspection into a central inspection
system, we bring together in a central place and in accord-
ance with some convenient arrangement all of the storage
points (or banks of material in flow) and the inspection
points, leaving in the shop proper nothing but the produc-
tion points, together with such work as is actually being put
through the machines at the production points in question.
This means, when the system is carried to the limit, that
after working hours all work in flow will be in the central
inspection spaces, and therefore there will be no work at
the machines, which condition insures a complete count
of each day's work and tends to prevent trouble of various
kinds, including the temptation to steal parts.
In concentrating the storage and inspection points at
some central place or places in the shop, the greatest econ-
omy will be secured by a shop arrangement that reduces the
PI Po p\ distances between any two
" / ~ consecutive points in the line
11 *2 l3/etc< of flow, Slt Pi, /i, 52, P2, 72,
s, sa S3) S3, P3, /s, etc., as much as
possible. For example, a
12/ good arrangement would be
1 10 In Ii2)etc- that shown in Figure 25.
PW~ ~^n~ " PM) The dotted line indicates
Figure 25 the separation between the
CENTRAL INSPECTION 125
shop proper, with its production points PI, P2, etc., and the
central inspection space or crib containing the correspond-
ing storage points and inspection points.
As a matter of fact, the diagrammatic arrangement just
shown gives an erroneous conception of the quantitative
space assignment required, because / and S ordinarily re-
quire much less space than P. Frequently / will represent
only a counting of the work, without inspection. It is in-
teresting to note, however, that a uniform distribution of
work in flow (especially when standard sized tote boxes are
stacked in piles) carries with it the condition that the spaces
provided for all storage points be the same in size. The
same thing can be expressed in much shorter form by say-
ing that Si = S2 = S3, etc., which, incidentally, is a nice ex-
ample of the saving in time from the use of symbols.
It is very likely, therefore, that the following diagram
(Figure 26) more accurately shows the relative size of the
space assignments for such an arrangement:
PI P* P, etc.
la
lao I2
la:
Is
I
s,
SIQ S2
Su
S3
s
)etc.
PIO PH P12 etc.
Figure 26
Construction of Central Inspection Cribs
It does not follow, by any means, that the collection of
the points 5" and / in a central inspection space requires
that this space be separated from the rest of the shop by
partitions. That is a question which must be settled by the
class of work involved and by the conditions attending its
126
THE CONTROL OF QUALITY
Figure 27. Transporting Rack for Rifles — Remington Armory, Bridgeport
Note especially the construction of the type inspection crib in the background.
CENTRAL INSPECTION
127
manufacture. In many instances it is only essential that
the central inspection space be indicated by lines painted on
the floor, or by some other means of showing the physical
separation of the principal functions that has been made.
A light railing may suffice.
When the use of a partition is indicated by the local con-
ditions, one of the best plans is to erect a light framework,
supporting woven wire to a height of 6 or 8 feet. Chicken
Braces-
Support_
luppo
2'k4
Closed in by sheets of
fiber board where
.female inspector are
employed.
-Woven wire, inside of supports
Gage & inspection
«- instruction cards,
sample parts, etc.
r\\
•J
Figure 28. Type Section of Central Inspection Crib
wire will do. (See Figure 28 showing a type section, of a
central inspection crib.)
The woven wire is preferably put up inside the line of
supports. This arrangement avoids lost space and objec-
tionable holes behind the inspection benches on the one
side of the central inspection crib, and permits more or-
derly storage of work in process banks on the other side of
the crib.
When partitions are used, it becomes necessary, of
course, to provide openings through which work may be
passed. If the work is bulky and each storage unit of parts
128 THE CONTROL OF QUALITY
is carried on wheels, for example, the opening should ex-
tend upward from the floor to a height just sufficient to per-
mit the comfortable entrance of the carrying device. Smaller
parts, that are handled in tote boxes or trays, usually require
only a passing window with a shelf. These windows should
be spaced close enough together to avoid too long distances
from machines to windows. At the same time they should
be spaced far enough apart to avoid interference with the
inspection benches. It is not good practice in this case, nor
is it ordinarily necessary, to have the machine operator de-
liver his work directly to the inspector who is to inspect and
count it. There is far less chance of connivance between
inspector and workman, together with less interference with
the actual work of inspecting and counting, if the work is
issued and received by the working foreman in the inspec-
tion crib, or perhaps by an assistant. Women inspectors,
for example, may be employed on quite heavy work if they
are relieved from having to lift tote boxes full of parts.
When the flow is rapid, a worker of the common labor class
will be fully employed in moving tote boxes to and from the
issuing windows and the storage points.
Referring again to the typical diagram, the introduction
of partitions with passing windows, or doors, brings about
the arrangement shown in Figure 29.
p p p
Figure 2). Floor Plan of Central Inspection Crib
CENTRAL INSPECTION
129
An Adaptation to Rough Work
It is now proposed to show the application of central
inspection in two cases, illustrating the extreme conditions
that are likely to be encountered. The first example is that
of a shop making a relatively small but bulky article, such
as heavy canvas bags. The processing involves cutting the
canvas and folding once, sewing the side seams, binding over
"i r
i i
i i
i i
i i
i i
i i
.J L.
Elevators
Stairway,
fashroomi ,
etc.
Figure 30. Floor Plan of Canvas Shop
and sewing the top seam, inserting a row of brass grommets
above the latter, and finally passing a gathering cord through
the grommets and attaching a fastening device to the cord.
The work is counted automatically by the issue of lots of
100 pieces (on lifting platforms) from a central inspection
space. Inspection,. however, is by sampling at the machines,
except after completion of the bags, at which stage there is
a 100 per cent final inspection. In this instance it is less
expensive to allow an occasional bad piece of work to slip
through than to provide a closer inspection.
130 THE CONTROL OF QUALITY
Each shop was located in a room approximately 100 feet
square, with machines, work benches, and work in process
scattered throughout, but arranged in a general way in the
order of operation sequence. The rearrangement is indi-
cated in Figure 30.
One end of the shop was darkened by elevators, stair-
ways, washrooms, and similar enclosures — a condition fixed
by the building. The dark space in the middle of the shop
(indicated by I-S) was cleared of machines, which were
moved out to the light (P, P, P). The center aisle lines
were closed, and the new aisle lines painted on the floor as
indicated by the dotted lines. The new aisles were kept
clear at all times. At each machine, two spaces (or platforms
for lifting trucks) were located to provide one place for the
lot of pieces ready for the machine and another place for
work just passed through the machine.
The Resulting House Cleaning
The central inspection space I-S was not enclosed, but
its boundaries were clearly indicated by the arrangement of
benches and of work in the storage banks. As a part of the
process of rearranging this shop, the foreman was instructed
to clean house, and in doing so to be guided by the rule that
everything not needed and used in the work must be dis-
carded. After he was through, a wagon-load of junk was
removed, in the form of unnecessary shop furniture, old
signs, ancient records, and what-not, extending even to
bench drawers that served no useful purpose. The subse-
quent application of a coat of white paint, and the introduc-
tion of the more orderly and systematic control of work in
flow, created an obviously different working atmosphere.
Incidentally the scrap value of the stuff removed paid for
the direct cost of the clean-up.
This simple case has been cited for the reason that it is
CENTRAL INSPECTION 131
typical of a large class of work (often relatively rough work) ,
to which the general principles and methods of central in-
spection can be applied with advantage.
An Adaptation to Close Work in Metal
Let us now proceed a very long way up the scale of appli-
cation of central inspection, until we reach the other limit.
In this case central inspection is to be applied to a shop mak-
ing in quantity, high-grade steel parts of relatively small
size — the machining is intricate, the limits are very close,
the parts are strictly interchangeable, limit gages are in use,
and the finish must be excellent. In short, the work is diffi-
cult, comparatively costly, and the standard of quality is
almost high enough to approximate to that required for the
very tools used in making the parts. Evidently, there will
be need for close inspection after all important operations,
sampling for practically all operations, and 100 per cent
inspection of all finished parts. Since such work is ordina-
rily found in large factories, we may assume as well that the
shop in question is only one of several such shops and that
it handles the machining of but one of the parts — or at most
only a few of them — that are to become components of a
complex mechanism.
In a case of this kind, central inspection is a machine
with a vitally important service to perform. Like any fine
machine it should be designed with the greatest attention
to details. It may have to be intricate, yet the design
should follow the simplest and most economical line for
accomplishing the desired result. Such an adaptation of
central inspection is the most highly specialized form of
inspection, and as such is the ideal instrument both for use
in controlling quality and for insuring a uniform flow of
work.
The usual type of factory floor for such work is from 60
132
THE CONTROL OF QUALITY
to 80 feet wide (a greater width interferes with lighting) ;
some 250 feet or more long; and built with sides con-
structed of steel and glass sash extending from the ceiling to
within about 3 feet of the floor. While the glass siding is
sometimes carried down to the floor, such construction is not
desirable for work of this kind, as the light shining up from
below the machines is trying on the eyes and therefore of
deleterious effect on the work. There will be no really dark
spaces in the shop, but the light may not be so good at the
exit and entrance, nor at one of the corners at each end of
Figure 31. Typical Modern Shop Floor Plan
the shop, if enclosed fire towers are built in at these points.
The state laws require that clear passageways be preserved
from end to end of the shop, for use in case of fire or panic.
A frequent arrangement of a typical shop floor of this sort,
as shown in Figure 31, provides for clear aisles at a, a, a, a,
between the rows of columns.
Aisle Arrangement
The aisles bb, connecting shop to shop may be found at
the middle or end of the room, and since they are used for
intershop traffic, must always be kept open.
Whether there are columns or not, it is usual to provide
for a central aisle, which is kept clear at all times (at least in
theory). Concurrently, it is necessary to have other aisles
CENTRAL INSPECTION 133
paralleling the main aisles, but out among the machines, to
permit of the passage of men and material to the machines.
These aisles are not so well defined, unless the machine ar-
rangement is a simple and orderly one. It should be noted,
however, that the aisles in question usually can be regulated
into clear and fairly well-defined passageways, thus per-
mitting the use of the former middle aisle for central inspec-
tion. In many cases, especially when combined with central
storage of work in process, this arrangement will result in
6
/A
C
<
\ [
1
J
\ B
\
D
d
Figure 32. Modern Shop Floor Arranged for Central Inspection
an actual economy of floor space, due chiefly to more effi-
cient use of the space otherwise taken up by work in process.
There is developed in this way the arrangement shown in
Figure 32.
The necessities of transportation and emergency exit are
met, under these circumstances, in two ways :
I. At least one fairly well-defined passageway is pro-
vided among the machines at each side of the shop, along the
lines abc and ade. There must be a passageway among the
machines; and since the machines are in fixed locations, the
principal cause of blocked passageways is eliminated when
the material at each machine is limited to one standard-
size lot of parts.
134 THE CONTROL OF QUALITY
2. These aisles are supplemented by providing double-
swing doors (if any are required) at the ends (AB and CD)
of the enclosed inspection space A BCD. The inspection
benches and material in process along the sides A C and BD
decrease the effective width of the former central aisle, but
not so much as to eliminate the passageway. The side
aisles are therefore supplemented by a more restricted cen-
ter aisle, and, all in all, ample gangway is secured.
There are many other arrangements, of course, in which
a shop can be laid out to provide for central inspection, but
the scheme just outlined, while of admitted uniqueness, has
much to commend it in many cases. It provides a central
place from which to distribute work, economizes the floor
space of the whole shop, and can be used in adapting central
inspection to many shops not originally arranged for this
system of control. Any such location of inspection cribs
carries with it a positive requirement for artificial lighting of
the inspection benches, but this is not a serious objection
because the more uniform light of good artificial illumination
has much to commend it for inspection purposes.
Advantages of Several Centralized Inspection Spaces
Whether this or some other plan is adopted for the loca-
tion of the central inspection cribs, it is well to observe that
central inspection does not imply one inspection room only,
nor even one room only in each shop. On the contrary, the
more efficient arrangement in a large shop is to place the
cribs at the locations where they give the maximum of serv-
ice with the least interference to traffic. The governing
conditions should be that each inspection crib be centrally
placed with reference to the machines it is to serve, and that
it be large enough to store its proper quota of work in
process.
The least interference with traffic is secured when the
CENTRAL INSPECTION
135
crib is parallel to and near the normal line of flow of work.
It will be found that there is much lost space in the ordinary
shop arrangement which can be made available if the shop
layout is carefully planned with reference to the space
occupied by work in process as well as that taken up by
machinery. Thus, if there is insufficient room for all of the
inspection work in the shop itself, the next logical place to
utilize is some space on the side of the passage from shop to
shop. It is quite usual to find unused space going to waste
in these locations. In such case it is clear that this space
should be utilized for the inspection work that can best be
spared from the neighborhood of the machines, i.e., the final
inspection of finished parts, and the salvage or reinspection
of rejected work.
Standard Arrangement Desirable
Reference already has been made to the fact that each
inspection crib should be designed with great care as to the
details, but, naturally, each crib should be laid out in ac-
w
L^
w
. T
F
< 1 >
— = >
n n a
a a a a
a a a
(
fe_S,— >
I
r r i - }
a i 6
U s J
i 1 1 :
1 l
i i
w~
W
Figure 33. Type Floor Plan of Central Inspection Crib
cordance with a general unified plan for all of them. To
illustrate, the outline shown in Figure 33 may be assumed
to be that of a central inspection crib which is typical for a
given factory.
The size of the crib will be determined in a general way
136 THE CONTROL OF QUALITY
by the amount of space required for storage of work in proc-
ess, for the reason that if this space is provided on one side
of the crib there is pretty sure to be room enough for the
inspection benches on the other side. The passing windows
w, w, — will be placed at fairly uniform intervals, but this
should not be a fixed rule, as the most convenient locations,
with reference to the number of machines to be served,
should be selected.
As the normal work bench with wooden top, back rail,
foot rail, and metal frame support is satisfactory for the pur-
pose, a number of them should be placed at i, i— and shop
stools provided. Reasonable bodily comfort is a great
relief to the confining tedium of bench inspection. Bench
drawers are not desirable in most instances. If it is neces-
sary to provide against the chance of gages being tampered
with outside of working hours, a cupboard, with a lock, may
be provided.
On the side of the crib opposite the inspection benches,
the space should be marked off for storage of work in flow.
If the two-bin principle is followed, each unit storage space
should have two sections, as Si (a) and (b). There is, of
course, a natural limit in the height to which any kind of tote
box can be piled with safety and this fact should be con-
sidered in laying out the storage point. Furthermore, the
height that corresponds with the number of boxes of work
required in each bank to maintain the flow should be in-
dicated on the side of the crib. With these refinements in
use, each storage point will be shown by a card or other
mark on the side of the crib, as shown in Figure 34.
A pointer may be used to indicate the issuing pile, but is
not necessary if the issuing and receiving sections are re-
versed automatically at given times.
The inspection benches should be marked off, or the
inspection points indicated by labels showing the operation
CENTRAL INSPECTION
137
symbols on the side of the crib above the benches. It may
be found very useful to supply a gage instruction card,
telling in detail how the gages are to be applied, and setting
forth the special points to be looked after. It is often de-
sirable to furnish sample parts, which should be tied to the
side of the crib over the bench, to prevent their becoming
mixed with the regular work. (See Figure 12, page 71.)
Assuming a di-
rection of flow
from left to right
in Figure 33, the
inspection points
will be arranged in
this order, a sepa-
rate bench being
provided at F for
the use of the
crib boss or work-
ing foreman of
the crib. Among
other purposes,
this bench will
serve as an issuing
point for working
gages, which is an essential feature of quality control, as
will be noted later under the subject of gage-checking.
Summary of Advantages
The advantages of providing, within the producing shop,
a central inspection crib combined with a storehouse for
parts in process, may be summarized as follows :
i. The work can be stored in self -counting trays. A
workman will come to the issuing window and obtain a box
of parts, which he will machine and return. The inspector
Figure 34. Type Arrangement of Material Storage
Point in Central Inspection Crib
138 THE CONTROL OF QUALITY
will find that some are good and some bad, and the work-
man will be credited accordingly. He will be paid for what
he does — and for no more nor less. This will insure, among
other things, the collection of accurate data as to what is
going on in the way of production and will tend to do away
with losses from stolen, destroyed, or lost parts.
2. There will be nothing at the machines outside of
working hours, and nothing at each machine but a box of
parts at any time during working hours — result, a clean
shop, and a clear one.
3. The systematic arrangement of all parts in flow makes
it possible to check up the flow by quickly visualizing its
condition, i.e., it is possible to plan with the material itself
rather than with figures alone. A walk through the crib
tells the story.
4. The control of quality is more certain, as the work of
the inspectors can be supervised to greater advantage and
the custody of work in process is well centralized. The in-
formation necessary for inspection can be so arranged in
useful form by providing each inspection point with stand-
ard samples, gaging lists giving the symbol of the gage to
be applied and the percentage of inspection, gage instruc-
tions, etc. All gages can be issued and controlled from this
point.
5. The routing and flow of work is under sure control.
CHAPTER IX
THE ORGANIZATION OF THE INSPECTION
DEPARTMENT
Designing the Instrument for Controlling Quality
Before plunging into the particulars of a subject like
" organization," a term which is often confused with the re-
lated terms "administration" and "management," it would
seem to be worth while to make sure at the outset of what
we mean by "organization." In order to separate out the
idea, let us first think of the inspection department as a
machine or an instrument for use in the control of quality,
together with certain secondary duties to be combined
therewith as a matter of economy. The organization of the
inspection department may be considered as comparable to
the design of the machine, and the administration or man-
agement of the inspection department as comparable to the
operation of the machine thus designed. In accordance
with the foregoing analysis, questions affecting the manage-
ment of the inspection department will be discussed in the
succeeding chapter:
The Development of Organization
The process by which organization develops may be
analyzed into three steps:
1. There is a union or grouping of individuals for a com-
mon purpose. From this fact, arises a necessity for organ-
izing.
2. The work necessary to accomplish the purpose is
divided and distributed so that each group of individuals
performs the work allotted to it with undivided authority
139
140 THE CONTROL OF QUALITY
and individual responsibility. This division of duties tends
to become more complex as the number of persons involved
increases or as the scope of the work broadens.
3. The interdependence resulting from the preceding
steps demands a co-ordinating of the work of the separate
parts or groups, in order to secure co-operative action, and
thus to weld all groups into one coherent whole so that all
work harmoniously toward the common objective.
Organization begins with the first of these stages, it is
developed by the second, and is completed and perfected
by the last. The higher the type of organization, the more
intricate is the distribution and division of labor; and this
fact, in turn, calls for better co-ordination, together with
closer and stronger co-operation.
In the light of these general observations we may pro-
ceed to design an organization for the inspection department.
As we are designing with men as our material the design
must conform to the capabilities of the men that are avail-
able; furthermore it must be suited to the conditions im-
posed by the character of the work to be performed. The
discussion that follows applies, as will be noted, to the or-
ganization of an inspection department for a large factory
doing high-grade interchangeable manufacturing, but the
same principles apply in simpler cases, and the organization
may be readily and suitably simplified for such situations.
The Chief Inspector
It is almost begging the question to say that if the right
man is at the head of the inspection department, there need
be no worries about the organization and management of
that department. But what type of man is called for? The
position is one of trust, hence character is an indispensable.
Good judgment is requisite, not only the judgment that
flows from "mechanical sense" and skilled ability as an
ORGANIZATION OF INSPECTION DEPARTMENT 141
engineer, but also plain "horse sense." In addition the
man must be an executive of no mean ability.
Many persons have been so accustomed to regarding in-
spection as one of the secondary features of manufacturing,
that they fail to realize what complex and extensive organi-
zations have been evolved for the inspection departments of
large factories. It is by no means an uncommon thing
nowadays to find an inspector for every 10 to 20 workmen,
and the proportion may be much higher. In the Wahl
Company of Chicago, which manufactures, among other
things, the ubiquitous Eversharp pencil, the proportion of
inspectors is i to 8.6 workers.1 In the S. K. F. Ball Bearing
Company's plant at Hartford, where every operation is 100
per cent inspection, 27 per cent of all the productive workers
are employed in the inspection department.2 Under diffi-
cult war conditions, the inspection department of one of the
munition plants reached a total figure of 2,200 employees,
and possibly there were larger inspection forces in other
plants.
Even under normal conditions, it will be recognized
from the above figures, the head of the inspection depart-
ment has an executive job of no mean size. The duty is
very greatly enlarged and complicated, moreover, by reason
of the fact that the inspection department is not concen-
trated into one definitely bounded shop, like the various
production departments. On the contrary, its work reaches
into nearly every part of the factory, and in consequence its
personnel is widely scattered. The character of the work
is at least as diversified as the processing, which fact still
further complicates the problem; for the inspection force
will have one group of workers in the wood-working depart-
ment, for example, while a thousand yards away it will have
1 Furnished through the courtesy of C. A. Frary, General Manager.
2 Courtesy of R. F. Runge, General Factory Manager of S. K. F. Industries, Inc.
142 THE CONTROL OF QUALITY
another group engaged in the inspection of metal parts made
to standards of accuracy so precise as often to split thou-
sandths of an inch. Therefore the chief inspector should be
generally familiar with all shop processes rather than a
specialist in a limited number of them.
Duties of the Inspection Department
Concurrently with selecting a man to take charge of the
inspection department, there arises the problem of outlining
what this department is to include. Conversely, the amount
of work that it is expedient to include will determine how
big a man should be selected to head the work. The two
things always go together, and the resulting solution is
usually a compromise. Obviously, the duties of the inspec-
tion department will often comprise a number of things
that, speaking strictly, are not inspection, but they will all
be related to inspection, and it will be economical and wise
to include them with inspection, in order to secure a more
complete control of quality.
In the first place, there will be the separate inspection
forces for each main group of the factory's work, as in the
case of an automobile factory making .both trucks and pas-
senger cars. Each of these main groups will be subdivided
into an inspection force for each shop, or smaller factory
unit, including the assembling shops.
Work Related to Process Inspection
In addition to this inherent duty, we may list the follow-
ing:
1. Raw material inspection, including the necessary
laboratories, chemical and physical.
2. Heat treatment inspection, including the metal-
lurgical and metallographic laboratories.
ORGANIZATION OF INSPECTION DEPARTMENT 143
3. Tool inspection, especially if the factory maintains a
tool-making shop.
4. Gage-checking and the verification of measuring
standards, all in close co-operation with the
chief engineer.
5. General supervision of the assembling department,
in some instances, where inspection in this depart-
ment is of unusual value in guiding the work of the
parts-making shops.
6. General supervision of the factory salvage depart-
ment, when it is specially desirable to safeguard
production from the return of defective work into
flow.
The inspection of machine tools and similar factory
equipment, as well as of the buildings and their appurte-
nances, has not been included as a possible assignment of the
inspection department, for the evident reason that the in-
spection and maintenance of all these constitute the prin-
cipal duty of the works engineer. It will be carried out by
the latter with due regard to the fact that every department
in the plant will be "on his trail" if he overlooks anything
that requires attention.
The general test for deciding whether a particular branch
of factory endeavor should be included in the inspection de-
partment is simply this — "Will the chief inspector handle
it to the better advantage of the entire plant or not?" The
answer depends, of course, to a considerable degree upon
who and what the chief inspector is.
Undoubtedly the term in widest use to designate the
head of the inspection department is that of "chief inspec-
tor." It has grown up in much the same way as the title
of "chief engineer," and it is possibly just as well to retain
its use, although there are many organizations in which the
144 THE CONTROL OF QUALITY
strict following of the plan used in the general factory organ-
ization chart would result in the more definite title of " man-
ager of inspection," or possibly that of " director of inspec-
tion." The matter of title, however, is of no great moment,
for the greater one's experience in factory work the less will
be the emphasis placed upon titles. But there is a matter of
marked importance which should not be overlooked for an
instant if the control of quality is to be assured — the chief
inspector should report directly to the highest executive
authority in the management, and to him only.
The Line Organization
In outlining the organization under the chief inspector's
jurisdiction, it is believed that the best result will be obtained
by a combination of line and staff, as in the case of the gen-
eral organization of the factory itself. The line organization
will consist of the usual executive heads of the different
groups of workers, i.e., general foremen-inspectors, foremen-
inspectors, subforemen or crib-bosses, and so on, making up
the " chain of command" through whom instructions will
pass from the chief inspector to the individual inspectors at
the bench.
The staff of the chief inspector will consist of a few
carefully selected specialists who have no executive authority
over the line executives, other than that which naturally
belongs to them by reason of the moral effect of their close
association with the head of the department.
Arranging the type form of organization in chart form
results in the arrangement shown in Figure 35.
It is generally conceded that no executive should have
more than a limited number of subordinates reporting di-
rectly to him. This number varies with circumstances, but
in work of this kind should not exceed ten or twelve at the
outside, as there is such a volume of small questions requir-
ORGANIZATION OF INSPECTION DEPARTMENT 145
I
— i
— *
I
o
111
146 THE CONTROL OF QUALITY
ing prompt settlement, to say nothing of the demands on
the chief inspector's time for continuous constructive work.
Therefore in a concern making several lines of product,
there should be an inspection superintendent (or a general
foreman-inspector) in general charge of each group of shops.
The principal assistant to the chief inspector may very
well be one of these superintendents. On the chart shown
(Figure 35) any other departments that may be assigned to
the care of the chief inspector (such as the laboratories for
raw material inspection, the gage-checking department, etc.)
should be added, as separate main divisions, on the line a-b.
The line c-d of the chart provides for a foreman-inspec-
tor in charge of each production department, and since in-
spection is best performed when strictly specialized accord-
ing to classes or kinds of work, it is suggested that there be
a separate foreman for each different kind of production
department in the group, even if this results in considerable
disparity in the sizes of the forces reporting to the various
foremen-inspectors. Thus the foreman-inspector of the
woodworking department in a small-arms factory may have
several shop floors under his care, while the heat treatment
department foreman-inspector has only one. In other
words, the inspection organization should parallel the pro-
duction organization in this respect, rather than attempt to
equalize the jobs by combining different small departments
under one head.
Special Value of Understudies
It is specially essential in inspection work that under-
studies be designated for foremen-inspectors and their more
important assistants. This arises from the fact that the
personnel of the inspection department's supervisory force
must be relied on to a large extent to see that standards of
quality do not shift; the need is great even when every care
ORGANIZATION OF INSPECTION DEPARTMENT 147
has been taken already to fix the working standards as
definitely as possible. In the work of keeping standards
from shifting, the inspection foremen accumulate a large
body of knowledge in the form of small details, which can-
not be quickly passed on from man to man, but must be
absorbed from contact with the work. It is therefore very
important that the organization provide for continuity in
this respect, so that what might be called the "complete
standard" will be carried along from shift to shift and the
gaps caused by the absence of any member of the super-
visory force safely bridged.
If a foreman-inspector has a department which com-
prises several separate floors or shops, he will need an assist-
ant in each shop. This man's duties, in addition to main-
taining discipline, will involve a continuous checking up of
the inspection work going on in the shop, deciding doubtful
cases — which arise principally in the reinspection of rejected
work — overseeing the care of gages, and attending to the
orderly storage of work in process. Each inspection crib
should have a working inspection boss — that is to say, one
of the ablest inspectors working in the crib should be desig-
nated to assume general charge of all the work going on in
the crib. The working force in each crib will consist gen-
erally of inspectors, counters, and in addition, especially if
the boxes of work are heavy and if the flow of work is rapid,
a common laborer or two. The counters are, of course,
engaged in the work of checking up the quantity of work
performed on operations that are not inspected, and are
listed separately merely to indicate that this work should be
performed at a lower rate of pay from inspection proper.
Duties of Inspectors
In this connection it may be noted that a misunder-
standing sometimes arises when the employment department
148 THE CONTROL OF QUALITY
hires men as inspectors, and the inspection department sub-
sequently places them in central inspection cribs where they
may have to do more physical handling and lifting of boxes
of work than they do inspecting. The individual thinks he
is going to be an inspector, but finds difficulty in distinguish-
ing between his work and that of a shop laborer. It is sug-
gested that this difficulty may be lessened by creating the
position of assistant inspector as an intermediate step
between common labor and bench inspector. If the em-
ployment department is careful to make clear to the appli-
cant what his duties are to be, there is less chance of a
misunderstanding later on.
Central inspection is usually reinforced by a small group
of floor-inspectors. These men should be of a higher grade
than the bench inspectors in the crib, and probably higher
even than the working foreman of the crib, since their duties
are performed more independently. Consequently they
should report directly to the assistant foreman in charge of
inspection in the shop, and not to the crib foreman.
The Chief Inspector's Staff
It was remarked on page 144 that the chief inspector's
staff should have no executive authority, other than that
which accrues to them by reason of their close association
with the chief inspector. The latter fact will naturally
give them all the prestige their work requires. The staff
organization should be laid out along functional lines so as
to provide a general service for the help and guidance of the
line executives. It must secure also, for the assistance of
the chief inspector, an inspection of inspection, without de-
stroying the individual responsibility or dividing the au-
thority of the chief inspector's subordinate executives. Such
division of authority is one of the greatest dangers in large
organizations of combined line and staff type.
ORGANIZATION OF INSPECTION DEPARTMENT 149
Thus each staff assistant will be a carefully selected
specialist, combining the work of an instructor in his line of
work with that of assisting the chief inspector in checking
up his assigned part of the work throughout the entire de-
partment. The staff duties to be performed may be listed
as follows, with the understanding that some of them may
be combined under one individual where the volume of work
warrants it:
1. Personnel matters, including the investigation of
questions affecting pay, promotion, discharge, as-
signment of new employees, etc. This work
usually requires the entire time of one man.
2. Follow-up of technical instructions from the chief
inspector's office to the inspection force, including
checking up the adherence to prescribed standards.
3. Care, use, and custody of gages, including making
sure that all gages pass through the gage-checking
department as scheduled.
4. Analysis of trouble reports from the foremen-in-
spectors, especially those relating to technical
difficulties encountered in the parts-making shops
and in the assembling department. This work
includes the further investigation of the reports,
also seeing that the more important ones are
placed before the chief inspector to bring to the
attention of the proper authorities in the general
factory organization.
5. Liaison duty with the production engineer to see that
the inspection department is collecting produc-
tion data for him in a satisfactory manner.
In addition, the chief inspector frequently has small
technical matters requiring the services of a junior engineer
to conduct the preliminary investigation. It is suggested
150
THE CONTROL OF QUALITY
ORGANIZATION OF INSPECTION DEPARTMENT 151
that such men be taken from time to time from the rank and
file of the inspection force, or from the laboratories. This
practice will serve to broaden the men in question, and will
accomplish the specific purpose in hand quite as well as if
they were permanently assigned to the staff of the chief
inspector's office. Under some conditions, as a more or less
temporary expedient in guiding the factory toward the best
compromise required by the commercial situation, the chief
inspector may be given a staff assistant taken from the sales
department. In this case the sales department may be re-
garded as the purchaser and the sales representative as the
purchaser's inspector.
The Inspection Department Personnel
Little has been said as yet about the qualities to be
sought for in choosing men for the duties of foremen-inspec-
tors, their assistants, and the working inspectors. The
problem is not one of choosing the kind of men who are best
qualified, but rather of making the best use of the men that
are available. There is ' ' history ' ' in the statement, as more
than one chief inspector can testify from sad experience in
recent years.
Some of the men who take employment in the inspection
department have had previous experience in technical work,
and some have not. If the experience of the former class
has resulted in a self-sufficient knowledge, they should be
replaced by men of the class who have no such technical
experience, and know that they do not have it, because the
inspectors must follow the standards set, without modifying
them in the light of their previous experience. In other
words, obedience to orders is the prime desideratum.
In assigning duties in the inspection department organi-
zation, therefore, it is necessary to place the personnel so as
to grade the amount of discretion to be allowed in matters
152 THE CONTROL OF QUALITY
requiring the exercise of judgment. It might be said that
the amount or quantity of judgment to be applied by any
individual meniber of the inspection force should be de-
creased as we go down the line from foreman-inspector to
the inspector working in the crib.
The Bench Inspector
The inspector applying gages at the bench, or inspecting
finish as to sample, should be the kind of person who has
reasonably good eyesight and tactile sense ; but more than
this' he must be temperamentally suited to doing exactly
what he is told to do. This will consist in sorting the work
he is inspecting into work that is clearly according to
standard, work that is clearly not according to standard,
and work about which he is doubtful, leaving the decision
as to the latter class of work to his immediate superior.
As stated before, this process implies reasonably definite
standards of quality in the first place.
The Floor-Inspector
The floor-inspector should be of entirely different charac-
ter. He has the important duty of first-piece inspection
before he authorizes a machine to begin a run of work. In
addition he may be given the right to order a machine
stopped if the work is not to his satisfaction. This calls for
good judgment backed up by practical experience, hence the
floor-inspector is usually a first-class machinist, to whom the
title and duties of inspector may make an appeal, or who
views this work as a step in the direction of a foremanship of
some sort — which it certainly should be.
Salvaging Native Ability
Practically every large inspection department possesses
a unique characteristic, and a very happy one. It is a veri-
ORGANIZATION OF INSPECTION DEPARTMENT 153
•
table "gold mine" of men possessing unusual native ability
and good character, but lacking experience in factory work.
Every once in a while, and for various reasons which do not
matter, some man decides to make a radical change in his
work. His very lack of acquaintance with factory life may
be the source of his desire to try it, and he presently appears
at the factory employment office. Having no knowledge of
machinery, he hesitates to attempt machine operation, even
if the way is made easy for him to acquire 'the necessary
skill; but the title of inspector may make a special appeal,
both as a dignified occupation and as an opportunity to
learn more about manufacturing methods at close range.
This is one explanation of the presence of such men in
the inspection department. As to where they are to be
discovered, the answer is, obviously, at the bench, usually
working quietly but nevertheless with their eyes open to
what is going on around them in the shop. Unless the fore-
man is an unusually human sort of executive, he will fail to
see the possibilities in these subordinates. Someone higher
up must keep an eye out for such men, and see that they are
given the chance they hoped for when they entered the
establishment.
A Case in Point
The circumstances just referred to came to my attention
for the first time a few years ago, in the course of reorganiz-
ing an inspection service of some 2,000 employees, where
an excessive labor turnover in this department was con-
sidered to be one of the primary reasons for defective con-
trol of quality. The problem of reducing the turnover was
attacked by direct action — the chief inspector had a personal
talk with every man entering or leaving the department.
The experience was somewhat arduous, but this was more
than offset by the results, which were felt almost immediately.
154 THE CONTROL OF QUALITY
A certain foreman-inspector complained regularly and
frequently that the men supplied him were " no good." The
foreman himself was a man of long experience in the busi-
ness, and by reason of this fact seemed unable to adjust
himself to the necessity of training the men supplied him
rather than expecting to find men already skilled in their
work — a situation resulting from the war time labor condi-
tion. Most of the men leaving his department gave every
reason but the right one for quitting, probably in the fac-
tory spirit of being good losers. Presently, however, a man
appeared in the chief inspector's office on his way out.
Character and personality were written plainly on his face.
Under pressure he told his story, and in a detail that showed
a keen grasp of conditions.
Briefly, the story was this. After completing a semi-
technical college course, he had taken a political job, and by
an unlucky swing of the political pendulum about fifteen
years later found himself under the necessity of seeking
other means of supporting his family. So he turned to this
particular factory because he had heard of possible opportu-
nities there. It looked to him like a fresh start with good
chances for a satisfactory career. After three months at
the bench as an inspector he confessed that he knew little
more about the intricacies of the business than when he
started. What he did know, he had been forced to dig out
by himself without encouragement from above. On the
other hand, he knew what was basically wrong in that shop
better than the foreman-inspector himself.
This experience was the cause of starting a school for
such men under an old foreman who possessed a heart as
well as a head, and who passed on enough of his practical
knowledge to enable his pupils to qualify as tool-setters and
gang bosses. After this, promotion was up to the individual,
but he was always encouraged to bring his problems back to
ORGANIZATION OF INSPECTION DEPARTMENT 155
his old instructor for helpful advice. The man whose case
was just referred to became assistant superintendent of a
large production department in about six months from the
time when he was ready to give up in disgust and discourage-
ment. Several other men, discovered in the same way, were
developed into excellent foremen instead of being lost to the
organization.
Study the Individual
All of which suggests that while the individual unit of
an organization may be, in one sense, part of a machine, he
nevertheless is a man, with all of the perfectly natural limi-
tations and variable potentialities of a human being. I ven-
ture to say that there is nothing in the entire work of organiz-
ing and running the inspection department (not to mention
the rest of the factory) that will yield so large a return, both
in actual accomplishment and in personal satisfaction, as
the study of the men themselves.
CHAPTER X
MANAGEMENT OF THE INSPECTION
DEPARTMENT
The Task
The chief end to be sought in the management of the in-
spection department is to obtain a firm control of quality
by holding the work to definite predetermined standards;
and to accomplish this with the maximum of economy. The
task presents at least two essential differences from the
management of a production department of commensurate
size:
1 . The working force is widely scattered and the work
unusually varied. Co-ordination is difficult.
2. The pay of inspectors is nearly always low in propor-
tion to their responsibilities, with attendant difficulty in
attracting and keeping the right kind of labor.
Co-ordination
The first step in co-ordinating the work of the inspection
department is to see that the chief inspector's office is lo-
cated as nearly as may be in the center of the plant.1 The
inspection force is concerned with every manufacturing
process going on in the factory and with many of the general
service departments. It reaches into every part of the plant.
Questions arise every hour of the day that call for settle-
ment by personal conference with the chief inspector or some
member of his staff. Much time and effort will be saved by
lessening the average distance to the point of trouble.
Furthermore it is greatly to be desired that both production
and inspection department executives feel that the chief
1 In the author's opinion, the same statement is true for all executive and managerial de-
partments. See "Production as Affected by Size of Plant," by G. S. Radford, Management
Engineering, Aug. 1921.
156
MANAGEMENT OF INSPECTION DEPARTMENT 157
inspector is in as close contact with the work as they are
themselves. The chief inspector's job is not in the front
office, but rather in the very heart of the works. Moreover
it is in every way a more sociable arrangement, and that is
desirable.
The Use of Conferences
In co-ordinating the efforts of his own executives, the
chief inspector will find use for all of the ordinary devices
of good management. He will find conferences with his
superintendents and foremen of special value.
Incidentally the main purpose of the conferences will be
obtained more surely if the chief inspector does not do all
the talking. The men in the room will be brought together
better if they come to accept the conference as an opportu-
nity to obtain the help of several minds in working out their
immediate and most baffling problems. The chief can
soon develop good fellowship and a common interest in the
work of the entire inspection department, by a little adroit
steering.
A conference of his immediate subordinates once a week
will be sufficient under ordinary circumstances, but it is
suggested that this practice be supplemented by an occa-
sional conference with the inspection executives of each in-
spection group, for the principal purpose of developing a
closer personal contact and acquaintance between the sub-
ordinate executives and the chief of their department. For
the entire department should be in harmony with the chief's
policies and therefore quick to react to his instructions as
they are passed down the line. Such flexibility of control
will be strengthened more certainly by personal acquain-
tance and through frequent contact the personality of the
head of the department will be reflected in the department
as a whole.
158 THE CONTROL OF QUALITY
Letters of Instruction and Advice
It will be found to be an excellent plan, in co-ordinating
the various units, if each foreman and staff employee is
supplied with a simple letter-size binder for keeping a file of
department bulletins. These bulletins should be issued
from time to time from the chief inspector's office as a quick
means of conveying his executive instructions to the entire
organization, defining his policies and supplying technical
information. The book should be kept on the foreman's
desk for the subforemen to read, and it should be the duty
of one of the staff assistants to question the subforemen
occasionally about the messages in the bulletins which
specially concern their work, so as to encourage them to
keep in touch with the plans and policies of the department.
The scheme will not work unless it is closely followed up,
but it can be made a most potent force in keeping men ' ' on
their toes" and working harmoniously, especially if the bul-
letins or instruction notices are explained and discussed in
conference.
Finally, it is in the general work of helping to keep the
entire department pulling together smoothly, that the mem-
bers of the chief inspector's staff will justify their employ-
ment. To make their work most effective, the chief should
encourage them to confer with him. Whenever practicable
they should make their headquarters in the chief's office.
Reduction of Turnover of Inspection Force
No matter how thoroughly standards of quality are
specified, there will be a certain amount of incompleteness
in the statement of them that can be filled out only from
the accumulated experience of the inspector. Again, it re-
quires a varying length of time for any inspector to acquire
the technique necessary to apply a given gage with the de-
sired accuracy and skill, or to conduct satisfactorily any
MANAGEMENT OF INSPECTION DEPARTMENT 159
given inspection operation. Because of these reasons it is
important that the personnel of the inspection force be as
permanent as that of other departments, or even more
permanent, if standards of quality are to be prevented from
fluctuating. This is in addition to the usual loss in quan-
tity of work performed, due to excessive labor turnover in
any class of work. The disparity in pay already referred to
is a disturbing element and the turnover in a large inspec-
tion department is likely to be unduly high in consequence.
Obviously, the primary action to take in order to stabi-
lize conditions is to employ people for inspection work who
are most likely to take to it kindly. For example, the in-
spection work is usually less strenuous than the operation of
manufacturing machines, which indicates the employment
of people (frequently women) who cannot stand the physical
strain of the heavier production work, and know it.
Provision for Promotion
When a relatively high degree of experience and skill are
requisite, as in the case of floor-inspectors, there should be
assurance that the inspection force will share in promotions
to assistant foremanships in the production departments, so
that the inspectors have something to look forward to when
higher vacancies are to be filled.
Since the easier way of the direct financial incentive is
mostly barred, resort must be had to every possible non-
financial incentive. That is to say, in brief, that the inspec-
tion department must be handled so that it will come to be
recognized as an excellent place in which to work — and more
important yet, a force that a man should be proud to belong
to. The work can be made pleasant if the inspector is
treated by his executives with just a little more friendliness
and courtesy than is customary in shops. I do not mean to
imply that his job should be made a soft one. On the con-
160 THE CONTROL OF QUALITY
trary, the spirit of the organization, and hence the dignity of
the work, will be greatly enhanced by stressing the value of
character, by cultivating a pride of achievement in terms of
accuracy, and by a rigorous demand for personal responsi-
bility. But all of this should be tempered by a very obvious
interest, on the part of the chief inspector and his assistants,
in the personal welfare and interest of everyone in the de-
partment. If this takes only the form of an evident will-
ingness to help the other fellow to help himself, the object
sought will be attained. All parties gain — the executive by
having a more contented and efficient force, and the sub-
ordinate by having a conscious increase in satisfaction in his
work, through the knowledge that his value to himself and
to others is growing all the time.
Wages
Owing to the fact that it rarely is practicable to measure
the work performed by inspectors, it is the general practice
to pay them on the day-wage, or hourly wage basis. It
frequently occurs that the inspection work must be per-
formed in a shop where the machine operators are paid on a
piece work or similar system based upon the quantity of
work performed. Hence it is not unusual to find a situa-
tion arising where ordinary machine operators are paid at
rates considerably in excess of those paid the men who in-
spect their work, and under such circumstances, there is
more than the usual difficulty in keeping the inspection force
in a contented frame of mind.
The easiest apparent cure is to raise the wage scale for
inspectors, but that way is rarely open, in spite of the fact
that the inspectors perform work in many cases that is
worth enough to warrant a higher scale. An economy in
total cost might conceivably be attained thereby, but in
nearly every plant, inspection is regarded as a necessary
MANAGEMENT OF INSPECTION DEPARTMENT l6l
but regrettable and non-productive expense. Consequently
the chief inspector is faced with the problem of doing the
best he can with a strictly limited pay-roll, and therefore is
forced to use the lowest rate of wages that will keep him sup-
plied with a grade of labor that will do.
As a result the chief inspector and his foremen will be
besieged with requests for raises in pay, and a relative de-
gree of contentment can be obtained only by having a
definite rate of promotion with graded rates of pay based
upon length of service in combination with efficient work.
This, I believe, has been found to be the best solution under
the day- wage system for all kinds of work. I have seen the
labor turnover actually decreased by the flat announcement
that no increase in pay would be considered for sixty days,
and this in the face of insistent demands for raises. In this
instance, however, there had been no systematic arrange-
ment for graded increases, so that the practice of asking for
raises had grown up, with the net result that the granting of
one request only served to encourage others.
Piece Work in Inspection
It is believed that inspectors working on small pieces
can be paid piece work to advantage in many more cases
than would ordinarily be supposed; but this system, obvi-
ously, can only be used to advantage when the work war-
rants a check inspection, or inspection of inspection by
sampling all work after the piece working inspectors have
gone over it. When this can be done without sacrificing
quality, the usual economy inherent in the piece work sys-
tem will be experienced, although the individual worker
makes more money. Inspectors employed on piece work,
however, must be penalized strictly by non-payment for any
boxes of work found to contain defective parts, and less
heavily for the rejection of good parts.
11
162 THE CONTROL OF QUALITY
Working Hours
Another potential source of discontent arises from the
fact that at least a part of the inspection force will need to
be on hand both before and after the regular working hours.
It is especially important that the inspection cribs be ready
to issue work before the beginning of work in the shop —
sufficiently early, indeed, to make sure that all machine
operators are supplied with work well ahead of time. Other-
wise the production force have a valid cause for complaining
that they are delayed in getting to work promptly. Then
again, it is often desirable that work turned in at quitting
time should be inspected at once. When choke-points
occur this may be imperative. The suggestion is offered
that much unnecessary hard feeling can be stopped by a
definite understanding, at the time of employment, that the
working hours of inspectors will be staggered a little out of
phase with the regular shop working hours. The total time
can be adjusted by allowing a longer time for lunch and by
a reasonable leniency in days off. The time outside of
regular hours need not exceed 15 minutes in most cases, so
that adjustments of total time are not difficult. Needless
to say, overtime should be avoided with care, as both costly
and conducive to the creation of additional and needless
overtime.
The Cost of Inspection
Most chief inspectors will agree that the average fore-
man-inspector, by reason of his being a foreman-inspector
and concurrently with his assumption of that duty, at once
develops an unusual ability to ask for more inspectors, and
for better inspectors, and for more gages. Now as all of
these things cost money, which is a relatively rare commodity
in so far as the chief inspector's disbursements are permitted
to go, some other way out must be found. For example,
MANAGEMENT OF INSPECTION DEPARTMENT 163
the foreman may be shown that more men does not neces-
sarily mean a corresponding increase in the amount of work
performed. Thus in the curve shown in Figure 37 — in which
the abscissae represent the total number of men in the work-
ing force, and the ordinates represent the total amount of
work performed — it is not unnatural to assume that output
will increase in direct proportion to the number of people
O
1"
No. of Men
Figure 37. Curve of Output and Number of Men
engaged in the work, as shown by the line OA — the more
men, the greater the total output.
As a matter of fact, a little consideration will show that
the curve OB C is more nearly true for any given job, for the
reason that a point, B, is soon reached where additional
help only interferes with the people already at work, until
at C the shop is so crowded that no one can move, and the
output returns to zero again. Hence it follows that for any
given output, OD, there are two limiting numbers of men,
DE and DF. It is the painful lot of the inspection depart-
1 64 THE CONTROL OF QUALITY
ment to work a little inside of the number of men indicated
by the point E. This may not be entirely convincing to
your foreman, but it at least shows them what they are up
against in asking for more men.
Teaching Inspectors
Rather than engaging more men, therefore, it is a mat-
ter of increasing the efficiency of the allowable force and
here it may be noted as a fortunate circumstance that in-
spection work lends itself readily to very marked economies
in the way of greater output per man, through the applica-
tion of many of the devices of modern methods of manage-
ment. This is especially true of bench inspection, under
the conditions of central inspection. The device of greatest
utility is a carefully planned use of sampling, insuring that
no more work is done than is necessary. Next comes the
matter of instruction in the work of inspection, to see that
each inspector knows just what he is trying to do, and the
quickest and easiest way to do it. There are so many
operations in inspection work which appear very simple,
that there is a strong tendency to show a new employee
what he has to do in a very casual and general sort of way
and then leave him to his own devices. The application of
a gage or two, or a viewing for surface finish, appears to be
transparently easy, but the mental attitude that regards
any piece of work as simple is a danger signal. It should
be borne constantly in mind that time and motion .study
began with handling pig iron and shoveling earth. It is not
unlikely, in fact, that the most striking economies are to be
realized in the most simple operations.
The instruction of inspectors is a staff job — that is, it
should be a staff job if the best results are to be obtained.
Perhaps this conclusion flows from the proverbial truth that
work which is left to everybody is rarely done right.
MANAGEMENT OF INSPECTION DEPARTMENT 165
Combine Instruction with Staff Supervision
The instruction should be combined with the work of
one of the technical men on the chief inspector's staff, as it
fits in well with a critical examination of each inspection
point taken seriatim and somewhat as follows:
1. Is the measuring device, gage, or what-not, such
that true results can be obtained?
2. Is the gage being applied so as to obtain true results?
3. Is the work being done in a way to secure the great-
est economy of inspection?
The first two questions are vital, naturally, since money
spent upon inspection is worse than wasted if the results are
not close to the truth. The third question opens up the
whole field of possible increase of efficiency. Frequently,
in fact, the most cursory use of motion study reveals large
possibilities for saving time in inspection, especially if the
inspector considers himself under the necessity of hurrying.
The most frequent loss arises from improper placing of the
boxes of work, so that unnecessary and overcrossing motions
are made. Then there are the losses that arise from awk-
ward posture and clumsy holding of the gage. It sometimes
happens that a separate support for the gage will help mat-
ters by leaving free both of the inspector's hands. In this
case attention should be given to seeing that the support is
flexible enough to permit automatic adjustment of a close
limit gage to the work.
A large saving can be secured through spreading the
message of careful handling of both work and gages. Pre-
cision instruments and fine work call for a certain amount
of gentleness, of the sort that the late A. J. Corbesier, the
honored fencing master at Annapolis, referred to when he
said, " Hold your foil as you would a bird — firmly, so it will
not escape; gently, so it will not be hurt."
1 66 THE CONTROL OF QUALITY
I recall an experience in a munition plant, where a room
full of foreign help was engaged in the inspection of high-
grade work. The gages were applied with such enthusiasm,
and highly finished parts were thrown into tote boxes with
such vigor that the anvil chorus would not have had a chance
to be heard. The ordinary bench inspector or machine
operator in our larger factories will easily fall into almost as
bad habits unless he is cautioned continually.
Unskilled Help in Inspection
Turning now to one of the greatest economies in inspec-
tion, especially in central inspection as previously stated ; it
is not necessary (except in certain kinds of floor-inspection)
to have a personnel already skilled in the work of inspecting.
In fact it is quite inadvisable to employ such people when
the object is to limit the use of judgment and to hold to a
close standard. But the employment of unskilled help
again indicates the necessity of providing adequate instruc-
tion, not alone by teaching, which always should be a large
factor in management, but also by providing accessible ref-
erence data, such as samples, large-scale drawings with
gaging points distinctly marked, gage instruction cards, and
so on. It should not be necessary to mention, except for
completeness, how important it is to begin this educational
work as soon as the new inspector is employed. There are
obvious advantages in "catching them young." The work
will be done more certainly, and probably better and quicker,
if it is followed up by a staff assistant.
Female Labor for Inspection Work
In speaking of the use of unskilled labor as a measure of
economy in inspection, the question of using female labor
deserves serious consideration. In fact, if female labor is
carefully selected with reference to the adaptability of the
MANAGEMENT OF INSPECTION DEPARTMENT
16;
Figure 38. Prestwich Fluid Gage as Used to Inspect Piston Pins
Diameter held to within 0.0002 inch — Packard Motor Car Company.
168 THE CONTROL OF QUALITY
individual to the class of work involved, it will be found that
women are able to do many more kinds of inspection work
than might be supposed, also that they almost invariably
perform it better than men. A higher grade of tactile sense
and skill can be secured for the same investment, together
with a stricter compliance with instructions in the matter of
holding to standard. The advantage to be gained in
greater contentment of the inspection force alone, makes the
employment of women highly desirable whenever possible.
It is realized that many factory executives hesitate to
introduce women into the inspection department in shops
where none but men are employed at the machines, and this
for reasons quite apart from their suitability for such inspec-
tion work. It may be stated as a fact, however, that the
feeling is not warranted if proper measures are taken at the
start to maintain discipline ; for the presence of women may
be made to secure an elevation of the entire tone of the shop.
To do this requires that the subordinate inspection bosses
be chosen from among the most dignified inspectors and that
they be duly impressed with the importance of their work.
It should be made a fixed rule also, that questions affecting
inspection be taken up by the production bosses with the
male foreman only.
In a large factory employing at the time none but men
in the shops, female help to the number of several hundred
were introduced into the inspection department in the en-
deavor to stabilize labor turnover in the department, as well
as to secure better control of the technique of inspection.
Because of the class of labor in the plant, the management
realized that matters might arise which would be reported to
them more certainly, and perhaps more easily and gracefully,
if the women could carry their troubles to a woman rather
than to a man. It was recognized, besides, that a high
standard of character in the inspection department was
MANAGEMENT OF INSPECTION DEPARTMENT 169
worth a great deal in controlling the quality of the factory
output. With this in mind, one of the secretaries in the
main office, who had been a working girl and who combined
rare judgment with a very human sympathy for her asso-
ciates, was asked to take the time to become acquainted
with at least one or two girls in each inspection group. The
plan proved to be an unqualified success, although it resulted
in the dismissal of a foreman or two, and a few of the inspec-
tion force, very shortly after the facts began to come in and
investigations were made. It was not long, however, before
that particular plant achieved the reputation among work-
ing people of being the safest factory in the state to which to
send their daughters for employment.
Women as inspectors will be found to work faster than
men, especially if their strength is conserved by providing
men to do the heavier work of lifting and moving tote boxes.
The amount saved is sufficient to pay for the greater com-
forts in the way of chairs, recreation and rest rooms, and
other conveniences, that must be provided for women. It
should be remembered, however, that women inspectors
should be required to adapt their dress to secure personal
safety, by wearing caps and suitably protected sleeves, as
in the case of female machine operators; for even women
inspectors are occasionally passing near machinery in
motion.
Women Inspectors on Heavy Work
From the technical standpoint, there are many kinds of
work not ordinarily inspected by women which could be so
handled to advantage, even in the case of comparatively
heavy pieces. This requires that the individual be chosen
for the job and given a preliminary course of training. The
inspection of the interior of rifle barrels has been performed
by women to great advantage, although it is technically
170 THE CONTROL OF QUALITY
difficult and the physical work of holding them up to the
light is tedious, to say the least. In the case I have in mind ,
the inspectors were chosen from among a number of obvi-
ously robust and sturdy individuals, whose eyesight meas-
ured very nearly perfect. They were then instructed in the
art by an expert foreman who believed that women could be
taught to do the work. It took ten days to graduate them,
and it only remains to be stated that they developed a pro-
ficiency that at first set too high a standard. It would, in
fact, have tied up production, if prompt measures had not
been taken to reinspect their rejects, until they could be
taught to hold to a more reasonably commercial standard.
And in spite of this experience the scheme was nearly wrecked
by their inspection foreman (a man of long experience and
great skill in the business), who stubbornly refused to be-
lieve that women could learn, in so short a time, work re-
quiring such skill. From this fact the reason may be de-
duced for emphasizing certain words in this paragraph. It
may possibly suggest in addition, that there is more than a
modicum of "bunk" about many skilled operations, so-
called, as is rapidly discovered when the problem of con-
trolling them is approached in a truly scientific manner.
Morale
No treatment of the management of the inspection de-
partment should close without stressing the special value
of a high morale. Just as the precision of measuring instru-
ments is fundamental in determining the degree of mechani-
cal accuracy that may be attained, so must fidelity to truth
be developed in the inspection force, to secure the predeter-
mined standard of quality that is desired. Thus character
is the first desideratum, and as a necessary element of it,
impartiality, thoroughness, and accuracy in developing the
real facts, and courage in bringing them to light. The chief
MANAGEMENT OF INSPECTION DEPARTMENT 171
inspector must train his people to secure this result; and
then, lest he lose the advantage, he must support them when
they are right, and must in his turn be supported by his
superiors in the management. Concurrently, the inspec-
tion force should be disciplined to a strict obedience in
carrying out the chief's instructions, if for no other reason
than to secure a quick flexibility and certainty of control in
developing the standards of quality, with freedom from dis-
turbing influences arising outside of the inspection depart-
ment.
The presence of this same discipline, administered always
with personal courtesy, will build up the individual's sense
of the value of his work to the entire organization; and with
the resulting realization of personal dignity and knowledge
of trust, there will come a feeling of responsibility and pride
in the work of the whole department — that is to say, an
esprit de corps.
CHAPTER XI
INSPECTION IN PRACTICE
Type Varies with Individual Factory
The development of a philosophy of inspection requires
that its principles be stated somewhat in the form of abstract
generalizations. It is believed, as has been stated, that
these principles are of much wider application than is gen-
erally appreciated and that industry would benefit greatly
if they were followed much more closely in practice. It is
equally true, however, that the translation of these prin-
ciples into action, as has been pointed out in several in-
stances, requires that they be interpreted with a leaven of
common sense, and applied in the form of whatever adap-
tation is economically most suitable for the particular case
involved.
Each manufacturing enterprise has its own peculiar con-
ditions to meet, and the arbitrary introduction of a fixed
system of any sort, without careful and intelligent modifica-
tion, is fraught with grave dangers. "What is one man's
meat is another's poison."
If the management is critically introspective, so to speak,
the way in which inspection is organized and applied is likely
to be well suited to the needs of the factory. Hence the
value of studying the inspection methods of well-established
industries, whose successful operation may be taken for
granted. Such study is the purpose of the present chapter.
As an introduction thereto the various modifying consid-
erations which are involved in special cases may now be
assembled.
172
INSPECTION IN PRACTICE 173
When to Use Extensive Inspection
Briefly stated, the most extensive and complex use of
inspection is desirable when:
1. The product demands frequent and thorough in-
spection, as when great accuracy is required.
2. When models are changed with frequency, as in a
swiftly advancing art.
3. When labor is unskilled or rapidly changing.
4. When quality standards are being raised.
5. When considerable judgment must be used because
standards are being shifted or have not been re-
duced to a definitely measurable basis.
Each of these cases may apply separately but when they
are cumulative, as in the case of unskilled labor working in
an industry that is advancing swiftly, the use of a much
more intensive form of inspection is indicated.
On the other hand, if the product is highly standardized
and if the workers are skilled mechanics well acquainted
with the requirements of the work, then inspection may be
greatly reduced. In fact, if the work is performed under
these conditions and on so small a scale that the manage-
ment is able to devote considerable attention to the details
of the business, the need for inspection almost disappears.
Cases of the latter sort are very rare, however, and are not
worth considering except as exemplifying the extreme or
limiting situation.
The following examples have been chosen from a number
of industries with the idea of presenting in brief form certain
general features of inspection methods which are typical.
Inspection in Automobile Plants
In looking for a good example of inspection as practiced
in its highest development, there is no better place to turn
174
THE CONTROL OF QUALITY
than to the automobile factories. The evolution of auto-
mobile design and manufacture is one of the great romances
of modern industry. For reasons that need no mention, it
has made tremendous demands upon every department of
engineering science and the technical arts, in order that
ways and means for meeting its requirements might be de-
vised. It has made it necessary to create a new school of
machine tool design, to carry tool-room precision into the
ordinary fabricating shops, and to install every reasonable
safeguard for controlling quality.
The Packard Inspection Service
Inspection in the factory of the Packard Motor Car Com-
pany l has been developed to a point that is best illustrated
by the organization chart shown in Figure 39. The chief
FACTORY
EXECUTIVE STAFF
CHIEF INSPECTOR
1
DIVISION SUPT
INSPECTION
ERATION SUPT.
I
1 1 f
1
FOREMAN FOREMAN F°JE
FORUE INSPECTION FOUNDRY INSPECTION | riNI*Kl£e
m*" FOREMAN
*$0«"AL | INSIDE INSP6C
FOREMAN
T,nu ROUGH STOCK
INSPECTION
1
1
INSPECTORS INSPECTORS INSPECTORS INSPECTOR
a INSPECTORS
Figure 39. Inspection Organization Chart — Packard Motor Car Company
inspector is responsible to the factory executive staff, com-
posed of the vice-president of manufacturing, the factory
manager, the assistant factory manager, and the general
1 The author is indebted to D. G. Stanbrough, General Superintendent of the Packard
Motor Car Company, for his courtesy in furnishing information relative to Packard inspection
practice and precision methods.
INSPECTION IN PRACTICE 175
superintendent. The chief inspector is responsible for
proper and efficient inspection throughout the inspection
organization, in accordance with standards set by the fac-
tory management.
Directly under the chief inspector is an inspection super-
intendent for each of the main divisions of the business,
namely, carriage, truck, and service. Each of these divi-
sions is further subdivided into three departments : outside
finished material inspection, inside inspection, and rough
stock inspection, with a foreman in charge of each depart-
ment to whom the individual inspectors report. In addi-
tion, there is an alteration superintendent, also responsible
to the chief inspector, whose duty is to see that alterations in
the dimensions or in the design of parts are properly put
through in the factory with the minimum of interference.
Both floor-inspection and centralized inspection are in
use. Large parts, such as cylinders, crank cases, etc., are
inspected on the floor near the machines, since manufac-
turing facilities are so arranged as to permit it conveniently.
Small parts, however, are removed to the department in-
spection cribs for inspection. When a workman machines
the first piece on a job, he is required to submit it to the
foreman or the job-setter. If the piece is done correctly,
the foreman or job-setter OK's the workman's time slip
and he goes ahead with the job. If the operation is not
done correctly, the foreman shows the workman how to do
the operation, and the time slip is not signed until the piece
is finished correctly.
Final inspection of each individual piece is maintained
on the following parts: heat treated parts and parts that
are held to close limits, such as cylinders, pistons, piston-
pins, crank cases, transmission parts, gears, steering
knuckles, etc. Ordinary small parts such as screws, nuts,
bolts, washers, etc., are subjected to a percentage inspection.
176
THE CONTROL OF QUALITY
The disposition of rejected parts is rigorously controlled.
Reference to Figure 40 shows this in detail. While the
production department may be consulted by the chief in-
N9 146099
DEFE
DATE
CTIVE
DiPI (OUNDIN
STOCK TAG 1
ON
OROCR
PICCC NO
inaricici;
DISPOSITION OATS
OR.O. O.PT.
RCPAIR
OROCR
oe" OHO°-
»PPUf ON TAO NO
OPtR. 0«F.
DIE NO.
QUANTITY DCFCCTIVC
NAME
„.
SCRA,
REPAIR
RCTURN
R«PLAC<
OC»CTS
._„
ACCCP
MOUOH
r
ASSCMBLK
FINISHCO
FOR RtPAIR INSTRUCTIONS 511 BACK Of NO. » COPT
REPAIR ROUTING
PRIC«
1
KXTCNStOP*
1
(MPMJM
Figure 40. (a) Inspector's Tag Disposing of Work (face) — Packard Motor
Car Company
INSTRUCTIONS FOR REPAIR
DEPT
OPERATION
8
Figure 40. (b) Inspector's Tag Disposing of Work (reverse)
spector, the fact remains that no piece once rejected can be
disposed of except in accordance with instructions issued by
the chief inspector in person.
The foregoing pertains to the methods of handling in-
INSPECTION IN PRACTICE 177
spection on forgings, castings, semifinished and finished
pieces. In addition to this, there is a metallurgical and
chemical department for the usual analyses of iron and steel.
This department, however, is separate from the regular in-
spection organization and is in charge of the chief metal-
lurgist, who is responsible to the factory executive staff.
The chief metallurgist also prescribes the requisite charac-
teristics for heat treated parts, although the actual work of
inspection of these parts is carried out through the regular
inspection organization.
Operating inspection on finished vehicles is also a sepa-
rate function in charge of the operating manager who is re-
sponsible directly to the president.
In addition to all of the above, the quality of the product
is further insured by a supervisor of quality (reporting to
the factory executive staff) whose function is to check the
work of the inspection organization. The method of the
supervisor of quality is to have his men take a complete
unit at random, which is then disassembled and checked up
in detail by his men.
Inspectors are paid day work, which is the almost uni-
versal practice. With a working force of 9,000 men, 500
inspectors were employed. It should be noted, however, in
connection with any data of this sort, that the proportion of
workers must vary considerably from time to time, depend-
ing upon the situation of the work and the number of work-
men employed. Consequently, the figures that are given
relative to the number of inspectors for any given working
force must be considered as applying merely to a particular
situation.
In its general features the above outline is believed to be
typical of the best automobile inspection practice, although
there are naturally a number of variations from factory to
factory. The proportion of workers to inspectors, for ex-
12
178 THE CONTROL OF QUALITY
ample, varies all the way from I inspector to 10 workers, up
to I inspector to 30 workers.
An Example of Former Practice
By way of contrast with the above, it may be of interest
to compare the inspection methods in use several years ago
in a plant which at that time was fairly prominent as the
maker of a high-grade car. In this factory the chief inspec-
tor reported to the chief engineer in matters affecting ma-
terial organization and the holding of the work to drawing
dimensions. He was responsible to the superintendent for
the routing and movement of all work in process.
The inspection department organization consisted of a
chief inspector, an assistant chief inspector, department-
inspectors, floor-inspectors, and inspectors. The depart-
ment-inspector had charge of all inspection in his depart-
ment and was responsible for the quality of the work and
the discipline of his force. There were in general 2 floor-
inspectors for every 150 operators and their duty was to
inspect all work in process at least four or five times a day.
They were required to check each new set-up before work
could start, after which the machine operator was held
responsible for all defective work.
The floor-inspectors inspected and had moved to the
various operations, all large pieces of work, such as crank-
shafts, axles, radius-rods, drive-shafts, and fly-wheels. These
parts were moved into the central inspection room only
when finished or at the time of being moved from one de-
partment to another, in order to fix departmental responsi-
bilities.
Work requiring skilled mechanics, such as grinding
crank-shafts, cam-shafts, cylinders, pistons, piston-rings,
gear-cutting and grinding, boring of crank cases and trans-
mission cases, was not considered to require floor-inspection.
INSPECTION IN PRACTICE
179
180 THE CONTROL OF QUALITY
The floor-inspectors were usually expert machinists receiving
(prior to 1914) about 70 cents an hour, and as an incentive
were usually next in line for promotion to assistant foreman
and foreman.
The amount of inspection given to each lot of pieces
depended upon the quality of the lot as determined by the
first few pieces inspected. That is to say, if the first few
pieces were good, the inspector examined about 25 per cent
of the lot. If any were bad he would then inspect the entire
lot. In each case he then counted the work and credited
the operator with the number of pieces passed.
For a force of 1,500 operators there were 40 bench-
inspectors, 8 floor-inspectors, 2 inspectors for commercial
work, I inspector for forgings and castings, and I inspector
on the scleroscope test. All of these men were paid on the
hourly basis, bench inspectors receiving from 50 to 65 cents
per hour. The drawing was the only standard allowed,
close dimensions being stated with the limits given in detail.
Limits of plus or minus o.oio inch were allowed on all di-
mensions which were stated in fractions. The standard of
finish was marked on the drawing to denote the points to be
finished, the allowance for grinding (say o.oio inch), and
the surfaces to be disc-ground or spot-faced, and no depar-
ture was allowed from the above without the written au-
thority of the chief inspector. It is of interest to note that
the company, being responsible only to themselves for their
standards, had permitted it to become the accepted practice
in the shops to shift the standards of workmanship and ma-
terial to suit the urgency of the demand for parts, keeping in
mind the ability of the assembling department to use them
without increasing the cost too much — this from the state-
ment of the chief inspector to the writer.
In the routing of work, in accordance with operation
sheets furnished to the inspector, the work was accompanied
INSPECTION IN PRACTICE l8l
by a route card, or traveler, which stated the part number,
order number, and quantity. This card moved with the
work from raw material to finished stock. When an opera-
tor finished his operation, he took the card to his foreman,
who then gave it to the time-keeper. The time-keeper then
made out an inspection ticket in triplicate, keeping one copy
himself. The remaining two went to the inspection depart-
ment where the inspector filled out the quantity accepted or
rejected. Of these two copies one was sent to the pay de-
partment and the other returned to the workman. The
inspector then made out a card, ordering the material out
of the inspection department and delivered by the trucker to
the next operation.
Machine Tool Industry
In the manufacture of machine tools, the organization
and methods of inspection do not differ widely from those
employed in the best run automobile factories. As might
be expected, however, the same degree of refinement has not
been reached, although there is evidence that inspection
methods are being overhauled rather carefully in several of
the machine tool making factories, as a result of their experi-
ence in the war. The ratio of inspectors to workers varies
all the way from i to 30 for ordinary machine tool work,
up to i to 15 in the case of small tools. Inspectors are paid
on an hourly basis. In many plants central inspection, floor-
inspection, and first-piece inspection are all in use together.
The most marked deviation in inspection organization
is in the relation of the inspection department to the rest
of the organization. In the Pratt and Whitney Company,
for example, the chief inspector reports directly to the works
manager, but this is by no means the general practice else-
where in the industry. In some factories the chief inspector
reports to the engineering department. In others he re-
182 THE CONTROL OF QUALITY
ports to the factory superintendent. These latter prac-
tices are of interest as indicating the results of an inherited
system.
Small Precision Work
Inspection methods have reached a high development
in many plants which are engaged in the manufacture of
small high-grade articles. For example, in the Elgin Na-
tional Watch Company's 2 plant the inspection work is per-
formed in a central inspection room or space, generally set
off at the end of each department. Each piece produced is
submitted to 100 per cent inspection. Out of a total work-
ing force of 3,500 the ratio of inspectors to workers averages
i to 10. All inspectors are paid by the day. Each main
factory division has its own inspection department with a
chief inspector in general charge.
At the Weston Electrical Instrument Company's 3 plant
at Waverly Park, Newark, central inspection is in use, but is
reinforced for certain classes of work by so-called "floating
inspectors" who move through the various departments
where inspection at the machine or at the completion of the
process seems to be advisable. In general, first-piece in-
spection is held to be a part of the responsibilityof the depart-
ment in which the work is done, and is not covered by the
inspection department except in special cases. Most of the
work is arranged in departments — the milling department,
the drilling department, etc., but no work is allowed to pass
from one department to another without first passing
through the hands of the inspection department.
The ratio of inspectors to workers averages about I to
10, and inspectors are paid on an hourly basis.
Every piece of the completed product, that is to say
2 From data furnished by DeForest Hulburd, second Vice-President.
3 Courtesy of Edw. F. Weston, second Vice-President.
INSPECTION IN PRACTICE
183
Figure 42. Inspection of Time Fuse Parts
War work of American Locomotive Company.
1 84 THE CONTROL OF QUALITY
every instrument, undergoes several final inspections. The
subassemblies and parts used in the production of Weston
instruments are subject to individual inspection. The only
exception is in the matter of unimportant parts (such as or-
dinary screws) which are inspected by sampling.
The chief inspector is responsible directly to the general
superintendent, and is assisted by a foreman and subf ore-
men, each subforeman controlling from 3 to 10 inspectors,
according to the nature of the work.
General Machine Shop and Foundry Practice
In industries whose work requires medium and heavy
foundry work, forgings and their machining, the inspection
department usually is more loosely organized, although in
highly standardized businesses of this sort, such as the man-
ufacture of power transmission machinery, it is usual to find
greater refinements in use, with a chief inspector reporting
directly to the management. Most of the work is inspected
on the floor, as a matter of necessity, but final inspection is
not infrequently performed in a separate department. In-
spectors are paid universally on an hourly rate. The ratio
of inspectors to producers is as low as I to 50.
Special Cases
The inspection methods in use in the manufacture of a
continuous product, such as paper or textiles, requires in-
dividual treatment, depending considerably on the grade of
the product. The general principles, as set forth for inter-
changeable manufacturing, are the same, but different
methods are necessary. All such work should be regarded
as an assembling proposition, with various preparatory
operations for the raw material and with appropriate finish-
ing operations after the materials have been brought together
in the goods. Errors are bound to occur and are almost
INSPECTION IN PRACTICE
185
always worked into the product in such a way as to defy
their correction. Consequently, inspection at the sources of
greatest error has an added value in checking undue loss.
Inspectors of high caliber are required, moreover, because
apparently insignificant
matters in the earlier
stages of manufacture
are likely to have a seri-
ous effect upon later
processes. The in-
spector thus requires a
wide knowledge of the
technicalities of the
business as a whole.
An interesting vari-
ation in the method of
inspection is occasion-
ally desirable for con-
tinuous processing — if
the workman is paid a
bonus for quality (and
consequently knows
that the defective work
will cost him money),
he automatically be-
comes an inspector of
work performed on the
material before it reaches him. In fact, it may be a desir-
able feature in any such scheme of quality control to re-
quire each operator to make a list of the defects he finds
in the work as it reaches him, and, where practicable, to
report the same before starting his own machine.
There is another class of inspection work which has not
been touched upon heretofore because of its very special
Figure 43. Perch for Inspecting Textile
Fabrics — The Shelton Looms
1 86 THE CONTROL OF QUALITY
nature. It is to be found in places where a volume of mail
orders are packed, and in similar operations which are more
in the nature of checking. For example, in the Charles-
William Stores 4 at a time when a force of about 500
girls was employed in packing orders for shipment, the
orders ran in about the general proportion of 300 freight,
3,000 express, and 30,000 parcels post. Obviously, it was
necessary to have some sort of check on the packing,
although it was equally true that the inspection of this
packing could not be carried very far without duplicating
the work of the packers. Satisfactory results were obtained
by the employment of 30 girls as inspectors, with a man-
ager or chief inspector. Arrangements were made to carry
the parcels through the inspection department on two 36-
inch belt conveyors. The inspection operation was per-
formed by sampling ; that is to say, an inspector would take
a package from the belt, get the papers in the case, and
check the order as filled and packed.
Ratio of Inspectors to Workers
As has been stated before, any figures giving the num-
ber of inspectors required, in proportion to the working
force, must be accepted with reservations based upon condi-
tions surrounding the work at the time. Consequently,
such figures can be used only as a general guide. As a mat-
ter of convenience, the following table summarizes the data
assembled from a number of industries :
Ratio of Inspectors to
Industry Workers
Ball bearings to 4 or 5
Small and very precise interchangeable parts to 8 or 10
Automobiles, high-grade close work to 10, up to I to 20
Simpler automobile work to 20, up to I to 40
Machine tools to 15, up to I to 40
Foundry and general machine shop to 50
4 Under the organization and methods developed by its president, G. H. Eiswald,
CHAPTER XII
QUALITY CONTROL IN PRACTICE
Complexity of the Quality Problem
Inspection is only a part, although a very important
part, of the wide and important subject of the control of
quality. As has already been pointed out, an analysis of
successful industries will show that these manufacturing
activities comprise three essential branches or stages :
1 . Planning or Engineering — the determination in con-
siderable detail, of what is to be made and how it
is to be made, before work is begun.
2. Production — the economical application of suitable
manufacturing processes whose output is con-
trollable to uniform standards of quality.
3. Inspection — the comparison of the work as produced
with the predetermined standards of quality, and
the filtering of unsatisfactory work out of the line
of flow of work in process.
The determination of what makes an enterprise success-
ful is a difficult matter in any case. Some things help,
others hinder, and some are merely carried along without
affecting the issue either way. Not infrequently success
results from a combination of circumstances which are
merely opportune, and vice versa. The resulting mixture of
causes is so complex that it is hard to analyze. If, however,
we approach the matter from the negative viewpoint, it is
simpler to determine what the basic causes of success really
are. The test in this case is: What are the things whose
non-observance will result in failure? As indicated above,
187
1 88 THE CONTROL OF QUALITY
it is believed that a very small oversight in any one of the
three essential branches of planning, production, and inspec-
tion may be disastrous ; while the same thing cannot be said
with equal truth of the other branches of factory endeavor.
By the above test then, we should expect to find un-
usually successful industrial enterprises accompanied by a
close attention to planning, production, and inspection.
The war furnished a number of examples which illustrate
the above in a conspicuous way, both by direct and by nega-
tive proof. Unfortunately, however, everybody was so
busy at the time that the most valuable lessons to be gained
from war time experience were missed, except by the people
who came in actual contact with the industries in question.
This is doubly unfortunate because the conditions were
especially good for proving in a very intensive way the
truth or untruth of the methods used.
It is, of course, difficult to choose typical examples from
such a quantity as are available, but the war work of the
American Locomotive Company, the Lincoln Motor Com-
pany, and the Remington Arms of Delaware may be selec-
ted as illustrating strikingly the points made throughout
this book.
The Shell Contracts of the American Locomotive Company
Early in 1915, the American Locomotive Company
undertook the manufacture of shrapnel and high explosive
shells for the British government. The work was carried
on under the direction of Vice- President C. K. Lassiter (in
charge of manufacturing). The excellence and importance
of this accomplishment are not generally known. Such
results, however, might have been expected of one who
already had an enviable record as a designer of highly effi-
cient machine tools, and as a production executive. As will
be observed from the accompanying illustrations, Mr. Las-
QUALITY CONTROL IN PRACTICE 189
siter's methods are characterized by directness, simplicity,
and effectiveness — in short, by that absence of frills which
denotes a genius for making things.
In order that the magnitude of the undertaking may be
appreciated (for it shortly grew to huge proportions), the
following summary of the work done by the American Lo-
comotive Company and its associated shops is of interest :
Manufactured complete, loaded 3-3-in. Shrapnel. 2,500,000
3-3
not loaded 4 . 5
« « 6
9.2
Extra cartridge cases, complete 3 . 3
4-5
H. E 2,500,000
H. E 1,468,000
H. E 1,468,000
H.E 300,000
H. E 125,000
3,886,000
1,147,000
time fuses, complete, loaded 3,200,000
" shell forgings — various sizes 2,733,700
During the last nine months of the undertaking this tidy
little job reached an average total daily output of 25,000 tons,
and employed 40,000 men. The average daily output of
cartridge cases alone was 58,000; while of 3.3-inch shrapnel
and H. E. shells it was 40,000. To accomplish these results
with an organization unacquainted with the work, however
skilled it might be in other lines, certainly would indicate a
thorough grasp of the fundamentals of manufacturing.
Beginning the Work
The first order undertaken was for 1,250,000 3.3-inch
1 8 pdr. shrapnel, and a like number of 3.3-inch high explo-
sive shell. Not one of these was rejected after delivery. Let
us now see how the thing was done, beginning with the car-
tridge case, which is the same for both shrapnel and H. E.
shell.
At the outset it should be noted that the contract pro-
vided only an outline plan without tolerances or limits.
The first step took the form of a visit to the Quebec Arsenal,
190 THE CONTROL OF QUALITY
where inquiries were made as to what these cases should be
like. In other words, Mr. Lassiter first endeavored to de-
termine what was wanted, in detail ; in fact, he frankly stated
that he and his associates approached the work as novices.
As a special result of this visit, two sample cartridge cases
which were satisfactory were obtained and brought back to
New York. These samples were then sawed in two, and the
hardness determined by careful and extended measurements
with the scleroscope. Dies were designed and a set of tools
made to produce the case from blank to finish, special atten-
tion being paid to see that the drawing processes were de-
veloped to secure the necessary coining at the points where
extra hardness was required. Tolerances and limits were
then worked out.
As an example of the processing, the annealing furnaces
were of the oil, overfired, perforated roof type. In order to
avoid scale, superheated steam was introduced, at a suffi-
ciently high temperature to permit uniform control.
Limit gages and 100 per cent inspection were provided
for all operations from rough blanks to finished cases. All
work rejected by either the company or the purchaser's in-
spection was forthwith removed from the line of flow and
sent to a hospital. Needless to say, the latter was pretty
large at times ; but this practice permitted an unbroken flow
of work from operation to operation. The value of this
practice was enhanced by the excellent handling devices
and conveyors, which were provided everywhere throughout
the shops.
No Rejections After Delivery
The plant for this work was laid out for an output of
9,000 per day of 20 hours, but the actual output reached
was 24,000. The quality of the first series submitted to the
purchaser was highly commended, even after firing some of
QUALITY CONTROL IN PRACTICE IQI
the cases three times. Not one series nor one single case
out of the 2,500,000 was rejected after delivery; and the
same statement holds for the complete and loaded shells.
Mr. Lassiter, in speaking of this part of the work, recently
said, "We were novices, so the first thing we had to do was
to find out what we had to make, then we had to make all
our processes alike, and finally we had to inspect everything."
To what extent the first thing was done, is shown very
clearly by the little yH by 3% inch booklets which were
supplied to the shops. Each booklet contains an index and
about 40 pages of blue prints, which give all the necessary
information as to the product, the tools for making it, the
shop arrangement, and so on. Sample pages are shown in
Figure 44. In connection with the simple but complete
way in which similar information was developed, attention
is invited to Figures 45 and 46. They contain no unneces-
sary information, yet everything needed is there.
Shells
The importance of getting processes under uniform con-
trol is illustrated even better by some of the difficulties
encountered in making the shrapnel and H. E. shells. In
general terms, the usual processing in the early stages is to
forge, rough turn, harden, and grind to finish. It was de-
sired to substitute finish turning for grinding, in order to
get greater production. The problem was to get them soft
enough to turn, but hard enough to meet the ballistic re-
quirements without the walls of the shell upsetting in firing.
This, of course, involves very uniform heat treatment.
A furnace was built 24 feet long, with six pyrometers
spaced along the sides. The shells were placed in special
triple pocket cradles, and were pushed into one end of the
furnace by a pneumatic pusher. The pyrometer at the
entrance fluctuated, but the sixth pyrometer was steady,
SHELL Q.F. 18 POUNDER SHRAPNEL
MARK IX/L/
H3.66
L3.64"
H 3.31"
L3.29"1
MM
Total Pressure =150 tons
Pressure per sq. in. «= 33,500 Ibs.
Gauge Pressure «=-1500 Ibs. max.
(Area of band after compression)
DRIVING BAND
R.L. 13413 A.
Figure 44. (a) Typical Page from Shop Instruction Book
American Locomotive Company practice.
192
SOCKET
_LH 2.515^JL 2.1
-H 2,425^-L 2.4
14 Thds.
per Inch
R.H.
CENTRAL TUBE
s-.08"Class "C" Metal or Mild Steel
Chamfer *fl Thds. per Inch R.H.
Figure 44. (b) Typical Page from Shop Instruction Book
13 193
MATERIAL STEEL CARBON 70% OR OVER
FINISH ALL OVER
PUNCH FOR
DRAWING OPERATION
PUNCH FOR
PIERCING OPERATION
|<— ln/w-
Figure 44. (c) Typical Page from Shop Instruction Book
194
MAP OF PRESSES IN
Tapering-4,5" 2nd Tapering-18* CARTRIDGE SHOP
(Toledo* 17
style*ll*
3rd Tapering-18* 1st Tapertng-18* Heading Press-18*
Flash
Anneal
urnace
Rack Press
Rack Press
Bliss
Trim-
mer
Bliss *5
Toledo *9
Style*857
Crank Press
Rack Press
Rack Press
Crank Press
Crank Press
Trim-
mer
1 Bliss *8 1
1 Style *78^2[
Crank Press
Crank Press
1 Bliss*! 1
|style*77^[
Crank Press
Toledo *5
Style *857
Rack Press
Crank Press
Crank Press
Figure 44. (d) Typical Page from Shop Instruction Book
195
No. 6. 7-0"ciearance
200 Ton
L6(Centers
5'Posts
No. 7. 7-0 Clearance
360 Ton
6V2"& 6'Centers
GVa'Posts
No. 5. 7-'o' Clearance
200 Ton
6y*'& 6'Centera
6 Posts
No. 8. 7-0 Clearance
350 Ton,
6V"& 6 Centers
61/-' Posts
No. 9. 7-0 Clearance
350 Ton,
6V2-& 6 Centers
GVsPosts
No. 4. 6-3 Clearance
3^0 Ton
^..Centers
7 Posts
No. 2. 7-6 Clearance
200 Ton
'& 6"Centers
5Tosts
No. 10. 7-0"Clearance
200 Ton
iters
Posts
No. 2. 7-8 Clearance
2$5 Ton
7 Slots, 4?/2 Centers
5Vil'Posts
No. U. 6-'3Clearance
350 Ton
e'Cenfte
•/Posts
No. 1. 5-0 Clearance
350 Ton
6W& 6 Centers
6^1'Posts
Figure 44. (e) Typical Page from Shop Instruction Book
196
QUALITY CONTROL IN PRACTICE 197
showing that the furnace was long enough to permit equilib-
rium to be reached. Presently it became possible to adjust
the temperature to suit the various "heats" of steel.
The furnace unloaded automatically through a low door
and into a cooling oil tank, which was equipped with an
elevator. As it soon developed that this cooling tank did
not provide constant conditions, a lo-ton refrigerating
plant was installed ; also two circulating pumps to keep the
oil bath uniformly mixed. A similar furnace equipment
was used to draw out the hard spots, which were found to
occur from time to time if only the heat treating furnace was
used. After heat treatment and annealing, all shells were
scleroscoped.
As a result of this process it was possible to substitute
finish turning with a very fine feed, instead of grinding, with
a resultant saving of 50 per cent in cost, no loss ballistically,
and no loss from failure to clean up in turning. The loss
from the latter cause, by the method previously used, had
run as high as 20 per cent at times.
Bullets
The first difficulty encountered was to get the required
amount of antimony into the lead, and in a uniform mixture.
This was met by adding the antimony in progressive steps,
one-fourth being put into the lead at each melting. The
metal was then extruded into ^-inch wire and wound on
reels. Each bullet press used 16 reels, and operated at 90
strokes per minute.
The little fins left by the press were tumbled off in slat
rumblers. Naturally some bullets got too much tumbling
and ran out of round. As the elimination of the latter by
means of the usual bean-sorting belt was deemed to be too
slow and costly, a simple, inclined, gravity, separation table
was provided. The bullets were allowed to roll down this
198
THE CONTROL OF QUALITY
QUALITY CONTROL IN PRACTICE
199
©
2!
Is
li
M!
Pi
it.
1 53
200 THE CONTROL OF QUALITY
table and thus classify themselves automatically, as regards
their lack of sphericity.
By such methods as those just related a supply of bul-
lets of the required hardness and roundness was soon ob-
tained. The plant requirements were 60 tons per day, but
they were soon able to supply other plants which had
encountered trouble in making bullets.
Time Fuses
Everyone knows of the grief encountered in making and
loading time fuses, so that a mere statement that the Ameri-
can Locomotive Company produced millions of them suc-
cessfully, with no explosions or injuries to employees, should
be indicative of the care that was taken. They had to find
out that no two lots of powder are sufficiently alike to per-
mit loading for a uniform burning time of 21 seconds + or —
0.2 second. They started without any knowledge of the
business and had to feel their way. But they did know the
principles which must be followed in making anything.
They developed a simple type of powder blender and
created a larger supply of uniform powder. Then they
learned that powder will not pack to burn accurately unless
the humidity of the air is constant, so the air for the loading
rooms was first dried by freezing, and then conditioned to a
standard humidity. In order to make sure of the ±0.2-
second limits in burning time, they paralleled the com-
mercial type of chronographic instrument with a time-
measuring instrument of their own design.
The following item is significant : The second lot of fuses
went wrong in burning time, and the trouble was located
promptly as occurring in one of the 17 separate loading sta-
tions. There were seven men in that room instead of the
usual five. In the hot weather this caused sufficient varia-
tions in humidity to affect the firing time. Would it have
QUALITY CONTROL IN PRACTICE 2OI
been possible to locate such a difficulty promptly without
an efficiently handled inspection service?
Quality First — Then Quantity Follows
Mr. Lassiter believes in inspection, just as he knows that
the first move toward quantity production is to make things
right. In this work the ratio of inspectors was i to every 4
workmen.
The percentage of work rejected in process inspection
varied widely from time to time, as must always be the case.
When the estimates were made for submitting proposals for
the contracts, a 5 per cent loss in manufacture was allowed
for. When starting on production, the inspectors were very
rigid and the temporary rejections amounted to about 19 per
cent. These rejections were held in suspense, however,
until a hospital could be organized for reclaiming some of
the product. This was done, as already stated, so that
rejections could not stop the progress of the flow of work
through the machines. As the work progressed and the
organization learned more about the business, rejections
began gradually to decrease, so that upon the completion
of the job it was found that the total losses from every
cause in the process of manufacturing was only 6 per cent.
The total loss therefore exceeded the estimated loss by I per
cent, but the reduction in cost below the estimated cost
greatly exceeded the I per cent excess of loss.
Mr. Lassiter states:
If we had not provided our enormous staff of inspectors, who
checked each operation on the work as it progressed through the
shops, with limit gages with very close tolerances our loss would
have run into an enormous sum of money. Therefore, one of the
causes of our great success in the economical manufacture of
shells was our large staff of inspectors, the tolerances which we
established on the limit gages and the system which we installed.
202
THE CONTROL OF QUALITY
-
* 1
QUALITY CONTROL IN PRACTICE 203
It is to be regretted that the very many other interesting
features of this work cannot be presented here. The meth-
ods pursued, as shown by the salient features already men-
tioned, strikingly illustrate the premises laid down at the
beginning of the chapter.
Liberty Motors at the Lincoln Motor Company1
The name of Leland has long been associated with the
idea of precision and fine workmanship carried to the nth
degree. Henry M. Leland began his career in the Spring-
field Arsenal, and later extended his experience from firearms
into the field of manufacturing sewing machines and ma-
chine tools. With his son, Wilfred C. Leland, he was one of
the pioneers of the motor car industry. Together they
carried the Cadillac factory to a point where hundreds of
machine operations were held within 0.0005 inch of the
absolute dimensions.
In 1917, they established the Lincoln Motor Company
to build Liberty engines for the United States Air Service.
The first contract, dated August 31, 1917, was for 6,000
engines, and contemplated an ultimate output of 70
1 2 -cylinder engines a day. Henry M. Leland, then 74
years old, made this pledge to General Squier:
It's true that we have no factory now. But we have the know-
how. We will guarantee to build within a specified time as many
motors and of at least as good quality as will be produced in any
existing plant.
The land was acquired and an $8,000,000 plant built and
equipped. This called for over 90,000 special tools, among
which were 6,522 separate designs. Mr. Leland told the
writer that the large number of tools and gages as well as the
time required to get started was questioned by some of the
1 The statements made are taken from "A Pledge Made Good by Deeds," published in
the Detroit Free Press, and are supplemented by data obtained by the author in conversation with
Henry M. Leland during a visit to the Lincoln Motor Company's factory.
204
THE CONTROL OF QUALITY
9-17-20 4 Sheets,
Sheet No. i
LINCOLN MOTOR COMPANY
OPERATION SHEET
PART NAME: HOUSING FOR TRANS. CONTROL LEVER PA^T No. 2002
Kind of
Machine,
Machine Size,
Oper.
Name of
Dept.
No.
& Special Tools
Tool
No.
Commercial
No.
Operation
No.
Req'd
Per Set Up
No.
Req'd
Tools Per Set Up
L. M. Co.
Mach. No.
5
Inspect
M-I9
Bench
i
Gauge for check-
ing depth of
core from un-
finished face
of boss 5 1/2
dia.
11948
10
Snag
K-i6
12
Inspect
M-36
Bench
13
Sand blast
K-i7
IS
Rough and fin-
K-23
#6W&S Screw
ish bore,
Machine
1965
i
i o" Face plate
rough tap
i
Face plate fix-
(Std. W & S)
large hole
ture and lay-
#i96-A
and rough
out
4128
i
i 3/4-i6 Go thd.
and finish
i
Tool block for
gage Go & No
face base
rough and fin-
Go
ish facing
base
4135
i
1.686 Go plug
gage with
handle
i
i. 690 No Go plug
2
Bar for roughing
gage handle
and finishing
i
i. 654 Go plug
inside dia.and
gage with
thread dia.
4U6
i
i. 656 No Go plug
gage handle
I
Gauge for set-
3
#641 Warner &
ting cutters
Swasey flanged
on finish bor-
tool holder
ing bar
4138
i
Shell reamer
I
Alignment bar
1.655 dia.
for i 1/4-1-
i
Holder for shell
3/8-i.6s4and
reamer #8 Std.
i. 686 holes
Tool Co.
with stop col-
lar for testing
i
Floating tool
squareness of
holder W & S
base
4506
I
#M-652
Figure 48. Typical Operation Sheet — Lincoln Motor Company
QUALITY CONTROL IN PRACTICE 205
M-i6 Part 2002
HOUSING FOR TRANSMISSION CONTROL LEVER
1 . Observe for burrs, cracks, sandholes and other casting defects, also
that radii, chamfers and countersinks are as per Blue Print.
2. Observe four 13/32 drilled holes and 3/4 dia. counterbore.
3. Check 8" over all height with Template Tool #4512.
4. Check 10-24 threaded hole with Go and No Go Plug Thread Guages.
The "Go" end of guage must enter to the depth as shown on
drawing. Threads may be passed as O.K. if they are a snug fit on
"No Go" end of gauge.
5. Check 1-3/4—16 threaded hole with Plug Thread Gauges. The Go
end of gauge must enter to a depth of 1/2" as shown on drawing.
Threads may be passed as O.K. if they are a snug fit on No Go
gauge.
6. Check .999-1.001 reamed hole with Plug Gauge.
7. Check 1.654-1.656 diameter bore with Plug Gauges.
8. Check .1 865/^75 diameter reamed hole with Plug Gauge.
9. Check .248/.25O hole with Plug Gauge Tool #4514.
10. Check .748/.75O diameter reamed hole with "Go" and alignment
Plug Tool #4915, also with "No Go" Plug Gauge.
11. Check alignment of .248/.25O and .999-1.001 holes with Tool #4508.
12. Check 1-5/64 counterbore depth and diameter with Template Tool
#45H.
13. Check depth of 3/8 diameter of counterbore with Tool #4920.
14. Check 3/8" thickness of bosses with Tool Snap Gauge .365-.3S5.
15. Check 7/8" dimension faces of bosses with Snap Gauge Tool #4509.
1 6. Check angle and radius on top with Tool #4707.
17. Check .3O7-.3I7 dimension with Tool #4919.
1 8. Check 1-5/8 dimension with Tool #4921.
19. Check 1.810/1.820 dimension with Bar Gauge, Tool #4513.
20. Check 1.624/1.630 dimension face of bosses with Bar Gauge Tool
#5440.
21. Check 7-1/2 dimension, 6-9/16 dimension and 5-7/8 dimension for
location in relation to 1-1/4 DOre with Tools #10540-10541 & 10542.
22. Check 7-11/16 dimension depth of bore to base with Tool #4510.
23. Check alignment of 1.654/1.656 bore with threaded hole and square-
ness with base, the 1.990/2.010 dimension, the .9O5/.9IO dimension
and 1.148/1.154 dimension, with fixture Tool #4507.
24. Check the 13/32 depth of .248-.25O hole with Tool #10775.
Figure 49. Typical Instructions for Inspection — Lincoln Motor Company
206 THE CONTROL OF QUALITY
government inspectors, but that he considered it absolutely
necessary to get things right before beginning production.
The company built up an organization of 6,000 people
and produced 2,000 Liberty motors within one year of its
formation. Before the close of 1918, it produced the largest
number of motors in a single day, the largest number in a
single month, and the largest total rolled up by any manu-
facturer. It completed its final contract 16 days ahead of
schedule, and received the highest commendation for its
motors.
It is stated that the leading English manufacturer, with
j years of aircraft engine experience and 10,000 employees,
was producing at the rate of 50 motors per week. With this
for a background, it is easier to measure the achievement of
the Lelands, for the Lincoln Motor Company, with 6,000
employees and after only i year's development, was pro-
ducing at the rate of 50 motors per day.
Mr. Leland has always been guided by a desire to do
things right. Quality is his hobby and he carries it to the
point of gathering his men together in little groups in the
shops and talking quality to them. Furthermore, he knows
the precision that is necessary for such work and how to get
it, as is evident to anyone who has the privilege of going
through the shops of the Lincoln Motor Company. The
shops show it in their equipment and management. What
is more important, the work in process shows it. Several
illustrations which bear this out are to be found throughout
this book, where they have been placed to exemplify certain
methods. In particular, attention is invited to Figures 6,
8, 12, 15, 48, 49, and 64.
Remington Arms Company — Springfield-Enfield Rifle Production
Our armies in the field never lacked American-made
small-arms and small-arms ammunition, a statement that
QUALITY CONTROL IN PRACTICE 207
hardly holds for any other of their arms equipment. More
than to any other one man, the credit for this fact is due to
the war time Director of Arsenals, Brigadier-General John T.
Thompson, U. S. A. (Retired), D. S. M. He developed the
war plans of the Army Ordnance Department as a result of
personal experience in the Spanish-American War, and had
charge of developing the Springfield rifle, thus gaining
recognition internationally as a small-arms expert. More
recently, in association with his son, Colonel M. H. Thomp-
son, he has brought out that remarkable arm known as the
Thompson sub-machine gun.
I Jj In September of 1914, he told the writer one afternoon,
on the front steps of the State, War and Navy Department
building in Washington :
We are going to be forced into this war sooner or later. I am
going into civil life (he had just re tired as a colonel) to help teach our
people how to make military rifles and rifle-making machinery.
There are not nearly enough military rifles in the world. This
country will be flooded with foreign orders, and these orders can
be used to get the private armories ready to meet our own needs
later on. All our military rifles have been made heretofore at
Springfield or Rock Island in government plants only : and making
sporting rifles is not the same thing as making millions of military
small-arms exactly alike.
So General Thompson joined the staff of the Remington
Arms Company, where he laid the plans for the huge armories
at Bridgeport and Eddystone. Subsequently he went to
the Eddystone plant (the Remington Arms Company of
Delaware) and acted as consulting engineer during the
manufacture of Enfield rifles for the British government.
When the United States entered the war he was recalled to
Washington to take charge of the production of small-arms
and their ammunition.
Some time later came the so-called "broomstick" in-
vestigation by Congress, following the tardy discovery
208 THE CONTROL OF QUALITY
that this country did not have rifles enough to arm our
troops. Of course we did not. Congress had never given
us a chance to have them. To those most interested tech-
nically, the outstanding feature of the investigation was the
discussion of tolerances. Many of the private manufac-
turers wanted tolerances and limits increased — "to get
greater production." General Thompson insisted that the
contrary was true, and that even closer limits would result
in greater production as well as in better arms. Not only
that, but he had the courage to insist on converting the
Enfield rifle to use the better Springfield cartridge ; hence the
Springfield-Enfield. This meant that 14 parts had to be
changed, and the necessary delay in changing tools and
gages had to be accepted. As a further step toward greater
precision, also at the expense of time at the start, the gages
of the different armories and arms factories were brought
into accurate agreement. Was the General correct in his
contention that quality preceded quantity production?
Let the facts speak for themselves.
In the first place, rifles were ready for all troops at least
by the time they sailed for Europe ; and they never lacked
them in the field. Several plants were engaged in making
these arms, but the greatest output was delivered by the
Eddystone armory, where the daily output reached the re-
markable total of 5,000. More interesting still, the number
of rifles finally assembled per man per day started at 40
(which according to the best data available, was formerly
considered a good figure for this rifle), then increased to 120,
and finally reached a figure of 160. As to the quality of the
American rifles thus produced, for this was undoubtedly a
factor in the fine shooting of our troops in the field, let the
Germans before Chateau-Thierry (and elsewhere) tell the
story. According to report, they repeatedly mistook rifle
fire for machine guns and shrapnel.
QUALITY CONTROL IN PRACTICE 209
Quality Is the Road to Production
To summarize: Mr. Lassiter developed an organization
of 40,000 men and produced 25,000 tons of munitions per
day with only 6 per cent of spoilage; Mr. Leland started
with not even the land for a factory, built a plant, gathered
6,000 workers and produced 2,000 Liberty motors to meet
rigid requirements — all in one year; General Thompson
directed the planning which resulted in our enormous war
time rifle production. At the basis of each of these diffi-
cult manufacturing achievements is the guiding principle of
quality control.
14
CHAPTER XIII
MEASUREMENT AND ERRORS
The Evolution of Measuring
Measurement is the foundation upon which the exact
sciences rest. Since the manufacturing arts are — or should
be — but the application of the laws of science in practical
form to meet our daily needs, it follows also that measure-
ment is the proper starting point in the arts just as it is in
the work of pure science. In fact, it has long been recog-
nized that the degree of accuracy with which measurements
are made is the best criterion of progress in the arts. The
process of measuring permits comparisons to be made and
recorded in form for use. By it we may note the differences
and likenesses of similar things, also the degree of such like-
ness or dissimilarity; and it is by such comparison that prog-
ress can be recognized. Some changes show retrogression
and others indicate improvement, but without the ability
to measure them it would be quite impossible to advance
either science or art in a way sufficiently systematic for
practical usefulness.
When the attempt is made to manufacture a number of
like things, some sort of measuring process is absolutely in-
dispensable. Hence the importance of understanding what
the process involves.
The history of the development of the standards of
measuring (used here in its widest sense to include weighing
or similar operations) presents a specially interesting and
fascinating picture of man's material progress.1 It does
1 See further " The Progress of Science as Exemplified in the Art of Weighing and Measuring,"
by Professor William Harkness, U. S. Naval Observatory — presidential address before the Philo-
sophical Society of Washington, 1887. (Smithsonian Report, 1888.)
2IO
MEASUREMENT AND ERRORS 211
not serve the present purpose, however, to digress in that
direction, other than to note the rise of accuracy that has
accompanied the evolution of our present standards. It is
relatively only a short time ago that the most precise and
scientific laboratory methods were quite incapable of real-
izing the accuracy that is commonly attained in modern
shop practice, with much less effort and care. Furthermore
we are able to measure many things today that our forebears
never thought of measuring — and the end is not yet.
There are some features of the evolution of measuring,
nevertheless, which must be considered in connection with
what follows. They are illustrative of the procedure which
must be observed in order to develop in a logical way the
processes of measuring necessary for controlling quality
in manufacturing.
The Selection of Characteristic Qualities for Measurement
Suppose we assume that we have to make a quantity of
articles — bricks perhaps. They are to be as nearly alike as
may be consistent with the commercial restriction of econ-
omy. Let it be assumed also that we have no means or
scheme of measurement. The first step necessarily must be
in the direction of selecting the characteristics in which the
articles are to agree. These characteristics, which deter-
mine the quality of the article, are, of course, sensed and
evaluated by us through the physical means with which we
perceive them. Thus if we were concerned with bricks, the
essentials would be shape or form, size, strength, weight,
surface finish, color, and so on. For practical purposes, we
could get along very nicely without paying any attention to
any of these points except shape, size, and strength, but as
the art of brick-making progresses, the demand increases
for greater uniformity in the less utilitarian and more
aesthetic characteristics.
212 THE CONTROL OF QUALITY
The economist says that manufacturing, as a process,
inhibits making beautiful things.
Individuality is the essence of art; to be beautiful it would
seem that a thing must bear the impress of its maker's personality.
There is little room then for specialization in the making of beautiful
things. If we want the material apparatus of life to be beautiful,
we must be content with less of it; we must choose between a great
many ugly and ordinary things and a few beautiful and unique
things.2
This statement is true only if we are content to permit it
to be true. It should be a pleasant duty for the manufac-
turer to dispel this somewhat common, although fallacious
belief, and the way to do it is by the first step just indicated.
Keen and searching analysis of a product will show its char-
acteristic qualities, some of which contribute to its useful-
ness while others make it pleasing to the senses. Economy
of manufacture reaches its greatest efficiency when every
characteristic is controlled to uniformity with deadly
accuracy, but its product need not be ugly or lifeless,
unless we choose to ignore all but the most utilitarian quali-
ties. If the model is beautiful, its beauty can be repeated
indefinitely with proper care and attention to the pertinent
details — a business in which little things become paramount.
Is not the modern automotive engine an article of beauty?
It is made so by precision manufacturing, which also makes
it an article of commerce. If it could be made, and were
made by the "individualistic" methods of the artist, no
ordinary man could afford to own one ; nor would the auto-
motive art have made such rapid strides.
Standard Samples
Having selected the characteristic qualities which we
wish to have alike in all the articles we are to manufacture,
2 Henry Clay, Economics for the General Reader.
MEASUREMENT AND ERRORS 213
the next step involves the selection of a standard of com-
parison, and this standard must always be some tangible
physical thing. To return to the case of the brick, we prob-
ably should select a brick and say, "This is of the shape and
size wanted. We will call this our standard sample for
shape and size." Then perhaps we might select another as
the standard sample to show the desired color.
As a matter of fact, the method of comparison by using
standard samples is the accepted practice in more than one
industry. In many cases it has to be. Take the matter of
making cigars. The tobacco must be graded in several
ways, as well as by odor (and possibly taste), to secure the
desired bouquet. There is no instrument as yet, to measure
such qualities — nor is there even a classification of them.
Any uniformity that is secured must be by comparison with
some sample or samples arbitrarily selected as standard as
regards both raw material and finished product. Even if
samples are not at hand, they exist in the memory of the
expert whose judgment is relied upon for the grading — and
the statement still holds in principle.
Color is measurable, but the methods and apparatus find
little application as yet outside of the physics laboratory.
The principal industries in which color is a dominating
quality, such as the textile industries and those of similar
type, have made the first important step toward standard-
izing by the adoption of the so-called " standard color card "
(see Chapter XXI), which shows the colors adopted as
standards in the form of classified standard samples.
The selection of a standard sample can hardly be called
measurement. It is rather the first crude step toward
measuring, as we understand the term " measuring" when
speaking of weight or dimension. But it is a very necessary
link in the chain of development. Perhaps it may be asked,
Why carry the process further if such samples will serve the
214 THE CONTROL OF QUALITY
purpose? The answer is best found by considering what
must be assumed when comparison is by standard samples.
Dangers of Standard Samples
The first assumption is that several samples are suffi-
ciently alike for practical purposes. If a number of samples
are available to choose from, this may reasonably be
assumed to be true, but only up to a certain degree of likeness.
Further progress toward general uniformity is blocked
when that stage is reached.
The most dangerous assumption which must be made,
however, is that the standard sample will not change with
time. It is bound to change. That is one of the few great
laws of nature we are sure of. Everything changes all the
time, and very few samples indeed could be found that
would not alter perceptibly — if we had anything to use as a
measure for detecting the change. What is more to the
point, the oftener we use our standard sample in practice,
the sooner does it alter in the very characteristic for which
it was chosen as a standard of comparison. Our old friend,
the brick, would soon wear, and abrade away from its
original size and shape, if we used it to compare with new
lots of bricks. Also, the one we selected as a sample of the
desired color would be quite sure to fade with exposure to
light, or to grow darker from handling. At best, any sys-
tem of uniform manufacturing which is based on standard
samples alone requires that the most unusual precautions
be taken to safeguard the standards. The use of master
gages and the care required in gage-checking may be in-
stanced in illustration.
Measurement by Comparison with a Standard Scale
The next move toward a more efficient means of making
comparisons in order to secure uniformity of product, is in
MEASUREMENT AND ERRORS 215
the direction of greater general usefulness, simplicity, and
permanence of results. Convenience, if nothing else, re-
quires that we obtain a standard of more general applicability.
Suppose we take dimension as the quality to illustrate this.
Once we assume an arbitrary standard of length with a
suitable scale of divisions, we can dispense with the business
of comparing brick with brick, so far as dimension is con-
cerned. In fact, with such a means of measurement, we are
in shape to compare dimensions by themselves, without
regard to the "particular articles whose size is involved.
Thus the idea of true measurement appears, because we are
able to reduce our comparisons to the abstract form of
figures. Any dimension is then expressed in the form :
the given length
The measured length
the standard of length
The point to be borne in mind is that when it becomes
desirable to carry the control of quality beyond the standard
sample stage, the first step is to develop a graded scale which
will permit us to express the measure of the quality in figures.
The latter makes us reasonably independent of the dangers
of standard samples. Needless to say, such a scale itself is
always, in the last analysis, based on some tangible and
arbitrarily selected object which is taken as the common
standard. But the general usefulness and wide applica-
tion of the selected object warrant the precautions neces-
sary to insure permanence. Thus dimension and weight,
the evolution of which has been carried to the practical
limit, may be taken as amply safeguarded. The standards
in this country are represented by certain weights, bars, etc.,
which are kept in the vaults of the Bureau of Standards in
Washington. (See Figure 50.) That is to say, all our meas-
ures refer back to certain objects which are arbitrarily
selected as the standards. The standard of length is now
216
THE CONTROL OF QUALITY
reproducible for any reasonable requirement of accuracy,
because its measure is known in terms of light waves.
Figure 50. The Standards of Weight and Length for the United
States
Kept in the vaults of the Bureau of Standards at Washington, D. C.
Nevertheless it is still true that we cannot get away from an
arbitrarily chosen standard even then, because we must use
a given light wave, such as sodium, and the light must be
MEASUREMENT AND ERRORS 217
made or taken from sources selected as standard, and
measured with a certain definitely selected and calibrated
equipment.
The choice of the fundamental units for measurement
should be made with care. They should be convenient,
should permit accurate comparisons with other quantities
of the same kind (see Professor Harkness as referred to
above), and should permit of accurate comparisons regard-
less of time and place. Scientists ordinarily use as funda-
mental units for physical measurements a definite length, a
definite mass, and a definite unit of time. Most of our
ordinary measurements are based on these units or some
combination of them, e.g., electrical measurements, etc.
Characteristic qualities which are not measured outside of
the laboratory as yet, usually will be found to be measurable
in terms of three constants. The fact that sound is meas-
urable in terms of tone or pitch, amplitude, and timbre indi-
cates a line of attack when the problem arises of measuring
noise due to vibration. The color constants are hue, purity
or saturation, and luminosity or brightness (see Chapter
XXI).
The Measuring Instrument
The final step in the evolution of measurement is the
development of instrumental means for making comparisons.
Their need springs from the desire for greater accuracy,
which requires the use of something that is less subject to
personal error and differences from individual to individual.
This impersonal quality of the instrument flows from the
fact that it is more positive in action than any unaided
comparison by means of our senses can possibly be — a result
that is accomplished ordinarily by enlarging or magnifying
differences in reading, so that errors may be detected with
greater ease.
218 THE CONTROL OF QUALITY
In using a finely calibrated scale, for example, the point
is soon reached where finer readings are impossible, and
further progress toward greater accuracy is blocked. Sup-
pose the scale is a high-grade flat steel scale 6 inches long,
marked off in fiftieths and hundredths of an inch. If this is
Figure 51. Method of Using Hub Micrometer Caliper #241 — -Brown and
Sharpe Manufacturing Company
applied in the attempt to measure a block of steel, say,
about 4 inches long, there will be considerable doubt as to
which of two of the hundredths marks is the closest to the
block's size. If the block is longer, the difficulty becomes
greater; and if it is longer than the scale, an accurate read-
ing is much harder to obtain. The use of a magnifying
glass permits closer reading, but the use of an end measur-
ing instrument, which makes positive contacts in place of
MEASUREMENT AND ERRORS 219
side-by-side comparison, renders easily possible a much
greater precision of measurement.
The use of instruments permits the application of means
for enhancing errors and thus permits closer reading. As
most of the means ordinarily employed for accomplishing
this are illustrated in the following chapters, we may note
meanwhile only some of the features which such instru-
ments should possess.
No instrument is worth using in the factory unless it is
sure to measure more accurately than can be done without
the instrument. At first thought this may seem a common-
place, but it seems so only at first thought, for the reason
that some instruments are apparently more accurate merely
because they are sensitive. An instrument has great sen-
sitivity when it answers (or shows a change in reading) for
a very slight change in the thing being measured or in the
conditions under which the measurement is made. It is
desirable to note this difference between sensitivity and
accuracy, because the two are sometimes confused. A
balance whose indicating pointer answers to a very slight
change in weight, may still be quite inaccurate.
The converse is true also, because an accurate instru-
ment may lack sensitivity. In the latter instance the fact
should be known, because it sometimes happens that the
lack of sensitivity results in a lag. It is therefore important
to know how long it takes a sluggish instrument to show a
correct reading. But in order to know what degree of
accuracy an instrument is capable of showing it must be
possible to check its precision, and this requires a more
exact standard for checking purposes. It is for this reason
that emphasis is laid on the necessity for control centers or
laboratories for the control of the quality concerned. Thus
a later chapter (XVII) deals with an ideal control center for
dimension, as typical of any su decontrol centers.
220 THE CONTROL OF QUALITY
In this discussion of instruments it will be noted that no
attention is being paid to certain general requirements for
measuring apparatus with which everyone is familiar, such
as ruggedness, precision, facility for making direct meas-
urements without corrections, general suitability to the
requirements of the work, and so on.
Danger of Overgraduation
It is desired, however, to direct attention to some of the
qualities in such instruments which are frequently over-
looked, and thus make accurate measurements out of the
question. One of these oversights, as a case in point, is
what may be termed an " overgraduation " of the instru-
ment. One of the great dangers faced by the technician,
as by everyone else, is that of fooling one's self. It is vi-
tally necessary in manufacturing to be sure of the facts —
especially as to measurement. Therefore an instrument
which is calibrated to permit closer readings than it is ca-
pable of making is to be avoided with care, or at least used
with a knowledge of its probable errors.
To illustrate — the chief engineer of a large concern was
criticized because his plans said that certain dimensions, on
tools, should be held within .0002 inch, the specific charge
being that such precision was uncalled for and would lead
to unnecessary cost in the tool-making shops. He answered
by asking "What do you think that requirement for .0002
inch means?" Of course, he was told that everyone as-
sumed it to mean .0002 inch, as stated. Much to their sur-
prise he replied— " It does not. I intended it to mean what
our tool-makers think is .0002 inch. In other words, what
I am after is the degree of accuracy in workmanship which
our tool-makers produce when they think they are working
to within .0002 inch of the stated dimension. If you think
that is the same as .0002 inch, suppose you check their
MEASUREMENT AND ERRORS 221
work with our Pratt and Whitney measuring machine. If
you do, you will find that what the tool-room thinks is a
precision of .0002 inch is actually over twice that, although
they are perfectly sincere in their belief. They are doing
the best they can with the instruments provided, which
happen to be calibrated in ten-thousandths. These instru-
ments may be capable of such accuracy, but as used in our
shops, no such result is obtained."
Every once in a while a factory is found whose drawings
call for exceedingly close adherence to the absolute dimen-
sion, although the shop is not equipped, except by the mark-
ings on the instruments, to work to any such degree of accu-
racy as is prescribed. Usually all hands are quite sincere in
believing that they attain the requirements stated on the
drawings, but they merely fool themselves. Why do so,
however, when it is so easy to possess the truth?
The Need of a Final Check
Not very long ago the chief inspector of a factory whose
work required a high order of accuracy for a very special
sort of work was asked to produce his final standard of di-
mension. He pointed out the usual standards supplied
with micrometer calipers. His questioner said, "But I
asked you to show me your final standard — your ' court of
last appeal.' ' The chief inspector blushed and said, "We
haven't any!" Later he added in self-justification, "I've
asked for gage blocks several times, but they never gave
them to me." Does your chief inspector, by any chance,
happen to be in the same fix?
By the same token it is equally erroneous practice to
expect accuracy when the instruments provided do not per-
mit of close enough reading. A pressure gage with a 2 -inch
dial, calibrated by 5-pound intervals, will hardly permit the
process to be held to closer than 5 pounds. Yet just such a
222 THE CONTROL OF QUALITY
case came to light during the recent overhauling of a process
in which a close adherence to a given standardized pressure
was vitally important for securing a uniform product from
that process. It is questionable as to which is worse — a me-
chanic who thinks he is doing accurate work because an
Figure 52. Setting a Johansson Adjustable Limit Snap Gage by Means of
Johansson Gage Blocks
inaccurate instrument says so, or one who is trying to do
accurate work without a clear reading instrument to guide
him. Neither condition need exist, which makes their
occurrence all the more lamentable.
The Choice of Instruments
In step with the preceding is the failure to realize that
practically all instruments are less precise over a part of
MEASUREMENT AND ERRORS 223
their range than they are for the greater part of their range.
Furthermore, at the part of the range where greater errors
occur the measurements are likely to be subject to greater
variations under different conditions of use. This is true in
marked degree for the smaller readings of instruments which
are inherently afflicted with an initial friction. It is true
also for instruments whose design and construction involve
backlash; and, naturally, the maximum errors may occur
where the backlash may develop to the greatest degree. As
an example of error resulting from initial friction, consider
a balance. It may be extremely accurate for large weigh-
ings, but will show very large errors indeed for weighings
made at the threshold of its scale. Accordingly the smaller
weighings should be made on a balance of smaller total ca-
pacity as the smaller readings are thus expanded to a size
that is perceptible. The conclusion is inevitable, that the
instrument should be chosen with reference to its capa-
bility to meet the requirements of a given situation. It
must not be expected to meet all requirements. You cannot
weigh everything with one huge pair of scales. But the
way to determine the suitability of the instrument, or to
select a suitable instrument for a given purpose, is to be pre-
pared to check the work of that instrument — by some
superior method of measurement, which is many times more
accurate than the instrument which is being checked.
Otherwise you cannot be sure of your facts.
The Precision of Measurement
In developing a method or process of measuring it was
observed that the first step involves the use of an arbitrarily
selected standard for comparison. Presently a point is
reached where observations fail to agree, and this point fixes
the limit of precision obtainable by such method. Further
improvement is to be sought through devising a scale of
224 THE CONTROL OF QUALITY
more general applicability which permits not only of stating
measurements impersonally in the form of abstract figures,
but also securing an additional degree of accuracy in most
cases. This method also soon reaches its limit of precision,
and further progress toward more exact measurement must
make use of still more impersonal methods by means of in-
struments. While this last step usually gains much greater
fidelity to the absolute measurement, nevertheless it too
reaches an ultimate limit of precision beyond which meas-
urements of the same thing under like conditions are not in
agreement. This situation follows an earlier stage where
measurements by different observers, working under the
same or slightly different circumstances, do not check.
Thus Langley, in the discussion of small irregularities of
his bolometer records of the solar spectrum, said :3
When we approach the limits of vision or audition, or of per-
ception by any other of the human senses, no matter how these may
be fortified by instrumental aid, we finally perceive, and always
must perceive a condition, a condition still beyond, where certitude
becomes incertitude, although we may not be able to designate
precisely where one ceases and the other begins. This is always
the case, it would seem, on the boundaries of our knowledge in every
department, and it is so here.
Inevitably, then, a certain critical point is reached for
any given set of conditions, where errors enter, and this is
entirely apart from the ever-present assurance of occasional
accidental errors. Of course we know that errors are bound
to occur — the theme of our study has been throughout that
quality is varying continually — consequently the readings
of our measurements of quality will vary.
The term "precision" is a confession that absolutely
correct measurement is impossible of realization. Accuracy
means exact conformity to the absolutely true standard.
3 Joel Stebbins, "Observation vs. Experimentation," Science, January 13, 1922.
MEASUREMENT AND ERRORS 225
Absolute accuracy implies freedom from error, hence for
practical purposes we are forced to speak of the degree of
accuracy rather than of accuracy itself. "Precision" is a
shorter term than "degree" or "rate of accuracy," and
means the same thing. Consequently precision is a per-
centage of the measurement. Thus, the precision of Swed-
ish gage blocks is stated as, say, one hundred thousandth of
an inch per inch of length; and, strictly speaking, we should
always state precision in that form. The attitude of the
physicist toward these terms is :
When the true value is known the ' ' Accuracy ' ' may be expressed
as the difference between the experimental quantity obtained and
this true value. Since, however, the exact or true value is seldom
known, the accuracy of the result cannot be stated, and it becomes
the more imperative to have methods of estimating the precision
measure or reliability of the result of a series of observations.4
Precision of Workmanship
Now, just as there is a limit to the precision of measure-
ment for any given situation, so is there a limit to the pre-
cision of workmanship that is possible for any given process
or operation. And this limiting precision in manufacture
follows after and is dependent upon the attainable precision
of measurement of the work produced by said process,
whether the measurement be made by a highly developed
instrument or by mere visual comparison with a standard.
What is true of the possible precision is equally true of the
precision that it is sensible to use commercially, for cost will
enter as the determining factor in the selection of the degree
of accuracy best suited to a particular case. It is usually
true, however, that a decidedly higher precision can be
obtained with little effort, if the effort is properly made.
Whether the attempt to increase precision should be
4 " Precision of Measurements," by Professors George V. Wendell and W. L. Severinghaus of
Columbia University.
15
226 THE CONTROL OF QUALITY
made is a matter of business judgment, and calls for a sen-
sible decision. A military gun stock demands much closer
fidelity to accurate dimension than does wooden furniture,
but it would save a deal of profanity if desk drawers did
not stick. The stores are full of all kinds of goods that indi-
cate the same situation. It is a mistake to say that any-
thing is good enough, for there must be some one dimension,
for example, that is best suited to any special case. If the
article, as designed, is best suited to the job, the manufac-
turer's constant endeavor should be to obtain a closer and
closer adherence to this ideal standard. This means the
refinement of manufacturing through the reduction of errors
—an undertaking that should be inaugurated by a study of
errors themselves.
The Theory of Errors
The most valuable thing to realize about errors, so it
would seem, is that they always have a tendency to occur.
They follow the general rule that it is easier to be bad than
it is to be good. Their number can be reduced only by the
vigilant use of foresight, care, and thoroughness. More-
over, like a snowball rolling downhill, they tend to
accumulate others of their own kind; so that an ounce of
prevention is worth many pounds of cure.
A knowledge of the theory of errors is so important in
accurate physical measurements that considerable atten-
tion has been given to it, and several substantial literary
contributions have been made. The application of their
conclusions are too much confined to the physics laboratory,
however, and should be more generally understood by man-
ufacturers. The physicist starts off by making a distinction
at once between mistakes — that is, mere blunders — and
errors. In the factory, mistakes are the order of the day,
and their best prevention lies in the direction of checks by
MEASUREMENT AND ERRORS 227
independent methods of one sort or another, as has been
indicated early in this work.
Individual vigilance and the habit of doing everything in a
careful and orderly manner are the only means of reducing such
inaccuracies to a minimum. It is often highly advisable to run
some rough independent check experiment or to test the final re-
sults with common sense to see that no gross blunder has been
committed.5
Professor H. M. Goodwin, in his "Precision of Meas-
urements and Graphical Methods," classifies errors as deter-
minate errors, whose value can be determined and their
effects eliminated, and indeterminate errors. He classifies
determinate errors as:
1. Instrumental errors, due to faulty adjustment or
construction of the measuring instrument.
2. Personal errors, due to the " personal equation" of
the observer.
3. Errors of method or theoretical errors, due ordinarily
to using an instrument under conditions for which
its graduations are not standard or correct.
»
It will be observed that some errors lead to incorrect con-
clusions, in spite of the fact that several measurements may
be in agreement. Thus if the instrument is out of adjust-
ment, or if the observer is, by nature, generous in his read-
ings, so that he constantly errs on the high side of the
measurement, or if the instrument is standard at 68° F.
but is used at 90° F., the measurements may in all cases
agree and still all be in error.
As to indeterminate errors — accidental or residual-
Goodwin says:
Experience shows that, when a measurement is repeated a
number of times with the same instrument and by the same observer
5 " Precision of Measurements," by Professors George V. Wendell and W. L. SeverinRhaus
of Columbia University.
228
THE CONTROL OF QUALITY
under apparently the same conditions, the results usually differ in
the last place or sometimes last two places of figures. Thus in sO
simple a measurement as the determination of the distance between
two lines with a scale graduated in millimeters, successive measure-
ments will not agree to one-tenth millimeter if fractions of a milli-
meter are estimated by the eye.
Such errors have been found to follow the law of chance,
which may be plotted graphically, as shown in Figure 53,
from the equation:
in which y is the frequency of occurrence of an error of
magnitude x, h is a constant related to the reliability of the
observations and called the "precision index," e is the Na-
perian logarithmic base (2.7183), and ir is the constant,
3.1416.
It will be observed from the curve that:
First — Small errors occur more frequently than large ones ;
Second — Very large errors are unlikely to occur;
Third — Positive and negative errors of the same numerical
magnitude are equally likely to occur.
V7T
Figure 53. Probability Curve, Showing the Frequency of
Occurrence of an Error
MEASUREMENT AND ERRORS 229
When Theory and Practice Differ
This law assumes an infinite number of observations,
but is reasonably true in most cases for a comparatively
small number — hence its value as a guide. It presupposes,
however, that the observer is trying to attain absolute accu-
racy as nearly as may be; and, in the case of factory work-
manship, this is where practice frequently departs from
theory. Being sane, the workman will do what he believes
to be to his own best interest. Consequently if there is a
penalty attached to spoilage of work, he will deliberately
keep on the safe side, since in that way he has a chance to
repair his errors.
Consider for a moment the case of a 2-inch shaft which
has a tolerance of .0004 inch. If the limits are set
o
inch (i.e., allowed .0004 inch over and o under dimen-
sion) the greater part of the work will hug 2.0004 inch,
because the operator will stay on the safe side and work
toward the full dimension. If that is what is desired, well
and good; otherwise the tolerance should be split up to
allow for this tendency. In closer work especially, it would
be better practice to set the limits as - - inch instead
.0002
OOO2
of : : inch, or ± .0001 inch. The probability and
chance would thus favor securing more work to the desired
ideal of 2.0000 inch.
If all errors were equally distributed as to size and occur-
rence, plus or minus, they would cancel each other to a large
extent. In the factory they do not do so, but accumulate
too rapidly for comfort. There are several ways in which
this occurs, and happily there are several ways to meet the
situation.
230 THE CONTROL OF QUALITY
The Chain of Inaccuracy
First, there is what may be termed a "chain of inaccu-
racy" due to slip in the transfer of measurements. The
master or reference gage is not quite like the model, the
reference gage template is not quite like the gage, and so on.
This error is negligible when a very precise method of
measurement is available for checking purposes.
The Chain of Wear
Then there is a chain of wear, resulting in systematic and
progressively increasing error. Granting the availability of
more precise control apparatus, the remedy for such errors
also is checking with sufficient frequency. As to the me-
chanical side of intentionally lessening wear, there is room
for considerable discussion and the resulting conclusions are
widely applicable — to tools, to measuring devices, and to
the product itself. Professor John E. Sweet was the great
apostle in this field as in many other practical problems.
In 1876 or before, he advocated the use, and pointed out the
advantages of equal length wearing surfaces; viz., the first
"straight-line" engine had a cross-head and guides of equal
length, which, after years of use, showed practically no wear.
In 1903, he stated, " Things that do not tend to wear out of
true do not wear much." This principle is worthy of much
consideration. In connection with it the present tendency
toward the use of gages with wider and larger anvils — or
gaging points — may be noted although it is true the use of
such gages is to be attributed in part to other causes than
minimum wear, inasmuch as they tend to give more accu-
rate results, by lessening the chance of applying the gage at
an angle.
Incidentally, it may be noted that we may profitably
extend the above principle to include the idea of even wear
for a number of like parts. Thus if everything wore at the
MEASUREMENT AND ERRORS 231
same rate, progressive errors would accrue, but their effect
would be less, due to the averaging process going on, and
thus tending to hold to uniformity. Take a multicylinder
automotive engine — if one of the several piston gudgeon
pins is a poor fit, all will tend to wear out of adjustment.
Suppose, even, that all the pins are fitted with beautiful
exactness by hand-reaming, but that some are larger than
others. Will they wear evenly? Will they continue to re-
main in adjustment as perfectly as if all were almost exactly
alike? Furthermore, not only does the idea of even wear
bear upon this matter of uniform dimension, but also upon
the question of uniform hardness, uniformity of material,
quality of finish, and so on.
The Cure for Errors
The cures for most errors will suggest themselves as soon
as a systematic effort is made to locate and determine their
causes. Whenever possible they must be hunted down and
stamped out at the source. Some errors may be reduced
by putting processes under uniform control, and in particu-
lar by averaging the errors through spreading them out
evenly. The experience of Whitworth in creating the first
accurate surface plate reveals a valuable lesson. Taking
three plates, alternately comparing them by contact, and
then scraping off the high spots, he used the errors to de-
stroy each other and thus created the basis of all our machine
shop precision — a true plane surface, relatively speaking.
The concluding observation to be drawn from the study
of measurement and of errors, beside the very obvious neces-
sity for care and thoroughness as to every detail, is the need
of providing control apparatus for the qualities with which
we are concerned. To be effective, such apparatus must
be safeguarded, and even then it is useful only in so far as its
use and the conditions surrounding its application are freed
232 THE CONTROL OF QUALITY
from possible causes of error. The ideal dimensional con-
trol center or dimensional laboratory to be described in
Chapter XVII, is to be considered as a guide to what, in
principle, any such control laboratory should be, regardless
of the quality concerned. Dimension has been chosen as
the type merely because dimensional control has been car-
ried to a higher degree of precision and its apparatus is more
highly developed than is the case with most other qualities
— such as color, for example. This condition, it seems prob-
able, will be modified as time goes on, and more and more
qualities are brought to the same state of accurate control.6
The fact that means do not exist at the moment for
measuring some of the characteristic qualities with which
industry is concerned, merely serves to indicate the direc-
tion in which the start should be made toward conscious
improvement of these qualities. If industry makes the
demand on science to develop principles, practices, and
equipment to meet its requirements, the needful things that
are lacking at present will be supplied.
6 The principle of measurement, in fact, is being extended to evaluate the functions of
management. See an editorial by L. P. Alford in Management Engineering, Nov. 1921.
CHAPTER XIV
QUALITY DEFINED— THE IDEAL STANDARD
Characteristic Qualities of Product Must Be Known
Thus far we have considered the subject of quality in its
various relationships and have traced the basic influence of
measurement in order to prepare the way for a better under-
standing of quality itself. We are now in a position to ask
— "What is it that constitutes quality?"
The first answer is that each attribute or characteristic — •
shape, dimension, strength, finish, color, and so forth —
which defines one kind of article is a quality of that article.
The more definite and specific we make the descriptions of
the dominating qualities, the more accurately do we under-
stand just what the product is intended to be, and, inciden-
tally, wherein it is to differ from other articles of the same
general class of goods. To state a quality at all accurately,
it must be compared with some arbitrarily selected standard.
For example, we might say a rod is to have length, but we
have not described the rod as regards dimension until we
state the relationship between its length and that of some-
thing else. We can secure a more exact definition of the
dimensional quality of the rod if we say that its length is to
be the same as that of a sample rod which has been selected
as standard. But, as a matter of fact, in this case the
comparison would be made with the well-accepted standard
of dimension and the length stated in standard units of feet,
inches, or both, depending on convenience.
This well-known and seemingly elementary example is
simple only because we have a thoroughly established and
well-known method of comparison or measurement for
233
234 THE CONTROL OF QUALITY
dimensional quality; but what about some of the other
qualities? With respect to color, for instance, there is, as
yet, no accepted method of analysis and comparison with a
standard. To say an article is to be painted red is nearly as
loose a definition of color quality as to describe dimensional
quality by saying that a rod had length — because there can
be an enormous number of tints and shades of red. In the
absence of a color scale for numerical comparison, we are
reduced to saying that the color will be like a given standard
sample. We must also take precautions to see that the
color of the sample itself does not change in the course of
time, and thereby carry the product away from the standard
as originally set.
The question of whether such qualities as color can be
reduced to a basis of definite measurement with the same
ease of treatment as dimension must be deferred, at this
time. Meanwhile, dimension will be used chiefly to illus-
trate the discussion as it proceeds. It should be borne
in mind, however, that the general principle applies to the
treatment of all qualities, that no quality can be described
without comparing it to some standard — which process is
measurement — and that the application of the idea of meas-
urement must not be confined to dimension alone. This is
one excellent reason why every industrial executive who
is interested in the subject under discussion should be
familiar, in a general way at least, with the principles under-
lying the precision of measurement and the theory of errors
—to secure an important attitude of mind and a necessary
sense of discrimination, of proportion and perspective.
Quality Varies Continually
One of the first things that this knowledge will reveal is
that there is no such thing as an absolutely accurate measur-
ment. No matter how carefully the unknown is com-
QUALITY DEFINED— THE IDEAL STANDARD
235
pared with an accepted standard, errors are bound to creep
in; and very shortly a certain critical point is reached be-
yond which these errors can be reduced only through the use
of extreme precautions, if at all.
This thought leads at once to one of the most important
Figure 54.
Checking Johansson Adjustable Limit Plug Gage with Gage
Blocks Mounted in Holder
conceptions of what constitutes quality, an idea that must
be kept in mind throughout the subsequent study of the
control of quality, namely, that quality is a variable.
Quantity relates to the product en masse, and in this sense
is abstract and impersonal. Quality, however, is different
for each separate article produced. Hence the quality of
the factory product varies from piece to piece. This fact
must be clearly appreciated before an attempt is made to fix
236 THE CONTROL OF QUALITY
upon the standards of quality desired, or to take up the con-
sideration of the organization and arrangement of manu-
facturing equipment and methods most suitable for securing
these desired standards with greatest economy. In prac-
tice, the degree of quality varies continually from the
standard desired. Further, the degree of quality varies
with respect to time, in the sense that the attempt to make
many things alike results inevitably in quality gradually
slipping away from this desired standard as the work pro-
ceeds. This tendency of quality in all its forms to vary and
change is always present as a potential force, and acts ex-
cept in so far as it is held in check by external means pro-
vided for control purposes.
Development of the Design
With the preceding in mind, it should be apparent that
the study of the control of quality must begin with an in-
tensive study of the product, from which should result what
is ordinarily called the "design." Now the production of
almost anything, let alone making accurately uniform arti-
cles, presupposes a definite standard, usually represented by
drawings, specifications, or a model; but preferably by all
three. This standard is purely ideal and cannot be repli-
cated exactly in quantity, because the absolute is unat-
tainable. Nothing ever was made in exact accordance with
the ideal design, or ever will be.
Under given conditions, the time and cost of production
in quantity varies with the degree of accuracy to the ideal
standard that is required. Hence the art of the designing
engineer and of the production engineer is called into play to
fix upon manufacturing standards, which vary from the ideal
by certain differences or allowed errors. This process sets
limits which constitute a tolerance for the actual fabrication
of the work. Returning to the example of the rod, the com-
QUALITY DEFINED— THE IDEAL STANDARD 237
plete design would state its length as so many inches plus or
minus certain stated limits, or allowable errors.
By way of summary, suppose now that we reverse the
preceding order for the purpose of more clearly developing
the following definitions:
1. The complete design (which will be referred to simply
as the " design ") is the exact description of the product, and
therefore sets forth in detail (with allowed variations from
exact measurements) the characteristics of all essential
qualities, i.e., the manufacturing standards. This pre-
supposes, of course, that the product has been thoroughly
analyzed and that a list of the desired quality characteristics
has been made.
2. The " ideal standard" is the bare design without the
allowed variations, and consequently is merely the outline
or shell of what the ideal product would be if quality were
not a variable.
3. The " theoretical standard" is what the ideal stand-
ard would be if it were designed with a view solely to obtain-
ing the best article for the purpose for which the product
is intended without regard to cost; i.e., it is the 100 per cent
standard for the class of articles to which the product be-
longs.
It is hardly proper to call these concepts by the formal
name of " definitions," as they have no special significance
except as a means of avoiding misunderstanding of the
following consideration of some ideas about design that are
essential to our purpose.
The Theoretical Standard
The principal value of the theoretical or 100 per cent
standard, to which attention was directed in Chapter II, is
to provide something to which we can refer in improving the
product, as time goes on and such improvements are com-
238 THE CONTROL OF QUALITY
mercially practicable. The latter are always desirable, if
the selling price is not increased thereby. The manufac-
turer who has a well-rounded out idea of what his product
would be if it were the 100 per cent article of its class, is
better able to guide future progress, also to know in what
directions such progress should take place. Incidentally
he may avoid the predicament of the modest advertiser who
illustrates a "perfect" product, only to announce incon-
sistently with each new season, an improvement of an al-
ready perfect thing — and this to a purchasing public which
is becoming increasingly critical and whose discrimination
is ever more intelligently applied.
No mention has yet been made of one of the greatest ad-
vantages in having a theoretically perfect standard to guide
the development of a design — namely it will help to coun-
teract the danger of copying the errors of the past, by
blindly doing things as they have been done before.
Professor John E. Sweet 1 expressed the idea as follows :
Whoever designs a new machine or an improvement on an old
one conceives of some feature or ruling object of his design or some
feature that is an improvement on present practice and neglects the
other features — simply follows common practice without consider-
ing whether the other features may not be as open to improvement
as the special feature he is working out. . . . And it all comes
from following habit, without reason ... it is only those who
come to think of the best way who are likely to do the best; and
those also who think that the "best way is bad enough."
It happens too often that betterment of the product is
blocked by prohibitive cost, simply because the designer
either was not informed as to the probable direction such
improvement would follow, or failed to take it into consider-
ation in designing earlier models. With a wider and
farther-seeing perspective, he would have been able to shape
'John E. Sweet, "Things That Are Usually.Wrong."
QUALITY DEFINED— THE IDEAL STANDARD
239
his design and make his factory arrangements so as both to
meet the present needs and to be adapted readily for an im-
proved product when the time is ripe for such refinement.
The Ideal Standard
The outline or skeleton design, without statement of the
permissible variations, is here called the "ideal standard"
—it is ideal in the sense that it cannot be realized exactly in
practice in spite of the fact that it is the desired standard.
As a matter of fact, one article might be made so very
nearly like the ideal that the errors could not be detected by
the available means of measurement, but its cost- 'would
Figure 55. Use of Johansson Gage Blocks and Sine Bar to Check Taper of a
Milling Cutter Shank
240 THE CONTROL OF QUALITY
place it beyond the pale of commercial possibilities. A
great telescope is an example of the sort. But the construc-
tion of two such articles alike to the same degree of exact-
ness would markedly increase the effort required, even if it
were possible. The manufacture of many such articles
would increase the problem enormously, and any attempt
to avoid errors wholly would certainly fail. On the other
hand, a relatively slight releasing of the requirements for
accuracy renders the task much simpler, so that it becomes
a true manufacturing proposition. In fact it is possible to
set a very high standard, provided the conditions of the
problem are appreciated and proper precautions taken at
the start to meet them.
To admit that the ideal or desired standard cannot pos-
sibly be realized, may at first appear like an attitude of
hopelessness, but that is not the fact. All progress requires
that we have in mind some rather definite ideals, which we
are trying to realize. It detracts in no degree from the im-
portance of the effort to realize these ideals, if it is admitted
that at best it will result only in approximation to them.
The fact remains that before we attempt to make anything,
we should know what we are trying to make ; and however
thoroughly we may know this ourselves, it is equally im-
portant that we describe it so clearly that all concerned in
the work may know what we wish done. The more def-
inite, exact, and complete this preliminary description
which makes up the skeleton design, the greater will be the
economy of effort, materials, and time in the work of con-
struction.
Progress Toward More Exact Designs
The increasing tendency toward the more specific
and complete definition of qualities is easily traced. It is
not necessary to hark back very far in the development of
QUALITY DEFINED— THE IDEAL STANDARD
241
engineering to reach a point where the design was developed
in large part as the work progressed. There is a quite
credible story to the effect that early wooden shipbuilding
was carried on in two stages of hull construction. The
Figure 56. Set-Up of Johansson Blocks for Checking Taper of a Special Plug
Gage
shipbuilder first erected the parallel middle body, after
which the construction of the bow and stern was taken up
by a ' ' bow-and-stern gang." Such a gang traveled from
yard to yard, sized up the job as it stood, perhaps made a
rough sketch on a piece of plank, and with this general
understanding proceeded to erect a bow and a stern to
suit the work already in place. This method certainly
16
242 THE CONTROL OF QUALITY
had the advantage of simplicity, to say nothing of reducing
overhead expense.
An examination of the early designs and construction
plans in any of our oldest machine shops, shows nearly the
same degree of rough-and-ready methods. There is much
sad experience to be read between the lines in following up
the evolution of the present-day drawing from its crude
start, through the later addition of more and greater refine-
ments, until we arrive at the finished plans of the modern
highly organized drafting-room. Notice that the tendency
is toward an ever-increasing exactness and completeness in
showing the details of what is wanted. We have learned, in
short, that it is cheaper to make our mistakes on paper than
to have to correct them in the materials of construction as
the work progresses.
The same development is to be noted in the specifica-
tions or written descriptions that supplement the drawings,
although not to the same extent, for even today most
specifications contain ambiguous language. The wise
manufacturer, while preparing his estimates, will be careful
to iron out as far as possible, before starting work, such ex-
pensive little pitfalls as "small surface scratches on this
part will be permitted in the judgment of the inspector," or
" variations in other dimensions will be allowed, but the
work must be to the purchaser's satisfaction."
Changes in Design Must Be Avoided
This lesson of past experience in design and manufac-
ture has been paid for dearly. It teaches quite clearly that
the time to make up our minds, as well as to do a lot of
thinking, is before commencing to make chips. But even
with the full knowledge of this principle before us, is it
rigorously applied? In the majority of enterprises it is not
so applied, and the particular way in which it is violated
QUALITY DEFINED— THE IDEAL STANDARD 243
most seriously may be summed up by the word ' ' changes ' '
—the great killer of economy in manufacturing, whether it
be of ships, automobiles, firearms, or what-not.
The design should be made with an open mind and the
designer given the widest latitude while he is designing.
Further, a method of attack has been indicated that
should make future changes in the details of the design a
matter of orderly development and progressive improve-
ment. Curiously enough, however, this freedom of action
must later give way to its exact opposite. Once the design
is completed and manufacturing started, the designer must
"sit tight."
Usually the production man himself is alive to the
serious delays and losses caused by changes in design made
after production has begun; but ordinarily the changes
originate from a source outside of the shops. Improve-
ments in design are rapid, and the temptation is great to
make changes that better, or seem to better, the product.
Consequently after all the trouble of getting out carefully
detailed plans, after making manufacturing arrangements
to carry them out, and even after material is in process, a
rumor comes into the shop that such and such a thing is to
be changed. The result is uncertainty and the beginning of
confusion. Then comes the order for the change, which is
usually made without the degree of care that was used in
presenting the original design, for as soon as the making of
changes begins, many ill-considered changes are suggested.
The general effect, then, is to mix experimental work with
production, instead of separating it out of the routine manu-
facturing shops as is done in any well-regulated factory.
When Improvement Changes Should Be Made
Some years ago in a large plant making a high-grade car,
changes in design were being made with such frequency that
244 THE CONTROL OF QUALITY
the effect on production finally demanded the installation of
a special system for handling these changes. It is true that
the art was moving forward with rapid strides. Without
doubt business considerations warranted the prompt adop-
tion of some of the new improvements. On the other hand,
the model was changed formally each year, and most of the
improvements should have been collected systematically
and saved for incorporation in the next season's car. The
chief engineer, however, was busy improving the car from
day to day, while the factory output was unnecessarily
slowed down and the work made much more costly to the
purchasing public.
It is frequently a matter of considerable doubt whether a
radical change in appearance is advisable, even when the
change is made for the ostensible purpose of modernizing
the design. A ''quality" article, for example, has been
developed in accordance with an ideal — otherwise it would
not be high grade. In the course of time, it acquires in the
eyes of its friends a distinctive but often intangible some-
thing which makes it different and gives it a distinctive
character. The time inevitably comes when there is a
temptation to bring the design up to date, but long before
the attempt is made, the necessary changes should be
mapped out along lines consistent with the basic ideal of the
design. Then the product can be modernized gradually
without losing the resemblance to the original which is as-
sociated with a reputation for satisfaction. The ideal on
which the design was made and on which the success of the
business is founded should never be destroyed.
Every Cause Has Several Effects
Some changes must be made. In such cases the greatest
care and attention should be applied to see that they are
put into effect so gradually as not to interfere with efficient
QUALITY DEFINED— THE IDEAL STANDARD 245
production any more than is absolutely necessary. It be-
comes the duty of the production man to impress that fact
strongly upon the designer. Very often the fact alone must
be accepted, because the sources of loss are so intimately
interwoven with the processes of production that separating
them out is too difficult to be worth while. It is a perfectly
safe statement that any change costs money in an amount
entirely out of all proportion to the direct work involved.
Finally, there comes to mind the principle laid down by
Herbert Spencer— " Every cause has more than one effect."
You may accomplish a slight local improvement, but you
should not forget that you have altered other conditions as
well. The very thing that improves one part of the design
may affect other parts adversely.
Precautions to Avoid Changes
Changes in work due to errors in design are almost bound
to occur, but every effort should be made to minimize them.
Careful work in the drafting-room will decrease such errors.
In small accurate work it is often helpful to make drawings
to a magnified scale, or even to make a large-scale model.
Many engineers hold that our drafting-room practice has
reached "such a degree of perfection that the making of a
model is unnecessary. There are some cases, however, in
which a model would seem to be advisable, if for no other
reason than to assist the draftsman's eye to a more readily
comprehended picture of the relations of the component
parts in a complicated assembly.
Further, in every sort of work which permits of making a
model or sample, it should be noted that every practicable
effort should be made to avoid changes occasioned by mis-
takes in the designs, by the obvious process of eliminating
the necessity for such changes before beginning manufactur-
ing operations. The way to discover and eliminate the
246 THE CONTROL OF QUALITY
ORDER FOR CHANGE IN DRAWING
Operation Mark Date
Tool Name
Description of Change
ison for Change - -.
Preliminary Action by Order Dept. on Outstanding Orders
Final Action by Order Dept. (taken after completion of change)
Drafting Room to check details of other tools that may be affected
by the above.
Suggested by Approved PWOCH8 IN01NIM
Classification of Change Accepted
PRODUCTION ENGINEER
Copies to
Process Engineer.
Chief Draftsman.
Order Superintendent.
Figure 57. Order for Change in Drawing
Form used at Remington armory, Bridgeport.
QUALITY DEFINED— THE IDEAL STANDARD 247
' ' bugs " in a new design of product is by careful and thorough
work in the experimental and research department. The
latter department will pay for itself many times over by
providing a smooth path of development and co-ordination
between the engineering department and the producing
shops. Without this procedure, experimental work, which
has to be done somewhere by someone in any case, is
mixed with production, and the resulting great waste is
quite likely to be lost sight of because no ordinary cost or
production system will reveal it.
CHAPTER XV
THE WORKING STANDARDS
The Compromise in Setting Tolerances
Granted that the ideal standard cannot be realized in
practice because quality varies continually, practical manu-
facturing or working standards must be determined. These
vary from the ideal standard by certain differences or allowed
errors, and by adding them to the outline design or ideal
standard, a complete design is obtained.
The use of the plural in referring to the working stand-
ards is intentional, since many differences from the ideal
design will occur in the shops, and from these must be se-
lected the variations that are to be allowed in the finished
article. This process of selection will fix the working stand-
ards. Needless to say, the determination of permissible
errors or variations is not always a simple matter, but rather
a task calling for the exercise of unusual discrimination and
good judgment. The designer, especially when freed from
responsibility for costs, will endeavor to have these varia-
tions as small as possible. He will insist on a close approxi-
mation to the ideal. On the other hand, the man who is
responsible for production will reason that the time and
cost of manufacturing under certain conditions will increase
with the degree of accuracy required; so he naturally will
seek to obtain the largest possible allowed errors.
If the situation is dominated by either of the above-
mentioned views, trouble is very likely to ensue. The unre-
stricted designer usually demands unnecessarily high stand-
ards, government work sometimes furnishing an extreme
example. Contrariwise, the unrestricted production man
248
THE WORKING STANDARDS 249
usually tends too strongly in the opposite direction. As is
usual in such cases, the truth lies somewhere between the
two extremes; hence the necessity for someone to apply
good common sense in the selection of the working stand-
ards. The best compromise is to be had, usually, when the
standards are selected by a well-balanced committee on
which engineering, production, and inspection are repre-
sented.
Raw Material Standards
The design states the kind of material from which a part
is to be made, and specifies the required conditioning of the
material (such, for instance, as heat treatment), also the
dimensions and form desired, the finish of the surface, and
frequently the requirements to be met in assembling and
functioning in service.
The selection of suitable raw material is a matter of the
utmost importance, in which the governing considerations
are uniformity, ability to meet service requirements, and
ease of working in the manufacturing process. First cost is
a subordinate consideration in nearly every case, in com-
parison with uniform behavior in manufacturing and uni-
form performance under working loads. A typical instance
is furnished by the motor industry, where a very low-priced
car has been built of the highest percentage of alloy steels.
There are better places for economy than in the raw
materials.
The determination of working standards for raw ma-
terial has received a great deal of attention in recent years
and need not be dwelt upon here. The preparation of
standard specifications for various kinds of material (and
for the different grades of each kind) by some of the great
railroads and manufacturing plants, by various governmen-
tal departments, and by the American Society for Testing
250 THE CONTROL OF QUALITY
Materials, has made available a large body of technical
data arranged in systematic form. It is only necessary to
select the specifications of a suitable material in order to
have the limiting conditions known.
In the case of metals, especially, the data are quite com-
plete. The permissible variations in the chemical constit-
uents are set forth, together with the limiting conditions
for pertinent physical characteristics. In the case of other
kinds of material, the essential characteristics are mentioned
and limits frequently stated. It would seem, however, that
much progress remains to be made in specifications for many
of the usual non-metallic materials, such as wood and fibrous
materials, principally in the way of information to be
collected and systematized through the application of the
microscope and the binocular microscope and other scien-
tific apparatus not applied as yet to any great extent in such
work. The use of micro-photography in the metallographic
study of metals has developed a wide and fruitful field. A
similar development will follow the application of these
methods to many of the non-metals.
Conditioning Standards
The determination of working standards for what, for
lack of a better term, may be called the "conditioning of
material" is not so simple a matter. A part made from
soft or untreated steel in order to permit economical ma-
chining or working, subsequently may require some form
of hardening or tempering in order to suit it to the duty it
must perform in the assembled mechanism. In fixing the
limiting conditions the scleroscope or Brinnell test is
available, or perhaps a file test may answer. Another ele-
ment is introduced, however, if appreciable distortion
occurs in individual parts to such an extent as to require
straightening. If straightening is necessary and the func-
THE WORKING STANDARDS 251
tion of the component part is an important one, some sort
of special test should be specified, of a kind to demonstrate
that the part will pass the maximum demands that are likely
to be encountered in service.
Important springs should have maximum and minimum
weighing tests to be made in a special fixture, and should be
set up for a specified period of time and to a given displace-
ment without more than an allowed set.
The time and order or the particular stage of manufac-
ture at which any such special tests should be applied may
possibly be of importance, hence the value of listing these
tests on operation sheets and route cards, just as if they
were ordinary manufacturing operations. Special tests
should be provided for important non-metallic materials
requiring special treatment or conditioning prior to or dur-
ing manufacture. The kiln drying of high-grade lumber is
a case in point, where the binocular microscope may some-
times be used to advantage.
Standards of Finish
There is considerable laxity in determining standards for
exterior finish. Probably the fact that more attention is
not devoted to setting standards of finish is due as much to
commercial considerations as to the difficulty of reducing
the degree of finish to measurable and tangible terms. The
manufacturer selects a finishing process sufficiently econom-
ical for the purpose, and then strives to get as good a finish
with that process as is reasonably possible, on the general
assumption that the shinier or prettier an article looks the
more it will appeal to the customer's eye. Unfortunately
there often is good reason for this attitude, many purchasers
prefering a polished surface where a good coat of paint over
a rough surface would be more durable and less expensive to
maintain. In competitive businesses, however, it is often
252 THE CONTROL OF QUALITY
wise to give the purchaser what he thinks he wants, even if it
may not be the best thing for him. Note, for example, the
face of a pressure valve flange. It has been faced off in
the lathe with a roughing cut, followed by at least one finish-
ing cut. Then one or two small circular grooves are cut for
the gasket to be squeezed into, in order, to secure tightness.
And yet one rough turned facing would accomplish the pur-
pose better by providing a multitude of grooves. This is
only another instance of perpetuating the errors of the past
by thoughtless imitation.
Oftentimes the allowable gradations in the hue, shade,
or tint desired for a colored surface are left to the judgment
of the production man or the inspector. Sometimes a sam-
ple is furnished which is to be approximated as nearly as
possible commercially. In such cases, it is well to obtain
the advantage of manufacturing to limits by providing
samples showing all extremes that will be allowed. When
standards for smoothness of finish are to be set, the same
practice should be followed, i.e., the use of standard samples.
Preferably a few sample parts should be used for small work,
some showing/acceptable work, and others showing work not
quite good enough to be passed. In other words, the sam-
ples should be selected close to the limiting conditions
desired. This general process is the best that can be
adopted until more and more of such qualities are reduced
to a basis of numerical measurement — a result that is sure
to come as the qualitative refinement of our industries
progresses.
Standards of Dimension and Form
In its ultimate effect the establishment of practical or
working standards for dimension and form covers the most
important and far-reaching subject of all. It is of the es-
sence of that great branch of repetition work which is known
THE WORKING STANDARDS
253
254 THE CONTROL OF QUALITY
as "interchangeable manufacturing," which will be consid-
ered in greater detail in the following chapter.
In determining the working standards for dimension and
form or shape, the relation of each part to the other com-
ponent parts of the mechanism must first be considered.
The ideal standard, as described in the preceding discussion,
fixes one size and shape, and it may be assumed that the
designer in articulating the mechanical movements involved
provided for the necessary strength and other physical
qualities required. These qualities have to do with what
might be termed the "main body" or "interior" of the
parts, whereas for present purposes we are concerned with
variations in the outer surfaces or exterior of a given part,
with special reference to the similar surfaces of the other
parts of the mechanism with which the given part works.
We know that these outer ends of the dimensions, so to
speak, are going to vary, and therefore we must determine
the limiting variations in the fit of the one part to the
other parts that will still secure a proper functioning of the
entire mechanism. In this way we can settle upon the
greatest distance from edge to edge of related parts, as well as
the smallest separation or play that is permissible, thus de-
termining the maximum and the minimum allowance for fit.
With the figures just referred to as a guide, the next
step involves the determination of the permissible variations
in the dimensions of each part, considered separately, and
these maximum permissible variations fix the limits of the
dimensions, the difference between any set of limits being
known as the "tolerance."
Allowed Variations Defined
The terms "allowance," "tolerance," and "limits"
have long been a part of the technical nomenclature of
repetition and interchangeable manufacture, but are only
THE WORKING STANDARDS 255
recently beginning to receive the detailed study they merit.
It is not the purpose of this book, however, to do more than
trace their application in the development of working stand-
ards of dimension, as a resultant of the basic idea that
quality is a variable.1
The following definitions are taken from the "Progress
Report of the Committee on Limits and Tolerances in
Screw Thread Fits, to the Council of the American Society
of Mechanical Engineers," as published in the Journal of
that Society for August, 1918:
Allowance — Variation in dimensions to allow for different
qualities of fit.
Tolerance — The allowable variation in size equal to the dif-
ference between the minimum and maximum limits.
Limits — Two sizes expressed by positive dimensions, the
larger being termed the maximum, and the smaller, the minimum
limit.
In some cases, as in mating threaded parts, or in moving
parts which must not touch each other (such as in turbines,
pumps, and so on), an actual clearance must be provided
for.
Clearance — A difference in dimensions, or in the shape of the
surface, prescribed in order that two surfaces, or parts of surfaces
may be clear of one another.2
The opposite situation arises in certain cases, when parts
are fitted with a "pinch."
Necessary Precautions
The process of working from the allowance to the
determination of tolerances and limits involves a nice ap-
plication of judgment (both to the theory of the design and
1 For an interesting discussion of this subject the reader is referred to a paper on " Gage Limits
in Interchangeable Manufacture," by Colonel E. C. Peck in the October, 1919, issue of Mechani-
cal Engineering; also to some notes on the "Theory of Tolerances and Comparison of Symmetri-
cal and Asymmetrical Systems," (Ibid., July, 1919), together with a very practical comment
thereon by J. Airey (Ibid., October, 1919).
2 British Engineering Standards Association definition.
256 THE CONTROL OF QUALITY
to the current shop processes), which should consider es-
pecially the following:
1. The effect on the allowance for one dimension, of the
errors accumulated from the variations in dimension of any
other mating part or bearing point, if any. For example,
if we are determining permissible variations in the diameters
of two mating gear-wheels, we must consider the effect of
the play to be allowed in their supporting bearings.
2. The effect of wear of the parts after the mechanism is
in use in service. The tolerances should be proportioned to
favor the parts that probably will wear most rapidly, with
the object in view of insuring uniform and even wear.
3. The relative difficulty of manufacturing the parts con-
cerned. The parts should be favored whose manufacture
involves the use of mechanical operations or processes that
are the most difficult to hold to dimensional accuracy.
4. The effect of wear of cutting tools, dies, fixtures, jigs,
gages, or other special manufacturing equipment, in order
to secure the greatest economy in their cost. The most ex-
pensive equipment should be given the longest wearing life.
The above process will give a set of limits for all im-
portant dimensions of the finished parts only, so that a proc-
ess, somewhat similar in principle, must be gone through
with to determine similar limits for the vital dimensions of
unfinished parts after each mechanical operation involved in
the process of manufacture.
If " close work," requiring a high quality of dimensional
accuracy, is involved, it is specially important to consider
the possible effects of errors accumulated from process to
process. This suggests, at once, the importance of a well-
worked-out list of mechanical processes to be used in making
any given part, which list should show not only the sequence
in which the work will be processed ordinarily, but also the
alternative arrangements of operations that may be used in
THE WORKING STANDARDS
257
Figure 59. Reading Inside Micrometers after Measuring Inside of Cylinder
Brown and Sharpe Manufacturing Company.
17
258 THE CONTROL OF QUALITY
case shop exigencies indicate the desirability of rearranged
routings. In this way we are enabled to foresee what ac-
cumulated errors may arise in the case of emergency changes
in routing, and, being forewarned, to guard against them.
The selection of locating and reference points is closely
inter-related with the above. Working from holes provides
a safe method when too much wear is not involved. The
same scheme may often be simulated by the use of tempo-
rary holes or by adding locating lugs which are cut away after
they have served their purpose.
It is sometimes desirable to minimize the effect of ac-
cumulated errors by distributing them — a procedure known
in precision of measurement as "solving the problem for
equal effects," i.e., the errors allowed in each variable are
calculated to give the same effect in the final answer.
Dimensional Working Standards
After the limits have been worked out, they should be
shown as a part of the working drawings. If these draw-
ings are then furnished to the shops as the final references
for production purposes, they become the practical working
standards for dimension, as the term is used herein. With
highly skilled operators, working on processes inherently ac-
curate, these plans may be all that is necessary. Where a
relatively small number of parts are to be made, and es-
pecially in large work, it would not be the part of good sense
to supply the shops with anything in addition to the plans
as the standards. In many cases all the information
required may be set forth on the working drawing for the
finished part, including both the limits for the finished work
and the amounts of stock to be allowed for grinding,
turning, and similar operations.
In passing from the classes of work just indicated, to the
quantity production of interchangeable parts of small size,
THE WORKING STANDARDS 259
we enter a field where economy of manufacturing indicates
the desirability of increasingly specialized equipment, such
as special cutting tools, holding devices, and gages. In such
cases if working plans are supplied to the shops at all, it
usually is best to do so only as a matter of information and
to substitute for adjustable precision measuring instru-
ments fixed-dimension gages of various sorts which have the
limiting dimensions worked into them in physical form.
It is safe to say that the next few years will see a great
extension of the use of limit gages in American factories,
with corresponding benefits as regards both quality and
economy. The introduction of a gaging system, however,
will cause new conditions to arise which will involve special
problems peculiar to the system in question. It is a matter
in which some very small things become paramount, and
hence require the most careful and systematic attention, as
will be discussed in a later chapter. For the present, at-
tention is invited to the fact that when gages are used, as
just stated, they constitute the working standards, and the
plans cease to function as the working standards.
It remains to be said, for completeness, that it may not
be considered desirable in certain cases to incorporate, in
the gages as furnished to the shops, the maximum limits
that may be used while still assuring proper functioning of
the parts after their assembly into the mechanism. This
practice of making the shops work to closer limits than the
inspectors are permitted to pass finds its justification some-
times in a longer useful life for the gages. The practice,
however, rests chiefly on the idea that it may help to reduce
the losses in spoiled work by permitting the salvage of
some of the parts that are bound to fall outside of the limits
given to the factory, while also encouraging the cultivation
of greater accuracy in the operators. This savors somewhat
of the theory of the traffic laws that have given rise to signs
260
THE CONTROL OF QUALITY
THE WORKING STANDARDS 261
reading "Speed limit 15 miles," which one so often sees out-
side small towns. The sign probably is put there in the
hope that the motorist will reduce his speed to 25 or perhaps
20 miles, depending on the degree of hopefulness of the
authorities, but usually he keeps his foot on the accelerator.
Now the machine operator will answer to the same psy-
chological reactions if he knows there are two standards in
use, unless and only in case conditions are so arranged that
he is made to realize it as being to his best interest to stick
to the limits given him. It may be necessary, in fact, to
keep the larger limits a secret, which involves using them in
a separate salvage department. As a rule, however, it
would seem to be better practice, with the possible excep-
tion of certain very special cases, to try for the same result
by the more direct route of frankly making known the
maximum permissible variations, and then taking proper
precautions to safeguard these limits.
Assembling Standards
Theoretically, in strictly interchangeable work it should
not be necessary to check up the fit of parts after they have
been assembled, except possibly as an additional assurance
that the constituent parts of the assembly are within the
allowed tolerances. As a practical proposition, however, it
is often advisable to provide for the verification of certain
important functioning dimensions in subassemblies, as,
for example, when parts are assembled on a tapering shaft,
or where the effect of improper fits is multiplied by a long
arm (as in the case of a long rod with a short bearing on one
end, working under conditions that make side play of the
other end of the rod undesirable) . In work made partially
interchangeable, such assembling standards should be pro-
vided for, by setting limiting dimensions for the assembled
parts in the case of all vital dimensions.
262 THE CONTROL OF QUALITY
Final Tests
After the parts of the mechanism have been assembled,
a final test, or series of tests, should be made, simulating the
maximum demands to be made on the mechanism after it is
placed in service. Strength tests are, in themselves, the
maximum limit — an armature will spin at twice its rated
speed without bursting, or it will not; a derrick will lift the
specified overload without permanent set, or it will not; a
gun barrel will stand a heavy proof charge without bursting
or bulging, or it will not. Thus, in such tests there is but
one limit. But, in many of the final tests and trials used to
demonstrate standards of quality, the same idea of permis-
sible variations in quality (expressed in terms of limits) finds
application, whether these tests are to be applied to the
complete assembly or to some subassembly. In the testing
of the trigger pull of a rifle, for example, the limits may be
set at given minimum and maximum pulls stated in pounds ;
or the economy and the speed regulation of a motor may be
demonstrated by trial to be within certain limiting per-
centages.
Final tests must be made under as nearly the same con-
ditions as the mechanism will encounter in service when
reasonably possible. If this cannot be done, the test con-
ditions should always vary from service conditions in a
known way and to the same degree, i.e., all mechanisms
should be tested under like conditions.
Recapitulation
Working from the theory that quality is a variable, and
hence that the ideal standard or design cannot be reproduced
exactly, the conclusion is reached that practical working
standards should be supplied to the factory in form to indi-
cate the limits within which it is desired to have the work
made. These practical standards should cover the various
THE WORKING STANDARDS 263
matters affecting quality, such as dimension, finish, and
so forth; and all should be formulated with a reasonable
mental attitude that makes provision for variations, because
they are bound to occur. With this clearly understood, we
are in a position to take up the consideration of the steps
necessary to secure results in the factory as nearly as may
be in accordance with the standards of quality desired, it
being noted in this connection that the above principles
apply regardless of what the product of the manufactur-
ing operations may be. Metal work has been used
merely because it is more inclusive and complete as an
illustration.
CHAPTER XVI
REPETITION MANUFACTURING
Uniformity for Economy
The thought of quality as something that is continually
shifting and varying, when translated into form for use in
the factory, gives rise, among other things, to the whole
subject of tolerances and limits. Thus it becomes ap-
parent that no design is sufficiently complete for intelligent
manufacturing purposes unless the limits for each and every
governing characteristic are known. Furthermore, just as
a clear appreciation of this idea of variations is essential in
repetitive work, so also is it desirable that the principles of
repetition manufacturing be understood.
True manufacturing involves making a quantity of the
same article, uniform within limits. In this respect it is the
diametrical opposite of art work. The manufacturer seeks
to make things alike, but the artist strives for the creation
of things that are different and individualistic. The first
system is far less costly; and therein lies the real value of
manufacturing, because its product is thereby made more
generally accessible to mankind. We make things alike
because it is cheaper rather than for the sake of having them
alike, although many secondary advantages accrue from
this property of uniformity. In fact, it is so very much
cheaper to make things alike that the manufacturer can
afford to incur very heavy expenditures in preparation alone
—merely for getting ready to manufacture. Because he
does incur this heavy initial expense, and because all his
later operations are more or less fixed and governed by these
preliminary arrangements, it becomes of serious importance
for him to make them correctly in the first place.
264
REPETITION MANUFACTURING 265
Uniformity of Product Means Uniformity Throughout Production
In making these preliminary arrangements the manufac-
turer must not consider the preparatory work in a general
way as affecting the finished product, but rather in its rela-
tion to, and effect on, each individual process. This raises
a point that is frequently lost sight of in repetition manu-
facturing, namely, the continuous manufacture of one product
of uniform and standardized quality implies an equal uniform-
ity and standardization at all stages of its production. Why?
Because it is cheaper to manufacture in this way, and it is
cheaper to manufacture in this way because large errors in
the earlier stages of the work require correction later on,
when it is not so simple to bring the work into line. Con-
sequently each component process should be considered as a
separate production point for the continuous manufacture
of uniform quality. If one process is left as a loophole for
large variations to enter, throughout the remaining processes
a constant struggle must be engaged in to correct them.
Obviously, this attention to uniform quality must be ex-
tended to include the raw material itself, clear back to the
original source of supply.
It will prove useful in what follows to note incidentally
that excessive variations in the finished product mean simply
that there are variations in the earlier processes. For differ-
ences in the completed articles are the algebraic sum of the
errors made in all of the earlier manufacturing processes.
Noting for the moment that interchangeable manu-
facturing is only one of the several classes of repetition
work, let us now use it as a specific example in studying
some of the interesting phenomena of such work.
Interchangeable Manufacturing
I have before me an Ingersoll watch of the Reliance
model, also an Eversharp pencil. Both are products of
266 THE CONTROL OF QUALITY
standard quality and must be made by the methods of inter-
changeable manufacturing. In other words, the attempt
is made, in manufacturing a quantity of any one of the com-
ponent parts, to make all of these individual parts so nearly
alike that any one of them may be used in the assembled
mechanism with the assurance of subsequent successful
functioning. Except for the crystal, the springs, and per-
haps one or two minor parts of the watch, there is no special
object in having any of the parts interchangeable after the
mechanism has been sold and placed in use, as there is little
likelihood of any of them having to be replaced. In fact,
if all our mechanisms could be proportioned and built as
perfectly as the "wonderful one-horse chaise," so that all
the parts would wear evenly and all become worn out at the
same instant of time, the only value of interchangeability
of parts in service would be in the rather remote case of an
accident. Nevertheless, there seems to be a somewhat
popular misconception that parts are made interchangeable
for the express purpose of securing the possibility of replac-
ing parts, whereas the real purpose is to secure certain
economies in manufacture that are possible only by the
methods of interchangeable manufacturing. The inter-
changeability of parts in service, while often convenient and
frequently important, follows as a by-product quite second-
ary in value to the primary purpose, which is economical
production.
The Industrial Revolution
Now let us see wherein making parts interchangeable
decreases manufacturing costs. When Adam Smith wrote
the "Wealth of Nations" (1776) he described the principle
of the division of labor by citing the well-known example
of the manufacture of pins, pointing out that if the work was
divided up into several operations so that one man concen-
REPETITION MANUFACTURING 267
trated on, say, heading pins, and so on for each worker, the
number of pins produced per man would very greatly exceed
the production of any one man making complete pins, with-
out this analysis or dividing up of the work. Thus there
results a saving or conservation of the experience and skill
gained in doing the same thing over and over, and we recog-
nize the outstanding feature of the great change in produc-
tion which is known as the " industrial revolution" — a
method that has almost entirely replaced the earlier house-
hold and handicraft methods of manufacturing.
The Mechanical Revolution
The application of labor-saving machinery to produc-
tion, known as the "mechanical revolution," is closely re-
lated to the industrial revolution, because as a very early
result of the division of the labor of manufacture into small
parts or operations, special labor-saving devices and ma-
chines were developed. Usually, in order to apply such
devices effectively, the work obviously must come from one
operation or mechanical process to the next operation in
pretty much the same shape and size. Thus the division
of labor involves making things very nearly alike, and in so
doing makes it possible to realize economy of effort through
the greater production secured. Furthermore, the smaller
subdivision of work permits an unskilled worker to acquire
quickly the skill necessary to accomplish his part of the
work. Incidentally, the fact that pieces are more nearly
alike means that substantially the same thing is done to
each piece at each stage of its manufacture, in order to ad-
vance it to the next operation. This must be easier than
if each piece required special treatment. Incidentally, a
better quality of work results, and quality tends to become
more uniform; and from uniformity marked commercial
advantages accrue.
268
THE CONTROL OF QUALITY
Afterward, and when, as an eventual working out of the
division of labor, certain processes are combined in an auto-
matic or semiautomatic machine, of course it becomes still
Figure 61. Height Gage Used with Johansson Blocks
more necessary to have the work more nearly exact to given
dimensions and shape. While the division of labor, how-
ever, leads to making parts alike, the parts do not necessarily
have to be so much alike on this account alone as to permit
REPETITION MANUFACTURING 269
full interchangeability, nor even such partial interchange-
abilty as will allow assembling by selection of parts that fit
each other well enough to function properly.
Economy in Assembling
The greatest economy, however, in making things suffi-
ciently alike to be interchangeable comes from the possibility
not only of the more rapid assembling of component parts
into the complete mechanism, but also of the use of less
skilled labor for this work. A workman of very ordinary
experience and skill can be taught to assemble all, or a por-
tion, of a complicated mechanism, provided he can use the
parts just as they are supplied. If, on the other hand, the
parts must be selected in order to secure an assembly that
will function properly, much more skill is required; and if
fitting of parts in the form of doing work on them in the
assembling room is necessary, then in all probability a very
high order of mechanical skill and experience is requisite.
Take the watch for example. Like all mechanisms contain-
ing a source of power, there is a means of regulating the
rate of power discharge of the mechanism, within limits.
While the limits may appear to be narrow, they are great
enough to take up the differences in action due to the dif-
ferent combinations resulting from assembling parts which
have been passed on to the assembling rooms as within the
allowed variations. Certainly such assembling is not a very
serious undertaking. But suppose the parts, or some of
them, required additional treatment in order to fit them
and adjust them into the mechanism in a way to insure
proper working. What sort of labor would be required
then, and how long would it take to complete an assembly?
Also, would the product be improved by the hand-fitting of
parts which would be required?
A small article like a watch is not an extreme illustration
270 THE CONTROL OF QUALITY
of this truth, as can be seen very easily by observing the
strenuous work involved in the regulation of inaccurately
punched plates in a ship or other steel structure. The work
required to get the plates into position for bolting-up and
riveting is greatly in excess of the effort required to punch
them accurately in the first place; and if the holes are
enough out of alignment to require reaming to a larger size,
still more unnecessary labor is expended, extra sizes of rivets
must be kept on hand, and so on. Furthermore, and most
important, any such corrective process is not the best
thing for the structure itself.
Naturally these same considerations govern in all lines
of manufacturing. There is a field, no doubt, for hand-
work in special and distinctive bodies for high-grade motor
cars, whereas hand-work on the parts of the engine (which
have been machined already to a high degree of accurate
conformity to the ideal standard) is not only out of place
from the standpoint of economy, but actually detrimental
as well. It is very rarely indeed that anything is improved
by tinkering.
The Work of Simeon North and Eli Whitney
It would be rather interesting to know just when and
why there arose the present general misconception that
work is made interchangeable for the simple purpose of re-
placing parts, inasmuch as the early exponents of the system,
like Simeon North, Eli Whitney, and their contemporaries,
certainly understood exactly what the principle of stand-
ardization really meant.
"Simeon North — First Official Pistol Maker," a memoir
by S. N. D. and R. H. North, was published in 1913. It is
a most interesting contribution to our knowledge of the early
development of interchangeable manufacturing in America.
This investigation has made it quite evident that North, for
REPETITION MANUFACTURING 271
reasons of economy, lack of skilled men, and similar consider-
ations, which had nothing to do with interchangeability for
its own sake, was willing to incur heavy initial expenditures
and delays in order to achieve an ultimately better result.
In a letter to the Secretary of the Navy dated November
7, 1808, he makes this significant comment:
I find that by confining a workman to one particular limb of the
pistol until he has made two thousand, I save at least one quarter of
his labour, to what I should provided I finishd them by small quanti-
ties; and the work will be as much better as it is quicker made.
His contract of April 16, 1813, with the United States,
for 20,000 pistols, contains the provision: ". . . the
component parts of pistols, are to correspond so exactly
that any limb or part of one pistol, may be fitted to any
other pistol of the twenty-thousand." But a later contract
for carbines (dated May 2, 1839) added to the requirement
for uniformity of parts and interchangeability the provision
that this must be done "without impairing the efficiency
of the arms" — showing already an evolution in preci-
sion requirements for better functioning of the complete
mechanism.
This early contribution to the economy of manufacture
is well illustrated by Simeon North's biographers, when they
quote Daniel Pidgeon's reference1 to the Connecticut man,
whose remarkable blending of the engineer and the mechanic
has done so much for American industry:
His method of attacking manufacturing problems is one which,
intelligently handled, must command markets by simultaneously
improving qualities and cheapening prices.
Continuous Standardized Production
In the early part of the present chapter, interchangeable
manufacture was referred to as one sort of repetition manu-
1 In "Old World Questions and New World Answers," by Daniel Pidgeon.
272 THE CONTROL OF QUALITY
facturing, and was used as an example to illustrate the
features that are generally applicable in repetition work.
In explanation of the statement, attention is invited to the
fact that interchangeable work applies particularly to a
mechanism built up of standardized parts in such a way as
to permit disassembling if need be. For even pieces that
are riveted together may be taken apart. On the other
hand, the same idea of standardized work applies in all
kinds of manufacturing. It is, in fact, at the root of suc-
cess in all production, and for precisely similar reasons.
The most inclusive definition of modern manufacturing,
from this aspect, is that it is the continuous production of
articles whose qualities have been standardized within given
limits. Since errors in the finished product mean errors all
along the line of manufacture, it follows as a corollary to
the general rule that the unfinished articles should be simi-
larly and at least equally standardized at each stage of their
manufacture.
The first need of standardized quality arises at the very
beginning, with the recovery of raw materials from nature.
Everything in nature varies, from place to place or from
season to season, and the variations are large, except in
unusual cases. It makes no difference whether we speak of
wheat, cotton, wool, iron ore, lumber, or what-not. It is the
duty of the basic industries which prepare these materials
so that they are suitable for use, to reduce the variations as
much as is reasonably possible.
Resort must be had first to separation of the raw mate-
rial into classes or grades. This, in a sense, divides the dif-
ferences up, and thus reduces them for practical purposes.
As a second step in the ordinary procedure, two courses are
open and usually both must be used. Differences due to
impurities may be removed, and differences in size, shape,
and so on rectified, and here both chemical and physical
REPETITION MANUFACTURING
273
processes come into play. Any remaining variations from
lot to lot of the same material may often be rectified and a
larger body of uniform material produced by using the
method of mixtures. Finally the need of some sort of
conditioning process may be indicated, before the material
is ready for use in the factory.
Vital Importance of Uniform Quality in Raw Materials
The importance, in repetition manufacturing, of raw
material of uniform character and condition cannot be
overstated. Very often_the lack of such uniformity is the
IS
Figure 62. Set-Up of Johansson Blocks to Check Drill Jig
274 THE CONTROL OF QUALITY
root source of the subsequent trouble encountered in trying
to make a uniform product. What is the value of accurately
standardized heat treatment, if each lot of steel is different in
behavior from its predecessor? It is cheaper in the end to
start with material of uniform character.
It may seem a far cry from steel to fibers and dyestuffs,
but the principle just stated holds generally. If textiles are
manufactured from fibers whose affinity for dyes varies ma-
terially from lot to lot, and if each lot of dyestuff is of dif-
ferent hue and strength, the work of producing articles
uniform as to color-matching is a great deal more difficult
than if the variations are reduced or removed by careful
standardizing of the raw materials.
One often hears complaints in the factory about lack of
uniformity and standard quality in raw materials, but what
a pitiful admission of weakness it is to throw the blame on
the producer of the material. He can hardly be expected
to know the needs of the consumer, and if the man who uses
the material will make his exact needs known, he is pretty
apt to get what he is after. Competition will gradually
force the producer of material into line, even if he is reluc-
tant to attempt finer standardization. But to be in a posi-
tion to call for better materials, the manufacturer must first
know what qualities he requires and why. Also, once the
required standards are set, means must be provided for
measuring the incoming deliveries, for it is useless to set
standards unless one is prepared to enforce them.
The factory should be protected by filtering out unsuit-
able material at the receiving platform of the stockroom.
This is the first place for the application of control labora-
tories of various sorts: physical, chemical, metallurgical, or
perhaps some new kind invented for the needs of particular
plants. The control of quality begins at this point, in so far
as the individual factory is concerned.
REPETITION MANUFACTURING 275
Continuous Processing
Perhaps the next logical class of industries, after the
basic order of raw material preparers, is that large group
which deals with the assembling of various raw materials by
methods which involve more or less continuous processing.
Paper-making and textiles, for example, are highly stand-
ardized as to their final products, which must be suited in
each case to meet some definite need of the consumer and to
render a definite service in relation to price.
Now, as we have seen already, a uniform product is most
economically obtained by making all the contributory proc-
esses equally uniform, as nearly as may be with consistency
to the requirements of manufacturing economy. Weaving
a piece of cloth on the loom is a continuous process of assem-
bling various standardized elements or like parts. It hardly
can be called interchangeable work, because there is no
possibility of interchanging parts after the goods are com-
pleted. Yet the general principle of standardization of the
process holds — it is advantageous commercially and techni-
cally to hold the process to a uniform standard within speci-
fied limits or allowed variations.
The fact that the errors are worked into the goods might
seem on first consideration to make a marked difference
between this type of manufacturing and so-called inter-
changeable work. In one sense, this is so, but from the
wider viewpoint, identical principles apply. Thus costs
would be raised to prohibitive levels if we tried to eliminate
all broken threads, all missing picks, and all other defects —
even if we could do so. The only practical way to handle
the situation is, first, to define what kind of errors and what
percentage of each kind are to be allowed for a given stand-
ard of quality, i.e., to set limits; and second, gradually to
raise these standards in step with the improvement of proc-
esses, increase in workers' skill, and so on, that will flow
276
THE CONTROL OF QUALITY
Figure 63. Special Milling Fixture Using Johansson Gage Blocks for Locating
Purposes
REPETITION MANUFACTURING 277
from attacking the production problem with quality as our
basic criterion.
Duplicate Manufacturing
There is a large class of manufacturing, known usually
as " duplicate manufacturing," which is distinguished by
the use of standards (usually of size, material, and form) for
the product. Screws, nails, and many other kinds of hard-
ware are typical. The ordinary uses of many of these
articles do not require such close limits as the manufacturer
chooses to follow. It is but another case where economy of
manufacture, resulting from the division of labor and the
use of labor-saving machinery, dictates the adoption of the
methods of standardized repetition work. It is cheaper
and the product is not only more useful but in every way
better, because quality yields to control when processes
are standardized and quality held uniform — within limits.
Partial Interchangeability
In the case of assembled mechanisms the various classes
of repetition work differ among themselves, chiefly in the
degree of accuracy with which the component parts are
made. Thus, in passing from work that requires fitting to
assemble, we find a sort of transitional stage before we reach
the ultimate form of complete interchangeability. This inter-
mediate class of work is known as "selective assembling."
The parts are accurate enough to require no hand-work to
prepare them for assembling, but are not sufficiently stand-
ardized to permit using any part in any assembly. Resort
must be had to selecting parts that go together properly.
This style of work should never be resorted to except
when the processes will not permit of the precision neces-
sary for complete interchangeability, which sometimes oc-
curs; it is a mistake in this case, just as it is generally wrong
278 THE CONTROL OF QUALITY
to assume that loose fits make for easy assembling, except
when very few parts are mated. A long series of inter-
related parts requires close work if the assembling is to be
done without adjustment. Such considerations at once
require modification of the generally accepted idea that low
cost and easier manufacture are best obtained through al-
lowing the greatest freedom in the fit of mating parts with-
out interfering with proper functioning.
The advantages of true interchangeability may be ob-
tained in selective assembling if the selected parts are first
segregated into classified sizes, thus simulating inter-
changeability by making groups of parts that assemble
without selection.
Production of Machine Tools
In concluding this chapter it should be noted for com-
pleteness, that the manufacture of machine tools follows the
general rule, but occupies a middle position. Economy of
manufacture requires the use of the methods of interchange-
able manufacture in the tool-making factory, whenever the
quantity made warrants its adoption. The great standard-
ized markets of this country, by providing conditions that
permitted the use of such methods, are largely responsible
for our advanced position in machine tool development.
The fact that the plants which are the users of the ma-
chine tool maker's product must standardize their proc-
esses, makes it incumbent on the tool manufacturer to
provide machines that are highly standardized as to per-
formance. But machines that give uniform results are
best made uniform in all their parts, and so the chain of
uniformity, once started, must remain unbroken. It may
be observed, moreover, that the quality of machine tools
should be controlled to a greater nicety than the work those
machines are to produce. This flows from the fact that
REPETITION MANUFACTURING 279
there is an unpreventable slip in accuracy between the work
and the pattern which the machine follows as a guide in
generating the work.
This need for great precision, combined with manu-
facturing relatively small quantities of machines, has re-
sulted in a certain amount of hand-work in assembling.
This work is necessarily done by highly skilled mechanics
and may furnish an explanation of the scattered character
of the inspection organization in many machine tool fac-
tories. The latter situation is especially interesting at
present in connection with the overhauling of inspection
methods that has been going on since the war in a number of
these factories.
The General Principle
We have just traced the ideas involved in the continuous
production to uniform standards of quality. Without any
attempt toward a strict classification of industries, we have
analyzed manufacturing sufficiently to show that the posi-
tive and continuous control of quality to definite standards
within limits and at all stages of manufacture is at the root
of production economy. Beginning with the preparation of
raw materials, it was observed that the same principles held
good, up to and including the highest type of interchange-
able work. In the latter case all types are present. Start-
ing with a uniform material from which are made uniform
parts, these like finished parts in their turn provide a uni-
form raw material stock for the assembler, who is thus
enabled to produce uniform articles to meet some special
demand of the ultimate consumer. The latter demands
uniformity because his needs are best met when he receives
a known performance and a known return in quality for his
money.
At each stage of the industrial line the general rule ap-
280 THE CONTROL OF QUALITY
plies — the output is greater, the effort is less, the quality is
higher. Hence it requires less of the consumer's labor to ex-
change for a higher degree of satisfaction of his needs; and
thus the economic situation of everyone is improved.
But when we generalize that it is best to make things
uniform, we must remember always that quality varies,
and that what we really mean is likeness, uniformity, or
standardization of quality within limits. This, in a word,
is why quality requires control.
CHAPTER XVII
THE DIMENSIONAL CONTROL LABORATORY
Practical Value of Precision
The most important advantages of precise dimensional
accuracy in manufacturing the component parts of an as-
sembled mechanism are:
1. The elimination of hand-fitting, with quicker and
cheaper assembling.
2. More even wear with consequent greater resistance
to wear and longer life in service, with correct
functioning of parts.
3. Less noise after use, smoothness of action, and
smaller power losses. "Noise is an automatic
alarm indicating lost motion and wasted energy.
Silence is economy. . . .MI
With the possible exception of some of the makers of
very high-grade machine tools, probably no industry has
advanced precision workmanship to such a high degree of
perfection as the automotive manufacturers. It is in recog-
nition of this fact, and with admiration for their achieve-
ments, that we must turn to them for examples of what our
methods should be in seeking to bring dimensional quality
under control. For this reason much of the accompanying
illustrative matter is taken from automobile factories. The
lessons are by no means confined in application to that in-
dustry.
The basic requirement of precision is that means shall
be provided for making very exact measurements, and the
1 From "Creative Chemistry," by Edwin E. Slosson.
28l
282
THE CONTROL OF QUALITY
THE DIMENSIONAL CONTROL LABORATORY 283
most sensible way to secure proper surroundings for the use
of this equipment is to provide a central place suitably de-
signed for this purpose.
The Laboratory Proper
Since uniformity of conditions is the great essential of
manufacturing, it is even more necessary for a control center
of quality in manufacturing. Let us now consider some of
the things which require attention at such a control point, in
order that influences which are disturbing to the personnel or
destructive to the equipment may be reduced to a minimum.
Temperature changes, the greatest cause of variation, due
to weather changes, can be eliminated by providing artifi-
cial heat and cold, under uniform control. When this is
done the temperature is held around 70° F. There remain
then three other principal causes of disturbance : body heat
of operators, heat differences of objects brought in from out-
side, and heat from light rays. The first can be dealt with
in various ways which are obvious, such as specially insulat-
ed holding places on instruments. (See Figure 52, page 222.)
Anything brought in from outside should be allowed to
stand until temperature equilibrium has been reached.
When heat from rays of sunlight or from an electric light
near the work is permitted to affect either work or instru-
ments, a serious error is likely to occur. For small dimen-
sions, direct expansion is quite small (for tempered steel it
is about 0.0007 mcn per inch for one hundred Fahrenheit
degrees, nevertheless the effect may be specially serious
when direct expansion is magnified by lever action, e.g., sun-
light striking the anvils of a snap gage for a few minutes
would have little effect, but might easily be serious if allowed
to shine on the handle side, because the effect of the direct
expansion would be increased and thereby materially change
the distance between the anvils.
284 THE CONTROL OF QUALITY
Humidity and cleanliness are matters requiring consid-
eration. It would not be extremely difficult or costly to
make the measuring room dustproof and to supply washed
dry air in connection with temperature control. The many
advantages hardly require mention. Such a system would
seem especially desirable in moist climates, where polished
steel rusts almost overnight at certain seasons of the year.
Any system of the sort should have automatic control and
should be designed to run continuously, as it will not make
for uniformity if operated only during working hours.
As regards lighting, daylight illumination should be from
the north in order to avoid the admission of direct sunlight.
Greater uniformity and, with certain work, better definition
will be secured for local illumination if the artificial light is
taken from ''artificial daylight" lamps instead of ordinary
tungstens. The Trutint lamps made by the Nela Special-
ties Division of the National Lamp Works (General Electric
Company) are made in an inexpensive factory-type fixture
suitable for such work. Care should be taken to place
artificial lights for local illumination so that their heat will
not be concentrated in objectionable ways. Good general
illumination requires white or light neutral gray walls, with
a dark dado at the bottom. It is always bad to have light
shining from below the bench level.
Vibration and noise should be avoided as much as is con-
sistent with convenient location of the room ; the latter be-
cause it is a distraction, the former because it is likely to
interfere with close reading. Accurate work with optical
projection apparatus which makes use of the optical lever
for magnifying (for screw threads, shape, etc.), is out of the
question if vibration is present to any appreciable extent,
and for such work a separate room may be required, well
removed from the machine shops.
Floor covering may be wood, or, better still, battleship
THE DIMENSIONAL CONTROL LABORATORY 285
linoleum, which may reduce, if not avoid, the occasional
accidental error due to dropping things.
Furnishings should be limited to articles of use in the
work, but all furnishings should be first class and kept so.
The laboratory is no place for an old wooden work bench or
rickety stools. There should be shelf space in cabinets for
all equipment not in use, and safe cabinets, or preferably
vaults, for master control standards and models. A con-
venient wash basin should be provided, unless there is a
complete toilet room handy. In the checking of accurate
measurements the tactile sense is no more helped by a coat
of grease and dirt than it is in mechanical drawing.
The Surface Plate
A true plane surface supplies the level foundation upon
which we build for accuracy. The control laboratory should
have one large surface plate say, 4 or 5 feet by 8 feet,
mounted on a firm foundation. Such a plate is of massive
construction and is not likely to become distorted from
irregularities of the supporting structure; nevertheless it is
certain to change with age and use, even if it is made from
well-aged metal in' the first place. Consequently, it should
be watched very carefully, and this may develop the need
for resurfacing at least once in its career. The danger of
its being affected by temperature changes is slight, if the
laboratory is kept at nearly standard temperature.
With careful surfacing when needed, it should be possible
to keep the surface within o.ooi inch of a true plane for the
greater portion of its area ; yet every surface plate will have
small hills and valleys whose location should be known and
allowed for in placing work for measuring. Large accurate
measurements should be checked by placing the work in
different positions. In checking the plate to locate these
irregularities, the first step should be to apply a long and
286 THE CONTROL OF QUALITY
accurate straight edge (with reinforced ribbed back) and use
a feeler gage. The second step should be to sweep the plate
thoroughly with a surface gage, mounting a sensitive dial
indicator at the end of the arm, a short arm being first used
and then a long extended arm. If a further check is desired ,
recourse may be had to the method Whitworth used in
creating the first standard, namely, by contact application
of other plates, using Prussian blue between the plates to
show the humps and hollows revealed by rubbing them to-
gether. In ordinary shop practice a smaller surface plate
may be used for this purpose.
Where much work is to be done, and for other reasons of
convenience, it is desirable to have one or more smaller sur-
face and bench plates. It is idle, however, to attempt small
measurements accurate to ten thousandths with such equip-
ment. For such work optically correct plates should be
used. The crome alloy steel, tool-makers' flats manufac-
tured by the Pratt and Whitney Company, are about 5
inches in diameter by % inch thick, hardened and heat
treated by a special stabilizing process. They are finished
by the Hoke method of lapping (like the Pratt and Whitney
Hoke precision gages) with surfaces (top and bottom) fin-
ished flat, well within .000,01 inch and parallel within half
that error. Precision gages will wring onto them as they
wring onto each other.
The Dimensional "Court of Highest Appeal"
Prior to the invention of the Swedish gage blocks, the
measuring machine was the only available device for very
accurate measurements. For some kinds of measuring,
such as occur in originating or duplicating manufacturing
standards, an instrument of this type is highly important.
Some sort of end measure (rod or bar) is often needed to
check positively an accurate large dimension, and it would
THE DIMENSIONAL CONTROL LABORATORY 287
be difficult to conceive of an easier way of insuring accuracy
than by the use of a measuring machine.
Resort to such instruments was necessitated by the
early attempts to obtain real standards of length. In 1742
beam compasses were used for that purpose in England,
using both parallel jaws and pointed ends as usual. By the
use of micrometer screws with graduated heads this instru-
ment was considered accurate to within 0.000,62 inch for
comparing yard length standards. At the same time the
French compared their standards to 0.003 inch, until La
Condamine, in 1758, said they should be compared to o.ooo,-
89 inch, "if our senses aided by the most perfect instruments
can attain to that." Fifty years later a lever comparator
was designed by Lenoir, "which was regarded as trust-
worthy to 0.000,077 inch." The use of high-powered micro-
scopes in combination with a carefully graduated scale in
later measuring instruments has brought this error down to
0.000,01 inch, although accurate comparison of length
standards of 3 feet and greater encounter a number of com-
plications, principally due to molecular forces in the ma-
terial and to temperature effects.2
From these beginnings various types of measuring
machines have been evolved. There are several European
models of modern design, while in this country the Brown
and Sharpe measuring machine (see Figure 65) and the
Pratt and Whitney machine (see Figure 66) are well known.
The Brown and Sharpe Measuring Machine 3
The Brown and Sharpe measuring machine (shown in
Figure 65) operates on the principle of taking measurements
by means of a moving scale under a microscope, used in
2 See Harkness, " The Progress of Science as Exemplified in the Art of Weighing and Measur-
ing," for these and further details. The way in which these figures are stated is significant of
the earlier failure to appreciate the principles of the precision of measurement.
3 From data supplied through the courtesy of Luther D. Burlingame, Industrial Superin-
tendent of the Brown and Sharpe Manufacturing Company, Providence, R. I.
288
THE CONTROL OF QUALITY
THE DIMENSIONAL CONTROL LABORATORY 289
conjunction with a micrometer screw and vernier, the entire
mechanism being supported upon a rigid bed of accurately
careful construction. Measurements are taken directly
from the scale and the machine can be set to measure up to
1 6 inches.
The micrometer wheel is graduated to read to o.oooi
inch and the vernier plate used in connection with the wheel
makes it possible to read to 0.000,01 inch. The accuracy
of the machine, of course, rests fundamentally upon direct
readings taken from the graduations of the scale, and thus
depends upon the perfection of the scale and the micrometer
screw. The sensitivity of the machine may be shown by
placing the hand on the bed plate between the slides and
holding it there for approximately 60 seconds, at the end of
which time the piece will drop from between the measuring
points. It is interesting to note, however, that the ma-
chine requires about 20 minutes to return to its normal
condition after this test.
The Pratt and Whitney Standard Measuring Machine 4
The well-known measuring machine made by the Pratt
and Whitney Company of Hartford, Connecticut (shown in
Figures 66 and 67) provides not only a scientific instrument
for use in the laboratory, but, because of simplified and
standardized methods of manufacture, it is sold at a price
which permits its wide commercial use and allows any man-
ufacturer to originate or duplicate his own standards.
The four principal factors which determine the ac-
curacy of this machine are the bed, the dividing screw, the
control of the measuring pressure, and the standard bar
from which the sliding head is located in known relation-
ship to the stationary head.
The bed is of cast iron, seasoned, machined, and lapped
4 From information furnished through the courtesy of Oscar E. Perrigo, M. E., engineering
department, Pratt and Whitney Company.
19
290
THE CONTROL OF QUALITY
straight and parallel for its entire length, and the processes
through which it passes are of such a nature that the finished
product is not materially affected by changes of tempera-
Figure 66. Pratt and Whitney Measuring Machine
ture or torsional strains which would tend to destroy its
accuracy.
f The dividing screw for the sliding head is cut on a spe-
cially designed engine lathe which is kept in the laboratory
where a uniform temperature is maintained at all times.
THE DIMENSIONAL CONTROL LABORATORY 291
Compensating devices and adjustment provide a screw of a
degree of accuracy far beyond that hitherto produced.
The mechanism for controlling the measuring pressure
is located in the stationary head. The control is accom-
plished by means of a sensitive spring arranged so that when
pressure is applied to the measuring anvil it is communicated
to another pair of anvils between which a small plug is sus-
pended by spring tension. When the exact measuring point
is reached the little plug drops from a horizontal to a vertical
position indicating that the reading can be taken. By this
means the human element is eliminated, with the result
that accurate measurements can be duplicated indefinitely
without dependence upon the "feel" of the operator.
The fourth factor is the method of locating the sliding
head in a known relationship to the stationary head. This
is accomplished by means of a standard bar located at the
rear of the machine. Mounted on this bar are a series of
buttons with highly polished faces upon which are etched
fine lines exactly I inch (or 25 millimeters) apart. The
graduations on the standard bar are transferred by specially
designed apparatus from a known bar furnished by the
Bureau of Standards at Washington, D. C., which, needless
to say, is accurate to within the narrowest limits permitted
by human skill.
In taking measurements the index circle is set to zero and
the sliding head located to the zero line on the standard bar.
A microscope (C, Figure 67) equipped with an electric light
enables the etched line to be seen, the microscope tube being
adjustable so as to obtain a clear definition. When the
cross line drawn on the ground glass at the bottom of the
microscope coincides exactly with the etched line at zero on
the standard bar K, the tailstock (A , Figure 66) is moved up
into contact (indicated by the fall of the drop plug) and
locked in position, where it remains.
292
THE CONTROL OF QUALITY
After the stationary head is located, the sliding head is
moved back, and then relocated, the compensating zero ad-
justment F taking care of any variation of position. A
tangent screw G and lock screw H are provided on the index
circle for obtaining the last fine adjustment when taking
measurements. Its multiplied leverage provides a slow
6 *
Figure 67. Details of Measuring Head — Pratt and Whitney Measuring Machine
THE DIMENSIONAL CONTROL LABORATORY 293
easy movement of the dividing screw and prevents "going
by " the measuring point (when the drop plug falls clear out
of contact). The index circle is also provided with a mag-
nifying glass E for easier reading of the scale, which is gradu-
ated to I/ 10,000 inch (or 1/500 millimeter). There are 400
divisions on the English circle and 500 on the metric. One
turn of the circle is indicated on the linear scale L.
Vernier. The index circle divisions (.0001 inch, or 1/500
millimeter) can be subdivided five times by estimation on
the older machines, but to assist in obtaining very fine ac-
curate measurements, a vernier is now supplied which will
subdivide to .000,01 of an inch, or 1/5,000 millimeter.
Adjustments are provided to take up any wear in the divid-
ing screw should it ever occur. All anvils are hardened,
ground, and lapped flat and parallel, and with reasonable
care the entire machine will give accurate service for years
with the simplest of adjustments.
The machines are set and are standard at 62° F. It is
not necessary to use them at the initial temperature, as
variations will affect both the work and machine practically
alike. When used for scientific research, however, the ini-
tial temperature should be closely adhered to. ' The ma-
chines are regularly furnished in 12, 24, 36, 48, and 80
inch, or 300, 600, 1,000, 1,200, and 2,000 millimeter measur-
ing lengths.
Cylindrical supports (B) for holding work to prevent
springing, are furnished regularly with the machines as
follows:
Two with 12-inch or 300 millimeter
Three " 24 ' 600
Four 36 ' " 1,000
Four 48 " 1,200
Six 80 ' "2,000
The machine regularly requires no special foundation, as
it has a three-point bearing on the case for equalization.
294 THE CONTROL OF QUALITY
The Johansson or Swedish Block Gages
We now open one of the most interesting pages of
modern technical achievement — a story of little blocks of
steel of unbelievable fineness of workmanship. It was in-
deed fortunate for the development of greater precision
in machine shop processes that a man of the mental qual-
ities of C. E. Johansson happened to work in a govern-
ment arsenal engaged in the manufacture of military small
arms.
The technique of this business several years ago required
something more nearly absolute in accuracy than the
measuring methods generally in use at that time in machine
shop work, for it was highly desirable to make military fire-
arms with the greatest degree of precision that was reason-
ably obtainable. In order to insure this result, I believe I
am correct in stating, it was the usual practice to resort to
positive end measures for all important dimensions, these
measures being used for checking master or reference gages.
The consequence was that each government arsenal soon
accumulated a large quantity of such gage templates, or end
measures, which constituted their own dimensional stand-
ards. This will account for the fact that by the use of
modern finely standardized measurements certain govern-
ment arsenals have been found to be using an inch which
varies slightly from the standard inch. It is interesting also
to note in passing that the use of limit gages is of fairly recent
adoption for such work. The output was generally small
(being just enough to keep the arsenal busy in peace time),
so that an organization of very highly skilled men was de-
veloped. Owing to their finely cultivated sensitiveness of
touch, and by taking careful precautions in gage-checking,
these men were able to produce extremely accurate work,
using a single fixed dimension on the working gage. All of
this procedure resulted in the accumulation of a very large
THE DIMENSIONAL CONTROL LABORATORY 295
quantity of end measures whose exact values in terms of the
standard inch were not known with any special precision.
C. E. Johansson, after three years in the United States,
during which he acquired both a practical and a theoretical
education, returned to Sweden and shortly afterward began
his work as a tool-maker in the Carl Gustavs Stads arms
factory at Eskilstuna, Sweden ; later he became tool-room
foreman. He soon came to note that the usual measuring
equipment differed in its results, which lead him to attempt
the creation of a system of measuring for such work which
would give beyond question the accuracy required. Realiz-
ing the great value of solid blocks of steel, or end measures,
and guided by the experience gained in the arsenal (which
adopted the tolerance or limit system in 1889, so that parts
could be made in quantities and assembled without fitting)
he proceeded to develop the famous Swedish or Johansson
block gages, which in 1906 he announced to the mechanical
industries at large.
Much more recently a factory has been established at
Poughkeepsie, New York, for the manufacture of the
Johansson standards in this country, where they find a
wide application in industry.
These blocks possess the following interesting character-
istics :
1. They are made of steel which has been heat treated
and seasoned to practically eliminate warping or "growing."
2. The surfaces are flat and parallel to within .000,01
inch or less.
3. These parallel surfaces are distant from each other to
within .000,01 inch or less of the absolute dimensions stated
on the block.
4. These accurate surfaces permit of wringing the blocks
together, and they are arranged as to dimension so that by
suitable combinations of the blocks, as indicated in the va-
296 THE CONTROL OF QUALITY
rious illustrations, practically any dimension desired may
be obtained without appreciable error.
When packed together in this manner, not only is the
variation per inch kept as low as .000,01 inch or less, but the
surfaces are in such perfect contact that they adhere to each
other (probably because of surface tension of the minute
film of oil between them) with a force far in excess of mere
atmospheric pressure. It is almost certain to result in
"freezing," if the blocks are left in contact for several hours.
As will be observed from the various illustrations, posi-
tive end measures of this sort find wide and useful applica-
tion in any tool work that requires accurate determination
of dimension. No matter how many sets are used in the
factory — and it is an economy to use several — each dimen-
sional control laboratory should be equipped with one set of
such blocks to be retained solely as a final check for dimen-
sional control purposes. If the blocks are given proper care,
they should remain practically unchanged from year to year.
Ordinary inaccuracies due to wear, accident, or abuse, may
be discovered quite readily by checking them against each
other in different combinations. The result is a court of
last appeal for dimension in the fool-proof form of flat steel
blocks, or end measures, in fixed sizes.
As an example of continued precision of the block, it may
be noted that a set (No. 3353) purchased in October, 1918,
was returned to the Johansson Company in October of 1920
for rechecking. This set bore an engraved copper plate on
the box stating that it was to be used only for checking other
Johansson standard blocks and could be used only upon
requisition by certain specified officials of the owning com-
pany, which happened to be the Ford Motor Company.
This reference set, of course, had received excellent attention
and very slight use. Inspection by the Johansson Company
at Poughkeepsie showed that two blocks had worn approxi-
THE DIMENSIONAL CONTROL LABORATORY 297
mately .000,01 inch below normal size. All the rest of the
blocks, including the 2, 3, and 4 inch blocks, showed varia-
tions from normal size of less than .000,01 inch and most of
them less than .000,005 inch.5
The Johansson methods of manufacture and measure-
ment have been kept a business secret, although Mr. Johans-
Figure 68. Special Set of Johansson Block Gages
Accurate to within one-millionth of an inch.
son has disclaimed the use of the interferometer or light
wave method of measuring, which has caused a good deal of
speculation on the part of mechanical engineers and tool-
makers as to just what method of measurement he uses.
Despite the absence of information on this subject, we
must nevertheless admire so remarkable an achievement.
In fact, one can form a fairly good idea of how much
mechanical sense anyone has by observing his attitude
5 From information furnished by Huber B. Lewis, Vice-President, C. E. Johansson, Inc.,
Poughkeepsie, N. Y.
298 THE CONTROL OF QUALITY
toward the Swedish block gage itself. As an example of
what can be done, attention is invited to the set shown in
Figure 68, which was made by Mr. Johansson in order to
provide a set of blocks accurate within the one-millionth
part of an inch.
The Pratt and Whitney Precision Gages
During the war the need for precision end measures of
the Swedish type was greatly increased, and it is much to the
credit of the United States Bureau of Standards that it
became possible to develop very precise gage blocks through
the Hoke method of lapping and the use of the interference
of light waves for measuring. William E. Hoke of St. Louis
began this development with the Bureau of Standards, and
later as a major in the Ordnance Department was enabled
to make further progress. Gage blocks are now made by
several concerns in the United States. An interesting de-
scription of how the Hoke type of gages are made by the
Pratt and Whitney Company may be found in the April,
1920, issue of Machinery. The method of measuring by the
utilization of light waves is described in the May 22, 1919,
issue of the Iron Age.
Comparators
It will be noted from a number of the illustrations of
gage blocks in use that the blocks are being applied with the
assistance of an instrument for accurately comparing meas-
urements. Figure 69, for example, shows the blocks being
used with an American amplifying gage, as made by the
American Gage Company of Dayton, Ohio. The American
amplifier operates on the lever principle re-enforced by a
dial indicator, as shown in the illustration. Figure 38
shows a similar application, using the Prestometer or Prest-
wich fluid gage, as supplied by the Coats Machine Tool Com-
THE DIMENSIONAL CONTROL LABORATORY 299
Figure 69. American Amplifying Gage Used with Swedish Gage Blocks
300 THE CONTROL OF QUALITY
pany, Inc., of New York. The Prestwich fluid gage largely
eliminates the sense of touch and measures differences of
dimension with extreme accuracy through the use of fluids
and capillary tubes in connection with metal diaphragms
and a micrometer scale. If this instrument is used with
care in the selection of suitable sized tubes for the work in
hand, and if the adjustments are made with reasonable atten-
tion to the elimination of air bubbles, setting to zero, etc.,
it is an invaluable auxiliary device for use with gage blocks.
While it is true that fairly accurate comparisons may
be made by using the holders or straight edges provided
with the gage block sets, very precise comparisons are much
simplified by using an instrument of the comparator type,
in which differences in reading are magnified by some form
of mechanical or fluid lever and the reading scales of which
can be set to zero for each dimension.
Miscellaneous Equipment
Various well-known miscellaneous auxiliary equipment
for measuring are listed in detail in most small tool cata-
logues, and these should be found in every dimensional
control laboratory. New devices of considerable usefulness
are continually coming to the front, however, such as the
following :
1. Optical projection apparatus for comparing screw
threads and profiles is valuable for several purposes, as re-
ferred to in ChapterXIXon the gaging of screw threads. It
should be noted that such apparatus requires freedom from
vibration.
2. The Johansson set of precision angle blocks. Thisisa
very useful outfit for precisely checking angles and should
find much wider application.
3. While not directly connected with dimension, various
control instruments for measuring hardness, such as the
THE DIMENSIONAL CONTROL LABORATORY 301
Brinell tester and the Shore scleroscope, should form part of
the laboratory equipment. The Bureau of Standards
Technologic Paper No. 1 1 gives a " comparison of five meth-
ods used to measure hardness."
Personnel
Thus far only the material equipment of an ideal dimen-
sional control center has been discussed. Needless to say,
the selection of the personnel of such a control center is also
extremely important. Probably everyone inexperienced in
the use of measuring apparatus starts out with the idea that
manual dexterity and tactile sense is associated only with
the slender tapering fingers of the so-called artistic hand.
But any such notion is quickly dispelled by observing the
accurate work turned out by men with fat pudgy fingers.
The only proper and scientific test of measuring ability is
actual trial. There is no reason why candidates for jobs of
this kind should not be tried out by actual measurement of
their work, which will soon reveal, if the test is scientifically
conducted, any lack of tactile sense, accurate eyesight, or
skilfulness in making fine adjustments.
One of the first requisites for the proper use of scientific
apparatus is cleanliness. The laboratory itself should be
kept immaculately clean and clear of everything except what
is needed for the work in hand. The same comment applies
to the personnel, who should be encouraged, by the provi-
sion of facilities for washing, to keep their hands clean. In
hot weather this may be especially important, because
there are some people whose perspiration quickly rusts and
soon destroys highly polished steel surfaces. "The Atlas
Ball Company of Philadelphia tests the hands of applicants
for the positions of inspectors, with a view to detecting acid
perspiration. The hands of many people affect a fine steel
surface seriously. In some cases breathing on steel dis-
302 THE CONTROL OF QUALITY
colors the surface. The Atlas Company also tests for
this."6
Assuming that the people engaged are well suited to the
work in hand, it is highly important to impress upon them
the wide influence of the control work they are performing.
In any work of the sort special attention should be paid to a
standard technique for making various measurements.
Many errors which cause lack of uniformity may be elimi-
nated if certain measurements are always made in the same
manner. It hardly need be added that a part of this warn-
ing applies equally well to the high cost of hurrying. Swift-
ness is one thing, and a very desirable thing, but hurrying has
no place in work of the sort, where one blunder will be almost
indefinitely repeated when the tools or gages get out into
the shop.
6 The Johansson Journal, Vol. I, No. i.
CHAPTER XVIII
GAGES AND GAGE-CHECKING
When Should Fixed-Dimension Gages Be Used?
Various types of gages have been developed for special
purposes, and in approaching any manufacturing problem
where the question of dimension is important it must first be
decided whether any special operation should be controlled
through the use of flexible measuring instruments, such as
micrometer calipers, or some special form of gage in which
the dimension is physically worked into the gage, usually in
permanent form. In each instance special consideration
should be given to such questions as :
Which type will give the best results from a mechani-
cal standpoint?
Which is best suited to use by the available labor?
Which is the more economical, both as to first cost and
in use?
Flexible measuring instruments such as micrometer
calipers require greater skill in their application and are
more subject to personal errors due to inaccurate reading of
the scale, incorrect remembrance of the dimension, and dif-
ferences in "feel." Ordinarily it takes more time to apply
the measuring instrument than it does to use limit gages
with fixed dimensions. This does not always hold true,
however, because there are many expert mechanics who
take very rapid and accurate measurements with microm-
eter calipers. It must be remembered also that such
measuring instruments are capable of application to several
different jobs and, consequently, should be used where the
303
304 THE CONTROL OF QUALITY
quantity of work prohibits the making of special gages,
although the recently developed commercial types of adjust-
able limit gages obviate this difficulty of expense for many
applications.
No gage, and especially no measuring instrument, should
be applied to work in motion. To prevent this requires a
certain amount of supervision and education of the operator.
It is by no means uncommon to see a skilled workman apply-
ing a micrometer caliper to work on a grinding machine or a
lathe with the spindle still in motion. Frequently, too, the
proper way of holding and applying micrometer calipers is
not appreciated. Through the courtesy of the Brown and
Sharpe Manufacturing Company a number of photographs
have been secured showing the proper way of holding and
using micrometers of various types. (Figures 4, 5, 51, and
60.)
Fixed-Dimension Limit Gages
Fixed-dimension gages without limits are practically a
thing of the past. They depend entirely upon the feel of
the operator and have nothing to commend them, for even
their expense of manufacture is little increased by making
a double opening, to the limit sizes of the tolerance.
There would seem to be little doubt that fixed-dimen-
sion limit gages are mechanically suitable for all work that
ordinary micrometers will handle. From the standpoint of
first cost their application depends upon the quantity or
work to be done, but since their use requires less skill and
greatly reduces the chance of error, it is probable that their
use will be widely extended.
Frank O. Wells in an article ] calling attention to the
probability that the widespread use of gages will be a dis-
1 "Future of Gages in Manufacturing," published in the March, 1920, issue of Industrial
Management.
GAGES AND GAGE-CHECKING
305
N9)
i
306 THE CONTROL OF QUALITY
languishing feature in American industry, makes the point
that "gages allow departments which cannot see each other,
which are separated by walls or courts or other departments,
to act in exact coordination." The following quotation
from his paper is of special interest:
A workshop establishing a definite tolerance system, in almost
every instance, unless the shop is in serious condition, will find that
the desired tolerance will be greater than has been taken advantage
of in the great majority of pieces made before a definite tolerance
was set. The installation of limit gages will merely find and throw
out the small minority of pieces which have wandered from the
standard the mechanics themselves set up, but have no definite
means of adhering to. It is the exceptions to the rule which cause
the most bother. The gage cuts out the exceptions.
In the automobile industry, which has brought dimen-
sional control to such a fine point, the use of fixed-dimen-
sion limit gages has been widely extended. In the Packard
Motor Car Company's factory, for example, over 40,000
gages are in use. Throughout all divisions of the factory
limit gages are used extensively and are set with tolerances
ranging from plus and minus 0.0005 inch to plus and minus
o.oio inch. On tolerances less than plus and minus 0.0005
inch better results are obtained by using an amplifying gage
or a fluid gage, as described later.
In gage design both economy and technical requirements
point to the advisability of using simple single-purpose gages.
The use of flat plate gages, on which several openings are
shown, has little to recommend it, for almost always some
one of the dimensions will show greater wear than the others,
so that if the gage is to be saved for future use this opening
must be peened. The appearance of the gage is thus de-
stroyed, and, as everyone knows, no battered -up gage ever
receives the same respect from the user, as one in perfect
condition.
GAGES AND GAGE-CHECKING
307
Adjustable Limit Gages
There are several types of adjustable limit gages on the
market which permit the economical extension of what are
practically fixed-dimension limit gages. (See Figures 52
and 54, showing the general features of the Johansson adjust-
Figure 71. Adjustable Limit Snap Gages — Pratt and Whitney Type
able limit gages, both snap and plug; also Figures 71 and
72, showing similar information for the Pratt and Whitney
gages.)
The wide anvil gage is coming into greater use and has
very much to recommend it, not only because of decreased
wear but because the greater bearing surfaces tend toward
more accurate results. Attention is invited to a similar
economy in the use of plug gages with reversible ends which
308
THE CONTROL OF QUALITY
Figure 72. Adjustable Limit Plug Gages with Reversible Ends — Pratt and
Whitney Type
GAGES AND GAGE-CHECKING 309
permit a longer useful life. (See Figure 72.) The fact that
ends are removable is advantageous, as the " no-go" end
always wears less than the other.
Multiplying Gages
It is an interesting fact that in the application of close
limit gages there may be a difference of as much as 20 per
cent or more in the number of pieces passed by the inspector,
depending upon his mental attitude and material surround-
ings. Very slight actual differences may thus become very
great quantitatively. A purchaser's inspector may differ
very decidedly from the factory inspector in the use of the
same gage. This fact alone accounts for the increasing use
of gages in which such small differences are enhanced or
magnified to a point where measurement becomes imper-
sonal. Where the work warrants the expense, the use of
such gages is almost always desirable for better work, and
especially so when it is necessary to use less skilful help and
to obtain a greater assuredness of results with such help.
The Packard practice, for example, has developed that for
tolerances less than plus and minus 0.0005 inch much greater
certainty is obtained by using an amplifying gage or the
Prestwich fluid gage. Figure 38 shows a photograph of an
operator using a Prestwich fluid gage on piston pins, the
size of which is held to plus zero and minus 0.000,25 inch.
These gages are set from a " master " and are checked against
the ''master" after every 100 pieces. The gages are used
in both production and inspection on such work, and at
times it has been found that, if the work is held to a closer
limit than plus or minus 0.0005 inch, the operator will hug
the high limit for fear of getting the pieces undersize. With
fixed gages on work of this kind, the points or anvils will
wear quite rapidly and as a result crib inspection would
show about 25 per cent of the pieces oversize.
310 THE CONTROL OF QUALITY
The principal types of multiplying gages are as follows:
1 . The multiplying lever type. With this type of gage
it is important to avoid backlash or slip by keeping the
chain of levers under pressure from one direction in order
that the spring or other tension device may quickly restore
the parts to the zero measuring position. The points of
juncture in the link work are important. Flexible tape
connectors or conical pointed ends in conical hollows are
desirable for great accuracy, but wear must be provided
against with care. All gages of this type should have posi-
tive adjustment for the zero point and should be provided
with standard test pieces.
2. Dial indicators may be used to accomplish the same
purpose of multiplying errors (see Figure 36), and so may
the micrometer heads which are commercially obtainable.
3. The amplifying gage (Figure 69), and the fluid gage
(Figure 38), which are primarily multiplying comparators.
These also are suitable for use in this connection, as has
been stated heretofore.
4. Flush pin gages. These are made to utilize the tactile
sense for the detection of small differences, as the finger-tip
is very sensitive and is able to feel very small errors. Their
use should be restricted, however, to work on which other
less complicated devices are unsuited.
Special Gages
Special situations may be handled by various designs of
gages and measuring instruments, in which there is room for
the greatest ingenuity and resourcefulness of the gage de-
signer. These include such devices as special testing fix-
tures, (e.g., as used for measuring cam-shafts, etc.); con-
tour, profile, or outline gages, and so on.
It is often useful, in drop forge work, to provide hot
gages for checking forgings more promptly. In such gages
GAGES AND GAGE-CHECKING 311
allowance is made for expansion of the work while hot.
Another method is to keep the gage hot and to fit an insu-
lated handle to it.
Modern methods of thread-gaging have developed a
great many special devices, including the use of the optical
lever in projection apparatus. A number of these special
devices are treated in detail in Chapter XIX.
Gage Tolerances
The economical use of gages requires that even greater
care be given to setting the tolerances on the dimensions of
the gages themselves, than for the work. Speaking mathe-
matically, this process is like the second differential, in
which the tolerance for the work is the first differential.
With adjustable gages the matter of wear is easily disposed
of, but there are many instances in which the task is not so
simple. As a general guide the rule is sometimes followed
of allowing a gage tolerance equal to 10 per cent of the tol-
erance for the work proper. It is good practice to make
limit plug gages 0.0002 inch full on the "go" end to allow
for wear, since the " go " end of any gage wears much more
rapidly than the ' ' no-go ' ' end . Copper plating is sometimes
resorted to, in order to build up the wearing surface for gage
anvils. It is good practice in many instances to have a
systematic plan for replacing worn working gages with worn
inspection gages.
The Application of Gages
Investigation will reveal that there is a great field for
educating workers in the use of gages. Special attention
should be given to gage instruction cards (see Figure 49,
showing a portion of one such card as used in the Lin-
coln Motor Company's factory). The technique necessary
for accurate application of gages demands separate study
312 THE CONTROL OF QUALITY
and there is undoubtedly great room for development of
motion study in this work. More gages should be mounted
upon flexible stands which will permit the gage to adjust
itself readily to the work as well as allow the operator to use
both hands.
Gage-Checking
The use of limit gages brings with it a special problem of
co-ordination. In a large factory using thousands of gages
there is every need for the intensive and practical applica-
tion of systematic methods in gage-checking. Troublesome
gages and gages subjected to hard usage should be checked
very frequently indeed. As a general rule gages with limits
of plus or minus one-quarter thousandth should be checked
at least twice a week, those with limits of plus or minus one-
half thousandth at least once a week, and those with limits
of over one-thousandth, at least once a month. In addi-
tion, to provide against accidental errors, all of the devices
for catching such errors should be utilized. These have
been listed in detail in Chapter IV, pages 60 and 61.
Naturally a problem of this sort requires that the individ-
ual gages be numbered, that there be a card catalogue sys-
tem and a tickler file, and, more important still, that some
responsible individual be charged with the duty of following
up this work. This control of dimension of course proceeds
from the dimensional control laboratory referred to in the
preceding chapter. The work will be more easily controlled
if handled entirely through the inspection department and
if all working gages are issued from inspection centers
throughout the plant, whether they be central inspection
groups or merely the offices of department inspectors.
As noted before, the fact that gages wear makes it
necessary to provide a chain of checking devices reaching
from the working gage (which is subject to the most wear)
GAGES AND GAGE-CHECKING 313
back to some master gage template or standard measuring
machine which is subject to extremely little wear and, there-
fore, reasonably sure of remaining constant. The number of
links in this chain is frequently dependent upon the number
of times the working gages are to be applied and upon their
relative wear. Thus, for a very close dimension, a soft steel
or even a hard steel template might be applied by an expert
in 1,000 checkings without serious wear. Then in such a
case, if the quantity of work contemplated more than 1,000
checkings or applications of the template, we should have
to construct one more link in the chain in order to have
something to check the template.
In building up this chain for dimensional control several
terms have been employed, but there is no set of definitions
in general use. The definitions recommended in the Prog-
ress Report of the Committee on Limits and Tolerances in
Screw Thread Fits, as published in Mechanical Engineering,
August, 1918, are:
Master Gage. A gage which is kept as a standard solely for com-
paring reference gages.
Reference Gage. A gage used by the manufacturer and by which
the workman's gage is tested. A copy of the master gage.
Standard Gage. The English term for Master Gage.
Shop or Workman's Gage. A gage used by the workman in
everyday practice. It is tested by or with the Reference Gage.
The above definitions are a sufficient guide for ordinary
purposes, but many gages will be checked with greater ease
if they are provided with close-fitting templates as an addi-
tional step in the chain. Further, for straight dimensional
work (that is, excluding special shapes, such as screw threads
and profiles) several of the early steps in the chain of control
gages may be eliminated by the use of Swedish gage blocks.
The basic principle, however, must be observed with care:
One master set of blocks should be retained solely for checking
3H THE CONTROL OF QUALITY
the other sets of blocks which are used in the direct dimensional
checking of gages and tools.
The Slip in Transferring Size
Another chain of error arises in the possibility of slip in
passing from dimension to dimension. With the feeling
that the Johansson Company's experience in the matter of
making fine adjustments would be of interest in this respect,
they were asked for their opinion on the matter. The follow-
ing information was furnished by C. E. Johansson, Inc.
through the courtesy of Huber B. Lewis, Vice-President:
It is possible to transfer size without any observable slip. We
do it regularly in our laboratory work. Our checking instruments
are, of course, of extreme delicacy and we are dealing, in most cases
with surfaces of extremely accurate finish^ It seems to us that the
amount of slip which might occur in the practical application of
measuring implements depends, first upon the sensitiveness and the
uniform accuracy of the comparator, and second upon the finish
of the surfaces being compared. As an illustration: if a
comparator were set by using a standard plug with a fine lapped sur-
face, a ground part checked on this comparator would probably
register large because of the surface irregularities. A clearer com-
parison might be the slip between the plug templet and a ring made
to fit this templet. In practical tests we have made on plugs and
rings I " in diameter, we find that a clearance of approximately .0001"
should be allowed in order for the plug to enter the ring with a nice
wringing fit. Actual measurement would, therefore, show the ring
to be .0001" larger than the plug to which it was fitted which would
probably establish for practical purposes, a slip in measurement of
.0001". By using extreme care in the finish of the surfaces of the
plug and ring, paying particular attention to roundness, this slip
can be reduced to .00005" and the plug inserted in the ring without
using force. On the other hand, a clearance of more than .0001"
would be required if the plug or ring were not round and smooth.
Two Johansson Standard Gage Blocks can be checked against
each other where the slip would not exceed .00001". Take two new
i" blocks which are exactly alike within .ooooi"or better, wr ng end-
radius jaws on one block ; the other block can be inserted in the recess
GAGES AND GAGE-CHECKING
315
between the extension jaws so that it will remain in place when sus-
pended, through the niceness of fit. It may be said that some slip
occurs in the union between the first block and the end pieces due to
the filament of oil or moisture between the surfaces; whatever that
slip may be, if at all appreciable, will also exist between the jaws and
the second block when it is inserted between the extension pieces.
This would also be true in rougher work, for instance, a snap gage
set to a templet. Assuming that some slip occurs in mating the
snap gage to the templet, a corresponding slip would occur between
Figure 73. Pratt_and Whitney Taper Gages
the snap gage and the parts checked by it so that the parts would
correspond very closely with the original templet.
Mr. Johansson illustrates this principle of fit in a very interest-
ing way. He takes a i" Standard Gage Block with the radius jaws
extending down each side and stands the block on the table before
him. By the side of the block he stands a i" plug gage, finished to
the same degree of accuracy as the standard block. After making
sure that both pieces are of the same temperature, he inserts the i"
plug gage into the snap gage opening formed by the i" block and the
end pieces. You will note that the surfaces of the plug gage and the
extension pieces are in contact only along a hair line on each side.
Notwithstanding the slightness of this contact, the fit is sufficiently
nice to permit Mr. Johansson to raise the entire combination by
lifting the end of the plug gage.
316 THE CONTROL OF QUALITY
Mr. Johansson then takes the standard block combination and
holds it in his hand while he counts five slowly. The plug gage is
again inserted and this time it is impossible to lift the standard block
combination with the plug due to the expansion of the block. The
plug is then held in the hand while he again counts five, thus bring-
ing the plug approximately to the same temperature as the block
again and this time the fit is the same as it originally was and it is
possible to lift the standard block combination by lifting the end of
the plug. The amount of expansion would, of course, depend upon
the difference between the body temperature and the temperature
in the room where the experiment is performed, but the change
would not account for more than two or three hundred thousandths
of an inch, perhaps, and this again illustrates the very small amount
of slip that may occur when surfaces of equal finish are compared.
After every precaution has been taken to see that the
proper gages, correctly checked from time to time and kept
to dimension, are provided, and even if they are properly
used, there still remains much to be done if precise work is
to be secured with certainty. For this reason in Chapter
XX will be found some comments on the points to be ob-
served in precision processes, as well as data indicating
the present state of the machining art in the matter of
dimensional accuracy.
Chapter XIX is devoted to the presentation of the very
special and intricate business of screw thread production
and gaging. Many of the devices and methods, however,
are more generally applicable to irregular outlines, contours,
and forms.
CHAPTER XIX
THREAD-GAGING1
Evolution of Thread-Gaging
The evolution of thread-gaging is an epitomized history
of all gage development, beginning with simple ring and
plug gages and micrometer calipers and then running the
gamut through a long series of specialized measuring and
checking devices up to the use of the latest methods of opti-
cal projection. This array of equipment and the great and
continued effort of many expert engineers involved in its
creation, is warranted by the value of the screw thread as
an element of mechanism and is made necessary by the diffi-
culties inherent in accurate thread-making.
The beneficial influence of munition and automotive
requirements are clearly traceable in this evolution. More
perfect interchangeability without sacrifice of dependa-
bility or strength in relation to weight have operated to en-
hance the importance of precision in the manufacture of
threaded parts. In fact these characteristics have been
greatly improved, with corresponding improvement in the
apparatus for controlling their quality in manufacturing.
So great a variety of gaging devices is now available as a
result of the recent intensive development just mentioned,
that the first practical problem encountered in building up
a control system for threaded work is the selection of appa-
ratus sufficiently positive in effectiveness without being too
cumbersome or complicated. It is very easy indeed to build
up a long chain of control from the working gage through
1 The author is indebted to the Honorable James Hartness, Governor of the State of Ver-
mont (and formerly President of the Jones and Lamson Machine Company of Springfield, Vt.)
for his kindness in furnishing much of the material presented in this chapter.
317
31 8 THE CONTROL OF QUALITY
inspection, reference, and master gages with their check
templates, up to final master models. But the ramifica-
tions thus introduced are all potential sources of error and
necessitate solicitous watching.
Anything that can be done without sacrificing efficiency
to reduce this complexity by shortening the chain between
the work itself and the final control equipment is highly de-
sirable for many and very apparent reasons. It has been
shown already how the chain may be shortened in simple or
single dimensional work by the use of Johansson block
gages. It is now proposed to show how the same thing
results in precise thread control from the use of modern
optical projection apparatus.
Again quoting L. P. Alford's frequent statement, "The
purpose of industry is to make goods," thread-gaging devices
are of no value for their own sake, but merely as a means for
assuring the production of threaded parts in accordance
with the desired standards. The more direct and simple
such devices can be made the better, but the first step, as
always in the control of quality, is to study the product, the
errors which enter into its production, the causes of these
errors, and the means of regulating the manufacturing proc-
esses where errors are made.
In the analysis of screw-thread elements essential to
strength and dependability, James Hartness states:2
On account of the vagueness of our general knowledge of the
conditions under which it takes its stress, we frequently underesti-
mate the importance of the screw, and, through ignorance, continue
practices that greatly increase the hazard of life in travel by rail,
• automobile or airplane, as well as lessen the reliability of perform-
ance of other pieces of machinery. A screw-thread fastening is very
dependable if the two component parts are properly fitted.
While it is not possible to attain perfection in this work, an
analysis of the various elements that are essential for strength and
1 "Optical Projection for Screw-Thread Inspection" in Mechanical Engineering, Feb.
THREAD-GAGING 319
dependability, and the reduction of weight, will greatly simplify our
efforts and make it possible to attain a point much nearer per-
fection.
Briefly stated, a screw's reliability depends upon the following
elements:
A Material
B Form of profile of the thread
C Diameter of the screw
D Lead or number of threads per inch.
After the foregoing general characteristics have been deter-
mined, we must consider the following details which depend on the
methods and skill employed in production :
1 Smoothness and density of surface
2 Fit, which relates particularly to the exact relationship of
the size of the two component parts
3 Precision of lead, which relates to the precision of advance
of the helix or degree of precision with which the
number of threads per inch are made
4 Uniformity or steadiness of advance of helix
5 Form, relating to contour of a single thr ad
6 Roundness, as relating to the circular path of the helix
7 Parallelism or taper.
These elements are all inter-related.
Inter-relation of Thread Elements
The last sentence is particularly significant. Before
threading, the problems of ordinary cylindrical or tapered
work are encountered, such as maintaining diameters, round-
ness or concentricity, and parallelism. These difficulties
are carried over into the threading, where they are accentu-
ated by the creation of spiral-warped surfaces which add the
complications of pitch or lead of the screw, the angular
form of the thread, and several diameters instead of one.
Thus errors accumulate in three dimensions. In the case
of a single screw thread considered alone the inter-relation
of errors must be carefully taken into account ; for example,
320
THE CONTROL OF QUALITY
Figure 74. An Exaggerated Form of Stud
To illustrate the fact that when there is a difference in lead between the screw and
the nut or threaded hole the middle threads do not touch either in the gage or the
work until the opposing end threads are crushed. It also illustrates the conflict
between the stresses at the two ends of the engagement. Courtesy Jones and Lamson
Machine Company.
THREAD-GAGING 321
a variation in pitch may involve a much greater error in
effective diameter.
When the investigation of inter-related errors in screw
threads is extended to include mating parts, as it ultimately
has to be in every case, the percentage feature of precision
is involved because the error in the lead of the thread varies
with the length of the thread. The possibilities in the latter
case are well illustrated in Figure 74.
The preceding general discussion of the elements of
threads and their accompanying errors assumes theoreti-
cally smooth surfaces. In practice, however, the surfaces
of threads are not smooth, nor are edges continuous lines
and true curves. The manufacturing processes inevitably
leave their marks in the form of irregularities, chips, and so
on, which vary in magnitude with the character of the work.
No matter how slight these irregularities, their effect, singly
or collectively, is to increase errors of gaging or measuring.
It is not the purpose of this book to go into the techni-
calities of the various features of design, and it is assumed,
therefore, that the design provides for safe clearances be-
tween mating parts, especially bottom and outside clear-
ances. It is assumed also that the design provides for
normal wear of cutting tools, especially at the points and
edges where wear may ordinarily be expected to reach its
maximum effects. With these assumptions, then, we are
chiefly concerned with the remaining factors of lead, pitch-
diameter, and slope or angle. The first two usually require,
and in fact warrant, the most attention. Their inter-rela-
tion is such that lead, especially in long screws, is of para-
mount importance.
Working Thread Gages
The usual gages for inspecting threaded parts in the shop
are of the well-known plug and ring type (see Figures 75 and
21
322
THE CONTROL OF QUALITY
76) . A series of similar gages can be made for gaging the
various elements of the thread separately, but it would
hardly be wise or worth while to furnish such a series as
working gages or even as inspection gages for use in the
shops. Consequently the use of several gages for such work
finds little application outside of the tool-room in thread-
chasing. The gaging system for practical shop use, there-
fore, reduces to limit threaded plug and ring gages which
gage all essential elements at once. . This involves for the
threaded hole:
(a) Threaded "go" plug of a length equal to the longest en-
gagement of work
Figure 75. Typical Thread Gages — Pratt and Whitney Company
THREAD-GAGING
323
(b) Threaded "not go" plug, made short and with clearance
for full and root diameters;
and for bolt or screw:
(a) Threaded " go " ring of a length equal to the longest engage-
ment of work
(b) Threaded "not go" ring made short and with clearance
for full and root diameters.3
The Hartness Comparator
Now, the fact is that such gages are blind in the sense
that the gage covers the work while the latter is being gaged,
and knowledge must be _
based upon the feel of the
fit of the gage with the
work. This might do well
enough were it not for the
fact that the work inevi-
tably carries with it the
little errors already re-
ferred to, such as rough-
ness of the surfaces, chips,
and slight variations or
wabbles in the pitch, in
addition to direct dimen-
Figure 76. Typical Thread Gage —
Pratt and Whitney Company
sional variations which are always present. These hidden
dangers are without doubt at the root of most of the
aggravating and perplexing troubles so frequently en-
countered in the assembling of threaded parts, troubles
which are augmented in marked degree with increase
in the precision required for neat fits and complete inter-
changeability. Owing to the conditions just set forth, the
use of snap and ring gages actually discards some of the best
3 "Progress Report of Committee on Limits and Tolerances in Screw-Thread Fits," Me-
chanical Engineering, Aug., 1918.
324
THE CONTROL OF QUALITY
threaded parts of a lot and accepts some of the worst. Con-
sequently, even with gages in excellent shape, it is important
to base our control system on the work itself, since gages of
Figure 77. General View of Hartness Screw Thread Comparator
this type are apt to be misleading. Furthermore, it is not
enough to know that errors exist because we can feel them ;
they must be brought out into the open and measured be-
fore we can proceed to correct them with any degree of
assurance as to final results. Several designs of optical
Figure 78. Another General View of Hartness Screw Thread Comparator
projection apparatus have been developed for this purpose,
both in this country and abroad, and these mark a decided
advance in apparatus for checking both threaded work and
thread gages.
The Hartness screw thread comparator, illustrated in
Figures 77 and 78, positions the work in a cradle or work-
THREAD-GAGING 325
holder (see Figure 79) , in such a relation to its helix and diam-
eter as to show the situation at a glance, by visual com-
parison of the projected outline or shadow with the tolerance
chart of the screen.
Internal threads may be checked with the same appara-
Figure 79. The Work Holder and Projection Lens of Hartness Screw Thread
Comparator
Showing a standard plug in the cradle. The machine is adjusted by use of a standard threaded
plug. The plug is a perfect check that may be used during the run of gaging.
tus by the use of sulphur casts, after the method long in use
in measuring the cartridge chambers of small arms. Graphite
may be mixed with the sulphur (7 per cent of graphite by
326 THE CONTROL OF QUALITY
weight) to reduce shrinkage and surface reflection.4 Or, the
tap used in threading the hole may be checked.
There is then made available a simple means for verify-
ing threaded work (both passed and rejected parts), so that
errors may be revealed and measured. This apparently is
the proper starting point for bringing the work under con-
trol. The same procedure is then extended to correct the
tool equipment so that it will produce work of the desired
character ; and finally to check such gages as are needed for
convenience, being guided always by the principle that it is
more useful as a measure of a gage's effectiveness to check
the work which the gage passes than it is to regard the
absolute measurement of the various elements of the gage
proper as final and conclusive.
It may be mentioned incidentally that there is a useful
field of application for projection apparatus in irregular
profile and contour work, as well as for threads; but in all
work with such equipment due attention must be given to
locating the apparatus away from troublesome vibrations.
Other Equipment for Measuring Threads
For a complete description of the equipment employed
by the Bureau of Standards in measuring thread gages, the
reader is referred to the paper by H. L. Van Keuren, men-
tioned above, which may be used as a guide in equipping
the control laboratory for thread gage-checking. The
gaging system should be adopted with reference to the
character of the work to be handled. For precise work the
optical projector will usually be supplemented by a special
lead testing machine. An excellent instrument of this type
was brought to a high state of perfection during the war by
Major H. J. Bingham Powell, who was Director of the Joint
Gage Laboratories of the British War Mission and the
< "The Measurement of Thread Gages," by H. L. Van Keuren, chief of Gage Section,
United States Bureau of Standards, in Mechanical Engineering, Nov., 1918.
THREAD-GAGING 327
United States Bureau of Aircraft Production. For such
work the West and Dodge Company's lead tester (see Figure
8) is often found in the dimensional control rooms of fac-
tories doing precise work. Similarly, the well-known three-
wire method for measuring the pitch diameter should be
provided for by supplying accurate apparatus for this work.
The method is a most useful one, but requires careful appli-
cation for accurate results.
Ordinary ring and plug gages are frequently supple-
mented in close work by special types of gages, such as com-
bined lead and diameter gages, using micrometer heads in
combination with compound levers or dial indicators for en-
hancing errors in the work — making them appear greater.
For simple work the ordinary type of screw thread microm-
eter still has a useful field.
Thread Gage Tolerances
There probably is no other branch of gaging which re-
quires so much attention to the effect of wear as does accu-
rate thread-gaging, and this, of course, brings in the matter
of gage tolerances. In this connection Frank O. Wells5
states :
One great difficulty with the business of manufacturing thread
gages is the unreasonable and useless accuracy of gage tolerance and
wear allowance sometimes requested by purchasing firms. When a
tolerance of 0.0002 in. is set on a gage specification it should mean
that the customer's tolerance on product is as close as o.ooi in. If
the purchaser's manufacturing tolerance is any broader than that,
there is no use in keeping the gage so close. A 0.0002 in. error would
be lost in the comparison. In order to facilitate the making and to
lessen the cost of thread gages, it is well to allow quite liberal toler-
ances in their manufacture, and we recommend the following as
being applicable for most cases where medium tolerances are
allowed on product:
5 "Present Practice in Thread Gage Making." by Frank O. Wells, President, Greenfield
Tap and Die Corporation; member Congressional Screw Thread Commission, in Mechanical
Engineering, Dec., 1918.
328 THE CONTROL OF QUALITY
From 4 to 6 pitch allow a tolerance of 0.0006 in.; from 7 to 18
pitch allow a tolerance of 0.0004 m- 5 from 20 to 28 pitch allow a toler-
ance of 0.0003 in. ; from 30 to 80 pitch allow a tolerance of 0.0002 in.
The foregoing applies to master gages. For inspection
gages the tolerances would be slightly wider, and would
begin where the master inspection gage tolerances leave off.
These would be as follows:
From 4 to 6 pitch a tolerance of 0.0009 m- 1 from 7 to 10 pitch a
tolerance of 0.0006 in. ; from 1 1 to 18 pitch a tolerance of 0.0004 in. ;
from 20 to 28 pitch a tolerance of 0.0003 m-I from 30 to 40 pitch a
tolerance of 0.0003 in.; from 44 to 80 pitch, 0.0002 in.
All of the foregoing tolerances would be applied plus in the case
of go male gages and no-go female gages ; and minus on no-go male
and go female thread gages.
The plus and minus tolerances given apply to pitch diameters
of all thread gages and also to root or core diameters of templets
or female thread gages.
The maximum, or go, templet gage represents the maximum or
basic screw and its manufacturing tolerances should be minus on
pitch diameter and root diameter. The minimum or no-go, templet
should be made to plus tolerances with an extra plus allowance on
the root diameter, which will insure this gage's really checking the
effective size of the screw. The wear and adjustment tolerance on
a gage should be coarse or fine on a sliding scale according to the
manufacturer's tolerance on his product.
As Mr. Wells shows, the matter of gage tolerances refers
back to the tolerances required for the work itself. The
latter subject has received much attention from engineering
organizations in recent years, and the results of their con-
clusions as set forth in various publications should have the
careful attention of manufacturers.
Precision Depends upon Service Requirements
It may be noted again that the problems of this subject
necessitate at the start a determination of the things we
wish to accomplish with our product. What service are
THREAD-GAGING 329
the threaded parts required to perform? What are the
elements of these parts which make the principal con-
tribution to the rendering of such service? What variations
from the ideal for the sake of economy of manufacture is it
sensible to tolerate without too greatly compromising effec-
tiveness? When the subject is analyzed in this order, it
may readily develop that the best results will flow from
easier tolerances but with closer adherence to these standards
in the dimension and finish of the product. Thus better
attention to the quality of the work may permit the gage
tolerances to be a fifth instead of a tenth of the tolerances
allowed for the work; especially when the work is more
positively checked from time to time by independent meth-
ods, such as by the use of the optical projection apparatus
referred to.
CHAPTER XX
THE PRECISE CONTROL OF PROCESSES
What Dimensional Precision Is Practicable?
In the study of dimensional control it is sometimes de-
sirable to consider what degree of accuracy is commercially
obtainable for a given job. The logical starting point for
such an investigation is the examination of the results
obtained in various processes which are in actual use at the
time. It should be observed, however, that any such figures
are subject to correction from time to time as the manufac-
turing arts are advanced toward greater precision. To be
sure, a very high degree of accuracy has been obtained in
certain businesses at the present time, and it would be diffi-
cult to see any advantage at the moment in further improve-
ment; but experience shows quite clearly that progress has
not stopped. As the advantages, both commercial and
technical, of higher precision come to be recognized, there
is no doubt that further and even more startling advances
will be made.
The manufacture of automobiles has developed a very
high degree of accuracy on a commercial scale, so that our
first examples of obtainable precision are taken from that
industry. In the Lincoln factory, for example, "there are
more than 5,000 operations in which the deviation from
standard is not permitted to exceed the one thousandth
part of an inch, more than 1,200 in which it is not permitted
to exceed a half of one thousandth; and more than 300 in
which one-quarter of a thousandth is the extreme limit of
tolerance." The large number of closely held operations in
this industry has been a matter of frequent and general
330
THE PRECISE CONTROL OF PROCESSES 331
comment. It is only a year or two since the Marmon Com-
pany, for example, at the Motor Show in New York put on
an exhibition in which two men took down and reassembled
a complete engine in I hour and 45 minutes. Such pre-
cision kills the need of hand-fitting.
Automobile Experience
A former associate, G. D. Stanbrough (in response to
the author's request), writes the following setting forth his
experience with precision work in the automobile industry :
With regard to commercial limits on different forms of ma-
chine work I may say that at the time a new model is placed in the
factory l the limits are carefully gone over by a committee represent-
ing the Engineering, the Manufacturing and the Inspection Depart-
ments. The committee sets the limits which the Manufacturing
Department knows from past experience are commercially possible,
and yet within the tolerances desired by the Engineering Depart-
ment. It is our practice to give all information necessary on the
drawing, as to roughing and finishing dimensions, also, forging and
casting dimensions.
It might be well to point out at this time that an understanding
is not always had as to the matter of limits in manufacturing. The
matter of design and its relation to limits is quite frequently mis-
understood and much trouble can be avoided by thoroughly under-
standing these functions. It should be borne in mind that the de-
sign of a piece of apparatus involves the strength of materials and
the appearances. That is, you must have the necessary strength to
perform the function and to have a finish compatible with the con-
dition under which the piece is used, or the particular ideas from
a sales policy that is to be carried out. While on the other hand the
matter of limits is purely manufacturing and involves the practices
of the shop in which the work is done.
It naturally follows that as closer limits are approached in man-
ufacturing, the design in turn can be improved. An automobile
manufactured to give satisfactory service over a long life must of ne-
cessity be built to close limits. Noise probably more than any
other one cause is responsible for the comparatively short period of
The Packard Motor Car Company's factory is referred to.
332 THE CONTROL OF QUALITY
time in which a machine gives satisfaction to the customer. In or-
der to manufacture an automobile that will give noiseless operation
over a period of years close limits are essential, and it has been our
constant aim in designing tools and in laying out our processes to
decrease our limits.
To date we are able to hold the grinding on such parts as the
piston pin, the cam roller pin, and other parts subject to reciprocat-
ing motion to a limit of plus .000 minus .00025. ^ e are holding
turning dimensions to plus or minus .0005 — this limit being held on
bushings and bearings. On milling work we are holding to plus and
minus .001, in fact we have a 4^2 " dimension on our crankcase which
is held to this limit. On milling key -ways we hold the width to a
limit of plus or minus .0005. On reamed work we hold to a limit of
plus or minus .0005 with the exception of the cramshaft sprocket,
the piston pin bushing, and some other close parts, where by hand
reaming we hold a limit of plus or minus .00025.
We are holding today, in the commercial practice of the shop,
to limits which but a few years ago were only called for on the most
accurate tool room work. However, this is the result of first class
inspection methods combined with properly designed jigs and fix-
tures.
Of course you realize that in the manufacture of large numbers
of interchangeable parts, speed in manufacturing can only be ob-
tained through close limits which give a high degree of interchange-
ability. Quality can be controlled, if quality is the idea of the
Management; if the people behind an enterprise have a genuine de-
sire to get quality and are willing to pay the price, it should be
borne in mind that it costs money initially to produce quality, to get
a job up to the highest standard of manufacture. However, once that
standard is reached it can be maintained cheaper than it is possible
to maintain a lower standard, owing to the fact that pieces assemble
with greatly increased speed when fitting in an Assembly department
is entirely eliminated.
With reference to the crankshaft and the camshaft, we check
the overall and intermediate dimensions in a fixture gage which has
stops at different points, allowing the use of a "go" and "no go"
feeler. Inspection by this method is quicker and more accurate.
We find that the twin-six crankshaft supported only on the front and
rear bearing will not sag anything over night, but in a test covering
a week's duration we found a sag of .0005.
THE PRECISE CONTROL OF PROCESSES 333
It might be of interest to you to know that our Liberty Engine
crankshaft supported on the front and rear bearing would sag over
night from .001 to .0015 while the sag in a week would be .003.
Of course, this was due to the extremely long shaft and a fair degree
of flexibili ty . However, I do not think that any close comparison can
be drawn as to the sag of a crankshaft, because so many items enter
into the consideration, such as: design, material, heat treatment
of the material, manner in which it is processed, the amount of
straightening that is done, room temperatures, and consequently tests
of this kind may be only considered comparatively. Of course,
comparisons will be useful provided they are made on shafts of simi-
lar design. This question, however, reaches into technical details
which are beyond consideration of ordinary inspection practice.
The tolerances disclosed in these cases are typical and
indicate the precision obtained in daily manufacturing in
those motor car factories where dimensional control has been
carried to the highest practicable standard of achievement.
Works of this sort employ from 20,000 to 40,000 limit gages,
whose cost runs into the hundreds of thousands of dollars.
The inspection of finished parts alone may require 72 hours
per car. Some other industries apply more gages, occasion-
ally as many as 50,000 in one factory; but few, if any,
achieve the precision of the automobile factories, on a
quantity production basis — day in and day out. With over
10,000,000 motor vehicles in the country, everyone has a
chance to familiarize himself with their various parts.
Consequently, the precision for principal dimensions gives
a pretty good general idea of commercial possibilities for
various sorts of machine work.
Tables of Tolerances
Another source of information as to precision is to be
found in tables of tolerances. In a sketch furnished by the
C. E. Johansson Company, Inc. (see Figure 80), various
kinds of fits are shown, together with two tables of tolerances
334
THE CONTROL OF QUALITY
Illustrating the Different C/asses of
F/ts Repaired in the Construction
of a Simple Drill Press .
L iyht Rurinlny Tit
>^
-^3,. r
_ i. -^^H Running fit
- Sliding fit
force Tit
Figure 80. Sketch of Drill Showing Various Fits — Johansson
THE PRECISE CONTROL OF PROCESSES
335
and limits (Figures 81, 82, 83, and 84). One set of data is
based upon the hole system, in which the hole is taken -as
the reference point of greatest accuracy, and the other is
based upon the shaft system. Since the recent develop-
ments in greater precision of work, especially as regards
grinding, there would seem to be little need of considering
DIAGRAM OF
LIMIT SYSTEM
SHAFT— BASIS
TOLERANCES: THE SHAFT - 1OO:
Figure 81. Diagram of Limit System — Shaft Basis — Johansson
whether we should work from the hole or the shaft, but the
figures are interesting as a guide nevertheless.
k-i In recent years considerable pioneer work has been done
in England toward assembling useful data on precision and
pioneer work of the same sort has started in this country.
In July, 1920, Mechanical Engineering announced the forma-
tion of a sectional committee of the American Society of
Mechanical Engineers for the purpose of studying and re-
porting on plain limit gage standards and machined fits.
336
THE CONTROL OF QUALITY
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THE PRECISE CONTROL OF PROCESSES
337
The questionnaire prepared- by the committee, as published
in Mechanical Engineering for February, 1921, states that
the practice of one well-known firm is as follows for various
classes of fits :
CLASS No. i LOOSE FITS
Machined fits of agricultural, domestic, and other machinery
of similar grade (wagons excepted)
Mining machinery
Controlling apparatus for marine work, etc.
Textile and rubber machinery, candy and bread machinery,
and others of similar grade
Some parts of ordnance
General machinery for manufacturing.
CLASS No. 2 MEDIUM FITS (MOVING PARTS)
2a High Speeds (over 600 r. p. m.) and Heavy Pressures
Electrical machinery
High-speed parts of woodworking machines
C. E. JOHANSSON
DIAGRAM OF
LIMIT SYSTEM
HOLE-BASIS
TOLERANCES: THE HOLE - 1OOs
Figure 83. Diagram of Limit System — Hole Basis — Johansson
22
338
THE CONTROL OF QUALITY
TOLERANCE SYSTEM WITH THE SHAFT AS BASIS
TABLE FOR TOLERANCES IN INCHES
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FUNCTION OF THE MACHINE PARTS
ALLOWS LARGER TOLERANCES
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THE PRECISE CONTROL OF PROCESSES 339
Sewing machines
Machine tools
Locomotives
Printing machinery
Automotive
Ordnance
General machinery for manufacturing.
A well-known firm uses allowances of 0.0005-0.004 in. up to 6
in. for work of this class.
CLASS No. 2 MEDIUM FITS
2h Ordinary Speeds (under 600 r. p. m.) and Light Pressures
Machine tools
Printing presses and machinery
Typewriters, calculating machines, etc.
Locomotives
Automotive — general parts
Textiles, rubber machinery
Ordnance
General machinery for manufacturing.
A well-known firm uses allowance of 0.0005-0.0025 in. up to 6
in. for work of this class.
CLASS No. 3 SNUG FITS
(Designated as the closest fit that can be assembled by hand.)
3a Slight Allowance (0.00025 to 0.00075 in.)
Gear trains and change gears for general work
Mating parts, fixed or not, moving on each other, such as
studs for gears and levers, keys
General machinery for manufacturing.
3b Close Fit (commonly known as wringing fit, no allowance,
not considered interchangeable manufacturing but selec-
tive assembling)
Crankshafts
Precision-ground machine spindles
Gears in index train of precision gear-cutting machines
Slots and tongues such as are used for grinding machines,
milling machines, etc.
Surveying and scientific dental instruments, etc.
General machines for manufacturing.
340 THE CONTROL OF QUALITY
CLASS No. 4 TIGHT FITS
4a Drive Fits for Light Sections
Automotive
Ordnance
General machines for manufacturing.
A well-known firm uses negative allowance from 0.00025 to
o.ooi in. up to 6 in.
4!) Force Fits for Heavy Sections
Locomotive and car wheels
Crank disks, armatures, flywheels
Automotive
Ordnance
General machines for manufacturing.
A well-known firm uses negative allowance from 0.00075 to
0.005 m- UP to 6 in.
4c Shrink Fits
Locomotive tires and similar work
Ordnance.
A well-known concern's practice is as follows : Where thickness
exceeds 3/8 in., 0.0005 to 0.005 m- UP to 6 in. in diameter. Where
thickness is less than 3/8 in., up to 6 in. in diameter, 0.00025 in. to
0.0015 i'n.
It is to be hoped that this committee will cover the field
of practicable precision of machining processes in consider-
able detail, and that this data will be kept up to date for
the guidance of industry.
Precautions for Obtaining Precise Work
Among the general considerations to which attention
should be given in bringing processes under control, one of
the most evident, but one of the least observed, is to make
the tool set-up a fool-proof one. There is so much need of
all available time, care, and attention to details in close
work that everything which can be done to free the operator
from unnecessary strain in these particulars should be done.
Not once but several times during the last years, the writer
THE PRECISE CONTROL OF PROCESSES 341
has heard superintendents or engineers say something like
this:
We can't seem to get results in the .... shop, and it is due to
nothing but the foremen's failure to handle their men so as to get the
answer. I know that the tools and gages are O.K., because I have
made the complete part myself. Only yesterday I carried a piece
through each operation personally and it came to the gages in fine
shape. That proves everything is all right except that the shop
executives don't exercise proper control over production.
As a matter of fact it proves nothing of the sort. All
it does prove is that a skilful mechanic with years of experi-
ence can make a good part with the facilities provided.
We knew that already. It has been done before.
Having detected the fallacy in the above remark, let us
consider some of the things that such a test does not prove.
In the first place, such a test does not show that unskilled
operators can produce good work with the available equip-
ment, nor does it prove that they will do so, especially if the
wage system is such as to create a strong incentive for quan-
tity of individual output. Most large-scale enterprises are
conducted in a way to place a heavy emphasis on quantity of
output. Nor does it indicate that the gages will be applied
correctly by unskilled inspectors, nor that the available
machine-setters and adjusters are trained to their work, nor
that the shop arrangements and system are suitable for the
general conditions as they exist in fact. In short, we are
faced with a condition and not a theory. The solution lies
in shaping everything to the actual environment. We must
deal with things as they are, not as they used to be, or as
they might be under different circumstances.
There is a way to meet the situation. When a task calls
for greater skill than the available labor possesses, split the
task into simple operations, any one of which will be within
the capacity of such labor. This is the old, well-known,
342 THE CONTROL OF QUALITY
thoroughly tested, but little appreciated, cure for the con-
dition— namely, a judicious application of division of labor.
Similarly the principle of analyzing everything into simpler
parts must be used to the end that each man's work will be
well within his capacity, for it is through these men that the
result will be achieved, and only through them. This simpli-
fying process must be used in every element of the project-
tools, gages, shop arrangement, shop systems, and organiza-
tion. This much is axiomatic; nor should it be forgotten
that such a differentiation greatly complicates the problem
of co-ordinating the different constituent parts of the work.
In the second place, the tool and gage designers can
help safeguard standards by eliminating process hand-work
as much as possible, and by simplifying the tool and gage
designs in so far as is practicable. Tool equipment should
be simple and much more rugged than heretofore. Forcing
light work should be made difficult. The factor of careless
machine operation should be discounted by skilful designing
for chip clearances and bedding points, because careful plac-
ing of work cannot be counted upon. The same line of
thought applies to gages — the complicated gage with sev-
eral gaging points, flush pins, etc., should give way to single
measurement limit gages. Adjustable limit gages can be
used to great advantage. In some cases working gages
should have closer limits than salvage gages, but this is a
practice that must be settled with reference to individual
problems. Templates of form, outline, or profile should be
preserved systematically and checked methodically for both
cutters and gages. In this checking there should be em-
ployed the most sensitive tactile skill obtainable.
In the endeavor to make things fool-proof — a process
in which nothing must be taken for granted and every detail
carefully considered because the effect of such details is
multiplied enormously through repetition, so that little
THE PRECISE CONTROL OF PROCESSES 343
things determine results — there is usually no occasion for
continuing to worry about such matters as keeping the
bedding points free from chips. A little care in the design
of the tool will permit chips to fall away from the work in-
stead of onto the bedding surfaces. Very often an auxiliary
device may be provided for blowing the chips away auto-
matically.
The work itself, as well as the tool, should be designed
so as to reduce the chance of error from forcing a tool and
so as to permit accurate holding of the work when it is pre-
sented to the tool. It is good practice when possible to
work from holes as locating points for a series of operations.
The objection to this practice for many operations lies in
the fact that the work is soft for machining, and the holes
wear. A little ingenuity will avoid this trouble. Very
frequently a false hole or slot may be created in the place
where the metal will be cut away later. When this cannot
be done, there seems no reason why holding lugs cannot be
added to the part, hollow-milled in a jig, used for bedding
points throughout the machining, and finally cut off. In
fact, there are cases where this has been done.
The Principle of Balance
For very careful and accurate control of a process used
in creating a uniform product, a nice balance should be
provided, as a direct and practicable application of Newton's
third law of motion — "action and reaction are equal and
opposite." Now in a machine tool the whole supporting
structure which presents the work to the tool should provide
a wall against which to build up the pressure imposed
by the tool itself. In laying out the equipment for any proc-
ess this principle should be carefully considered if a nicely
balanced application of force must be made. The same
idea is applicable in many other processes where irregular
344 THE CONTROL OF QUALITY
or jerky action may be avoided by balancing the opposing
forces.
When difficulties are encountered in bringing processes
under uniform control, one good way of deciding whether
the method is correct is to carry it to the extreme in the
opposite direction. Thus, Professor John E. Sweet states:
To demonstrate that this is right, a good way in this, as in most
mechanical problems, is to carry the wrong way to an extreme and
note the consequences, and it will be found that the right way has
already been carried to the extreme in the right direction.
The Effect of Finish on Accuracy
One of the most important points to be observed in in-
structing machine operators is care of the work. Attention
to quality brings about the creation of finer work and that
of itself usually demands respect ; nevertheless our factories
are full of workmen who would treat bricks with much more
respect than they do steel parts — bricks would break if they
were thrown around, whereas steel parts only become
dented. But dents and scratches require more polishing,
more grinding, and uniformity of dimension is lost. On the
machine itself one way to insure greater uniformity is to
remove vibration, but this is merely another application of
the principle of balance referred to above. To meet the
same condition, it is probable that finishing operations,
such as automatic polishing and tumbling, will see wider
application and greater refinement in the future because of
their marked advantages.
Quick Checks on Precision
It will be found useful, from time to time, to apply the
method of taking check "borings" in the factory, in order
to develop additional information as to what requires cor-
rection for greater uniformity. It is suggested, for example,
THE PRECISE CONTROL OF PROCESSES 345
that some important part be independently checked and
measured, beginning with the tools and gages and conclud-
ing with the measurement of the parts themselves, proceeding
from operation to operation straight through to the com-
pletely assembled mechanism. There are other quick tests
which may be applied. For example, a check on the uni-
formity of heat treatment may be obtained by supporting
like parts in like positions for the same length of time and
measuring their sag. It was in connection with getting
data for such a test to check up the work of a certain factory
that the information relative to sag of crank-shafts (referred
to on pages 332 and 333 of this chapter) was obtained.
The work as performed in the Packard shops was taken as
standard in comparing work in a somewhat similar shop do-
ing cruder work and located many hundreds of miles away.
The results were very interesting indeed, because of their
divergence and lack of uniformity.
CHAPTER XXI
THE CONTROL OF COLOR1
Application of Measurement to Other Qualities
Up to this point we have dealt with dimension as ex-
emplifying cases where excellent means of measurement
exist. Very often in such work special tool equipment is
provided which works from a pattern made with the
greatest care, the tools almost automatically following this
pattern over and over. Even in the case of straight ma-
chine work without special tools, a high degree of precision
is possible. Many other processes, however, have not yet
been regulated with such precision. Bringing them under
uniform control involves the process outlined in Chapter
XIII, "Measurement and Errors," but before we are in a
position to tabulate the various errors in the work produced
by such operations or processes, it is necessary to develop
some systematic method of recording both the kinds of
errors and their relative occurrence both as to frequency
and size. Color is a typical instance of this general class of
work— a class which is extremely large in industry today,
but which will be gradually reduced and brought under
control as time goes on and the fight continues for greater
production of better and more uniform qualities at a lower
expenditure of effort.
In discussing the subject of measurement in Chapter
XIII, it was shown that the control of any quality depends
upon measurement as a starting point, and that measure-
ment itself is a process beginning with the selection of an
1 For an authoritative and most interesting treatise on the subject of color, the reader is
referred to "Color and Its Applications," by M. Luckiesh, Director of Applied Science, Nela
Research Laboratories of the National Lamp Works, General Electric Company.
346
THE CONTROL OF COLOR 347
arbitrarily chosen sample which is suitable as a standard of
comparison for the quality under consideration. The next
stage consists in developing a scale of values to permit
measures of the quality to be stated in figures, and the final
step is the development of impersonal measuring instru-
ments. Dimension and weight, for example, have reached
the last stage and very precise instrumental means are
available for control purposes. Many other qualities,
however, have barely reached the first stage of control by
direct comparison with standard samples.
Appearance and Color
Of the several qualities that define the character of the
factory product, certainly appearance is not the least im-
portant, and throughout a wide range of industries color is
one of the important, if not the most important, quality
which goes to make up appearance. Frequently, as in the
case of chemicals and food products, color is an indication
of other qualities in addition to appearance. Just how
valuable a uniformly good color is as a commercial asset
must be decided in the light of the special business situation.
If color is worth controlling to a commercially uniform
standard, then, as in the case of the qualities of dimension
and form, we must define the standard which is to be fol-
lowed, adopt processes for its creation that are uniformly
controllable within the limits set, and provide a means of
comparing the results by some suitable method of measuring.
Now measurement, as we have seen, is the proper start-,
ing point, and this involves the selection of a standard for
comparison. If the standard is one which permits com-
parisons in figures, like the standard of length, so much the
better. Then, instead of saying that an article is ' 'slightly
red" or a "little too green," we should be able to say how
red it is, or how much too green. In that event we might
348 THE CONTROL OF QUALITY
hope to do with color what we have already accomplished
with dimension, by working out the relationship between
cause and effect. When it became possible to measure in
ten- thousandths of an inch, we were presently in a position
to work to that degree of accuracy — but not until then.
Hence, in the case of color, the first step is to search for a
proper basis of establishing such a standard of measurement.
Standard Samples
The simplest scheme would be to select a series of samples
of the goods and grade them according to an arbitrary scale
with reference to their appearance. Thus, ten samples ar-
ranged in a scale, in which each one differed from its neigh-
bors by an equal amount of color, or luster, or smoothness,
would provide us for comparative purposes with a scale of
ten. Sometimes, a simple scheme such as this is all that con-
ditions warrant, or perhaps it may be the best we can do;
but it is entirely too coarse for precise and careful work.
The lack of quantitative comparison greatly hampers any
systematic attempt to evaluate deviations from standard
and therefore to develop means for correcting such errors.
The Standard Color Card
The first movement in our industries for standardizing
color for commercial purposes was made by The Textile
Color Card Association of the United States, in developing
a series of color cards which find wide use in most of the in-
dustries engaged in the manufacture of clothing and the
basic materials of clothing. The fact that the paint, paper,
and some other industries are making use of these color
cards indicates their great practical value in reducing losses
of various sorts. A numbering system is used in accordance
with the following scale, standard colors being indicated
by the letter 6" used as a prefix :
THE CONTROL OF COLOR 349
1st, 2nd, 3rd figures indicate the rela- 4th figure indicates the strength of the
tive proportion of the component color designated by the first three
parts of a color : figures :
1 White i Lightest
2 Red 2 Second lightest
3 Orange 3 Light
4 Yellow 4 Medium light
5 Green 5 Medium
6 Blue 6 Medium dark
7 Violet 7 Dark
8 Gray 8 Second darkest
9 Black 9 Darkest
o No change
To illustrate: Turquoise is "S. 6153"
6i53
BLUE WHITE GREEN LIGHT
Principal Principal Secondary Strength
Color Blend Blend
The establishment of this systematic classification of
colors for commercial purposes in the textile and allied
industries is evidence of a highly commendable and far-
sighted attitude toward solving the problem of color con-
trol. It will be noted, however, that in its last analysis
any such classification depends upon the integrity of the
standard samples supplied by the color cards themselves;
the samples on the various cards must be alike for a given
color, and each sample should be as little likely as possible
to change as time goes on. The necessity for such assump-
tions can only be offset when the art has been advanced to
a point where construction formulas for the reproduction of
standard colors can be stated in terms of the exact propor-
tions of the color-creating factors, and the colors them-
selves can be stated in impersonal figures.
A similar practical contribution towards color standard-
ization was made by the late A. H. Munsell in the form of a
color notation and an atlas of colors.2 The atlas consists
2 A. H. Munsell, "A Color Notation"; "The Atlas of the Munsell Color System."
350 THE CONTROL OF QUALITY
of a series of charts in which colored samples are arranged in
accordance with the Mimsell color system. A scientific
investigation of this system was undertaken by the Bureau
of Standards and a very interesting report of it is published
under the title of "An Examination of the Munsell Color
System."3
Dangers of Standard Samples
The great trouble with standard samples is that we have
no assurance that they are not continuously changing.
On the contrary, we can be sure that they do change, and
by such insidiously small increments that the changes are
hard to detect. The sample is one thing today and some-
thing else almost before we know it. More dangerous yet,
we may not know that its appearance has altered. In
many plants, where this is fully appreciated master stand-
ards are kept. When it is the custom of the color expert
to carry in his mind and to allow for any slight difference
between the working and the master sample, the practice
usually leads to interesting results.
Just as in the case of dimension, precise control of color
requires a more absolute method of measurement. But to
fix upon that, we must first get some idea of what makes
color. Perhaps this would be expressed better by saying
that our first problem is to determine, as nearly as we can,
what color is.
What Is Color?
If a truism may be pardoned, color (and for that matter
any quality which goes to make up appearance) is some-
thing which you see with your eyes. What else can it be?
And the eye is sensitive only to light. It makes no differ-
3 Bureau of Standards, "Technologic Paper No. 167," by Irwin G. Priest, K. S. Gibson, and
H. J. McNicholas.
THE CONTROL OF COLOR 351
ence whether the particular kind of appearance we are deal-
ing with is caused by a mechanical treatment of the surface
of the article, or by stains, pigments, or dyes, or whether
the subjective sensation of color is due to some inherent
property of the raw material from which the article is
made. But irrespective of the cause of color, the effect is
light, so that as a starting point the use of optical methods
is indicated at once as the only sure way of attacking the
problem, both for standardizing the final result and for
measuring the effects as a step toward controlling the agents
used to create that result. Thus, color considered as the
final effect must be reduced to a measured basis for com-
parison with a view to studying the causes of errors or
differences, as well as the means for modifying errors and
making the results more uniform.
In approaching the subject, then, from the standpoint
of color considered as light, it should be observed that three
principal factors are involved, since without any one of
these three there will be no color — first, the illuminant, or
source of light, which may be regarded as the effector;
second, the subject, or the thing which is said to have
color; third, the eye of the observer, which, as the receptor
of the sensation, is merely a lenticular instrument adjust-
able within limits but varying from individual to individual
and from time to time even for the same individual. Let us
now consider each of these subjects separately.
The Illuminant
The sensation of light is now generally considered to be
caused by a form of radiant energy which occurs in a va-
riety of wave lengths and frequencies of vibration, but
which passes through empty space without appreciable
change in velocity. The nervous system of the eye is
sensitive to this radiant energy only within a comparatively
352
THE CONTROL OF QUALITY
narrow range, as indicated in Figure 85. 4 Beyond this
range, in one direction, are found the ultra-violet rays,
whose presence is made known by their chemical or actinic
properties. In the other direction are the infra-red rays,
which are noticeable on account of their heating effect.
It will be noted also from the relative visibility curve
1.0U
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Ultra-Violet Violet Blue
500
540 580 620
Green Yellow Orange.
G60
700
Red
740 780
Infra- Red
Figure 85.
Chart for Spectral Analysis of Color Showing Relative Visibility
Curve
(Figure 85) that the eye is not equally sensitive to all the
visible rays, but that these rays begin to become visible at
the edge of the ultra-violet region, reach a maximum effect
in the greens and yellows, and then gradually fade away and
disappear at the beginning of the infra-red region.
Since radiant energy is transmitted in the form of
waves, and since each wave length of the visible rays is
associated with a very definite color sensation, we have a
4 This follows the chart used by the Bureau of Standards in the Munsell color examina-
tion already referred to.
THE CONTROL OF COLOR 353
convenient way of exactly indicating any particular hue
due to a given wave length, or a small group of similar
wave lengths, by stating that wave length in figures. This
is especially useful since the eye itself is capable of a very
sensitive differentiation between the various wave lengths.
The lower scale of Figure 85 shows the wave lengths as-
sociated with the principal colors. The figures stated for
wave lengths are in millimicrons, or millionths of a milli-
meter (about a 25-millionth of an inch).
White light is, of course, a mixture of all these rays in
more or less definite proportions, depending upon the
source of light. For practical purposes it may be taken as
the effect on the eye of average noon daylight. It should
be noted also in this preliminary summary that daylight
itself is varying all the time and from place to place. Con-
sequently, it is usually anything else but pure white light.
This fact must be remembered in connection with any
careful work with color for the reason that, no matter what
the subject is, only such color can be seen as has correspond-
ing colored rays in the source of the illuminant. Thus, a so-
called green surface, which reflects only green light, if illumi-
nated by a red light will appear black, because no light is
reflected. Consequently, the importance of having a stand-
ard illuminant for color work becomes obvious, and as it is
merely common sense to keep all of our work in consonance
with the ordinary conditions with which we are acquainted,
a light source as nearly as may be like natural north sky
daylight is generally taken as most suitable for color-match-
ing and study. Such lights are obtainable commercially
and are made by filtering out the rays which are in excess of
those contained in average north sky daylight. When the
light is reflected for instrumental use, it is the usual practice
to employ a white magnesia block or some equivalent, as
the standard white for comparison.
23
354 THE CONTROL OF QUALITY
The Subject
In studying the characteristics which cause an object to
have color, let us consider the limiting cases first. A per-
fect mirror would reflect practically all of the light from the
illuminant and the result would be the same as looking at
the illuminant. At the other extreme, a perfectly black
surface would absorb all of the light and reflect none. If
the object, on the other hand, reflected only a portion of the
incident light without changing the relative distribution of
the constituent light rays, the color of the object would not
be different from that of the illuminant, but it would be less
bright. Thus, if the illuminant were a white light the object
would appear gray. We have now defined white light or
white, black or the absence of light, and the neutral grays,
as intermediate stages between the two extremes of white
and black.
Suppose, however, the subject does not equally reflect all
of the incident rays, but that it absorbs some of them and
reflects the remainder. This process of selective absorption
and reflection brings about an unbalanced distribution of
the light rays as compared with the normal distribution in
white light, with the result that some one group of rays
becomes dominant. For example, if a red predominates
in the light reflected by the subject, we say that the subject
is colored red.
If the subject is a fluid, essentially the same process of
selection takes place, except that in this case certain rays
are absorbed and others transmitted so that we have selec-
tive absorption and transmission. That is to say, the words
used are different, but the ideas are identical.
Color is caused in several other ways, such as by the
interference of light rays (as for example, by a drop of oil on
water) , or by dispersion of light (with a prism) , or as in the
case of fluorescent and phosphorescent substances, or by
THE CONTROL OF COLOR 355
polarization, to mention a few instances of color phenomena.
In industrial work, however, selective absorption is by far
the most frequently encountered.
The Eye
For our present purpose the eye may be considered as
an optical instrument of lenticular form which is the inter-
mediary between the brain and the external causes of light
and color. The eye views a group of colored rays, or rays of
different wave lengths, solely as an intermingled group and
sees only the average result of the mixture, e.g., white light.
In this sense it is a synthetic instrument incapable of ana-
lyzing the light presented to it, or of separating out the in-
dividual rays. In order to accomplish such analysis, the
eye requires the assistance of an instrumental device such
as the prism, or the ruled grating, or a color filter, as will be
shown presently. Without such a device it is impossible to
view the constituent colors of any mixture separately.
Thus when one mixes a blue powder with a yellow, the eye
presently sees only the green effect of the combination.
The Color Constants
On the other hand, the eye can analyze color with ref-
erence to three so-called color constants known under vari-
ous terms as set forth below. Says Dr. M. Luckiesh:
One of the greatest needs in the art and science of color is
a standardization of the terms used in describing the quality of
colors and an accurate system of color notation. ... The
quality of any color can be accurately described by determining
its hue, saturation or purity, and its brightness.
Hue (sometimes called "color tone" or "quality") is the
kind of color with reference to the spectral color scale. Thus
a color whose predominating group of rays are in the red is
said to have red as the dominant hue. When color is
356 THE CONTROL OF QUALITY
measured instrumentally the dominant hue is stated in
figures as the wave length of the spectral color correspond-
ing to the dominant hue. The hues of the non-spectral
purples are handled by taking the dominant hues of their
complementary 5 colors.
Purity (also called "saturation," "chroma," "strength,"
or "intensity") indicates how closely the constituent rays
approximate to none but rays of the dominant hue. Spec-
tral colors are pure, but other colors are composed of many
other rays than those which predominate — hence the purer
the color, the nearer it is in composition to the spectral color
of corresponding hue.
In instrumental measurements of color, since any color
may be matched by diluting a given spectral color with
white light, the relative quantity of white light required for
the match is used as the measure of purity and is expressed
in figures as a percentage. The purity becomes greater
as the percentage of white light required for a match be-
comes less. As stated under "hue," purples form an excep-
tion, but these are handled by working in terms of the cor-
responding complementary colors.
Brightness (also called "luminosity," "value," or
"tone") relates to the total amount of light reflected or
transmitted, regardless of hue or purity — thus a neutral
gray photograph of colored objects shows variations in
brightness only. It is measured by comparing the subject
with a surface of known brightness, the result being ex-
pressed as a percentage of the standard of brightness.
The ideas conveyed by the above definitions will be clar-
ified by referring to the graphs shown in Figure 86. Curve
a is a gray because it contains equal proportions of all the
special colors and differs from white only in reduced bright-
ness. Curves b, c, and d, are all colors of red hue, of which d
5 A complementary color may be defined by stating that when white light is split into two
parts the colors thus formed are complementary to each other.
THE CONTROL OF COLOR
357
is the brightest, since it reflects the most light, and c is the
purest because it has the least admixture of other rays
than red rays. Curve e is a blue. Differences in purity
may be accentuated by plotting the curves on logarithmic
paper.
Tints are formed by diluting a color with white, i.e., by
reducing the purity; e.g., spectral colors are pure — pinks,
i.oo
1.00
Figure 86. Chart for Spectral Analysis of Color Showing Typical Color
Analyses Plotted as Curves
which are tints of red, are not found in the spectrum. Shades
are produced by admixing black, i.e., by reducing brightness
without affecting hue or purity.
The above facts are of interest in the practical study of
color, for the reason that it would seem desirable to analyze
and measure color in terms of the dimensions, such as hue,
purity, and brightness, which the eye is capable of seeing
without instrumental assistance. This would appear to be
the natural way to approach color problems instead of
358 THE CONTROL OF QUALITY
using some system of combining primary colors, but in
either case practical difficulties must be overcome in any
given industrial application.
Color Vision
As might be expected, the human eye is quite variable
in the way in which it sees color. It varies from time to
time with the same individual and very seriously from in-
dividual to individual. The lack of a definite and precise
terminology for color among the general public has resulted
in a looseness of usage which accentuates this source of per-
sonal error. Many cases of so-called color blindness have
been found to be nothing but lack of education of the eye.
The eye of a highly trained color expert or matcher is
extremely sensitive to very small color differences and dis-
tinctions. This fact is, in the writer's opinion, one of the rea-
sons why color in the arts has not been reduced to a basis of
measurement to any considerable extent, outside of the
physics laboratory. The chemistry of dyestuffs and pig-
ments has received very intensive study, because for their
intelligent application such study has been absolutely nec-
essary; but the very ability to perceive small differences in
the color effects resulting from the use of such tinctorial
agents has lead to ignoring the very desirable and vitally
important features of measurement. Thus, in the factory
one hears such expressions as the following: "The color is
a little too much on the red " — " It has a slight red cast "
" 1 1 is too fine ' '— ' Too nice ' '— ' ' Too quiet ' '— ' ' Not enough
depth" — and so on. The absence of any means for quan-
titative measurement, or the failure to develop and utilize
means for stating in figures how much these color errors are,
has stood in the way of progress toward finding out the
proper adjustments and corrections of processes so that
they could be standardized.
THE CONTROL OF COLOR
359
Methods of Analyzing Color
Color can be analyzed for purposes of study in much the
same way that it is created, if use is made of various devices
which break up light into its constituent parts. Thus, dif-
fraction by the use of a parallel-ruled grating is one means
which may be used, but the best known device is a simple
prism when used as a means of dispersion. As shown in
Figure 87, light rays of different wave lengths bend differ-
Figure 87. Sketch of Prism and Spectrum
ently in passing through a prism of glass of triangular cross-
section and thus are dispersed in a systematic way. The
consequence is that the rays of different wave length are
separated so that viewing a ray of light which has been
dispersed by a prism shows a band of separate colors which
is known as the ''spectrum."
In other words, each color in the spectrum' is a small
group of light of similar wave lengths and is the nearest to a
truly pure color to be found in nature. It is for this reason
that purity, as denned on page 356, is expressed as a per-
centage, indicating its nearness in this respect to the spectral
color of the same hue, and showing its degree of freedom
from all other colors except the dominant hue.
The use of a simple piece of glass to produce a spectrum
360 THE CONTROL OF QUALITY
should be a constant reminder that the world is not only
given to us as a great problem to solve, but also that the
means of working out the problem are at hand and in fact
very often exist in very simple and readily accessible form.
Who would suspect that the ordinary white light of a gloomy
day contains the hidden beauty which is to be found only in
the pure spectral colors? The eye cannot see them with-
out the assistance of very simple means, yet it was not until
1666 that Sir Isaac Newton used the prism to create a rain-
bow at will.
Analysis by Primary Colors
Color may be analyzed also by allowing light to pass
through monochromatic niters. Viewing a subject or,
more properly speaking, the ray of light from the subject
through a filter (of stained glass or gelatin) which allows
only green to pass, will give a very good idea of the amount
of green present. Similarly, the use of other color filters per-
mits a more complete analysis. Further, as is well known,
it is possible to match any hue with a suitable combination
of three primary colors. There are two or three things to
remember, however, when speaking of primary colors.
First, since the eye is an averaging instrument, there are
several combinations of three colors which will yield the
same result to the eye although upon analysis the spectral
composition would prove to be quite different in each case.
In other words, the same effect may be brought about by
mixture of different sets of carefully selected colors.
Second, colored lights may be mixed by addition of colored
light rays and each addition tends toward the production of
white. This will be evident from a consideration of the fact
that white light itself is the summation of all the colored
rays. The "additive" primaries are red, green, and blue.
Third, color as ordinarily produced in the arts is the result,
THE CONTROL OF COLOR 361
on the other hand, of the successive subtraction of light, due
to the fact that each stain, dyestuff, or pigment selectively
absorbs some of the incident light. Consequently, as Pat-
erson6 says, "every admixture of colour is a step towards
darkness." The " subtractive " primary colors are ordi-
narily termed red, yellow, and blue. Luckiesh states, how-
ever, that they would be more exactly described as purple,
yellow, and blue-green. These subtractive primaries are
what most people ordinarily call the primary colors. As a
matter of fact, they are only primaries for color-mixing of
stains, pigments, and dyes. They are, moreover, the com-
plementaries of the additive primaries for mixing colored
lights.7
Instruments for Measuring Color
A large number of instruments for analyzing and meas-
uring color are in constant use in the physics laboratory.
These instruments are based on various adaptations of the
principles outlined above. Although some of them have
been employed in the arts, their main use has been in labora-
tory work. In general, they have not been used to any-
thing like the extent that the resultant economies to be
obtained from their application would warrant. This is
partly owing, as already stated, to the failure of manufac-
turers to realize the vital importance of measurement in
bringing some of our long-established processes under more
precise technical control, and partly owing to the fact that
some of the instruments require modification to make them
more suitable for general industrial use, as will be presently
indicated.
Basic control instruments belong to the spectrometer
class. Some of them look quite complicated, but they really
6 See David Paterson, "Textile Colour Mixing," p. 34.
7 "Color and Its Applications," by M. Luckiesh, Chapter III.
362 THE CONTROL OF QUALITY
consist of a simple application of some equally simple optical
parts. A prism (or sometimes a grating) is used to break
light up into its constituent colored rays, lenses mounted in
telescopes are used to magnify the image of the spectrum
thus created by the prism, and these elements of the instru-
ment are mounted in such an adjustable relation to each
other that a scale can be marked off on the instrument to
show the wave length of each color. To accomplish the
latter purpose, either the telescope or the prism is revolved
to bring each spectral color into the viewing axes, and the
corresponding wave length is shown on a calibrated scale.
The Spectrophotometer
The Spectrophotometer is an instrument for breaking up
light from the subject into its constituent rays (this is the
spectroscopic part of the instrument) and for measuring the
quantity of each part of such light against, or as a percent-
age of the same rays from a standard white light (this is
the photometric part of the instrument). Obviously, by
reason of the fact that it measures the relative quantity of
each colored ray present in any light, the Spectrophotometer
is the basic control instrument for color. As shown in Figure
88, it consists of two spectroscopes mounted so that the
intensity of rays of like wave length in the two spectra can
be compared by placing them side by side in the field of
view. Light is taken from a standard source 6" and from
the subject Si. The two rays enter a Lummer-Brodhun
photometer cube so arranged that after being dispersed by
the prism they may be viewed in juxtaposition through the
telescope. It is thus possible to select one spectral color
after another and by the use of a flicker or other type of
photometer, to measure the quantity of said color as a per-
centage of a standard spectral color.
The result obtained is more clearly shown by reference
THE CONTROL OF COLOR
363
to Figure 86, in which the curves of several spectrophoto-
metric measurements are plotted.
The Monochromatic Colorimeter
As has been seen, the spectrophotometer gives us a com-
plete analysis of any color, and when the results are plotted
graphically it is possible to get a very fair idea of the domi-
nant hue, the purity, and the brightness. To measure
hue, purity, and brightness of a color in terms of figures
directly and without computation requires, however, one
other instrument, which may be regarded as the second
basic control instrument, known as the monochromatic
#
Sj- Light from Subject
Photometer
Cube which
results in a
Field of View
as below.
--- ^S-Standard Light
Eye of Observer
Figure 88. Diagram of Spectrophotometer
(After Luckiesh)
364 THE CONTROL OF QUALITY
colorimeter, of which the Nutting colorimeter (made by
Adam Hilger, Ltd., London) is doubtless the latest and best
known type. It consists essentially of a spectrophotometer
with an additional arm to permit the admixture of a known
amount of white light. Briefly stated, the hue of the sub-
ject is matched by varying the angular position of one arm,
the purity is matched by varying the amount of white light
added, on the principle that any hue can be matched by
mixing white light in suitable proportion with the corre-
sponding spectral hue, and the brightness is measured by
the photometer attachment.
By means of these two instruments it is possible com-
pletely to analyze a color, and to state the color in terms of
figures for the constants, hue, purity, and brightness. Need-
less to say, the use of figures as a measure of color in the arts
should be accompanied by the use of plus and minus limits,
as in dimensional work. Quality varies in the case of color
just as it does in dimensional work, and the same phenomena
must be met by practices alike in principle. The precision
used will vary with the character of the commercial require-
ments for the given case and with the economic and techni-
cal possibilities of the processes.
The spectroscopic type of instrument is available for
control laboratory purposes. This apparatus may be used
as a guide in the control of quality of basic materials, such as
dyestuffs and pigments, and for the completed product,
with this qualification that many of the colors used in the
arts are what are known as "mode" or "fashion" colors,
most of which are quite dark. A great many textiles, for
example, reflect less than 5 per cent of the incident light and
it is difficult to get precise measurements with instruments
which themselves absorb a quantity of light in the optical
parts. A sufficiently intense demand from the arts will
doubtless bring about the development of instruments of
THE CONTROL OF COLOR 365
this sort more suitable for general application and in which
the light from a larger area is concentrated in order to
provide sufficient light to analyze and measure with ease and
precision. There is need also for an instrument which will
more readily permit of analyzing color in terms of the re-
agents used to create that color. Such an instrument also
will be merely an improved adaptation of existing instru-
ments and will be used in conjunction with a technique for
working out quantitatively the combinations of pigments,
dyes, or stains required to produce a given color effect.
Auxiliary Instruments
A number of devices are available in which the method
of analysis consists in filtering through monochromatic
filters. It should be observed, however, that such instru-
ments do not analyze color in terms of hue, purity, and
brightness as the eye sees color. They are, nevertheless,
suited to certain applications in the arts, although they do
not give the same complete range of measurement obtain-
able by the use of the spectrophotometer.
A useful instrument for many sorts of industrial purposes
is known as the Hess-Ives Tint-Photometer. With this
instrument it is possible to take readings of a subject as a
percentage of the light reflected from a block of magnesia,
and to compute the brightness therefrom. For bright flat
colors, such an instrument yields a measurement of the
color in terms of the primaries, red, green, and blue-violet,
expressed as percentages of light taken through the same
filters from the 100 per cent magnesia standard.
Other filters are provided for special industrial uses.
For the darker shades or mode colors the measurements
would be less than 5 per cent and hence would be useless
for practical purposes. For work of this sort, a neutral
gray standard may be constructed for use instead of the
366 THE CONTROL OF QUALITY
magnesia block, care being taken to see that the new stand-
ard is a true gray. It may be made by mixing lamp black
with magnesia (carbonate or oxide). The use of a gray
standard will throw the measurement well up into the scale.
The author had used such standards which reflected less
than 10 per cent of the magnesia standard and consequently
multiplied the scale readings by 10 or more. The instru-
ment may be used also for direct comparisons between a
standard sample and the unknown subject.
Reduction of Errors in Color Work
Those who are interested in color work in industry would
do well to make a close study of the phenomena involved
from the physical standpoint, i.e., the study of color from the
standpoint of light. Such a study should reveal the need
of a more definite and precise terminology, the desirability
of measurement in all its applications, and for the evolution
of simple measuring apparatus, as well as of evolving appa-
ratus more nearly suited to the needs of applied science.
When instrumental means are not used, inspectors in
color-matching should be checked by actual test, even if
more exact methods are not available. In this manner, the
dangers of large personal errors due to idiosyncrasies of
color vision may be minimized. Everyone working with
color should be warned against the errors due to contrast,
and instructed in the relief of eye fatigue, caused by looking
at brilliant red, for example, by such a simple expedient as
an occasional glance at an equally brilliant green. The
value of standardized matching lights would hardly seem
to need mentioning.
Such a study as that recommended will reveal industry's
great need for the measurement of color in terms of figures.
The possibilities for resulting economy in the arts are aston-
ishing.
THE CONTROL OF COLOR 367
Standards of Appearance
Needless to say the extension of the same precise con-
trol scheme to other industrial problems besides color holds
forth interesting opportunities for reducing errors and
minimizing losses. It is not at all unlikely that a similar
application of optical methods may be profitably developed
to reduce various sorts of finishes, such as polished metal
surfaces, to a basis of definite standardization. Optical
instruments of other sorts have already been used exten-
sively in a variety of industrial applications (e.g., the sugar
and oil industries) and it is only reasonable to expect the
adoption of such methods in other fields.
Appearance, as previously indicated, is in reality nothing
but light, but the qualities of this light which characterize
a given appearance may be caused by a variety of things,
such as the finish and texture of the surface, for example.
That is to say, color is but one of the qualities which go to
make up appearance; nevertheless, all of these qualities
are subject to the same general treatment of analysis (both
qualitative and quantitative), followed by the ascertain-
ment of the relations between the final results and the
causes thereof — in short, by the usual methods of science.
CHAPTER XXII
THE SCIENTIFIC ATTITUDE OF MIND
AND ITS METHODS
Science and the Arts
It is usual for the people of the present day to observe
with pride the progress made in the arts and sciences during
the last century — a story of advances greater probably than
in all previous time, and made at a rate that is still accelerat-
ing. There are one or two aspects of this situation which
are not so much of historical interest as they are of value in
pointing the surest way to further and more rapid progress,
especially in the manufacturing arts.
The first of these thoughts is that the recent rapid im-
provements in industry are dependent upon and followed
after a great advance in the sciences. As Jevons says :
A science teaches us to know, and an art to do, and all the more
perfect sciences lead to the creation of corresponding useful arts.
Astronomy is the foundation of the art of navigation. . . .
The industrial arts have existed on a broad scale for
ages, but in former times science shows only as a dim light,
from time to time and in scattered places. Modern manu-
facturing followed the wonderful scientific movement which
began in force but a few generations ago ; it has progressed
only so far as it has applied these scientific discoveries.
The second and somewhat startling thought is that the
arts, in large part at least, have whole-heartedly and strenu-
ously resisted every attempt to introduce and apply the
discoveries of science. Everyone is quite inured to the
attitude of labor leaders in opposing the adoption of labor-
saving devices, in spite of the fact that the greatest hope
368
THE SCIENTIFIC ATTITUDE OF MIND 369
of the rank and file for a greater share of the good things of
this world, lies in the production of more goods and better
goods, with less effort. And the extra effort thus released
is available to produce still other things which never ex-
isted before. This attitude is an old story and a stupid
one, but it is not entirely what is referred to here. For the
source of much opposition to the adoption of improve-
ments, or in fact of any conscious preplanned program for
advancing industry, is to be found in the attitude of indus-
trial executives, from foreman to manager to owner — es-
pecially the latter, or scientific workers would be better paid.
Science and the Practical Man
In short, there exists the contradiction that industry
owes its present high position to science, but industry
habitually opposes further improvement. Industry, how-
ever, will agree with one of science's principles, namely,
that there must be a cause for every effect. That being so,
there must be a cause for such a situation ; which leads quite
naturally to the conclusion that it ought to be worth the
time and trouble to consider this matter rather carefully.
Perhaps the inquiry may result in working out a compro-
mise attitude of service to both parties.
It must be admitted at once that conservatism is a useful
thing, provided it is not reactionary. Sane opposition to
change is doubly valuable. If men rushed to adopt every
new device without careful consideration and practical
test, we should all be living in the chaos of Sovietism, if we
succeeded in holding ourselves even at that level. Further-
more, opposition to change is necessary to secure the ad-
vantage of the change. Newton said this in his third law
of motion — " Action and reaction are equal and opposite."
A force requires something to push against in order to
build up its potential; and the opposition which must be
24
370 THE CONTROL OF QUALITY
overcome is the thing which develops real strength in any
movement. Thus the measure of your belief in a principle
depends upon and varies with your willingness to fight for
it. With this realization, you will prepare yourself better
to convince people that your plans are correct and to per-
suade them that your ideas should be adopted. To do so,
you must be thorough in your own preparation, which will
result in having something better to sell than you had at
first. In fact, a reasonable disagreement is encouraging
because if everyone accepted what you said at once and
without discussion, you would have nothing new or worth
while after all.
In the factory, however, one often encounters — perhaps
I should say, one usually and very certainly encounters-
something that is more than just conservatism. This at-
titude is the particular hobby of the "practical" man, who
takes genuine pride in being out of patience with all "the-
ory." In the extreme form this type of factory executive
recalls Lord Beaconsfield's definition of a practical man as
one who practices the errors of his forefathers.1 This at-
titude of mind can be spotted at once, by recommending
some slight improvement or change in method of carrying
out a process. The "practical" man will assert that he has
been doing it successfully as it is for the last twenty years
(thirty-five is a favorite figure also) ; and will then talk
about his experience. The best way to meet this attitude
is by education — proving the point by teaching, step by
step. It sometimes requires almost infinite patience to
save such a man from himself.
Theory or Theorists
In all fairness, it must be said that there is a good deal of
justification for the practical man's rejection of theory, and
1 "An Introduction to Mathematics," by A. N. Whitehead (p. 40).
THE SCIENTIFIC ATTITUDE OF MIND 371
especially of theorists. The man who has the job of mak-
ing things has to confine his interest to proved methods;
his business does not provide time for speculation or ex-
perimentation in working hours. When goods produced
is the measure of achievement, as it must and should be in
the shop, there is bound to be objection to even taking a
chance of failure. Such losses should be confined to the
laboratory, which should be kept separate from the shop for
that reason.
Too often also, the charge is true that the scientific
worker is wholly out of touch with the practical details of
the arts which should depend upon his work for their future
progress. The scientist finds some measure of explanation,
when this situation exists, both because his work is apathet-
ically received by the practical man, as well as because he
is professedly in search of knowledge for its own sake rather
than for its immediate money value. ' ' There is a necessary
unworldliness about a sincere scientific man; he is too pre-
occupied with his research to plan and scheme how to
make money out of it."2 His greatest compensation lies
in the realization, as Dr. George Sarton has so ably said,3
that man's intellectual advancement is the only real meas-
ure of progress. Anything which helps to solve the ever-
present problems which the world offers, means progress
to the true man of science. If the solution is not useful
now, it will be later on; and, if in the meantime he can carry
on in his chosen field only at great personal sacrifice, then
all the more reason to speak the truth at any personal cost
and to worry little about the criticism or opposition of the
moment.
There is evidence on all sides of a lack of correlation of the
sciences and the arts which doubtless is due to the difficulty an
'• "The Outline of History," by H. G. Wells.
3 See his essays in Scribner's on " The Message of Leonardo " and " Hidden History."
372 THE CONTROL OF QUALITY
individual encounters in adapting himself to these two viewpoints.
For the benefit of his art, the artist should acquaint himself with the
general sciences upon which his art is founded ; and for the benefit of
progress the scientist should bear in mind the viewpoint of the artist.
There should be no misapprehension regarding the relation of science
and art, because the former supplies the enduring foundation of the
latter. For this reason it appears that those who primarily possess
a scientific viewpoint should attempt to bridge the gap by laying their
course upon facts.4
The Engineer as Co-ordinator
Granting that nothing but good can come from bridging
the gap between science and industry, the only question to
be answered is — "Who is the man to do it?" The engineer,
either as executive or consultant, logically seems the man
for the job. He either is or should be pretty close to both
sides. If he is a real engineer he must be a fairly good
scientist. If he is of any use in the manufacturing plant he
must be practical in his viewpoint. As the friend of pro-
duction, he will analyze its needs for science's help, and in
the light of a sympathetic understanding bred of contact
with the work. His observation, moreover, will be guided
by a knowledge and appreciation of the methods of science,
and his acquaintance with science will tell him where to
look for further guidance. Once he knows the answer, his
real task is to put it into form for practical use, and to make
clear and convincing explanation of its fine points and ad-
vantages to the man who must do the actual work.
The engineer's purpose in industry should be to save
effort by making it possible to do the job in hand more
easily, and with a better product for a given effort. There
are so many things to be done which have not even been
started yet, that it is greatly to everyone's interest to free
ourselves from just as much effort in doing our present work
4 From the introduction to "The Language of Color," by M. Luckiesh, Director of Ap-
plied Science, Nela Research Laboratories, National Lamp Works of the General Electric Co.,
Cleveland.
THE SCIENTIFIC ATTITUDE OF MIND 373
as we possibly can. To carry out this project in syste-
matic form requires recognition of the fact that material
progress rests upon an intellectual foundation; and, as we
have seen, this in turn receives its greatest impetus from a
peculiar mental attitude or method of thinking which is
known as "scientific." Let us consider some of the special
characteristics of this attitude.
The Scientific Attitude
Every small boy, unless he is most unlucky, passes
through the stage of learning, rather early in his career,
that he gains nothing by lying, crookedness, or not playing
fair. Seemingly men have had to go through with much
the same process in their constant fight with nature. The
world is a pretty decent place if we are careful to conform to
nature's laws, but we are sure of defeat when we do not.
The bridge that is designed to suit a present fancy, instead
of being in strict conformity with the established laws of
statics and the proved strength of its materials, is certain
to fail. All engineering practice owes its rapid progress to
the truthful observance of and strict adherence to known
principles and proved facts.
There are several ways in which such a body of knowl-
edge can be secured, and when systematized into form for use
it may be called ' 'science." If this knowledge is obtained
by the slow and expensive process of trial and error in
actual practice, each success provides an indication of one
limiting condition and each failure shows another limit;
but the method can hardly be called scientific. That is the
old method by which the arts used to advance. What
special features distinguish the newer method ?
One of the most obvious distinctions is that science is
not satisfied merely to know that such and such a thing is
true — it must know why. That the ultimate why is un-
374 THE CONTROL OF QUALITY
knowable merely adds zest to the game — it extends our
horizon to the limits. Having discovered why, we are in
a position to extend the application of the principle in-
volved. Without knowing why, we could only repeat what
had been done before. Thus the search for knowledge in
the form of principles of general application is one of the
chief characteristics of the scientific method. Its most
obvious application in manufacturing is to know, in detail,
the principles involved in the processes in use in the factory.
Upon what elementary laws of nature do they depend, and
what special adaptations of such laws are involved ? Look
around you and see how many processes there are not, whose
true inwardness is known. Many of the oldest will be
found in this class. The latest, such as those peculiar to
electrical work, have been able to profit by the discoveries
of the science which made them possible. Even the proc-
esses we think we know something about, still provide
room for intensive study; which brings us to another char-
acteristic of this special sort of mental attitude.
The scientist approaches his problem with humility.
Constant pondering over natural phenomena can have no
other effect than to make clear the huge number and vast
range of the knowable things which we still have to find
out about. Against such a background, what we today
call knowledge seems puny indeed. In this realization
lies one of the scientist's greatest sources of power. Know-
ing how little he knows, he makes very sure to see that his
work is done with such precision that error is reduced to a
minimum. He pays great attention to minute details, so
that nothing shall be left out, because the answer may lie
in some insignificant fact which is obscured by its very
obviousness. Nothing is taken for granted, and although
influenced by practical experience, he is careful to avoid its
dangers by freeing his mind of traditional untruths.
THE SCIENTIFIC ATTITUDE OF MIND 375
The Scientific Method
However humble the scientific man's attitude in pre-
paring his mind to attack his problems, he nevertheless
goes into action with confidence of success, because he has
a method which works. Applied with determination and
guided by good judgment, the scientific method is the one
method that is certain to produce results sooner or later.
For its guiding principle is fidelity to truth, and in this sense
the achievements of scientific research are the greatest pos-
sible vindication, in practical form, of the great moral law
of honesty, in its broadest application. This is the first
thought which should be driven home to every student of
the engineering sciences. There is but one safe way to deal
with natural phenomena, namely, to make sure, with pain-
ful accuracy, that your facts are correct and complete, also
that the conclusions drawn from these facts are sound in
every particular. Then, if the principles and practices
thus developed are translated into action with the same
fidelity to truth, really useful results are sure to follow.
The success of any other method is a matter of chance.
In the effort to present in convincing form conclusions
reached by the scientific method, the engineer would do well
to take a leaf from the book of the lawyer, who must neces-
sarily make very sure of the truth and completeness of his
facts, and be certain that his deductions are both logical
and precise. The literature on argumentation and the very
practical methods for testing evidence and building briefs
contain many useful hints which the engineer may adapt to
his situation with profit. Not the least of these is the way
in which the lawyer deals with the technical and scientific
matters which arise within his purview. Realizing his own
ignorance, he first makes sure to learn the story himself.
Then he assumes an equal ignorance on the part of his
readers and writes a clearer exposition and more convincing
376 THE CONTROL OF QUALITY
presentation of the technical matters involved than does
the discoverer of these very phenomena.
Then again, scientific work yields high returns for con-
structive imagination. The latter is one of the rarest and
least used of the mental processes, yet because of its for-
ward-looking attitude it should be strongly developed. The
mere statement that something is good enough as it is, or
that further improvement is impossible, should be a sure
sign to the engineer that right there is an opportunity.
The situation may call for all his ingenuity, and surely for
plenty of hard thinking. All the anticipatory and con-
structive imagination he possesses may well be focused on
the problem; but if this follows a thorough and truthful
analysis of the problem in the first place, his hard work and
late hours will be amply rewarded by results of practical
value.
The Place of the Engineer
The reason for inviting attention to the preceding dis-
cussion of the scientific attitude of mind and its methods,
is to indicate the way in which we should go about the ad-
vancement of the arts of manufacturing. The most suc-
cessful method is obvious. It remains only to select the
man to direct the job, because without a definite assign-
ment and a systematic program we shall get nowhere.
" Everybody's business is nobody's business."
As already stated, the technically trained engineer is
the logical co-ordinator of science and industry. Atten-
tion is directed to the phrase "technically trained," because
some men go through college without achieving that result,
and others acquire education without going to college at all.
But the man must be an engineer in the truest sense, regard-
less of the route by which he has arrived at that specialized
intellectual condition.
CHAPTER XXIII
THE METHOD OF ATTACK TO CONTROL
QUALITY
The Approach to the Problem
There is a lesson for everyone contained in the Chinese
philosophy which says that no theory has any value except
in so far as it is translated into action or, at least, is trans-
latable into action. Therefore if there is any merit in this
theory of controlling quality, completeness requires that
some plan be advanced for approaching the task of bringing
quality under control.
Since quality of output is the ultimate result of tech-
nical processes in one form or another, it follows that the
best way of solving problems in the control of quality is to
use the scientific method. It is the best method for ob-
taining rapid and certain returns. But it must be applied
in a strictly practical engineering way because this is a com-
mercial application of the method rather than a purely
scientific search after knowledge for its own sake. The
sort of knowledge wanted in this instance must be of im-
mediate and economic use.
Uniformity within Limits
In crystallized form, the underlying object of any
manufacturing enterprise is to make more and better goods
for less money — to obtain a greater output of standard
quality for less effort. In planning to bring quality under
control, therefore, every step is made with a view to re-
moving obstacles to greater and better output by regulating
the deviations from standard. In every instance these
377
378 THE CONTROL OF QUALITY
deviations or errors represent losses in the use of material,
labor, and manufacturing plant. Perfect quality implies
freedom from errors. But there is a limit to which quali-
tative refinement can be carried with economy. Conse-
quently, while it is true that we seek uniformity, it is a
modified and reasonable degree of uniformity — that is,
uniformity within commercial limits. The economy of
manufacture requires that the limits be suitable for the
case in hand at the moment — they must not be too large or
too small.
The scientific method is to be applied, then, to manu-
facturing problems with quality as the criterion, but every
solution worked out in this way must be mentally projected
against a background of dollars and cents, and our conclu-
sions modified accordingly to suit the present commercial
situation.
Getting the Facts
In applying any such method to a given industrial situ-
ation the first desideratum would appear to be an unbiased
scrutiny of the business as it is. The art of seeing things as
they really are is often a gift, but it can be cultivated also.
The industrial executive is so close to the details of the
business that the most obvious things escape him. Unless
he recognizes this failing and stops to take stock of the
situation he is very apt to get into a fix where "he can't see
the woods for the trees." Yet an accurate viewing of the
problem is prerequisite to any measure of success in laying
out a program for constructive work.
A prominent manufacturer who has a faculty for con-
cise expression says that industry should heed the warning
of his boyhood riding-master. The latter was in the habit
of concluding his advice about sitting up straight and so on,
by barking out — "Get off your horse and look at yourself
THE METHOD OF ATTACK 379
riding." Many a factory would be the better if its con-
trolling executives would get off their horses and watch
themselves riding — they wouldn't look so humped up to the
disinterested outside observer.
But after all, isn't this just another way of starting in to
practice the things we have been considering in the last
chapter? As we have just observed, one of the outstanding
features of the scientific method is the collection of basic
data, and the testing of such data to make sure that it is
correct; so that the first step is to get the facts in the case —
starting with the general business situation and its trends as
affecting quality, and then in all the detailed ramifications
of the business itself. The first or general viewing has to
do with external or commercial relationships, while the de-
tailed study is for the most part a matter of regulating
conditions within the factory.
Analysis
In securing the facts in detail it soon becomes evident
that resort must be had to analysis. Manufacturing prob-
lems are too large to be solved as a whole and must be
broken up into parts which are small enough to suit the
limitations of our intellectual equipment. Getting the
facts is often the hardest part of the entire process, and the
way in which the preliminary analysis is made becomes of
great importance.
Of course there is no exact and arbitrary scheme of
analysis which can be rigorously applied to every case, but
certain general guides should be followed, just as in the
case of collecting and testing legal evidence. The first step
is to make sure that we have all the facts and that they are
facts — to test their truth. The next step is to exclude those
which are clearly not pertinent to the problem in hand, as
well as those which obviously are of such little influence as
380 THE CONTROL OF QUALITY
to be unworthy of consideration. Finally, the remaining
data should be measured to determine the influence (and
the relative influence) of each fact upon the problem as a
whole. Thus measurement takes its place as a part of
analysis, or more accurately, as a necessary accompani-
ment to analysis.
Tripartition or Tripartite Analysis
Since there appears to be no generally accepted scheme
for making sure that an analysis is complete and that all
pertinent facts have been collected, I am venturing to sug-
gest the use of a general guide or working rule which has
proved of value in personal work. This working rule is that
any complete analysis should be made from three principal
viewpoints (or from at least three different angles). Its
practical application works in this fashion — if you have
examined a question from only one or two points of view,
there probably is something missing; hence at least one
more division of the subject should be made. On the other
hand, in ordinary practice three main divisions of the sub-
ject are enough.
For example, it has been fashionable for labor and capi-
tal to consider themselves as solely interested in so-called
labor problems, whereas both sides to the controversy
would have done well to consider the interests of the great
third party — the public — which in this case holds the decid-
ing vote. Another example more closely related to the
work in hand is to be found in the common error of assum-
ing that any cause has but one effect. The truth is that
every cause has several effects. As a simple instance of
this, suppose that a greater output is sought by the means
of providing a high incentive in the form of a greatly in-
creased piece rate. The cause (one element) is the higher
incentive; the direct effect (the second element) is greater
THE METHOD OF ATTACK 381
output, but unless the accompanying additional effects
(the third element) are considered and arranged for, the
quality of the output will drop. Consequently, a complete
analysis would provide at the start, with tripartition as a
guide, for an adequate stiffening of the provisions for in-
spection as a means of controlling quality to the desired
standards.
It may be mentioned incidentally and as a matter of
interest that I adopted this tripartite guide in analytical
work after observing the frequency with which careful
thinkers divide their subjects into three main sections. A
little consideration will show, however, that there is a basis
for the method in the physical world all about us. Thus
the three physical constants generally used as a foundation
for measurement are mass, time, and space, each one of
which (and many other physical things) again divides into
three elements.
The use of the three divisions of time (i.e., past, present,
and future) will be found very useful in the analysis and
subsequent solution of many factory problems. This
time relationship as affecting the planning, production, and
inspection groups in organization has been traced in Chapter
V. It may often be utilized in the study of an individual
process. For example, deviations from standard may be
caused in the process itself; or they may be carried over
from, or result from some cause in a previous process; or
they may even be due to the influence of a subsequent
process. All three possibilities should be considered.
Thus, if the later processes are in need of work, the workers
whose operation is in trouble may be unduly hurried; or
they may be assuming that any errors they make will be
corrected by subsequent and more precise operations.
This third element (the possible influence of later opera-
tions) is too frequently overlooked.
382 THE CONTROL OF QUALITY
The subject of color quality has been treated in Chap-
ter XXI in accordance with the tripartite guide.
Quality Records
The basic data for analysis will be obtained from various
sources. Such production and cost records as are at hand
should be used as a starting point, but it generally will be
found that the facts presented by such records are not
sufficient nor are they arranged in the most useful form for
the study of quality problems. As noted in Chapter VI,
a well-organized inspection service is a very useful instru-
mentality for the collection of facts relating to quality.
But a preliminary analysis should be made and used as a
basis for the quality records.
Since quality involves uniformity within limits, the
control of quality requires that quality records deal with
variations from the working standards. They must show
where and when these variations, or manufacturing errors,
occur. This involves an analytical list of all the kinds of
errors which do occur. They must show for each kind of
error the relative frequency of its occurrence, and, in a
general way at least, the size of the individual errors — all of
which involves some form of measurement.
Quality records, then, should present a list of character-
istic qualities, a list of the kinds of error for each quality, a
statement of the number and sizes of each kind of error,
and a notation of when and where the error occurs. The
cause of the error should be added if known, but, strictly
speaking, the determination of causes is a matter for sub-
sequent treatment. And all of the data is a subject for
treatment by the methods of analysis and measurement.
When the character of the quality prohibits a strict appli-
cation of measurement for determining the relative size of
errors, then the idea of measurement should be utilized by
THE METHOD OF ATTACK 383
comparison with standard samples graded in such a way as
to provide limits.
Using the Facts — Synthesis and Adjustment
The scientific method, as we have seen, is not content
to stop with a statement of facts — it must know why. In
practical application this brings us to the determination of
the causes of variations from standard. Once the reasons
for the variations are known, we are a long way on the road
to their correction. Again, it is a matter for analysis, for
carefully thorough and logical reasoning, and for the use of
constructive imagination in developing proper conclusions.
For instance, errors which occur intermittently are prob-
ably due to the way in which processes are applied. Pro-
gressive increase in the size of an error probably indicates
wear or change in equipment, and so on.
Skill in this part of the work as well as in the selection
of the most promising points of attack is something to be
acquired solely by practice. No arbitrary rule applies and
the solution in each instance will differ in details, although
the methods used are alike in principle.
After the problem has been analyzed and each small
part treated separately, the separate parts must be put
back together and adjusted. The procedure is analysis,
synthesis, and adjustment (or compromise), as already dis-
cussed in several places — notably in Chapter XVI, "Repe-
tition Manufacturing." Thus the tolerance on a given
dimension is a matter for agreement between engineering,
production, and inspection. Correct and complete analysis
is a very large part of solving the problem, because a de-
tailed knowledge of the truth usually suggests the cure.
Synthesis and its concomitant, adjustment, ordinarily re-
quire a much shorter time to execute, but their vital im-
portance cannot be too strongly stated — they call for all
384 THE CONTROL OF QUALITY
the available skill and good judgment which can be brought
to bear upon them.
The Order of Procedure
When we come to the application of the method out-
lined in the preceding, it is very evident that the approach
from the standpoint of quality must begin with an intensive
study of the product itself. This is the only sure and com-
plete way of taking the true measure of an industrial situa-
tion when quality is to be the primary guide. As suggested
in Chapter II there should then follow a similarly careful
study, first, of the processes used to create the product,
then of the organization employed to apply these processes,
and, finally, of the system used to measure the achieve-
ments and control the operation of the organization.
Admittedly the method of approach which starts with a
searching analysis of the product and processes may be
found to be somewhat arduous and exacting, but it soon
becomes most interesting because of its great practical
influence on the enterprise. Sometimes minute details are
considered uninteresting, but as Gilbert K. Chesterton
has remarked : " There is no such thing on earth as an unin-
teresting subject; the only thing that can exist is an unin-
terested person."
Quality is a variable. Oftentimes the variations are
small, but it is the amount of attention which is paid to
just such little things that determines the difference between
success and mediocrity.
Begin with the Product
Starting with the product, the first step is to analyze it
as it is, and with reference to its characteristic qualities.
In what respect should the individual articles making up the
company's output be alike? The next step is to reduce
THE METHOD OF ATTACK 385
these characteristics to some basis of measurement for pur-
poses of impersonal comparison. We can then determine
to what degree of likeness it is sensible to make the indi-
vidual pieces and establish tolerances and limits accordingly.
This involves the determining of how far the articles may
be unlike. At the same time, and by the same means, we
may observe the direction which future improvement of the
product should follow toward closer approximation to the
ideal standard.
Proceeding next to a study of the processes used in
creating the product, the investigation takes the form of
studying both processes and product together. The first
object sought is a uniform product conforming with the
predetermined working standards. This requires that the
processes used to create the product must be controllable
to an equal uniformity. To bring them to this condition
we must proceed to list the various kinds of errors (or dif-
ferences in the product), their magnitudes, and the fre-
quency with which each kind of error occurs. The next
step involves listing the possible and probable causes of
these errors, as a step toward determining their actual
causes. When the last-mentioned thing has been deter-
mined, it is no very difficult problem in most cases to de-
velop means and ways for reducing the errors — and often
to eliminate them for all practical purposes.
If the solution of the problem is not so easy to find, then
we must turn back to pure science — the master teacher — -
and develop new methods from a fresh start. If your task
seems too difficult, it will reassure you, perhaps, to take a
look at the obstacles others have overcome. One trip
through a plant making electric light bulbs, for example,
is quite cheering. The winding of wire filaments too small
for the eye to see the coils without the use of a microscope,
and the actual use of the latter on production machines is
386
THE CONTROL OF QUALITY
Figure 89. Precision Torsion Balance — Roller-Smith
THE METHOD OF ATTACK 387
typical; as also is the weighing of these filaments to a pre-
cision of I per cent for weights of less than 12 milligrams
(see Figure 89), and this as a regular production proposi-
tion.
Written Descriptions of Processes
Presently, as a result of this study, we shall know how to
perform each process. As a matter of fact, in work where
the product cannot be described by a plan (like heat treat-
ing, or weaving, or making some chemical compound), the
only method of description available is to build up an aggre-
gation of explanatory descriptions, or written instructions
for doing the work. Of course these process descriptions
must be in complete detail, if they are to be of use either in
analyzing matters affecting quality or for use in instructing
workmen. The creation of such records involves learning
your business in detail, but that is a knowledge the man-
agement of any business should have if it intends to run the
business, instead of letting the business run the manage-
ment.
There is one great distinction, however, that you can
learn the technical details of the business by the scientific
method, even though you are not actually able to do the
work yourself — at any rate, you need not be able to do it
as well as the man who is continually engaged in produc-
tion. This is a bitter pill to the extreme type of " practi-
cal" man. He is unwilling to disparage the results of
years of devotion to his work — consequently he is quite
likely to reject your advice for improvement by asking (of
himself, at least), "How can anyone, who avowedly knows
little if anything about this work, teach me how to do it
better? Haven't I been working right at this same job for
the last twenty- five years?"
But, as doubtless you have already observed, this atti-
388 THE CONTROL OF QUALITY
tude fails to distinguish between knowing the methods and
principles used in doing the work, on the one hand (the
why and how) and the skill required for their execution,
on the other. One could write out the most particular
instructions for shooting a rifle, but would only acquire
the skill necessary for accurate shooting through continuous
practice. Yet almost anyone could learn to shoot by follow-
ing the written instructions exactly.
It is a safe statement that man is not capable of doing
anything which cannot be analyzed by the scientific method
of attack and reduced to a description written in clear and
simple language. Further, such a description may be used
as the basis for improvement, once the governing principles
have been worked out; and it can be employed as well to
start any other intelligent person toward acquiring the skill
needed in its execution.
As a general rule, the oldest processes, which have not
yet been subjected to such an investigation, are the most
fertile field for its application. There is no mystery in any
industrial process, although it may well be that great skill
is required for its proper execution, and even the latter
may be simplified.
The Assemblage of Processes
After the processes have been considered in detail, it is
in logical order to consider them as merely the principal
working parts of a great manufacturing machine — the
factory as a whole. Shop arrangement (especially with a
view to care of material in process) will show new values
for system and order in physical form, as distinguished
from mere paper systems. Consider the shop and inspec-
tion arrangements with a view to planning with material
and taking full advantage of the possibilities of the principle
of centralized inspection.
THE METHOD OF ATTACK 389
Organization and System
Taking up the organization next — is it well balanced as
regards the main functions of planning, production, and
inspection? For this much is fundamental in controlling
quality. Is the factory personnel organized in a way to
provide for bringing to the attention of the workmen, in
effective form, the things they should know if quality is to
be maintained as it is, and systematically improved there-
after? Also, does the organization provide a competent
person, whose duty is that of directing this improvement
with the idea of making progress conscious and intentional ?
Usually some form of committee system will be found
useful as a means of educating the rank and file in the
details of quality manufacture. It is well-nigh useless to
spend money in bringing valuable facts to light, unless pro-
vision is made for using them. Education is the first step
toward accomplishing this, and to be effective, it should
be reinforced by methods which make it clearly to the in-
terest of the producer to put these lessons into practice.
Finally, some economical sort of system, or systems,
should be devised to present the statistics of the business
(costs, qualities, and quantities) in clear and useful form
for the guidance of the organization in correcting errors and
eliminating wastes. The cost system especially should
locate charges for damage and waste against the responsible
department rather than against the department where they
occur.
In short, the whole process of controlling quality in-
volves applying the scientific method to the industry, in a
practical engineering way. Beginning with an untiring
and systematic search for facts, we pass to a truthful, ac-
curate, and sensible use of them in refining our work. The
method is an invincible one for securing increased output,
at less expense of effort, and with higher quality.
390 THE CONTROL OF QUALITY
Conclusion
Whether as a part of some general trend for which the
times are opportune, or as the working out of economic
laws, or as a combination of both (which is the most prob-
able), business as a whole is working toward greater truth
and fidelity to accuracy. This increasing tendency toward
exact definition, which is the precursor of improved and
better regulated quality, has shown itself rather promi-
nently at times. Some years ago, for example, there began
a great movement for "pure food." More recently, similar
action has been taken for pure advertising, and one form of
truthfulness which the latter has urged is the frank and
open publication of technical details. Things are being
called what they really are, and the proof supplied, instead
of making mere assertions about quality and performance.
This situation is encouraging, especially if you are one
of those who believe that the business of the future will be
built upon a sounder basis of merit, service, and worth,
than ever before. If this is a correct viewpoint, then is
not the control of quality the first step in that direction?
Surely it is the basis for both service and the profit which
follows real service. American industry has been famous
for quantity production. Why should it not be distin-
guished also for qualities that are definite and certain?
When capitalists and industrial executives regard quality
in this light, the biggest step toward the qualitative im-
provement of industry will have been taken, because there
is no serious difficulty in the way of its achievement.
Very happily, quality is like many other things which
you can have if you only want them badly enough. In his
essay on "The Art of Seeing Things," John Burroughs says
that the secret of the successful angler's effort is no doubt
due to love of the sport. "What we love to do, that we do
well." Without the strong desire for quality, beginning at
THE METHOD OF ATTACK 391
the very top of the organization, there is little chance for
securing quality. Thus it is one of the prime responsibili-
ties of ownership and management.
There is no danger, either, in setting our ideal standards
too high, because the fact that the realized standards are
lower need not be discouraging. For it does not prevent
the ideal from serving a most useful purpose, by indicating
the direction improvement should take. "Ideals"- - said
Carl Schurz — "are like stars. You cannot touch them
with your hands but like the seafaring man on the desert of
waters you choose them as your guides and, following
them, you reach your destiny."
Granted that quality is a desirable thing to have, the
way to approach the task of placing it under sure control
is the simple one of seeking true facts and being guided
thereby, in accordance with a definite campaign. In the
main, the methods most useful in the control of quality are
merely the old-fashioned, time-honored ways of engineering
with perhaps a little different slant. "Engineering is the
art of organizing and directing men, and of controlling the
forces and materials of nature for the benefit of the human
race." There is nothing especially dramatic or mysterious
about engineering methods, but the results of their intelli-
gent and earnest application are pure magic. They present
the most romantic possibilities for solving the problems of
the world that confronts man in his upward climb.
INDEX
Accuracy, (See "Errors," "Measure-
ment," "Precision")
Adjustable limit gages, 307
Illustrations, 222, 235, 307, 308
Aisle arrangements, for central inspec-
tion system, 132
Chart, 133
Alford, L. P., quoted, 14
Allowance,
defined, 254, 255
precautions in working from, to
determine tolerances, 255-258
American amplifying gage, 298
American International Corp.,
inspection form, 80
American Locomotive Co.,
Illustrations, 18, 51, 96, 183, 192-
196, 198, 199, 202
quality control in war work, 188-
202
bullet manufacture, 197
inspection, 201
Illustrations, 51, 183
shell manufacture, 188-197
Illustrations, 192-196
time fuse manufacture, 200
Illustrations, 18, 198, 199
Appearance,
relation of color to, 347
standards of, 367
Armstrong Cork Co.,
experience with quality bonus, 21,
23
Assembling,
department, inspection's aid to, 79-
83
example of selective assembly, 82
Assembling — Continued,
repetition manufacturing, economy
in, 269
standards, 261
Automobile industry,
example of highly developed form
of inspection, 174-180
at Packard Motor Car Co., 174-
177 (See also "Packard Motor
Car Co.")
former practice, 178-180
degree of precision, obtained in,
331-333
B
Bench inspection, 164
Bench inspectors, qualifications, 152
Block gages, (See "Johansson block
gages,"" Pratt & Whitney gages")
Bonus, quality (See "Quality bonus")
Brightness, a color constant, 355
Brown and Sharpe Co.,
gages,
Illustration, 305
measuring machine, 287
Illustration, 288
micrometer calipers, proper method
of using,
Illustrations, 28, 31, 218, 253,
257, 260
Bulletin boards, suggestion for im-
provements in, 90
Bulletins, department, 158
Bureau of Standards, 215, 216, 350
Carnegie, Andrew, quoted in "Auto-
biography," 17
393
394
INDEX
Central inspection, 49-52, 115-138
advantages, 137, 138
arrangement of shop, 123
adaptation to high-grade close
work, 131-134
adaptation to rough work, 129-
130
line of flow of work first step in,
123
Chart, 123
several spaces, 134
at Lincoln Motor Co.,
at Packard Motor Car Co., 175
Illustration, 37
cribs (See "Central inspection
cribs")
forms of, 115
self-counting trays, 116-122
Illustrations, 118, 119, 120, 121
two-bin system, 122
most highly specialized form of
inspection, 115
standard, desirable, 135
Central inspection cribs,
Illustration, 126
arrangement of material storage
point in, 137
Illustration, 137
construction, 125
Illustration, 127
floor plan, 128, 129
aisle arrangements, 132-134
Charts, 128, 129, 132, 133, 135
layout, 124
Charts, 124, 125
Charles-William Stores, inspection
methods, 186
Chief inspector, (See also " Inspection
department, management of")
bulletins issued by, 158
location of office, 156
organization of work, 144
Chart, 145
qualifications, 140-142
Chief inspector — Continued,
relation to organization,
at Packard Motor Car Co., 174
at Pratt and Whitney Co., 181
staff,
duties of, 148-151
subordinates, 144
understudies, 146
titles, 143
use of conferences, 157
Church, A. Hamilton, quoted, 14
Clearance, defined, 255
Color, 346-367
analysis of, methods, 359
instruments, 361 (See also sub-
heading "measuring instru-
ments" below)
monochromatic filters, 360
prisms, 359
appearance and, 347
as light, factors of, 351-355
eye, the, 355
illuminant, the, 351-353
subject, the, 354
constants, 355
brightness, 356
hue, 355
purity, 356
control by standard samples, 348
atlas of colors, 349
color card, 213, 348-349
dangers of, 350
errors in work, reduction of, 366
measurement of, 213
measuring instruments, 361, 365
monochromatic colorimeter, 363
spectrophotometer, 362
Diagram, 363
tints and shades, 357
tone, 355
vision, 358
Comparators, 298
Hartness, 323
Illustrations, 324, 325
INDEX
395
Conditioning of material, standards,
250
Conferences, use of, by chief inspec-
tor, 157
Continuous processing,
importance of uniformity in, 275
Continuous product,
practice in regard to inspection of
manufacture of, 184
Costs,
decreased by,
quality control, 15-19
repetition manufacturing, 264-
. 280
selling, 24
Defects, remedy of, combined with
inspection, 53
Design, the, 237
changes in,
avoid if possible, 242, 245
improvement, 243
progress towards more exact, 240
Dimension, (See also "Dimensional
control laboratory," "Measure-
ment")
working standards, 252-254, 258-
261
basis of repetition work, 252
definitions for, 254, 255
Dimensional control laboratory, 281-
302
material equipment,
Brown and Sharpe measuring
machine, 287
Illustration, 288
comparators, 298
Johansson block gages, 294-297
Illustration, 297
miscellaneous, 300
Pratt and Whitney measuring
machine, 289-293
Illustrations, 290, 292
Dimensional control laboratory —
Continued,
Pratt and Whitney precision
gages, 298
surface plate, 285
physical conditions,
cleanliness, 284
floor coverings, 284
furnishings, 285
humidity, 284
lighting, 284
noise, 284
temperature, 283
vibration, 284
Dispatching, relation of inspection
to, 113
Duplicate manufacturing, 277
E
Elgin National Watch Co.,
ratio of inspectors to workers, 182
Employees,
dimensional control laboratory,
301
discovering native ability among,
153-155
effect of inspection data on,
reduction of fatigue, 93
stimulus to interest, 90, 91
inspection force (See "Inspection
department, management of"
and "organization of")
number of, relation between out-
put and, 162
Engineering department, 64
relation to inspection, 72
Engineer, the, as co-ordinator of
science and industry, 376
Errors,
in color work, 366
in measuring, 232
classes of, 227
cure for, 231
396
INDEX
Errors — Continued,
frequency of occurrence, 228
Chart, 228
reasons for accumulation of, 226-
232
Eye, the, as a factor in color, 351
Gages — Continued,
special, 310
standard, defined, 313
thread-gaging, (See "Thread-gag-
ing")
tolerances, 311
Finish,
effect on accuracy, 344
standards, 251-252
First-piece inspection, 59-61
Fits, (See "Precision")
Fixed-dimension limit gages, 304
Floor-inspection, 52
at Packard Motor Car Co., 175
qualifications of inspectors, 152
Flow of work in process, (See "Work
in process")
Foundries, practice in regard to
inspection, 184
Gages, 303-316 (See also "Measuring
instruments")
adjustable limit, 307
Illustrations, 222, 235, 307, 308
application of, 311
checking, 312, 313
Illustration, 48, 282
constitute working standards, 259
fixed-dimension limit, 304
fluid, 298
Illustration, 167
master, defined, 313
micrometer calipers, proper method
of using,
Illustrations, 28, 31, 218, 253,
257, 260
multiplying, 309
types, 310
reference, defined, 313
shop or working, defined, 313
slip in transferring size, 314
Hartness comparator, 323
Illustrations, 324, 325
Hartness, James, quoted, 318-319
Hoover, Herbert, quoted, 94
Hue, a color constant, 355
I
Illuminant, the, a factor in color, 351-
353
Industrial management, costs (See
"Costs")
employees (See "Employees")
engineering department, 64
relation to inspection, 72
inspection, (See also "Inspection")
purpose, help, 69
recognition of importance of, 63
relation of to engineering and
production, 68
inspection department, 67 (See also
"Inspection department")
organization parallel with govern-
mental, 67
planning (See "Planning")
problems, advantages of quality
control,
costs decreased, 15-19, 24
labor relationships improved,
12-15
output increased, 15-19
production department, 66
relation to inspection, 72
quality a prime responsibility of,
391
real vs. apparent organization, 70
Industrial revolution, the, 266
INDEX
397
Inspection,
American Locomotive Co., war-
time work, 201
amount necessary, 54-57
automobile plants, example of
highly developed form of, 173-
180
at Packard Motor Car Co., 174-
177
Chart, 174
former practice, 178-180
bench, 164
central (See "Central inspection")
continuous processing, 185
continuous product, 184
contribution of to general service,
74-94
arrangement, care, and analysis
of work in process, 83
collection of useful information,
74
handling rejected parts, 85-89
in assembling department, 79-
83
provides production data, 89
reduction of fatigue, 93
stimulus to interest of individual
workers, 90, 91
trouble reports, 75-78
Forms, 76, 80
cost, relation between output and
size of inspection force, 163
cribs (See "Central inspection
cribs")
denned, 36
relation to quality and quality
control, 36
department (See "Inspection de-
partment")
economies in, 61
elimination of unnecessary, 57
evolution of, 39
extensive, when desirable, 173
automobile factories, 174
I nspection — Continued,
machine tool manufacture, 181
small precision work, 182
first-piece, 59-61
floor, 52
at Packard Motor Car Co.,
175
qualifications of inspectors, 152
force (See "Inspection department,
management of," and "organiza-
tion of")
foundries, 184
gear, Lincoln Motor Co.,
Illustration, 88
general machine shop, 184
individual piece, final, Packard
Motor Car Co., 175
machine tool manufacture, 181
relation of inspection department
to organization, 181
mail order houses, 186
necessity for, 35-45
operating, on finished vehicles at
Packard Motor Car Co., 177
relation to,
engineering and production, 68
planning, (See "Planning")
rough stock, Packard Motor Car
Co.,
Illustration, 58
sampling, 59-61
small precision work, 182
tool and gage, Packard Motor Car
Co.,
Illustration, 42
types of, 46-53
governed by special factory situa-
tion, 46
loosely organized, 184
office, 47
raw materials, 46
tool, 49
work in process, 49 (See also
" Work in process, inspection ")
398
INDEX
Inspection department, (See also
"Industrial management")
importance of, recognition of by
management, 63
management of, 156-171
bulletins, 158
conferences, 157
co-ordination of work, 156
instruction of inspectors, 164-166
female labor, 166-170
location of chief inspector's
office, 156
morale, value of high, 170
overtime, 162
permanent personnel, desirability
of, 159
piece work, 161
promotion of employees, 159
proportion of output to size of
force, 163
Chart, 163
task, 156
wages of, 1 60
working hours, 162
organization of, 139-155
basis, amount of work to be
done, 142
bench inspector, 152
chief inspector, 140-142 (See
also "Chief inspector")
combination of line and staff,
144
Chart, 145
development of, 139
floor-inspectors, 152
inspectors, 147-151
personnel, discovering native
ability among, 152-154
personnel qualifications of, 151
ratio of inspectors to workers
(See "Ratio of inspectors to
workers")
related work, 142
staff duties, 147-151
I nspection department — Continued,
understudies to chief inspector,
146
purpose, 69
relation to organization,
engineering and production de-
partments, 64-69, 72
in machine tool manufacture,
181
Inspectors (See "Chief inspector,"
"Inspection department, man-
agement of" and "organization
of")
Instruments, measuring (See "Meas-
uring instruments")
Interchangeable manufacturing, 265,
272 (See also "Repetition man-
ufacturing")
Johansson, C. E., 295
Johansson block gages, 294
Illustrations, n, 222, 235, 239,
241, 268, 273, 276, 297, 299
remarkable accuracy of, 296
secrecy of manufacture, 297
Jones and Lamson Machine Co.,
Illustrations, 320, 324, 326
Labor (See "Employees")
Labor relationships,
improved by quality control, 12-15
Lassiter, C. K., quoted, 201
Law of chance, 228
Chart, 228
Lewis, Huber B., quoted, 314-316
Liberty motors, example of successful
quality control, 203-206
Light, color as (See "Color")
Limits,
defined, 254, 255
precautions in determining from
allowance, 255-258
INDEX
399
Lincoln Motor Co.,
Illustrations, 37, 48, 71, 88, 204,
205, 282
central inspection in,
Illustration, 37
quality control in war work, 203-206
Forms, 204, 205
Luckiesch, M., quoted, 355, 371
M
Machine shops, general,
practice in regard to inspection, 184
Machine tool manufacture,
by interchangeable manufacture,
278
example of highly developed form
of inspection, 181
relation of inspection department
to organization, 181
Mail order house,
inspection methods at Charles-
William Stores, 1 86
Management (See "Industrial man-
agement")
Manufacturing,
and art, difference, 264
economies in (See " Repetition
manufacturing ")
repetition, 264-280 (See also " Rep-
etition manufacturing")
schedule, basis of space assign-
ments, 109
Master control sheet, 101
Master gage, denned, 313
Material in process,
necessity for continuous supply
of, 99
space assignments for, in
two-bin system of storage, 122
Measurement, 210-232 (See also
"Dimension," "Dimensional
control laboratory")
absolute accuracy impossible, 234
denned, 234
Measurement — Continued,
errors in,
accumulation of, 229-231
classes of, 227
cure for, 231
frequency of occurrence, 228
Chart, 228
theory of, 226
evolution of, 210-222
comparison with graded scale,
214
instruments, 217-222 (See also
"Measuring instruments")
selection of qualities for, 211,212
standard samples, 212
foundation of exact sciences, 210
instruments (See "Measuring in-
struments")
precision in, 223-225 (See also
"Precision")
starting point of quality control,
210
units of, choice of, 217
Measuring instruments (See also
"Dimensional control labora-
tory," "Gages," "Measuring
machines")
choice of, 222
color, 361, 365
monochromatic colorimeter, 363
spectrophotometer, 362
Diagram, 303
comparators, 298, 323
Illustrations, 324, 325
danger of overgraduation, 220
precision, 223-225
requirements, 219
Measuring machines,
Brown and Sharpe, 287
Illustration, 288
Pratt and Whitney, 289
Illustrations, 290, 292
Mechanical devices, inspection by, 53
Mechanical revolution, the, 267
400
INDEX
Micrometer calipers,
proper method of using,
Illustrations, 28, 31, 218, 253,
257, 260
Monochromatic colorimeter, for
measuring color, 363
Monochromatic filters, use in ana-
lyzing color, 350
Multiplying gages, 309
types, 310
N
North, Simeon, early exponent of
interchangeable manufacturing,
270
O
Office inspection, 47
Operation data sheet, 104
Form, 100-107
Operation study sheet, 104
Form, 105
Operation symbols, 102-104
Organization (See "Industrial man-
agement")
Output, increased by quality control,
15-19
Overgraduation of instruments,
danger of, 220
Overtime, inspection force, 162
Packard Motor Car Co.,
Illustrations, 42, 58, 65, 167, 174,
176, 179
inspection,
example of highly developed
form of, 174
organization, 174-177
Chart, 174
tool and gage,
Illustration, 42
Personnel (See "Employees")
Piece work,
in inspection department, 161
Piece work — Continued,
interfered with by uneven flow of
work in process, 98
Planning, 95-114
dispatching, relation of inspection
to, 113
manufacturing schedule, 109
master, 101
master control sheet, 101
materials in process,
necessity for continuous supply,
99
space assignments, 1 1 1
operation data sheet, 104
Form, 106-107
operation study sheet, 104
Form, 105
operation symbols, 102-104
raw materials, necessity for con-
tinuous supply, 98
route tags, 108
Form, 108
work in process,
allowance for losses in, 109
determining quantities, 1 10
disadvantages of uneven flow,
97, 98
flow of, 95
Planning department (See "Plan-
ning")
Polakov, W. N., quoted, 15
Pratt and Whitney Co.,
gages,
Illustrations, 150, 307, 308,
315, 322, 323
adjustable limit,
precision, 298
taper, 315
thread,
measuring machine, 289
Illustrations, 290, 292
relation of inspection department
to organization, 181
INDEX
401
Precision (See also "Dimensional
control laboratory")
advantages of, 281
depends on service requirements,
,328 .
dimensional, 330-345
automobile experience, 331-333
checks, quick, 345
degree practicable, 330
effect of finish on, 344
obtaining, precautions in, 341
tables of tolerances and limits,
333-34°
Illustrations, 334-338
gages, Pratt and Whitney, 298
in manufacture of small high-grade
articles, 182
in measuring, 223, 224
in workmanship, 225
instruments, handling, 165
torsion balance,
Illustration, 386
Prestometer or Prestwich fluid gage,
298
Illustration, 167
Prism, use in analyzing color,
Illustration, 359
Product,
study of, starting point of qual-
ity control, (See "Quality con-
trol")
Production department, 66
relation to inspection, 72
Purity, a color constant, 356
reducing, makes tints, 357
Quality (See also "Quality control")
a prime responsibility of manage-
ment, 391
defined, 4, 233-247
essence of, 5
incentive to increased production,
91
Quality — Continued,
inspection the instrument for meas-
uring (See "Inspection")
records, 382
standardization alone does not
bring, 5
standards (See "Standards")
variability of, 235
vs. quantity, 3, 19, 235
Quality bonus, 20
Armstrong Cork Co.'s experience,
21, 23
The Shelton Loom's experience,
21
Quality control (See also "Inspec-
tion")
advantages of, in management
problems,
costs decreased, 15-19
labor relationships improved,
12-15
output increased, 15-19
selling expense decreased, 24
color (See "Color control")
complexity of problem of, 187
dimensional (See "Dimensional
control laboratory")
failure, instances of, 9
measurement, relation of to, 210-
232 (See also "Measurement")
method of attack, 377-391
analysis of facts, 379, 380
beginning with the product, 384
getting the facts, 378
order of procedure, 384
organization and system, 389
quality records, 382
study of processes, 385-388
synthesis and adjustment, 383
root of production economy, 279
study of processes of making prod-
uct, second step in, 385
assemblage of, 388
written descriptions of, 387
402
INDEX
Quality control — Continued,
study of product, starting point,
25, 236, 384
consumer requirements, 26
design, 26-30, 236
need of inspection, 33
operating organization and rec-
ords, 32
processes, 31
raw materials, 30
workmanship, 32
war time success in, examples of
188-209
American Locomotive Co., 188-
202
Lincoln Motor Co., 203-206
Remington Arms Co., 206-208
Quantity,
vs. quality, 3, 19
R
Ratio of inspectors to workers, 186
American Locomotive Co., 201
General machine shops and found-
ries, 184
machine tool industry, 181
Packard Motor Car Co., 177-178
small precision work, 182
Wahl Co., 141
Raw material,
importance of uniformity of, in
repetition manufacturing, 273
inspection, 46
necessity for continuous supply of,
98
standards, 249
Reference gage, defined, 313
Rejected parts,
handling of, 85-89
at Packard Motor Car Co.,
176
Form, 176
percentage of, American Locomo-
tive Co. war work, 201
Remington Arms Co.,
Forms and Illustrations, 105,
108, 126, 246
quality control in, 206-208
Repetition manufacturing, 264-280
basis of, establishment of working
standards, 252
economy in,
assembling, 269
labor, 267, 269
development of,
industrial revolution, 266
mechanical revolution, 267
duplicate manufacturing, 277
. interchangeable manufacture, one
class of, 265, 271
machine tool production, 278
partial interchangeability, 277
precautions in working from allow-
ances to determination of toler-
ances and limits, 255-258
purpose, economy of production
uniformity,
at all stages essential, 265
basis of, 264
in continuous processing, 275
in raw materials, 273
work of Simeon North and Eli
Whitney, 270
Roller-Smith Co., precision torsion
balance,
Illustration, 386
Route tags, 108
Form, 1 08
Samples, standard,
color, 348
atlas of, 349
card, 348-349
dangers of, 350
selection of, in measurement, 212,
213
dangers in, 214
INDEX
403
Sampling, in inspection, 59-61, 164
Scientific attitude of mind, 368-376
Self-counting trays,
use in central inspection, 116-122
Selling expense,
decreased by quality control, 24
Shell manufacture,
American Locomotive Co., 188-
197
Shelton Looms, The
Illustration, 185
experience with quality bonus, 21
Illustration, 22
Shop arrangement (See "Central in-
spection, arrangement of shop")
Shop gage, denned, 313
S. K. F. Ball Bearing Co., proportion
of inspectors, 141
Spectrophotometer, for analyzing
color, 362
Diagram, 363
Spectrum, use in analyzing color,
359
Illustration, 359
Springfield-Enfield Rifle production,
quality control in, 206-208
Stanbrough, D. G., quoted, 331-333
Standard gage, defined, 313
Standardization,
quality not secured by alone, 5
Standards,
appearance, 367
ideal, 233-247
attainment of, difficult, 240
defined, 239
the design, 236-237, 239-247
variations from, 235
manufacturing, 236
measuring,
development of, 210
for United States, 215, 216
graded scale, comparison with,
215
samples, 212-214
Standards — Continued,
necessary in order to state a quality,
233
theoretical or 100 per cent, 237, 238
uniform,
basis of repetition manufacture,
279
securing, 7
working,
allowable variations from, 254,
255
assembling, 261
conditioning of material, 250
determination of, 248
dimension and form, 252-254,
258, 261
finish, 251
gages control, when used, 259
precautions, 255-258
raw material, 249-250
tests, 262
Surface plate,
in dimensional control laboratory,
285
Swedish block gages (See "Johansson
block gages")
Sweet, John E., quoted, 238, 344
Symbolization, 102-104
Taylor, Dr. Frederick W., theory of,
regarding inspection, 64
Thompson, Gen. John T., quoted, 207
Thread-gaging,
equipment, 326, 327
Hartness comparator, 323
Illustrations, 324, 325
working gages, 322
evolution of, 317
interrelation of elements, 319
precision depends on service re-
quirements, 328
purpose of, 318
tolerances, 327
404
INDEX
Time fuse manufacture,
American Locomotive Co.,
Forms and Illustrations, 18,
198, 199
Tingley, Edward H., quoted, 117-
122
Tolerance,
denned, 254, 255
gages, 311
precautions in determining from
allowance, 255-258
tables of, 333~34°
Illustrations, 334-338
thread gage, 327
Tool inspection, 49
Trouble reports, 75-78
Forms, 76, 80
Turnover,
inspection department personnel,
158
Two-bin system of storage for mate-
rial in process, 122
U
Units of measurement, choice of, 217
W
Wages,
inspection force, 160
piece work system, 161
Wahl Co., proportion of inspectors,
141
War work, quality control in, (See
"Quality control, war time suc-
cess in")
Wells, Frank O., quoted, 306, 327, 328
\Veston Electrical Instrument Co.,
inspection organization, 182
W'hitney, Eli, early exponent of inter-
changeable manufacturing, 270
Wolf, Robert B., quoted, 14
Women as inspectors, 166-170
Work in flow (See " WTork in process")
Work in process,
analysis of, 85
arrangement of, 83, 84
determining quantities of, no
flow of, 95
Illustration, 96
disadvantages of uneven, 97, 98
line of, first step in arranging
shop, 123
Chart, 123
inspection, 49
by special mechanical devices, 53
centralized, 49-52
combined with remedy of defects,
53
floor, 52
losses in, allowance for, 109
Working hours inspection force, 162
Working standards (See "Standards,
working")
Working or workman's gage, defined,
313
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