The American steel worker; a twenty-five years' experience in the selection, annealing, working, hardening and tempering of various kinds and grades of steel

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The American
Steel Worker

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A TWENTY-FIVE YEARS' EXPERIENCE IN THE SELECTION,
ANNEALING, WORKING, HARDENING AND TEM-
PERING OF VARIOUS KINDS AND
GRADES OF STEEL

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BY

E. R. Markham

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First Edition
1903

New York

II fi n LIRRARr

Copyright 1903 by E. R. Markham,

Words are not adequate to express the debt
I owe one, who, more than all others, has been
instrumental in instructing, advising and assisting
me along lines that have led to whatever success
I may have attained.

As an humble acknowledgement of my grat-
itude, I dedicate this work

To My Father,

RUSSELL MARKHAM.

The American
Steel Worker.

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Introduction.

An experience which covers twenty-five years of
actual practice, in the various branches of machine
shop work, has taught the writer that much more
depends on the condition of the various cutting tools
used, than mechanics in general realize.

The various machines used in working iron and
steel to shape have been improved, and made heavier
in the parts subjected to strain, in order that heavier
cuts and faster feeds might be taken to reduce the cost
of production.

If a tool is doing the maximum amount of work
possible for it to do, when it is used in a light machine,
it would be folly to purchase a heavier, stronger ma-
chine and use the same tool in it. But it has been
found in many cases that cutting tools could be made
that would take heavier cuts and faster feeds than the
older types of machines could carry. Consequently it
has been necessary to re-design most types of machines
iised to remove stock, in order to bring them into
shape to be used as tools, parts of machines, and other
apparatus.

Competition has made it absolutely necessary that
every possible means be taken to reduce the cost of an

Cheapening cost of production.

article without reducing the quality. Where possible
the design is changed so the article may be made more
cheaply. And as labor is, generally speaking, the princi-
pal factor to be considered, it is necessary to reduce as
far as possible the number of operations, or simplify
those necessary, and so reduce the cost of the manu-
factured article.

If by the use of machinery especially adapted to
the work to be done, it is possible to do in one opera-
tion the work which formerly required four separate
operations, then the amount paid for labor has been
very materially reduced, without necessarily reducing
the pay of the operator. In fact it is found possible in
many cases to increase his compensation, and at the
same time reduce the cost per piece of work very
materially.

Now, in order that improved machinery may do its
maximum amount of work per day, it is necessary to
have the cutting tools, fixtures, etc., made in a manner
that allows them to do their part of the work. If a
milling machine were bought and set up in a shop, and
it was found that the fixtures formerly used in holding
the pieces of work were not strong enough to hold
them when the new machine was taking the heaviest
cut possible, heavier fixtures would be made at once in
order that the investment of money made in purchas-
ing the machine might not be considered as having
been thrown away. Following out the same line of
reasoning, it would be necessary to make cutting tools
of a design that made it possible to take as heavy cuts,
and use as coarse feeds, as the strength of the machine
and fixtures would allow.

While manufacturers in general recognize the im-

8

Waste through improper handling.

portance of having machines especially fitted for their
needs, many times the good work stops right at this
point. They are not educated to a point that makes
it possible for them to comprehend the importance of
having the cutting tools hardened in a manner that
insures their doing the amount of work possible.

While it is often necessary to re-design cutting
tools to get added strength, many times this needed
strength may be had by proper hardening.

A manufacturer of a high grade tool steel, in con-
versation with the writer, said, if he could have one per
cent, of the value of steel in this country spoiled by
improper hardening, he would not exchange his income
for that of the President of the United States. By the
value of steel, he meant its value at the time the article
was hardened. A piece of steel which cost fifty cents
in the bar, may be worth many dollars when ready for
hardening, and represents to the manufacturer the
total cost of steel and labor.

This line of reasoning might be carried a great
deal further. If a tool which is made to do a certain
job is ruined, the time the machine or machines stand
idle waiting for another one to be made, many times
represents a greater loss than the money value of the
tool. This is especially true where the time given to
complete the job is limited.

If a tool is hardened in a manner that makes it
impossible for it to do as much or as good work as it
ought, the loss may be greater than in either of the
cases before cited, yet this loss is seldom taken into
consideration.

The writer's experience has convinced him that
few mechanics realize the vast waste of time in many

Increase of productive efficiency.

shops, because tools are not capable of doing the amount
of work possible were they properly hardened. Take
for instance a milling machine cutter which runs at a
periphery speed of thirty-six feet per minute, milling a
mild grade of machinery steel. It is found necessary
to stop this machine once in twenty working hours to
sharpen the cutter, milling in the meantime five hun-
dred pieces. A cutter is made from the same bar, and
hardened by a process that makes it possible to run the
tool at a periphery speed of eighty feet per minute, and
it is then found necessary to grind but once in two hun-
dred hours; milling in the meantime eight thousand
pieces. Not only is the efficiency of this machine
increased many fold, but the expense of grinding, and
the necessary delay incident to stopping the machine,
changing cutters and setting up, and the cost of tools
per piece, is reduced very appreciably.

Does some one ask. How is this trouble to be
remedied? The answer is, men must be educated to
see the enormous waste going on all the time; the
waste of steel, of time required to make the tools, of
the time valuable equipment is laying idle, and the
small percentage of work produced per machine, all go
to reduce dividends, and this because so little attention
is given a subject which should receive as much con-
sideration as any one branch of machine shop work.

When the trouble is apparent, then it is necessary
to find a remedy. The physician must necessarily un-
derstand the human body in order that he may diagnose
diseases. If one would be a successful hardener of
steel, he must understand the nature and peculiarities
of steel. As a study of drugs alone would not fit one
to practice medicine, neither will practice alone fit one

Necessity for the study of steel.

to harden steel, especially if new problems are con-
stantly coming up.

At the present time when libraries are accessible
to nearly every one, and books and mechanical journals,
treating on steel and the proper methods of its manipu-
lation, are within the reach of all, there is no good
reason why ignorance of a subject so interesting, and
at the same time of such vital importance to both
manufacturer and mechanic, should be so general.

A study of the nature of steel will convince one of
the importance of extreme carefulness when heating
either for forging, annealing or hardening. A man
who understands the effect of heat on high carbon tool
steel is often amazed at the careless manner which
many old blacksmiths assume when heating a piece of
steel. A difference of loo to 200 degrees of heat after
the steel is red hot, does not, according to their idea,
injure the steel in the least, but in reality it makes a
vast amount of difference in the strength of the piece.

In some shops a man is called a successful hard-
ener if he is fortunate enough to avoid cracking the
pieces he is called upon to harden. Apparently no
account is taken of the capability of the tool to perform
a satisfactory amount of work. A man who devotes
his attention to hardening steel in a manner to avoid
cracking, regardless of the utility of the tool, is not
worthy of the title of a successful hardener ; he should
be styled, as an eminent mechanic calls this class,
a non-cracker. Now, it is possible to harden steel in a
manner that does away with the liability of cracking,
yet gives it the amount of hardness necessary, in order
that it may do the amount of work expected of it.

A study of the effects of expansion and contraction

II

Expansive properties of steel.

of steel in the fire and baths is necessary in order to
select the proper forms of furnaces and bath, so that
the best results may be obtained. Suppose a micro-
meter is left for some time in a room where the tem-
perature is 40 degrees Fahr. , a piece of work is placed
between the contact surfaces, as shown in Fig. i.

Figure 1

Illustrating expansion of steel.

Now grasp the micrometer by the frame at the portion
marked by with a warm hand; in a few seconds the
metal will have expanded to a degree that allows the
work a to drop from the gauge, thus proving that but
a very small amount of heat is needed to expand the
steel sufficiently so the contact points no longer touch
the piece between them.

Now, if a few degrees of heat will expand steel so
it can be readily observed, it is apparent that a heat of
900 to 1,200 degrees Fahr. must cause the process of
expansion to be carried to a much greater extent. The
amount of heat necessary to give steel, in order that it
may harden when plunged in some cooling bath, varies
with the make of steel, the percentage of carbon it con-

Desirability of not overheating.

tains, and also on the percentage of other hardening
elements in the steel. Jarolinech places the critical
temperature at 932 degrees Fahr. (500 Centigrade) as
determined by him experimentally. The lowest heat
at which a piece of steel will harden satisfactorily is
termed the refining heat, because the effect of the
operation of suddenly cooling steel heated to this tem-
perature is to refine the grain, making it the finest pos-
sible.

The writer does not propose giving a scientific
explanation of the changes which take place in a piece
of steel when it is heated to the hardening heat, and
quenched in the cooling bath, but the practical sides of
the question will receive careful attention.

Every man and boy working in a machine shop
knows that steel heated red hot and plunged in water,
will harden, but it is necessary to know how hot it
must be heated in order that satisfactory results may
follow. We should thoroughly understand the action
of too great an amount of heat on the structure of steel,
in order that overheating may be avoided. It is also
necessary to have a correct understanding of the effects
of baths of various kinds on steel, if it is dipped in
them when red hot.

It is an acknowledged fact that the lowest possible
heat at which steel will harden, leaves it the strongest
This is illustrated elsewhere. Knowing this, it will be
seen that an article made of steel is very much less
liable to crack when hardened at a low heat, than if it
were heated to a temperature which caused it to be
brittle.

Commencing with cold steel, every degree of heat
applied changes in a measure the size and structure

13

Uniform expansion in heating.

of the piece, until a certain limit is reached. Now, if a
change in temperature of a few degrees changes the
size of a piece of steel, the reader is asked to imagine
the change in size and structure which must take place
when it is heated red hot. This means a change in
temperature of about i,ooo degrees, and the effect of
heat on steel is to expand it, while the opposite effect
is accomplished when it is cooled. The more rapidly
it is cooled the harder it will be. It is indeed wonder-
ful that a piece of steel can undergo the changes which
take place in its size and structure, and remain intact.
When steel is cooled in the hardening bath, the outside
of course chills and hardens first, while the inside is
hot and consequently soft for some little time after-
ward. Now, the outside, being hardened, is practically
inflexible, while the inside continues to change in
structure until cold. This is especially true of pieces
having teeth or projections on their surface.

Understanding the fact that heat causes steel to
expand, it will readily be seen that it is absolutely
necessary that it should expand uniformly throughout
the piece. If the corners and edges are hotter than the
balance of the piece, then it is unevenly expanded, and
consequently will contract unevenly. Now, if one part
of a piece of steel contracts more than another, or not
uniformly with another part, it is liable to crack from
the effects of the unequal contraction; if it is not
cracked when taken from the hardening bath, it is liable
to crack at some future time for no apparent reason.
This applies especially to large pieces, and steel having
a high percentage of carbon.

14

The Workman

CO

The writer's professional experience in the various
methods of working" steel, brings him in contact with
men of all degrees of intelligence. Some men are
really skillful in the particular line they are engaged
in; that is, they are very careful when heating and
dipping in the bath, and get excellent results. But
they do not know the difference between a steel of ^
per cent, carbon and one of i ^ per cent ; in fact, they
do not know anything about percentages of carbon,
and don't care ; they say so in as many words. The
steel they use is always the same make and temper.
They have never used anything else. If they should
get hold of another make, that worked differently
from that they had always used, they would condemn
it, saying it was no good, because it didn't act just like
the steel they were accustomed to handling.

Now, if anything should happen to the steel mill
making their particular brand, they would be obliged
to learn the art of hardening all over again, or go out
of business. When it becomes necessary, or the con-
cern who employs these men considers it advisable,
to change the steel used; or if it is necessary to
have the composition changed to get some desired re-
sult, this poor fellow is all at sea. He doesn't know

15

The workman who "knows it all."

what to do, and he doesn't want anyone to tell him
what to do. His only cry is, *' The steel isn't good for
anything," when in reality it may be the best on the
market. Such a man is to be pitied, but he is a very
expensive man for those in whose employ he happens
to be, and a very unpleasant fellow to attempt to teach
anything.

Another example is the man who banks on his
twenty or fifty years' experience, and considers that
because he has been allowed to exist for that length
of time and occupy a position as blacksmith, or
hardener, that he must necessarily know it all. To
him steel is steel; he treats it all alike. If there is
some particular steel good-natured enough to stand his
treatment, that is the only brand on the market fit to
use — according to his way of thinking — and he gener-
ally has such an unpleasant and forcible personality,
that he either has his say or goes where he can. He
never investigates the merits of different makes of
steel ; simply condemns every make that will not stand
his abuse.

If every man of the type under consideration ad-
vocated using the same steel, there might be a plausi-
ble excuse for looking into the merits of that particular
brand, to the exclusion of every other, but you will
hardly find two of them advocating the use of the same
steel. I am happy to say this class of hardener is not
in as great a majority as formerly; their number is
gradually diminishing. It is impossible to teach him
anything, because that long experience of his stands in
the way ; it is his only stock in trade, and he presents
it every time anything is said on the subject.

Now, a long experience in any particular line of
i6

The workman who doesn*t care.

work is a good thing for a man, provided it has been a
real experience, rather than an existence, and in no line
of business is it more valuable than in the working of
steel, if the man has kept pace with the procession.
If not, then he is no farther advanced than when
he fell out of line, and as it is a law governing all our
lives, that no man stands still, he must of necessity
either advance or go backward. The man who has not
kept pace with the progress of events, must necessarily
go backwards.

Another class we meet with is the jolly, good-
natured fellow, who wants to please everybody, but
does not know how, and is too lazy to find out. He had
rather tell a story than to keep his eyes and attention
on the piece he is heating, consequently he has all
kinds of luck. There is no remedy known for this
chap. He is willing to be told how to do, but is too
lazy to assimilate and put in practice what is told him.

A class of hardeners which are few in numbers,
but who should get into some other business as soon
as possible, consists of men who are practically color
blind. They cannot distinguish between the various
shades of red, neither can they discern the temper
colors as closely as they should. Some of them are
extremely intelligent, capable men, but they have
missed their calling, and missed it most decidedly,
because a man to be a successful blacksmith or hard-
ener, must have good powers of distinguishing colors
and shades.

There are many other classes that might be con-
sidered, but it would be a waste of time, so we will
look in upon the successful hardener. There are vari-
ous degrees of success, but we will consider the man

17

The successful steel worker.

who is a success according to the generally accepted
idea.

The successful hardener is one who finds out what
is wanted or expected of the article he is to harden;
whether extreme hardness, toughness or elasticity, or a
combination of two of these qualities. He also under-
stands the nature and pecularities of the steel he is
using ; he considers the fire he is to use, and the bath
in which the steel is to be quenched after it is heated.

His spare moments are not spent hanging around
street corners, or saloons, but in reading and studying
such books and mechanical journals as treat on subjects
in his line. In this way he becomes familiar with the
nature of steel and knows what to do when certain
conditions which are out of the ordinary arise ; he gets
the experience of others and his knowledge makes it
possible for him to discriminate between that which
will be of value to him, and that which will not.

When a piece of work is given him he studies the
shape of the piece, the best method of heating and
quenching, in order to get the desired results. To him
steel is not simply steel, which must be treated just
like every other piece of the same metal, but it is a
valuable tool or piece of machinery which he takes
pride in hardening in the best possible manner. If he
hears of a brand that is giving some one trouble, he is
anxious to get a piece of it, and experiment and find
out why they can not get good results from it.

If he hears of a brand that some one claims gives
extra good results when using, he is anxious to get a
sample and test it, and see for himself if the steel is
all the makers claim it is.

He is not above learning, takes advantage of every

i8

The two kinds of steel.

opportunity to get the ideas and experience of others,
especially men who have had a wide experience. To
him the articles he is called on to harden represent so
much money entrusted to his care, and he takes every
means possible to get it out in a satisfactory manner.

Does some one ask, where do you meet such men?
The writer is happy to say such men are not the ex-
ception. To be sure they are not in the majority, but
the number of men who are making a careful study of
this subject is really encouraging.

Steel.

CO

Although there are many makes of steel and, in
most cases, several grades of the same make, yet to the
average mechanic there are two kinds of steel, viz.,
machinery steel and tool steel.

Machinery steel is used in making such parts of
machines, apparatus or tools as do not require harden-
ing in order to accomplish the result for which they
are intended. Or, if they require hardening at all, it is
simply a surface hardening, the interior of the piece
being soft with a view to obtaining greater strength.
This class of steel is of a lower grade than tool steel.
It is softer, works more easily, both in the operations
of forging and machining, and can be safely heated to
a higher temperature without harm to the steel. It

19

Tool steel — what it is ; what it's for.

resembles more closely wrought iron and is sometimes
scarcely to be distinguished from it. Machinery steel
is used whenever it will answer the purpose, not only
on account of its being more easily machined, but its
first cost is only ^ to -j^ that of ordinary tool steel,
and for most purposes where it is used, it answers the
purpose as well or better.

Although it is considered advisable to group steel
under two heads, as mentioned, namely, machinery
steel and tool steel, yet on account of the different
grades of the article under each head it will be neces-
sary to distinguish them somewhat as they are con-
sidered under the various processes of hardening.

Tool steel is made with the idea in view that it is
to be made into such tools, appliances or parts of
machines as require hardening in order to accomplish
the desired result. Although the term "tool steel"
is applied to steel intended to be made into cutting
tools, there are many makes of this article, each make
differing in some respects from every other make. Not
only is this so, but most makers put out tool steel of
different tempers. Now, the word "temper," as used
by steel makers, means the quantity or percentage of
carbon the steel contains. It is low temper, medium,
or high, or number or letter so and so, according
to the understanding of the marks in each particular
mill. The following are considered by steel makers as
the most useful tempers of tool steel :

Razor temper (i^ per cent, carbon). This steel
is so easily burnt by being overheated that it can only
be placed in the hands of very skillful workmen.
When properly treated it will do many times the work
of ordinary tool steel when working hard metals, etc.

Percentages of carbon in tool steel.

Saw file temper (i|^ per cent, carbon). This steel
requires careful treatment, and although it will stand
more heat than steel of i ^ per cent, carbon, it should
not be heated hotter than a low red.

Tool temper (i ^ per cent, carbon), A very useful
temper for turning tools, drills and planer tools in the
hands of ordinary workmen.

Spindle temper {i}i per cent, carbon). A very
useful temper for mill picks, circular cutters, very
large turning tools, screw thread dies, etc.

Chisel temper (i per cent, carbon). An exceed-
ingly useful temper, combining, as it does, great
toughness in the unhardened state, with a capacity of
hardening at a low heat. It is well adapted for tools
where the head or unhardened end is required to stand
the blow of a hammer without snipping off, and where
a hard cutting edge is required, such as cold chisels, etc.

Set temper (^ per cent, carbon). This temper is
adapted for tools where the surface only is required to
be hard, and where the capacity to withstand great
pressure is of importance, such as stamping or pressing
dies, etc.

The following also gives the steel maker's mean-
ing of the word ''temper " :

Very hard 150 carbon -f

Hard loo — 120 carbon

Medium 70 — 80 carbon

In order that the reader may understand some-
thing of the significance of the terms used to designate
the amount of carbon a piece of steel contains, the fol-
lowing brief explanation is given. A point is one
hundreth of one per cent, of any element. 100 points
is one per cent. A 40 point carbon steel contains forty

21

Peculiarities of tool steel.

one-hundreths (.40) of one per cent, of carbon. The
same explanation applies to any element that goes into
the composition of steel. The steel is sometimes desig-
nated by the number of points of carbon it contains —
as 20 carbon or 60 carbon steel. The amount of carbon
the steel contains does not necessarily determine the
quality of the steel, as the steel maker can give an
ordinary low grade stock a very high percentage of
carbon. This would harden under the ordinary condi-
tions, but would be practically useless if made into
cutting or similar tools.

It becomes necessary many times to procure a low
grade steel having as low a percentage of carbon as
possible. Then again it is advisable, where a greater
amount of strength is required, to give the steel a
higher percentage of carbon. This will be briefly
alluded to from time to time under the various topics.

The reader will readily see from the foregoing that
it is the presence of carbon in steel that causes it to
harden. The amount of hardness and the degree of
heat necessary when hardening depending on the
quantity of carbon the steel contains. Tool steel is
hardened by heating it red hot and plunging into some
coeling bath. The more quickly the heat is extracted
the harder the piece will be.

Tool steel has certain peculiarities which must be
understood if one would be a successful hardener. The
outside surface of a bar of steel, as it comes from the
steel mill or forge shop, is decarbonized to a consider-
able depth. This is because the action of the oxygen
in the air causes the carbon to be burned out of the
steel at the surface during the various operations when
the steel is red hot. In order that the decarbonized

Decarbonized surface of steel.

portion may not give trouble, it is necessary to cut
away enough of the surface to remove this portion
before hardening. If a tool which is to finish ^ inch
diameter is to be made out of round steel, it is neces-
sary to select stock at least -jV inch diameter larger than
the finished tool, or the outer surface will not harden
sufficiently. For sizes from ^ to i inch diameter,
select stock -^ to }i inch larger. For sizes from i to
2 inches diameter, select stock from }i to -^q of an inch.
For sizes above 2 inches, about ^ of an inch should be
cut off.

It is necessary when centering round steel to have
the center hole very near the center of the stock, as
shown in Fig. 2, in order to take off an equal quantity

Figure 2, Figure 3.

Proper and imnroper centering.

of the decarbonizing surface all around. If a piece is
centered, as shown in Fig. 3, the decarbonized surface
will be entirely removed from one side of the piece
and scarcely any of it taken from the opposite side ;
consequently, the side from which it was removed
will be hard, while the opposite side will not harden,
or at least will not be as hard as the other side.

Extravagant economy.

So it will be very readily seen that this simple fact,
which is often entirely overlooked in machine shops,
is a cause of a great amount of trouble.

Tool makers, as a rule, understand this fact in
regard to steel, but some one in authority, wishing to
save money for the manufacturing concern, gives the
job of centering to the "tool room kid, " as he is termed
many times. He fails to instruct him in the proper
manner, the boy does not understand the nature of
steel, and as a consequence, it is centered, as shown in

Fig. 3-

Now, if the tool maker were given the job, he
would readily see that it was centered wrong. But the
spirit of economy still prevails, and the boy is allowed
to rough out the piece. As a consequence, the outside
surface is removed, and all traces of the eccentric cen-
tering are eliminated. The piece is made into a reamer
or some other tool, and when hardened it is soft on one
side, the other side being hard enough. There is no
one that can be blamed but the hardener, so he, poor
fellow, has to "catch it." It wouldn't be human
nature to stand by and say nothing when blamed for
something one didn't understand, so he, in turn, says
the steel is no good.

As a consequence, the make of steel is often
changed and another kind is procured, and as it is
desirable to test the steel before making any quantity of
it into costly tools, the tool maker is told to cut off a
piece of the stock and make a reamer just like the
one that wouldn't harden properly. He centers the
piece, as shown in Fig. 2, turns it to size, cuts the teeth
and gets it ready for hardening. It comes out all
right. The steel is pronounced O. K. and a supply is

No mysteries in steel handling.

ordered. A large batch of reamers is made up and the
same boy is given the job of centering and ** roughing "
them, and the results are the same or worse than when
the former lot was hardened. Now, it is evident to
every one that the hardener must be to blame. He
hardened one reamer from this same steel and it was
satisfactory. Well, the only conclusion is that he made
a mistake when he did that one^ and isn't on to his busi-
ness, so he is nagged and found fault with until he can
stand it no longer and gets out. The next man has
the same results, and those in charge say, * * You can't
get a decent hardener now-a-daj^s. " All this trouble
and expense because some one wanted the reputation
of being a good manager.

Now, a boy can center and rough out stock and do
it all right, but he must be told how and he must be
watched. If a make of steel that gives satisfaction
suddenly shows freaks, do not at first condemn the
steel, but look for the cause. Many people have the
idea that there are unaccountable mysteries connected
with tool steel, and that hardening is a thing which
must be attended with luck, or bad results follow.
Now, as a matter of fact, if a good steel is used, the
cause may be found for all troubles which occur when
it is hardened, and many times they will be found to
result from some penny wise and pound foolish notion.

Another peculiarity of steel is that if the position
of any of its molecules is disturbed when the steel is
cold, there is apt to be trouble when the piece is
hardened. For instance, if a piece of steel that is to
be hardened for any given purpose is cut from a bar
of tool steel and it is found to be so bent that it would
be impossible to turn and make straight and remove

Steel of difFerent makes vary.

all the decarbonized surface, the piece should be heated
red hot and straightened. If it were straightened cold,
then finished to size and hardened, it would be almost
sure to spring. The writer has seen men at work
making blanking dies for punching press work who,
when they made the openings too large at any point,
would take a hammer and pene the stock into the
opening without heating the die. They would plane
the top of the die for shear and then finish it and swear
about the hardener when the piece cracked in harden-
ing directly under where they pened. Possibly, it
would not show any bad results at that time, but
when the die was used, the portion referred to would
crack off. Or if the punch were a tight fit, it would
lift a piece of steel from the face of the die the shape
of the hammer pene or of the set used.

Steels of different makes vary in their composition.
A successful hardener will experiment with a new steel
and find out just what he can do with it. One make of
steel will harden at an extremely low heat ; another make
will not harden in a satisfactory manner at that heat.
It requires a higher heat in order to harden it. Now,
if we were to heat the first steel as hot as we were
obliged to heat the other, we should ruin it, or at least
harm it. For this reason it is not advisable, generally
speaking, to have a half a dozen different kinds or
makes of steel around a shop, unless someone knowing
the nature and peculiarities of each is to do the harden-
ing. And even then trouble will follow unless a ticket
accompanies each tool stating the kind of steel, and
this in the ordinary machine shop would lead to end-
less confusion.

A steel which gives satisfactory results should be

a6

Steel is usually all right.

selected and then used until convinced that some-
thing better is to be had. The judgment of an ex-
perienced hardener is not always to be relied upon as
to the best brand of steel for a particular purpose. It
may be that he has had excellent results with a certain
brand because he has methods of hardening particularly
fitted to that brand of steel; but it may be true that
were he to change his methods to adapt them to
another steel, much better results would follow.

The writer was at one time brought in contact
with a hardener whose complaints in regard to the
steel furnished had caused the superintendent of the
shop to change the make of steel several times. Each
time a new steel came into the shop the result was the
same, until finally by the advice of one of the steel manu-
facturers several tools similar to those previously hard-
ened with unsatisfactory results were made from each
of the condemned steels and given to a man who was
considered an expert hardener. When they were hard-
ened and returned they were all found to be in a satis-
factory condition, not a crack visible in any of them.
They all gave good satisfaction, proving that the
man rather than the steel was at fault.

Almost any of the leading makes of steel in the
market will give good results if treated properly, but
the same treatment will not answer for all makes.
Some makes are more satisfactory than others for
certain purposes, but better results may be obtained
from most of them than is often the case.

Steel may be purchased in bars of various shapes.
The more common shapes are round, square, flat and
octagon. If steel is to be cut from the bar and ma-
chined to shape, it is advisable to purchase bars wliich

»7

The choice of proper steel.

allow of machining to the desired shape, at the least
expense and with as little waste of material as possible.
Always remember that it is necessary to remove the
decarbonized portions previously mentioned.

If a tool which is to be cylindrical in shape is to be
made, use a piece of round steel. If an article which
is to be finished square, use a piece of square steel, etc.

Steel of the same quality and temper is furnished
in all the common shapes on the market. It v/as for-
merly considered necessary, if best results were de-
sired, to use octagon steel when making cylindrical
pieces of work, but now all steel makers claim to
make round steel of exactly the same quality as the
corresponding sizes of octagonal shape, and the exper-
ience of every mechanic who has tested the two under
similar circumstances substantiates the claim.

The steel maker puts on the market steel of dif-
ferent tempers, but he advocates the use of the par-
ticular temper which he considers best adapted to the
work in the individual shop. As a rule he does not
make any mention of any other temper, because he
knows that if steel of several different tempers are kept
in stock, that in all probability the labels will be
removed in a short time and any distinguishing marks
be thrown away. Then no one in the shop will know
one temper from another, and when a piece of ^ per
cent, carbon steel is made into a shank mill or similar
tool, and a piece of i ^ per cent carbon steel is made
into some tool that must resist the action of heavy
blows, trouble will follow and the steel be condemned.
For this reason it is considered advisable to advocate
the use of a temper that will give satisfactory results
when put to most uses. But the fact remains that

aS

Carbon necessary to proper results.

steel, in order to give best results, should contain the
proper percentage of carbon for use on the particular job.
In shops where detail is followed very closely, the
steel is kept in a stock-room, each different temper by
itself, and so marked that there is no danger of it get-
ting mixed. Much better results are then obtained,
provided a competent man does the hardening, than if
one temper was . used for everything. But in a shop
where there is only one rack, and sometimes no rack,
the stock, machinery steel, tool steel, and everything
else is kept on this one rack, or in a pile on the floor, it
is not advisable to have steel of different tempers
lying around, or results anything but satisfactory are
sure to follow.

Percentage of Carbon Necessary to Produce
Desired Results.

In the first part of this section is given a table of
percentages of carbon present in steel for various pur-
poses. This table is generally accepted as a guide to
those desiring steel for any given purpose, and, gen-
erally speaking, it is safe to use stock of the tempers
given, but modem competition has made it necessary
to harden steel harder and yet have it able to stand
more than was formerly the case. When these condi-
tions prevail, it is necessary many times, especially in
the case of cutting tools, to use steel having a higher
percentage of carbon than is given in the table.

When steel containing a higher percentage of car-
bon is used, then extra care must be observed when
heating. For the operations of forging, annealing, or

29

No one steel best for all purposes.

hardening high carbon steels should not tinder any cir-
cumstances be given to a careless workman, or to one
not thoroughly familiar with the effects of heat on
steel of this character.

When high carbon steels are used and treated
properly, they will do more work than steels contain-
ing a lower percentage, but unless they are to be
handled by a competent man, they generally prove to
be a very unsatisfactory investment.

When long articles which are to be hardened are
made of tool steel, the writer has had excellent results
by taking the steel as it came from the bar, or after it
was roughed out for annealing, or even after it was
forged in the smith's shop, by heating it to a forging
heat. Then, standing it on end on the anvil, or on a
block of iron on the floor — if it were long — and giving
it one or more blows on the end with a hand hammer or
sledge; the weight of the hammer depending on the
size of the piece. This operation is sneered at by many
expert steel workers, but the writer's experience con-
vinces him that better results will follow when the
piece is hardened, if this precaution is taken, the ten-
dency to spring is apparently greatly reduced. Should
the piece be bent by the operation, it should be straight-
ened while red hot, because if straightened cold, it most
surely will spring when hardened.

The writer has no intention of advertising any
make of steel, as he does not believe any one make is
best for all purposes, but experience has convinced him
that some makes of steel give better results for certain
purposes than others, also that some makes are better
adapted for ♦* all around " use than others.

If a party is using a steel with unsatisfactory

3°

Cheap steel not necessarily cheap.

results, it is advisable to take measures to ascertain
whether the trouble is in the steel, or in the method of
working it. The writer has seen one of the best steels
on the market condemned and its use discontinued,
because the workman who did the hardening had been
accustomed to a steel containing a lower percentage of
carbon. The steel he recommended was adopted, the
results so far as hardening were concerned were satis-
factory, but the tools did not produce nearly the
amount of work they should.

After a time, the services of an expert were sought.
He advocated the use of the very steel they had dis-
carded. A tool was made from it, the expert harden-
ing the tool. When put to actual use, it proved itself
capable of doing many times the amount of work
between grindings that could be obtained from low
carbon steel.

The hardener, like a sensible man, allowed the
expert to instruct him in the proper methods to pursue,
with the result that he became one of the best hardeners
the writer has ever had the pleasure of meeting.

A steel should never be selected because it is cheap^
becaiise it often happens that the steels which sell for the
least money are the dearest in the end. It is possible
to put $100.00 worth of work on a piece of steel costing
25 cents. Now, if the tool was found useless when
hardened, then $100.25 ^^^ been expended in vain.
On the other hand, if steel adapted to the purpose had
been used, and it had cost 50 cents, there would have
been a clear saving in money of nearly $100.00. This
is not an exaggerated comparison, as such cases are
frequently met with by the writer.

On the other hand, it is folly to pay 75 cents a

31

"Pipes" in steel bars.

pound for steel, when i6 cents will buy one exactly-
suited to the job. Good steel is cheaper at any price
it would be apt to bring in the open market, than steel
not adapted for the purpose would be if it were a gift.
A steel not adapted to the purpose is dear at any price.

The writer has had charge of tool rooms employ-
ing large numbers of tool makers, and experience has
convinced him that it is a saving of money in every
case to test every bar of tool steel received into the
shop that is to be made into tools.

If the steel is kept in the stock-room, the stock
keeper can — when the hack saw, or cutting off machine
is not in use — cut a piece from the end of each bar,
stamping the piece cut off and the bar alike. These
pieces can be given to an experienced hardener, to
heat them to the proper hardening heat, and quench
them in a bath of water or brine. After they are
thoroughly dry, break as near across the center as pos-
sible, examining the center of fracture for pipes. A
pipe is a cavity which of course makes the bar un-
sound. It may run the entire length of the bar. If a
bar having a pipe is discovered, the steel maker will
gladly replace it with a sound bar. Any make of steel
is liable to have cavities of this kind, although the
inspector at the mill generally discovers it in the ingot,
thus preventing it being made into bars ; but it some-
times escapes even the most careful inspection.

If a tool costing $50.00 were made from a bar that
was piped, it would in all probability go all to pieces in
the bath when hardened, unless the tool were of a
character that allowed the piped portion to be re-
moved. It is safer, however, to inspect the bar before
any costly tools are made from it. If the bar proves

3»

Inspection an economy.

sound, the grain should be examined; if this is fine,
and of the proper appearance, it may be tested for
hardness with a file.

If the piece proves to be all right, the bar may be
stamped O. K. or given some distinguishing mark;
should it prove otherwise, the manufacturer should be
notified and the steel returned to the mill.

This system of inspection may seem like a need-
less waste of money, but the cost of one tool which is
of no use when finished, would pay the necessary
expense of testing all the steel used in a machine shop
of the ordinary size in five years.

When a tool is required to do extra hard work, that
is, cut hard stock, or run at a higher speed than is
ordinarily employed in the shop, it is advisable to get
a steel having a greater percentage of carbon than the
steel used for tools for ordinary work. When high
carbon steels are bought, they should be distinctly
labeled or stamped, and kept by themselves away from
the rest of the steel, because if the identity of the
piece is lost, it is liable to be made into tools and hard-
ened without the hardener knowing that it differs in
composition from the steel ordinarily used. As a con-
sequence he would heat it to the same temperature he
was accustomed to give the steel regularly used, and it
would in all probability be cracked from the heat which
was higher than was necessary.

33

Methods of Heating.

c-o

The method employed when heating steel for any-
particular purpose depends on the facilities furnished
by the individual shop. As it is not, generally speak-
ing, the office of the hardener to purchase the equip-
ment of the shop ; biit to use such equipment as may
be furnished him, it is necessary that he adapt himself
to circumstances as he finds them. The successful
man is one who makes the best use possible of the
equipment furnished him.

If there are but a few tools to harden, and they are
of a character that could be treated in a satisfactory
manner in an ordinary blacksmith's forge, it would not
be considered advisable to purchase a costly furnace,
even though it were known that the work could be done
more cheaply per piece, because the limited number of
pieces would not warrant the extra outlay of money for
equipment.

On the other hand, if work was to be done in large
quantities, it would be wise to procure the necessary
equipment to do the work in a satisfactory manner at
the least cost possible. If the total amount of harden-
ing done in a shop in any one year was 6 or 7 diamond
point turning tools and 2 or 3 side tools, it would be
folly to invest several hundred dollars in a muffle fur-
nace and an elaborate system of baths. But if the pro-
duct of the shop was several hundred taps, reamers or

34

Hardener should do his best.

similar tools per day, it would not be considered gooJ
business policy to heat tliem for hardening in an ordin-
ary blacksmith's forge. It would not be possible to
do the work as cheaply, neither would it be done in as
satisfactory a manner as though apparatus especially
adapted to this class of work were used.

But, as previously stated, the hardener should make
the best possible use of apparatus furnished him. If
obliged to use a blacksmith's forge for heating steel
either for forging or hardening, he should see that his
fire is clean and that it is high enough above the blast
inlet so no jet of air can strike the heated steel.

It is possible to heat comparatively small articles
in a satisfactory manner in an ordinary forge by using
care in regard to the size and condition of the fire and
the location of the piece of work in relation to the
blast inlet.

It is always advisable to build a fire large and high
enough so that the portion of the piece being heated
will be covered to a considerable depth by the coals.
Otherwise the action of the oxygen in the air would
cause the carbon to be burned out of the surface of the
steel, leaving it decarbonized ; in this condition it can-
not harden.

If the cold air from the blast strikes heated steel,
it causes it to crack, particularly if there are teeth or
projections, as these are more susceptible to the action
of heat and cold than the heavier portions. The steel
would expand from the action of the heat, the air
striking the projections would cause contraction, and
the repeated expansion and contraction would cause
the steel to crack.

If large pieces are to be hardened, a large high

S5

Action of charcoal on steel.

fire should be built, as a low fire in a forge having a
tuyere — blast inlet — of the ordinary size would not be
sufficiently large to heat the piece uniformly. It is
always advisable when heating large pieces to use a
fire of new coals if charcoal is used as fuel, as coals
which have been used for some time are burned to the
extent that the fire is dead unless considerable blast is
used, in which case the result would be a lot of cracked
work.

Charcoal is generally considered the ideal fuel to
use when heating tool steel. As it is a form of carbon,
it is generally given credit for imparting carbon to the
steel heated in it. Now, this is the case, if low carbon
steels are packed in a tube or box with a good quality
of charcoal, away from the action of the fire and air,
and run for a considerable length of time. Carbon will
then be absorbed by the steel. Before the process of
making crucible steel was discovered, iron bars or rods
were packed in tubes with charcoal and run for a suffi-
cient length of time to charge the iron with carbon,
thus making a union of iron and carbon, or steel, as
it is familiarly known. This process is known as
"cementation."

It does not seem probable that a piece of tool steel,
high in carbon would absorb any extra carbon in the
brief time it was exposed to the action of fire, in heat-
ing for hardening. On the contrary, if a piece of high
carbon steel is heated in this manner, it is apt to lose
some of the carbon at the surface. For this reason, a
piece of high carbon steel is not so liable to have sur-
face cracks if heated for hardening in a charcoal fire.
But from experiments, it can, I think, be truthfully
claimed that a piece of 1.5 per cent, carbon steel will

36

The use of mufHe furnaces.

not be as hard on the surface if heated in a charcoal
fire, as if heated in a fire burning coke.

But if steel must be heated in a fire, exposed to
the action of the burning fuel, it is advisable in most
cases to use charcoal, because it does not contain im-
purities injurious to the steel.

On the other hand, high carbon steel will not be as
hard on the surface if heated in a charcoal fire, as if
heated in some form of furnace where the article is not
exposed to the action of the burning fuel, and as most
of the other fuels contain impurities injurious to the
steel, it is best to heat in a manner that removes it
from the action, not only of the burning fuel, but also
from the action of the air. In order to accomplish the
desired result, the article may be placed in a tube or
iron box, or a muffle furnace may be used.

If many pieces are to be hardened, it is advisable
to procure a furnace especially adapted to the class of
work. The neatest, most easily managed furnace, and
the one which gives as good satisfaction as any, is a
form made to bum illuminating gas as fuel. These
can be procured of almost any size. A very satisfac-
tory style of this type is known as a muffle furnace,
from the fact that the piece of steel to be heated is placed
in an oven or muffle. The flame circulating around
the muffle heats it to any required degree of heat.
The steel is heated by radiation, consequently it is not
subjected to the injurious effects of the products of
combustion; and as the door may be closed, there is
little danger of oxidation of the heated surface. If the
furnace is not provided with some means whereby the
work being heated may be readily observed without
removing the door, it is advisable to drill one or two

37

Types of muffle furnaces.

one-incli holes in the door, covering them with mica.
These furnaces are by far the most satisfactory for
general use of any form the writer has used. Figs. 4

and 5 represent
two styles of
these furnaces.
If it is not con-
sidered advis-
able to purchase
a furnace of this
description and
one is to be
made on the
premises, it is
possible to make
a very satisfac-
tory furnace
quite cheaply.
If large or long
pieces are to be
heated and a
furnace is to be
made of a type
where the steel
is placed in con-
t a c t with the
fuel, it is advis-
able to use char-
coal, as either
coke or coal do

Figure 4. Muffle furnace for hardening. ^^^ fumish a

satisfactory means of heating under the circumstances
mentioned. The grate should be made the size of the

38

'TheDerryCoUariCo.-

Muffle furnace for hardening.

Types of muffle furnaces.

inside of the furnace, as in this way a uniform heat
may be maintained in all parts of the furnace, and it
will not be necessary to use a blast. A natural draft
will be found sufficient.

Fig. 6 shows a furnace of the type mentioned, the
dimensions depending on the size and character of the
work to be heated.
A damper should be
placed in the smoke
pipe in order to check
the fire if there is
danger of its becoming
too hot. This damper
should not be of the
type usually put in the
pipe of a coal stove, as
these dampers are made
with a hole to allow for
the escape of gas. It is
not desirable to have
this hole in the damper,
as it is impossible to
check the fire on a
windy day. The lower
door must also be fur-
nished with a damper,
in order to furnish

Figure 5. Muffle furnace for hardening.

draft when desired. It is possible with this furnace
to do very excellent work.

If it is desirable to build a muffle furnace, one
may be made to use either charcoal, coke, or hard coal
as fuel by taking the one represented in Fig. 7 as a
model, and changing the design to meet the require-

39

"Home-made" muffle furnaces.

ments. The interior of the muffle is represented by A,
B is the fire box, C the ash pan. The heat and smoke
passing up from the fire box follow the direction of the
arrow passing under the muffle and out of the smoke
pipe at D. A damper should be placed in the smoke

Figure 6. A '*home-made" furnace.

pipe and one in the ash chamber door. By means of
these dampers the draft can be regulated very nicely.
This form of furnace works very nicely in heating
dies and similar work.

When small articles are hardened in large quan-
tities a furnace may be made of the design shown in

40

"Home-made" muffle furnaces.

Fig. 8, where a represents the fire box which bums
hard coal, charcoal or coke ; b the ash box ; and c the
chamber for heating the work. The front plate has a
number of holes corresponding to the number of tubes
it is considered advisable to heat at a time. The tubes
are made by taking a gas pipe, plugging one end as

The Derry Oollard Co.

Figure 7. A "home-made" furnace for burning
charcoal, coke or hard coal.

shown as Fig. 9, the other end being left open. A
number of pieces of work may be placed in each tube
and the tubes placed in the openings. The tubes at
the bottom will heat more quickly than those at the
top, so it is advisable when a tube in the bottom row
is taken from the furnace to fill its place with one from
one of the top rows. The tubes as they are filled may
be placed in the top rows and allowed to heat gradually

41

"Home-made" muffle furnaces.

and later removed and placed in the lower row. By
following this plan it is possible to heat the work

o o o o

o o o
o o o o

liw Ddrry CoUard Co.

Figure 8. A "home-made" furnace for
heating small pieces.

gradually and yet harden a large amount of work in a

given time. The tubes should be turned occasionally

in order to insure even heating and satisfactory results.

When but a few small pieces are to be hardened

*f/w/////ww///w///^vw.'//WA'w;/w////w//////w/w///^^^^^

The Derry ColUrd Co.

Figure 9. Construction of tubes in
"home-made" furnace.

a gas blast of the form shown in Fig. lo answers very
nicely. If the pieces are of a size that guarantee their

42

Apparatus for heating small number of pieces.

heating quickly it is safe to hold them in the flame,
having a piece of fire brick to reflect the heat. By
this means the heat is utilized to much better advan-
tage than if nothing were placed back of the work. It

Tlw Deny C«U*rd C5o,
Figure lo. Gas blast for heating a few pieces.

is possible by forming a cavity in the brick or making
a small oven as shown in Fig. 1 1 to heat a much larger
piece of work in an ordinary blow pipe than would
otherwise be the case.

Figure x i . Another form of gas blast for heating

A crude but satisfactory method of economically
heating small pieces is furnished by the idea presented
in Fig. 12, in which case a small oven is built of fire
brick, or a casting of the desired shape may be

43

Gas blasts for heating a few pieces.

obtained. In either case a flame from gas blast should
enter at one or both sides through holes provided.

Small articles may be heated by using a Bunsen

Figure 12. Small "home-made" gas blast oven.

burner, as shown in Fig. 13, which can be applied to a
gas pipe in place of the ordinary burner, or may be
connected by means of a piece of rubber tube. When
using a burner of this description the work can be
heated more readily if a piece of sheet iron is placed
over the burner at the proper height, the article to be
heated being placed beneath this, the sheet metal
reflecting the heat and thus increasing its utility.

It is also possible by means of a blow pipe to heat
very small articles sufficiently for hardening by means
of an ordinary gas jet or the flame of a spirit lamp, as
shown in Fig. 14. This is an expensive method when
work is heated in quantities, but answers very nicely
for one or two pieces.

When heating for forging or any work where the
outside of the steel is afterwards to be removed it is

Heating small articles.

advisable to use a form of furnace where the direct
heat of the fire comes in contact with the steel, as it is
much more economical and is, generally-
speaking, a quicker method than heating
in a muffle furnace. It is advisable many-
times when heating large pieces of steel
for hardening, to use a furnace, as de-
scribed, on account of economy. In case

/,

The Derry CoUard Co.

Figure 14. The blow pipe
way of heating.

the outer decarbonized surface is to be
ground away, the results will be satisfactory ;
but if the outer surface must be hard, then
it is necessary to protect the
surface from the action of
the products of combustion.
This may be accomplished
by several different methods.

The Derry CoUard Co

Figure 13. Bunsen burner, for
heating small articles.

45

Covering paste, and how to make it.

One method is to place the portion of the piece, which
must not be decarbonized, in a box with carbonaceous
materials — as charcoal or charred leather — and subject
to heat until the piece has reached the desired uniform
temperature, being- careful that the part which is
exposed to the direct heat of the fire does not get
over-heated.

Another method which is used when an article
must be hard on all its surfaces is to cover the piece
with a carbonaceous paste, consisting of the following
ingredients :

Pulverized charred leather 2 parts.

Fine family flour 2 *'

Fine table salt i part.

Mix thoroughly while in a dry state. Water is then
added slowly to prevent lumps ; enough water may be
added to make it of the desired consistency, which
depends on the nature of the work and the length of
time it must be exposed to the action of the fire. If
the articles are small and will heat to the proper temp-
erature for hardening in a few minutes, it should be of
the consistency of varnish. If, however, the pieces are
large and require considerable time for heating, it must
be made thicker.

Various substances are heated red hot in crucibles
or iron dishes, and pieces to be hardened are heated in
them. These exclude the air and so prevent oxidation
and decarbonization of the surface of the steel. Among
the substances used are lead, tin, glass, cyanide of
potassium, a mixture of salt and cyanide of potassium.

Lead is heated in a crucible in a furnace of the
forms shown in Figs. 15, 16. It furnishes a very excel-

46

Heating in molten lead.

lent means of heating- work which is hardened in large
quantities. When making furnaces to heat lead red
hot for use in hardening steel, some means should be
provided for carrying off the fumes of the lead, as they

are very injuri-
ous to the work-
man. They are
especially hard to
dispose of, as
they are heavier
than the atmos-
pheric air ; conse-
quently cannot
be disposed of as
readily by means
of a ventilating
shaft as other
fumes. It is nec-
essary to furnish
a pipe connected
with an exhaust
fan. This pipe
may be at the back of the furnace instead of over it, as
is generally the case when gases or smoke are to be
carried off. It should not be arranged in a manner
that will cause the surface of the lead to become
cooled by a current of air passing over it.

If illuminating gas can be procured at a reasonable
rate, it furnishes an ideal method of heating a crucible
of lead. Furnaces burning illuminating gas can be pro-
cured of a size and shape adapted to the work to be
done. If, however, it is considered advisable to make
a furnace for this purpose, one may be made which

The Derry Collard Co.

Figure 15. Lead hardening furnace.

47

Heating in molten lead.

will give good satisfaction. It can be made to bum
oil, coal, charcoal or coke. If oil is the fuel to be used,
it is advisable to install a system especially for this
method, and as circulars and full explanations can be

The Derry Collard Co.

Figure i6. Lead furnace for hardening.

procured from manufacturers who make these outfits,
it would not be wise to go into their details here.

If it is considered advisable to make a furnace
burning charcoal, hard coal or coke, the design shown
in Fig. 17 may be used or changed to adapt it to
these fuels. The outer shell may be made of cast
iron, although it may be possible to procure an old

48

^Home-made" lead heating apparatus.

BACK HALF. TOP PLATE

FRONT HALF

boiler, which can
usually be bought
very cheaply. A
piece the desired
length may be cut
from this, that an-
swers the purpose
very nicely. A round
grate and the neces-
sary frame to support
it may be procured
from a stove dealer.
The form of grate

mill I ■ 'Hill

2:^

Figure 1 7. Coal, coke or charcoal furnace for lead heating.
49

"Home-made" lead heating apparatus.

used in the ordinary cylinder parlor stove will answer
every purpose. The frame should be attached to the
shell or blocked up from the bottom of the ash box, to
allow the grate to be turned in dumping the contents of
the furnace. The interior of the furnace may be made
of circular fire brick, which may be supported by the
slab which forms the base or bottom of the ash box and
designated as the bottom plate. In case fire brick are
used, the grate frame may be built into the brick work
as shown. If, however, a stove lining of the desired
size can be procured, the bricks need extend only up
to the frame, the lining extending from the frame to
the top of the shell. It is necessary to cut an opening
in the ash box in the front of the shell. This should
be covered with a swinging door, containing a sliding
damper. This door is necessary in order to remove
the ashes.

A smoke pipe must be provided to carry off the
smoke and gas from the fire. This should be con-
nected with the shell at the top on the back side of the
furnace. Over the top of the furnace must be placed
a plate, having a hole in the center about one half inch
larger than the size of the crucible to be used. This
plate should be cast in two pieces, having more than
one-half of the hole in the part that goes at the back.
The smaller or front half may be moved forward, thus
affording an opening to feed the coal to the fire. The
object in having more than one-half the opening in the
back part of the cover is to prevent the crucible from
tipping over when the front plate is removed, when
there is not sufficient coal in the furnace to support it.
It is necessary to place a piece of fire brick in the
center of the grate for the crucible to rest on in order

so

Cyanide of potassium furnace.

that the fire may be beneath it. The smoke pipe
should be provided with a damper, to enable the
operator to properly control the fire. This form of

furnace gives
best satisfaction
when hard coal
is used as fuel.

Red-hot c y a -
nide of potassium
is used with ex-
cellent results in
heating tools for
hardening. It
not only heats the
steel uniformly,
but, being lighter
than steel, the
latter sinks in the
fluid, thus effect-
ually excluding
the air from the
surface of the
steel. It also has
the effect of mak-
ing the surface
somewhat harder
than it otherwise
would be, without
making the steel
more brittle.

It should be
borne in mind
that cyanide of

Derryt3ollard Co,

Figure 1 8. Furnace for heating in
cyanide of potassium.

51

Heating cyanide by gas furnace.

potassium is a violent poison, and great care should be
exercised in its use. Not only is it poisonous when
taken into the stomach, but the fumes are highly in-
jurious to the workman if inhaled. However, if fur-
naces are properly designed and set up, the fumes may
be disposed of in a manner that does away with this
trouble.

In Fig. 1 8 is shown a form of furnace made es-
pecially for use in heating in cyanide of potassium.
The fuel used is illuminating gas, the products of
combustion passing up the pipe E to the main pipe F
which also conveys the fumes of the melted cyanide
into the chimney or ventilating shaft. The burners
enter the furnace at A and heat the crucible B, which
contains the cyanide. A hood C, which is provided
with a door D, keeps the fumes from entering the
room as they are conveyed into the pipe F. The
lighting holes G G are closed by the plugs shown
when the fire is well under way.

When a comparatively small number of small
pieces are to be hardened, it is possible to heat the
necessary amount of cyanide in a small iron dish in an
ordinary forge. The pieces may be held in this until
the desired effect has been accomplished, when they
may be quenched.

As the work heated in this manner is usually hung
from the edge of the crucible by means of wire hooks,
it is generally considered advisable to use a square
crucible rather than a round one when work is done
in large quantities.

When a furnace is to be made for this purpose, the
form represented in Figs. 19-20 will be found to give
good results. This furnace burns hard coal. The cruci-

52

"Home-made" cyanide furnace.

ble which is made of cast iron is square in shape and

hangs from the flange,
which is cast around
the upper edge. The
top of the crucible is
below the top of the
back of the furnace.
An opening into this
allows the fumes to es-
cape into the chimney.
A quantity of salt
is placed in a crucible
and heated red hot.
To this is added cya-

Figures 19-20. A "home-made'
cyanide heating furnace.

Crucible

??vi???7?????rr;rrr<t;rfW??

Fire Box

Grate

Ash Box

nide of potas-
sium until
the steel
heated in
it shows
the proper
amount of
hardness.
This method
is used by
manufactur-
ers of taps
and similar
tools, who
claim excellent results by its use. The same general

53

The Derry Collard Co.

Where furnaces should be located.

remarks apply to this metliod as to heating in cyanide
of potassium.

Glass heated in a crucible until it is red-hot is the
means used by some watch makers to heat the hair
springs of the watches. It is claimed that the nature
of steel heated in this manner will not change in the
least.

Very little attention is paid in most shops to the
location of the forge or furnace used in heating steel ;
generally any out-of-the-way place is selected. If
there is any portion of the shop that cannot be utilized
for anything else, it is given up to this purpose.

The fire for heating steel should receive more con-
sideration, so far as location is concerned, than almost
any other part of the equipment. It should never be
located where the direct rays of the sun or any strong
light can shine in it, or in the operator's eyes, for un-
even results will surely follow. It should never be
located in or near a window, neither should the roof be
constructed with skylights which allow any of the
sun's rays or any strong light to enter the portion of
the room where the furnace is located.

An ideal place for the location of a furnace used in
heating steel for hardening, is in a room so constructed
that no rays of sunshine or direct light can enter it.

It is extremely important that due consideration
is given the subject of ventilation. Some means
should be provided whereby pure air can be freely
supplied without creating drafts, which would cause
the operator, who is perspiring freely, to take cold.
The room should be so located that it will not be damp,
or the health of the workman would be hazarded.

Too often in the past the precautions noted have

54

Heating tool steel.

received very little consideration, because those in
charge did not realize the importance of a properly
equipped or located room in which to do this class of
work.

Heating Tool Steel.

CO

Tool steel is very sensitive to the action of heat.
A slight difference in temperature after a piece has
reached the proper hardening heat will be noticeable
in the grain of the steel. When heating for hardening,
the lowest possible heat that will give the desired
result should be used. The amount of heat necessary
to produce this result depends on the make of the steel,
the percentage of carbon it contains, the percentage of
other hardening elements that may be in the steel,
the size of the piece, and the use to which it is to be put
when hardened — all these must be taken into con-
sideration. A steel low in carbon requires a higher
heat than a piece of high carbon steel in order that it
may be as hard. A small tool does not require as much
heat as a larger one of the same general outline. A
tool with teeth or other projections will harden at a
lower heat than a solid piece of the same size made
from the same bar of steel. There is a proper heat at
which a piece of steel should be hardened in order to
produce the best results, but this heat varies^ as pre-
viously explained.

If two milling machine cutters were made from

55

Refining heat, and what it means.

two different makes of steel the writer has in mind,
and were heated in a manner that would give excellent
results in the case of one, the other would not harden
satisfactorily. Now, were the operator to heat both to
the proper hardening heat for the other make, the first
one mentioned would be unfitted to do what was
expected of it. Either make of steel would give good
results if heated to its proper heat.

The commonly used expression of degrees of heat
which tool steel should receive is a cherry red. The
writer cannot dispute the appropriateness of this term,
but cherry red is a varying color when applied to the
hardening heat of tool steel, and also when applied to
cherries. Mr. Metcalf, in his work on steel, styles
this heat as the refining heat, and this seems to express
the idea nicely.

Steel should be heated to a temperature that, when
hardened and broken, the fracture will show the grain
to be the finest possible, and the steel will be hard.
Now, if we heat a piece from the same bar a trifle
hotter and break it, the fracture will show a coarser
grain. The hotter the piece is heated, the coarser the
grain becomes ; and the coarser it is, the more brittle
the steel is. While, to be sure, steel heated a trifle
above the refining heat will be somewhat harder than if
heated to the refining heat, yet the brittleness more
than offsets the extra hardness ; and if it is to be used,
it will be found necessary to draw the temper in order
to reduce the brittleness to a point where it is practical
to use the tool.

After taking the necessary means to reduce the
brittleness as described, an examination of the tool
will reveal the fact that in drawing the temper we have

56

The use of test pieces.

softened the piece to an extent that it is not as hard as
the piece hardened at the refining heat. Neither will it
do anywhere near the amount of work, as the grain is
open and when the pressure is applied in the operation
of cutting, the surface caves in because of the open
grain. The surface has not the backing it would have,
were the grain close or fine.

A method which the writer has used in his experi-
ments and also in demonstrating the effect of heat on
the grain of steel is to take six pieces of steel that can

The Derry CoUard Cw.

Figure 2.1. Test pieces.

be readily broken. Cut the required number from a
bar I inch to i^ inches diameter, having the pieces
about ^6 of an inch thick. Now heat the pieces one at
a time in a furnace so situated that no rays of the sun
or any strong light can shine either into the fire or into
the eyes of the operator. It is advisable to have the
furnace located in a room that can be darkened so that
it is neither light nor extremely dark, but it must be
uniform throughout the experiment. Now heat one
piece until it shows somewhat red, yet a certain black
is discernible in the center of the piece. Dip into the
bath and work it around well ; leave until cold. Now

57

What test pieces will show.

heat another piece until it shows the lowest red pos-
sible throughout with no trace of black. Heat the
third piece a trifle hotter, and continue to heat each
piece hotter than the preceding one until they are all
hardened, heating number 6 to what is familiarly-
termed a white heat.

Previous to heating, each piece should be stamped
in two places, as shown in Fig. 21, in order that the
pieces may be broken across the center, as indicated by
the dotted lines, and yet the halves of the same piece
be easily recognized. When heating, commence with
the piece marked i, and heat consecutively. After
hardening them all at the different heats, dry thoroughly
in saw dust or by any means whereby the surface may
be made perfectly dry, after which they may be broken.
This can be done by screwing the piece in the jaws of
a vise, putting about one half of it below the tops of
the jaws. With a hammer the upper part may be
broken off, being careful that the piece does not fly and
strike so as to stain the walls of the fracture ; or the
part projecting above the vise may be caught between
the jaw^s of a monkey wrench and the piece broken.

An examination of the piece marked Fig. 22 will
show it to be somewhat hardened. The grain will not
be especially fine and will have a peculiar appearance.
No. 2 will be very hard and the grain will be very fine.
It will break with very ragged walls, as shown. No. 3
will also be very hard and the grain not as fine as No.
2. The grain of No. 4 will be coarser than No. 3.
No. 5 will be coarser than No. 4, while the grain of
No. 6 will be extremely coarse and the steel unfitted
for anything but the scrap heap.

It will pay any man who is desirous of learning to

S8

C
be
o

Temperatures for different steels.

harden steel properly to try this experiment. The steel
will cost him but a few cents, and it need take but a
short time to heat it ; but the knowledge gained of the
action of heat on tool steel will be of inestimable value
to him, as he can readily see the effects of proper and
improper heating on the structure and strength of steel.

If the operator notes carefully the heats, he will
be surprised at the difference in the amount of force
necessary to break a piece of steel hardened at the
refining heat and one heated slightly above this tem-
perature, which, in fact, is hardly discernible to the eye
in the light of an ordinary blacksmith's shop. The
difference in the strength of a piece hardened at the
refining heat and one heated to 2l/uII red is especially
noticeable. In the former case it seems almost impos-
sible to break it by a blow of a hammer, and it seldom
can be broken across the center, so great is the adhesion
between the molecules that make up the piece of steel,
while in the case of a piece heated to a full red, the
piece may be broken easily, as compared with the
other. When one takes into consideration the fact that
the ordinary workman heats steel when hardening to a
full red oftener than to the refining heat, it is wonder-
ful that the results obtained are as satisfactory as they
are.

As stated, the temperature to which a piece of
steel must be heated in order to refine it, depends on
the composition of the steel. Tests of different steels
have led authorities on this subject to the conclusion
that it is necessary to heat a piece of steel to a tem-
perature between 800° and 1200° Fahr. in order that it
may harden when plunged in a cooling bath. Jaroli-
neck places the temperature at 932° F. (500° C.) as

59

The uniform heating of" steel.

determined by experiments made by him, while other
authorities claim best results when the steel was heated
to 1200° F. (about 650° C). As this difference (268° F.)
involves a wide range of heat, it is evident that steels
containing different percentages of carbon were used
in the various tests.

If a piece of steel be heated to the refining heat and
then quenched as soon as the heat is uniform through-
out the piece, the steel is in the best condition possible
for most uses. It should be quenched as soon as it is
uniformly heated to the proper temperature. If sub-
jected to heat after it reaches this temperature, it will
become somewhat hotter. In fact, it has been ascer-
tained by experiment that after steel is heated to a low
red the temperature may be raised, and the difference
in the heat not be discernible to the eye. For this
reason it is advisable, if best results are desired, to
quench as soon as the desired unifor?n heat is attained.

It is also important that steel should be heated
uniformly. If a square block be heated so that the
center is of the proper heat and the ends and corners
are hotter, strains are set up in the piece, and it is very
liable to crack when hardened. This also applies to a
piece of any shape. While it is extremely necessary
that the operator observe the greatest possible care in
regard to the quantity of heat given steel, yet it does
not harm steel as much to heat it a trifle too hot as it
does to heat it unevenly, for while the higher heat un-
fits it for doing the maximum amount of work possible,
the uneven heat is very liable to cause it to crack when
hardened.

A piece of steel should not be heated faster than is
possible to maintain a uniform heat. By this is meant

60

The condition of the grain of steel.

the heating should not be forced so that the outside is
red hot while the center is black because in all prob-
ability the furnace would be so hot that the outside of
the article would keep growing hotter while the center
was getting to the desired heat. The result would be
an uneven heat. Neither should a piece of steel be
any longer in heating than is necessary, because after it
is red hot, it will, if exposed to the action of the air,
become somewhat decarbonized on the surface, thus
materially affecting the steel. Tool steel should be
heated as fast as it will take heat, and no faster. A
piece should not be forced by heating the furnace to a
temperature that will affect the surface while the heat
is equalizing. Steel should never be heated too hot,
and allowed to cool to what is considered the proper
heat, and then hardened, as the grain will be as coarse
as if dipped at the high heat.

The grain of steel remains in the condition the
highest heat received leaves it, until it is reheated,
when it is adjusted to that heat. The condition of the
grain of the steel is an unvarying guide as to the
amount of heat it received the last time it was heated.
For instance, a piece of steel is heated to the tempera-
ture of the piece marked 4 Fig. 2 2 in our experiment.
Now, take one of the broken pieces and reheat it to a
temperature given the piece marked 2, which was the
refining heat. Break this piece. An examination will
reveal the fact that the grain has the same structure as
the piece marked 2, thus proving that the grain of steel
conforms to the last heat given it. This does not
necessarily prove that a piece of steel is capable of
doing the amount of work after it has been heated
hotter than it should have been, and then reheated to a

6x

Harden on a "rising heat."

lower heat, thus closing the pores ; but it is better than
if in the condition the high heat would leave it.

Steel should always be hardened on what is known
as a ''rising" heat, never on a ''falling" heat, is the
advice an old hardener gave the writer when a boy,
learning his trade, and he has found it true. It also
agrees with the advice of most writers on this subject.
It is quite necessary, in order to get uniform results, to
move the articles around in the furnace and turn them
over occasionally. When round (cylindrical) pieces of
steel, having no teeth, projections, or other irregulari-
ties on its surface, are being heated for hardening, it
is necessary to turn them occasionally, as, if left in one
position without turning, until it is red hot, no matter
how uniform the heat may be, it will, in all probability,
have a soft line the entire length of the top side as it
lay in the fire. It will also be found by experiment
that round pieces are more liable to crack from uneven
heating than pieces of almost any other shape ; neither
will they safely stand as high a degree of heat as some
pieces, on account of their shape, which makes them
offer greater resistance to a change of form.

If possible, when heating articles having heavy
and light sections adjoining each other, as shown in
Fig. 23, heat the heavy portion first, then the lighter
one; but if this is not possible, have a slow fire, in
order that the light part may not be overheated before
the heavy one is to the required heat. The muffle
furnace furnishes a very satisfactory method of heating
steel, because the products of combustion cannot come
in contact with the steel, and oxidation from the action
of the air is done away with or reduced to the minimum.
If it is not possible to use a furnace of this description,

6z

When coals should not be used.

very good results may be obtained by enclosing the
article in a piece of pipe or tube and beating in an open
fire, because in this case the steel is not exposed to the
action of the fire. It is necessary to turn the work
over occasionally in order to get a uniform heat.

It is never advisable to use any kind of fire where

the air from the blast

Tlie D-irry Collard Co.

Figure 23. A piece for a slow fire.

can strike the piece be-
ing heated, or it will
crack in innumerable
places. The steel will
look as though it were
full of hairs. For this
reason, if obliged to use
a blacksmith's forge, build a fire high enough to do
away with any tendency of this trouble. A fire of old
coals should not be used if the article to be heated is of
any size, as the goodness is burned out of the coal,
and it will be found necessary to use a strong blast in
order to have a fire hot enough to heat the piece.
As a consequence, the air strikes the piece with the
result mentioned.

Steel should not be heated in a manner that leaves
one side exposed to the air, or the exposed side will
become oxidized to a considerable extent, and as the
piece is turned in the fire the whole surface becomes
oxidized and resembles a piece of burnt steel. The
surface is not of any use, as the carbon is burned out,
and it cannot be hardened. Some makes of steel give
off their surface carbon very readily if exposed to the
air when red hot. If a tool made from one of these
steels be heated in a manner that allows the air to come
in contact with it, the outside becomes decarbonized.

63

The indifference of some hardeners.

and consequently is soft, while the metal undemeatli
the surface is extremely hard. Now, this might not be
harmful in the case of a tool whose outer surface was
to be ground away, but if the surface of a tap, formed
mill or similar tool becomes decarbonized, it is practi-
cally useless. Now, if these same tools had been
heated in a muffle furnace or in a piece of pipe in the
open fire, removed from the action of the fire and the
air, the result would have been that the tool would
have given excellent satisfaction. While all makes of
steel are not so sensitive to the action of the fire and
air when they are red hot, yet any steel gives better
results if it is removed from their action while in this
condition.

A man experienced in the effects of heat on steel
is surprised at the apparent indifference of some hard-
eners when heating steel. A tool hardened properly
and tested for strength in a testing machine will be
found very much stronger than if heated a trifle hotter.
When we consider that hardness, toughness and close-
ness of grain are the qualities desired in a cutting tool,
we realize that there is nothing gained by heating tool
steel above the refining heat for most work. Steel
quenched at this heat is very hard, tough, and the grain
is the finest possible. Now, every degree of heat which
it receives above this point unfits it for doing the
maximum amount of work possible, because it causes
the steel to be brittle and makes the grain coarse.

The writer has made exhaustive experiments in
regard to the effects of heat on the strength of steel,
and assures the reader that a piece of steel hardened at
the refining heat requires a much greater force to
break it than one heated to a full red. Knowing this,

64

Reheating to remove strains.

the reader can judge how much heavier cuts can be
taken with a tool properly heated than with one heated
too hot, as the steel is made brittle, and in this condi-
tion is more liable to chip or flake off under pressure.
The grain being coarse does not present a dense body,
but the internal structure has a honeycomb appear-
ance ; consequently when pressure is applied the surface
caves in, because it does not have the backing it would
if the grain were compact.

Reheating to Remove Strains.

As steel heated red-hot and cooled quickly con-
tracts, and as the outer surface hardens and becomes
rigid before the interior of the piece has ceased con-
tracting and altering its form and the position of its
molecules, the molecules that make up the interior of
the piece cannot assume the exact positions they
should ; consequently, strains are set up. Now, if the
outer portion of the article is sufficiently strong to
resist the tendency of the interior of the piece to alter
its form, it may not crack or it may resist the strain
for a considerable length of time. But for some cause
a certain portion of the exterior of the piece becomes
weakened, or the conditions are such that the outside
can not longer resist the internal strain, and the piece
is cracked, or it may burst. Many times large, heavy
pieces of steel will burst with a report as loud as a gun,
and pieces of the steel will be carried for some distance
by the force exerted.

Now, in order to avoid this tendency, it is neces-
65

Pliability of hardened steel.

sary to reheat the piece as soon as it is taken from the
hardening bath, to a temperature that allows the vari-
ous portions of the piece to conform to one another.
A piece of hardened steel becomes pliable to a degree
when heated, the amount of pliability depending on
the temperature to which the piece is heated. This is
illustrated elsewhere in the case of articles crooked in
hardening, which are straightened after heating to a
certain temperature. After cooling they remain the
shape given, but were we to attempt to spring them as
much when cold, they would certainly break.

It is advisable, after taking a piece of hardened
steel from the bath, to hold it over a fire or in some man-
ner subject it to heat, in order that it may become
pliable enough to remove the tendency to crack from
internal strains.

The method pursued in removing the strains
varies. If an open fire is at hand, the piece may be
held over this until heated to the proper temperature.
It should be constantly turned, in order to insure uni-
form results. When pieces are hardened in large
quantities, this is a very expensive practice. In such
cases, it is advisable to have a tank of oil, which is
kept at the desired temperature, this being gauged by
means of a thermometer.

A very satisfactory method, and one used by the
writer for many years, consists in using a tank of
water, the contents of which are kept at the boiling
point (212°). When a piece of hardened steel is
removed from the bath, it is immediately dropped in
the boiling water. The tank has a catch pan to receive
the work, as shown in Fig. 24. A steam pipe is con-
nected with the tank in order to keep the water at the

66

The removal of internal strains.

Perforated Catch Pan

\'<'«'<'<'<'<'<'<'<'W<'<'<'/^/W<'<'('<'/^<l

desired temperature. It is, of course, necessary to
provide an overflow pipe, as represented.

When it is not considered advisable to procure a
tank, as represented, a kettle of water may be placed
over a fire and brought to the boiling point and used
as described.

When it is thought to be advisable to remove the

tendency to crack
from internal
strains and draw
the temper at the
same time, it may
be done by heating
a kettle of oil to
the desired tem-
perature, gauging
the heat by a ther-
mometer. The
pieces, as they are
taken from the
hardening bath,
may be dropped in
this and left long
enough to insure
uniform heating.
Should it be considered advisable to heat articles
of irregular shape, having heavy and light portions
adjoining each other, it would not be advisable to sud-
denly immerse them in liquid heated to 300°, 400° or 500°
Fahr. , as the unequal expansion might cause the pieces
to crack where the heavy and light portions joined.
In such cases it is sometimes considered advisable to
place them in a kettle of boiling water first, removing

67

\^^

Th« Derry Collard Co.

Figure 24. Tank of boiling water
for removing internal strains.

Forging troubles.

them from time to time and placing in the kettle of
oil, heated to the temperature to which the pieces must
be heated in drawing temper; or two kettles of oil,
heated to different temperatures, are sometimes used,
the first being kept at 250° or as as near that as possi-
ble, the other being the desired temperature. When
the pieces are removed from the first kettle and placed
in the second, it, of course, reduces the temperature of
the oil, but it gradually rises to the desired point when
the articles are removed.

Forging.

CO

It is not the writer's intention to devote much
space to explanation of the method in which steel
should be forged for the various cutting tools. In
order to do the subject justice, it would be necessary
to devote more space than can be spared, but the forg-
ing and hardening of a tool are so closely identified, it
seems necessary to briefly consider the subject.

Many tools are rendered unfit for use by the treat-
ment they receive in the forge shop, and as it is the
custom in many shops to have the forging done by one
man, and the hardening by another, a great amount of
trouble is experienced, because each tries to lay any
trouble that comes from the hardened product to the
other.

Heating is the most important of the operations to
which it is necessary to subject steel, whether it be for
forging, annealing or hardening.

6S

Superiority of hammered steel.

Unless steel is uniformly heated throughout, vio-
lent strains are set up; when the piece is hardened
these manifest themselves. If the steel is not heated
uniformly throughout the mass, it cannot flow evenly
under the blows of the hammer, consequently the grain
is not closed in a uniform manner.

While it is necessary, in order to get satisfactory ,
results, to heat steel hot enough to make it plastic, in
order that it may be hammered to shape, care should
be exercised that it is not overheated, or the grain will
be opened to an extent that it can not be closed by any
means at hand in the ordinary forge shop.

If a large piece of steel requiring considerable
change in size is to be forged, and means are at hand
to forge it with heavy blows, it can safely be given a
higher heat than a smaller article which does not require
much change of size or form.

If tool steel is hammered carefully, with heavy
blows while it is the hottest, and then with lighter,
more rapid blows as it cools, the grain will be closed
and become very fine.

When the temperature is reduced to a low red,
care should be exercised, for when traces of black begin
to show through the red, it is dangerous to then give it
any heavy blows, as they would crush the grain.

By actual test it has been proven time and again
that steel, which has been properly hammered, is super-
ior to the same steel as it comes from the steel mill,
but unless the work is done by an intelligent smith,
who understands the effect of heat on the structure of
steel, the forging will have the opposite effect to the
one desired.

Many steel manufacturers advocate the purchase
69

"Hammer refined" steel.

of steel in bars of the desired size, and do not advise
forging, claiming best results if tbe article is machined
to size and shape. The reason for this is, that there
are many careless, ignorant workers of steel in the
various blacksmith shops — men who either do not know
the effects of improper methods of heating and ham-
mering, or knowing, do not care. As a consequence,
a great quantity of steel is annually rendered unfit for
doing the work it might do were it treated properly.

For this reason it is advisable to machine a piece
of steel to shape, rather than to have it forged by any
but a skillful smith. Yet the fact remains that a piece
of steel heated and hammered properly will do more
work than a tool of the same description cut from the
same bar and machined to shape, even if it is hardened
in exactly the same manner.

A piece of steel properly forged is known by tool
makers as * 'hammer refined" steel, and is highly valued
by them for tools which are expected to do extra hard
work. Tool steel is furnished in bars, blanks or forg-
ings of almost any desired shape.

The smith should bear in mind that heats which
are too high open the grain, thereby weakening the
steel and making it incapable of doing the largest
amount of work possible. If steel is hammered when
too cold, the grain is crushed, causing it to crack when
hardened ; or if it does not crack, the cutting edges will
flake off when in use. If the steel is unevenly heated,
that is, the outside heated hotter than the inside, the
outside portion being softer will respond to the action
of the hammer more readily than the less plastic in-
terior, and the outer portion will be torn apart.

T-^o often it happens that when the smith is rushed

70

The object of annealing steel.

with work he will attempt to heat a large bar of iron
for forging, and while that is heating, will try to forge
or harden tools someone is waiting for. The spirit of
willingness to accommodate is commendable, but a
decided lack of judgment is noticeable, because a fire
suitable for heating a piece of iron to a forging heat
is in no ways adapted to heating a tool either for forg-
ing or hardening.

Then again, if the smith is heating iron to its
proper forging heat, his eyes are in no condition to
properly discern the correct heat to give a piece of tool
steel.

Annealing,

CO

According to the generally accepted definition of
the term, the object of annealing steel is to soften it in
order that it may be machined at the minimum cost of
labor and tools.

The method pursued in annealing steel depends, as
a rule, on the facilities which the shop possesses for
doing this class of work. A piece may be softened
somewhat by heating red-hot and laying it to one side
to cool in the air, provided it is not placed on any sub-
stance that will chill it. Neither should it be placed
where any current of air can strike it, or it will cool
too quickly to become soft. In fact, it would very
likely be harder than if worked without attempting to
anneal it.

The young hardener should understand that a

71

How annealing is best done,

piece of steel is hardened by heating red-hot and cool-
ing quickly ; the more rapid the process of cooling, the
harder the steel will be. Annealing has the opposite
effect. Steel is annealed by heating red-hot and cool-
ing slowly ; the greater the amount of time consumed
in the cooling operation, the softer the steel will be,
everything else being equal. Now, it is evident that,
if a piece of steel be heated to a red and placed on an
anvil or other piece of cold metal or thrown on the
floor, the portion laying on the cold substance will
chill and the process of hardening, rather than anneal-
ing, will be carried on.

The same is true if a piece is placed where a cur-
rent of air can strike it, even if it is warm air, as it will
be cooler than the steel and the heat in the steel will be
taken up by the air. Thus, the operation will be the
opposite of the one desired.

It is the custom in many shops to anneal steel by
heating and putting it in a box of ashes or lime. Now,
this may be advisable, or it may not be, according to the
condition of the contents of the annealing box. If the
room in which the box is kept is damp, the ashes or
lime, especially the lime, will absorb enough moisture
to chill the piece of red-hot steel, particularly if it be
small or thin. So we have again a piece of steel
hardened to a degree, instead of annealed. When steel
is to be annealed by this process, it is advisable to heat
a piece of iron or scrap steel and bury it in the ashes
or lime, leaving it there until the piece to be annealed
is properly heated, when it may be removed, and the
piece to be annealed put in its place. The ashes or
lime being heated, and every trace of moisture removed,
the process of cooling will be slow and the results

72

Methods of annealing.

satisfactory. A box of lime furnishes an excellent
method of annealing steel, if the precaution mentioned
is observed.

A very satisfactory method of annealing, which has
been used by the writer many times where there was
only one or two pieces to anneal at a time, consists in
taking an iron box, putting two or three inches of ashes
in the bottom and laying a piece of board a trifle larger
than the work on them. Heat the pieces to be an-
nealed to the proper
degree, lay them on
the board, lay an-
other piece of board
on top of them, and
fill the box with
ashes, as shown in
Fig. 25. The pieces
of board will
smoulder and keep
the steel hot for a
long time. The pro-
cess of cooling will
be very slow.
There is a method of annealing practiced in some
shops which, while it has many advocates, cannot be
recommended by the writer, except as a means of an-
nealing a piece of steel that is wanted right away. It
is known as cold water annealing. This method has
advocates among old hardeners, some of whom get
excellent results; but as a method of annealing to be
practiced by one who is not thoroughly familiar with
the action of fire and water on tool steel, its use is
hardly to be advocated. The steel is heated to a red

^s

= = = —

fLTLnj;;;

Work

-= — !~-^

^=^^^

'^— — ' — —-T-

Ib=^=I:=^=^fj

1

Figure 25.

An iron box filled with ashes for annealing
between boards.

73

Annealing in gas furnace.

and allowed to cool in the air where no current of air
can strike it, held in a dark place, and when every
trace of red has disappeared, plunged in water and left
until cold. The steel will be softer if plunged into
soapy water or oil.

This answers in an emergency, but on account of
the ends cooling faster than the center and the smaller
portions cooling more rapidly than the larger ones, it is
apparent that the piece of steel must be of an uneven
temperature throughout when cooled.

The method practiced in many shops of heating a
piece of steel in a furnace to the proper annealing heat,
using gas, oil or gasoline as fuel, then shutting off the
supply and allowing the work to cool down with the
furnace, is attended with varying results. While many
mechanics advocate this method and claim excellent
results, and it has been used by the writer to his entire
satisfaction, yet several cases have come to his notice
of late where parties had annealed this way with re-
sults that were far from satisfactory. Investigation
showed that in heating the steel the furnace had been
forced in order to heat the piece quickly, and as the
steel was heated by radiation it was necessary that the
walls of the furnace should be hotter than the piece of
steel being heated.

When the steel had apparently reached the proper
heat, the supply of fuel was shut off, but the inside
walls of the furnace, being much hotter than the work,
imparted heat to the steel after the fire was put out,
with the result that the steel was overheated and
injured, and in some cases entirely unfitted for the use
it was intended for. A steel maker of national reputa-
tion says that **many thousand dollars' worth of steel are

74

Annealing in iron boxes.

ruined annually in this way, and it is in every way about
the worst method of annealing that was ever devised.''

Knowing the vast amount of trouble caused by
attempts of various parties to use this method, the
writer feels it his duty to condemn a method he has
used successfully under favorable circumstances, be-
cause all mechanics are not so favorably situated.
They do not use the same care in heating steel, especi-
ally when it is nearly to the proper temperature, but
insist on forcing it, not only to the detriment of the
edges and comers, which are bound to heat faster than
the center. In this way the whole piece is ruined or
injured, because the furnace is hotter than the steel,
and when the fire was extinguished, the furnace was
closed and there was no means of looking in to deter-
mine the amount of heat the steel was receiving, but
the results showed it had been heated too much for its
good.

Now, if a comparatively small furnace is used, or
one having light walls, which will not hold the heat for
a very great length of time, the danger of over-heating
by radiation after the fire is extinguished is reduced to
the minimum. But on the contrary, if the furnace has
heavy walls of masonry, capable of retaining the
excessive heat for a considerable length of time, the
liability of overheating is very great.

A method of annealing that gives universal satis-
faction when properly done, and is used in many shops,
consists in packing the steel in iron boxes and filling
the spaces between the pieces of steel with powdered
charcoal. It is necessary when annealing by this
method to place one or two inches of charcoal in the
bottom of the box before putting in any steel. Do not

75

Box method of annealing.

allow the pieces of steel to come within one-half inch
of each other in the box, or within one inch of the box
at any point.

When nearly full, fill the balance of the space with
charcoal, put on the cover and seal the edges with fire-
clay. The reason for keeping the steel from coming
into contact with the box is that the iron, especially

The Derry Collard Co.

nzzi nz2 L

IZZ3 czzi i:=zi
[z:] czi cm

[IZI cm LU

Myy/My///^//////////^^^^

Figure 26. Iron box for annealing.

cast iron, has a great affinity for carbon, and will,
when they are both red hot, extract it from the steel,
leaving the latter somewhat decarbonized at the point
of contact.

In order to be able to determine when the contents
of the box are heated to the proper degree, several ^
inch holes should be drilled through the center of the
cover and a -^ wire run down through each of these

76

Process of annealing in boxes.

to the bottom of the box, as shown in the sectional
view, Fig-. 26.

When the box has been in the fire long enough,
according to the judgment of the operator, to heat
through, draw one of these wires by means of a pair of
long-handled tongs, or by a pair of ordinary length,
slipping a piece of gas pipe on each leg to give the re-
quired length. If the wire drawn shows hot the entire
length, the operator may rest assured that the steel is
of the same temperature, because the wire v/as run
down between the pieces at the center of the box. If
the wire did not show red-hot, wait a while and draw
another. When a wire is drawn that shows the proper
degree of heat, the box should be left long enough to
insure its being heated uniformily throughout, then the
fire may be extinguished. If the walls of the furnace
are much hotter than the boxes, the door may be left
open until they are somewhat cool. If the furnace
shows a disposition to heat the boxes too hot with the
door open, they may be removed for a few minutes
until the furnace is somewhat cooler, when the boxes
may be returned to the furnace, the door closed and
the work allowed to cool slowly.

A method that insures excellent results is to plan,
if possible, to empty one furnace of work to be hard-
ened some little time before the work being annealed
is sufficiently heated. Keep the first furnace closed to
retain the heat as much as possible, so that it will pass
the stage where it is liable to overheat the articles, and
it will commence to cool down somewhat. When the
work being heated for annealing has been subjected to
the heat a sufficient length of time, the boxes may be
removed from the furnace they were heated in and

77

Blocking out work for annealing.

Figure 27.

An irregular milling
cutter.

placed in the first furnace. All danger of heating too
hot from radiation is done away with. This method
cannot, of course, be prac-
ticed if there is but one
furnace.

While it is generally un-
derstood that the object of
annealing steel is to make it
soft enough to work to ad-
vantage, yet from the hard-
ener's standpoint annealing
has another and more import-
ant office than simply to
make steel workable.

A piece of steel as it comes from the steel mill or
forge shop is very apt to show a difference of grain in
various parts of the piece, due to uneven heating and
an unequal closing of the pores in the process of rolling
or hammering ; consequently
there exists in the piece internal
strains. In order to overcome
the effect of these internal
strains, which must manifest
themselves when the steel is
hardened, the work should be
blocked out somewhere near the
shape and annealed. If the
piece is a milling machine cut-
ter, punch press die, or similar
tool, having one or more holes
through it, the holes should be made somewhat smaller
than finish size before annealing to remove strains. If
it is a milling machine cutter of irregular contour, as

78

Figure a8. Irregular milling

cutter blocked out for

annealing.

How to straighten work after springing.

shown in Fig. 27, it should be blocked out as repre-
sented in Fig. 28. The benefit gained in pursuing this
course is that it is heated for annealing under as
nearly as possible the same conditions, so far as shape
is concerned, as when heated for hardening; conse-
quently the tendency to change shape will be overcome
in the annealing.

Long pieces of steel that are to be hardened will
give much better results if roughed out — that is, all
scale and outside surface removed by planing or turn-
ing— then thoroughly annealed. Should the piece
spring when annealing do not straighten when cold, as
it is almost sure to spring when hardened. If it is not
sufficiently large to turn out without straightening, it
should be heated red-hot and straightened. The hard-
ener is blamed many times because a costly reamer or
broach or similar tool is crooked in hardening, when in
reality the blame rests with the man who turned or
planed it to size.

After it was annealed he tested it in the lathe, and
finding it running out somewhat he takes it to an iron
block or an anvil, and commences to hammer. He fin-
ally gets it fairly straight, and feels quite proud of his
job. He doesn't like to see a man machine a piece of
steel that is crooked even if it will finish out, when a
few strokes of a hammer will fix it all right.

He has, by means of hammering, set up a system
of internal strains much more serious than the ones
removed by the process of annealing. He commences
to machine the piece. Every time he goes below the
effects of a hammer mark, the particles of the piece of
steel **goes " or moves in some direction at this point,
and it is necessary to repeat the operation of hammer

79

Shifting the blame.

persuasion again, with the effect that by the time the
article is ready to harden, it is in no condition to be
hardened. It is either crooked in all directions, or it
is only waiting for the fire to relieve it and allow it to
go where it will. When the hardener gets through
with it, it looks like a cow's horn, and of course the
hardener is blamed.

If he happens to be a man without any machine
shop experience, or does not understand the nature and
peculiarities of steel, he does not know where to place
the blame, and perhaps it wouldn't do any good if he
did.

He, of course, isn't going to shoulder it, so the
fault is laid to the steel, and, in consequence, if the
trouble continues, another make of steel is bought be-
cause the man in charge does not know or cannot spend
time to locate the trouble. It cannot be the fault of
the man in the shop, they say ; it must be the steel ; or
they decide it must be the hardener, because some
other concern with whom they are acquainted use this
same steel and have no trouble, so the hardener has to
stand the blame.

A successful business man is quoted as saying:
**If I were to drive a mule team, I would study the
nature of mules." A man to be a successful hardener
must study the nature of steel. He must know what
steel is liable to do under certain conditions, and how
to avoid undesirable results. No matter whether it re-
lates to his department or some other department, he
should know that it is possible for the tool maker to
treat the steel in such a manner that results anything
but satisfactory must follow when it is hardened. He
should also imderstand that he may make the steel un-

80

The wrong way to anneal.

fit for use by overheating when annealing, or he may
not heat it uniformly throughout, and consequently
does not remove the tendency to spring from internal
strains. If a satisfactory steel is furnished, the hard-
ener should never blame the steel for bad results which
are caused by his ignorance or carelessness, because he
may be furnished with an undesirable steel next time.
And in time those over him in authority will tire of
complaints about a steel that another concern is satisfied
with.

A method of annealing steel which the writer has
seen practiced in some shops, but which should never
be used when annealing tool steel, is to pack the articles
in a box with cast iron dust or chips. Now this method
works nicely when annealing forgings or other pieces
of machinery steel which were hard and show glassy
spots and cannot be softened by the ordinary processes
of annealing. The cast iron seems to have an affinity
for the impurities liable to be present in the low grade
steels, and the result is very soft and easily worked
pieces. But if the method is applied to tool steel the
carbon is extracted to an extent which is highly injur-
ious to it. To be sure, tool steel can be annealed very
soft if packed as described, but the result is anything
but desirable.

The writer had charge at one time of a hardening
plant where, among other things, many hundred pairs
of bicycle cranks were hardened every week. A lot
of ten thousand crank forgings were received and
started through the regular routine necessary to get
them in a condition for hardening. When the first
batch reached the hardener it was found impossible to
harden them by ordinary processes. And, by the way,

8i

Results from wrong annealing.

samples had been forged and sent us ahead of the main
batch which had been tested and found all right. They
hardened and tempered in a satisfactory manner and
stood the required tests.

The first test was made by placing each end of the
crank on the two projections of an iron block, as shown
in Fig. 29, and struck in the center a blow with a
heavy hammer in the hands of an experienced inspec-
tor. They were then taken to a testing machine and
given a very severe test, which consisted in holding
the end which went on the axle in a fixed position.
Pressure was applied to the
other end until the crank
was bent a certain amount.
The pressure
was removed
and the crank
was supposed
to come back
straight, but
the cranks in
the large
batch would
not harden.

Investigation at the forge shop where we procured
them, showed that through some mistake the cranks,
after being forged, were packed in cast iron dust or
chips in the annealing pot. Orders had been given to
anneal some machine steel forgings in this manner and
to anneal the cranks in charcoal, but someone got the
orders mixed, and hence the trouble. The cranks were
made of 40-point carbon open hearth steel. We reme-
died the defect by packing them in iron boxes with

82

The Derry Collard Co.

Figure 29. Testing a bicycle crank.

"Expended bone" for annealing.

wood charcoal, and submitting them to heat in the
furnace for several hours after they were red-hot. In
this way we got them in condition to harden.

Another method which works nicely when applied
to annealing machinery steel, but which is entirely un-
fitted for tool steel, is to pack the pieces in annealing
boxes in expended bone — i. e., bone that has been
previously used in case hardening. As before stated,
machinery steel packed in this manner, and heated,
gives excellent results. It is also an excellent way of
annealing cast iron (by this is meant small castings, as
typewriter parts, etc. , which must be very soft in order
to machine nicely).

But tool steel should never be packed in any form
of bone, as bone contains phosphorus, and this is the
most injurious of any of the impurities which tool steel
contains. The steel maker uses every eJffort possible
to reduce the percentage of this impurity to the lowest
possible point, for while it is a hardening agent, its
presence makes tool steel brittle, so that it is folly to
pay a good price for steel on which the manufacturer
has spent much time and money to rid of undesirable
impurities and consequently must charge a high price
for, and then use some method whereby the steel is
charged with these very impurities.

In concluding, it may not be amiss to emphasize a
few facts that have already been mentioned. Do not
overheat steel when annealing or it will be perma-
nently injured. Do not subject it to heat for a longer
period of time after it becomes uniformly heated
throughout than is necessary to accomplish the desired
result. For while it is necessary to heat the steel when
annealing to as high a heat as will be needed in harden-

83

Uniform annealing heat necessary.

ing, and while the steel must be subjected for a period
of time to heat that insures its being of the same tem-
perature in the middle of the piece as it is at the sur-
face, yet we must be careful not to overdo it.

Steel kept at a red heat for a long period of time,
even if it is not overheated, will betray the fact when
the temper is drawn after hardening, if it does not at
any other time. A piece of steel which is kept hot for
too long a period when annealing, may apparently
harden all right, but when the temper is drawn the
hardness apparently runs out — i. e., when the piece is
heated to a straw color it may be filed very readily,
whereas a piece from the same bar not annealed, or
which was properly annealed and then hardened and
drawn to the same temper color, would show all right
— i. e., a file would just catch it.

Uniform temperature when heating for annealing
is as desirable as when heating for hardening. If a
large block is unevenly heated, its corners and edges
are hotter than the main part of the block. Violent
strains are set up at these points, so it will be readily
apparent that uniform heating during the various pro-
cesses is one of the secrets of successful hardening of
tool steel.

There are other methods of annealing steel,
methods whereby the surface does not become oxidized
by the process of heating, as when heating drill rods,
etc. , but as these methods are not likely to be used by
mechanics in every day shops, their consideration
would be entirely out of place at this time.

Lastly, remember that any process of annealing
that takes from the steel any of its hardening proper-
ties should never be used, no matter how soft it will

84

Baths for hardening.

make the steel. It is better to work a piece of steel
which is hard, than to unfit it for doing its maximum
amount of duty when finished ; but it is possible to an-
neal most steel so that it will be workable and yet
harden in a satisfactory manner ; in fact, in a much more
satisfactory manner than if not annealed.

When annealing high carbon steel, and it is desir-
able to retain the full amount of carbon in the steel, it
is advisable to pack in the annealing box with charred
leather, instead of wood charcoal.

When it is desirable to harden the surface of low
carbon steel harder than it would naturally be, it may
be machined nearly to size, packed in a box with charred
leather and run for a length of time sufficient to give
the desired results. After machining to shape, it may
be hardened in the ordinary manner.

Hardening Baths.

When steel is heated to the proper hardening heat
it is plunged into some cooling bath to harden. The
rapidity with which the heat is absorbed by the bath
determines the hardness of the steel. Knowing this,
it is possible by the use of baths of various kinds to
give steel the different degrees of hardness and tough-
ness. A bath that will absorb the heat contained in a
piece of steel the quickest, will make it the hardest,
everything else being equal. A bath of mercury will
cause a piece of steel plunged in it to be harder than if
it were plunged in any of the liquids commonly used

85

Brine in "saturated solution."

for this purpose, but as such a bath would be extremely-
expensive, it is but little used. Clear cold water is the
one more commonly used than any other, and for most
cutting and similar tools gives good satisfaction,
although many old hardeners claim better success with
water that has been boiled, or that has been used for
some time, provided it is not dirty or greasy.

A very excellent bath that is used very extensively
is made by dissolving all the salt possible in a tank of
water, or what is known as a ''saturated solution."
Salt water, or "brine," as it is commonly called, is
used in most shops on certain classes of work, and in
some shops it is used altogether where a bath of water
is desired.

Different kinds of oil are also used to accomplish
various results. When small or thin cutting tools re-
quiring a hard cutting edge are to be hardened, a bath
of raw linseed oil, or neat's foot oil, is used.

When toughness is the desired quality, as in harden-
ing a spring, a bath of tallow, sperm oil or lard oil is
used. But the nature of steel of different makes varies
so much that no one bath answers best for all purposes,
or for the same purpose, when applied to steels of dif-
ferent makes. Sometimes it becomes necessary to use
a bath containing two or three ingredients in order to
accomplish the desired result.

I have in mind a manufacturing concern who made
a great many heavy springs. Until they changed the
make of steel they had been using for years they had
excellent results from hardening in lard oil, but after
changing they could do nothing with this bath. After
considerable experimenting they were advised to use
the following mixture : Spermaceti oil 48 parts, neat's

?6

Bath for hardening and toughening.

foot oil 45 parts, rendered beef suet 4 parts, resin 3
parts. They had very good results with this bath until
a drummer came along with good cigars and a steel
two cents a pound cheaper, and then trouble was the
result.

By the way, I have visited and known of several
shops where a few good cigars or an occasional wine
supper, which some glib-tongued salesman was willing
to put up for the man who did the buying, caused more
trouble than a little in the hardening department. But
to return to the hardening of the springs. When the
new steel came, the springs would not harden sufficiently
in the mixture mentioned. They were finally advised
to try a bath of boiling water, and this worked very
nicely.

Very small cutting tools, as taps, reamers, counter-
bores, etc. , harden nicely in a bath made by dissolving
one pound of citric acid crystals in one gallon of water.
This proportion may be used in making a bath of any
size.

The following is recommended when it is desired
to have the tools hard and tough :

Salt Yt, teacupf ul.

Saltpetre ^ ounce.

Pulverized alum i teaspoonf ul.

Soft water i gallon.

The following bath gives excellent results, but care
must be exercised in its use, as it is deadly poison. To
six quarts of soft water put in one ounce of corrosive
sublimate and two handfuls of common table salt.
When dissolved it is ready for use.

Sulphuric acid is added to water in various pro-
portions, from one part acid to ten parts water, to

87

■Rotting" steel by add baths.

lllllllllill II

IL!|i!lll|i'!!!ll!ii:il

i!io)i]j{[[;i-i

TTmrrrTTTTTTTTT
i :i!|l| I

equal parts of acid and water. Some even use clear
acid, and although excellent results, so far as the
hardened surface is concerned, may be obtained by the
use of this acid, steel makers do not advocate its use,
claiming that the after-effects are injurious to the
steel, that is, it '•"rots'" the steel, and the writer's ex-
perience substantiates the claims of the steel makers.
I do not advocate the use of any of the acids which act
directly on steel, provided any other form of bath will
give satisfactory results.

There are many other compounds used with suc-
cess in various shops. Some of these will be mentioned

in connection with
hardening various
tools. As a rule,
tool steel that is fit
for use for cutting
tools will harden in a
satisfactory manner
in clear water. If the
outline is irregular or
it is desirable that
it should be extra
hard, a bath of brine
answers admirably.
Articles of an irregu-
lar shape made of
steel liable to crack
when hardened should be dipped in water or brine (that
is, warmed somewhat), the temperature of the bath de-
pending upon the liability of the piece to crack.

Tools, as milling cutters, made from high carbon
steel, are many times hardened to advantage in a bath

^/.W////////////M'/;7777Z^^.

The Detry CoUard Co,

Figure 30. Oil and water bath
for hardening.

Methods of cooling for hardening.

of water having one or two inches of oil on the surface,
as shown in Fig. 30. The article is brought to the
proper temperature in the fire and immersed in the
bath, passing it down through the oil into the water.
Enough oil adheres to the red hot steel, especially in
the corners of
the teeth or
projections, to
prevent the
water acting as
suddenly as it
otherwise
would, thus do-
ing away in a
great measure
with the ten-
dency to crack.
It is a good
plan when hard-
ening large
pieces of almost
any shape to
first dip in water

or brine and allow them to remain in this liquid until
the surface is hard, then remove and instantly plunge
into a tank of oil, allowing them to remain in the oil
until cold. This works especially well in the case of
such tools as milling machine cutters, punching press
dies, etc. , where it is not necessary that the hardened
surface be very deep.

The depth to which a piece is hardened depends
on the length of time it is left in the water. For this
purpose old hardeners allow the article to remain in the

89

Supply

Ov«cfloyy

Figure 3 1 . Hardening with jet
from bottom.

Various cooling methods.

water until it ceases to "sing." This is the peculiar
noise occasioned by putting a piece of red hot steel in
water. When the piece stops singing it is removed
from the water and plunged in oil and left until cold.

When pieces are to
be hardened, and it is
necessary to harden
the walls of a hole or
some depression, as
the face of an impres-
sion die, or forming
die, or any similar
piece, it is necessary if
good results are de-
sired, to have a bath
which has a stream or
jet coming up from the
bottom, as shown in
Fig. 31. If clear water

The Derrjs Collard CO.

Figure 32. Continuous brine bath.

is used in the bath, the inlet pipe may be connected
with some constant supply, but if brine or some solu-
tion is used, it becomes necessary to have a supply tank
having a pump as shown in Fig. 32. The contents of

90

Various cooling methods.

the bath are pumped into the supply tank and run

down the supply pipe as shown.

At times it is desirable to have a tank in which

there is no gush
or jet of fluid, but
where the con-
tents of the bath
are kept in mo-
tion in order to
force the steam
away from the
surface to be
hardened. There
are several ways
of accomplishing
this. Fig. 33
shows a bath hav-
ing a pipe com-
ing up from the

'}//////////////////y///?/////,

■mM^s^^^

The Derry CoUard, Co.

Figure 33. Bath with perforated
bottom plate.

bottom, the jet striking the plate which
spreads the fluid. It then comes to the sur-
face through the perforated plate shown.

Fig. 34 shows a bath in which the
contents are
kept in motion
by some me-
chanical means
contained in the
tank. Such a
bath may be
made by follow-
ing the sugges-
tions contained Figure 34. Bath with agitator.

9»

V<-f-^'^^^'';^c^^^fh^^^=i^i^^'-^i^^''i^,

Ml

About heating baths.

in the illustration. A tank of any convenient size
may be made having a partition as shown. The por-
tion of the tank marked a is intended to be used
for the immersion of the articles being hardened,
while b contains a pump, Archimedian screw or some
similar device for forcing the water into the side a.

If a pump is used, the water is forced through the
pipe shown. If an Archimedian screw is used, the parti-
tion shown should not extend way to the bottom, the
water being forced under it. In either case it returns
to h over the top of the partition c as shown, thus
insuring a rapid circulation of fluid. This form of bath
is especially to be desired where brine or some favorite
hardening solution is used. It is also possible to heat
the contents of the bath when it is considered advis-
able, as in the case where articles are to be hardened
that are liable to crack in contact with extremely cold
liquids. Much more uniform results may be obtained,
especially when small, thin pieces are hardened, if a
uniform temperature can be maintained in the bath.

In order to keep the contents of the bath at some-
where near a uniform temperature, a small coil of
steam pipe may be placed in the tank, and a ther-
mometer may be so placed as to readily show the con-
dition of the bath. While it may seem unnecessary to
be so particular about the temperature (and it is un-
necessary on most work, as an experienced hardener
can determine the temperature very closely by the
sense of feeling), yet there are jobs where it is essential
that a certain uniform temperature be maintained in
order to get uniform results. I do not mean by this
that it is practical to attempt to keep the temperature
within a few degrees of a given point, but it can be

9*

Figure 35. Die with hole.

Cooling dies with holes.

kept somewhere near in order to get the best results

possible.

Sometimes it is necessary to harden the walls of a

hole that does not go way through the piece, as a die

used for compression work or

some forms of dies for striking

up cylindrical pieces. Fig. 35

shows a sectional view of a die

having a hole part way through

it as described. Now, if a piece

of work of this description were

hardened in a bath where the

contents were not agitated, it

is doubtful if the walls of the hole would be hardened

in the least. The steam generated would blow the
liquid out of the hole, and none
could enter until the steel was cooled
to a point where it could not harden.
Better success would
follow if it were dipped
in a bath having a jet
of water coming up from
the bottom of the tank,
but in this case it would
be necessary to invert
the piece in order to get
the liquid to enter the
hole, and if it were

dipped in this position, it is probable that enough

steam would rise to keep the contents of the bath from

affecting the walls near the bottom.

Now, in order to get satisfactory results when

hardening work of this character, it will be found best

Figure 36. Method of cooling
holes in dies.

93

Cooling a shank mill.

to have a bath so constructed that the liquid can run
into the hole by means of a faucet or pipe, as shown in

Fig. 36. If the hole is deep and

there is danger of the steam pre-
venting the liquid effectually work-
ing at the bottom, a pipe may be run
nearly to the bottom, as shown in the
sectional view of Fig. 37. The pipe
must not be as large as the hole, or
the results will not be satisfactory.

Figure 37. Cooling a deep
hole in a die.

Sometimes it is necessary to
harden several pieces of a kind
whose outline betokens trouble
if dipped in a cold bath, and
yet it seems necessary to use a
cold bath in order to get the
desired result. Take, for in-
stance, a shank mill of the
shape shown in Fig. 38. If this
mill is heated to the proper degree of heat and plunged
in a dish containing just enough water or other liquid
to harden the teeth before the water gets hot, the teeth

Tlw Derry Collurd Co,

Figure 38. Cooling a
shank mill.

94

About using dirty water.

will harden in a satisfactory manner, and the water will
heat so as to do away with any danger of cracking the
cutter from internal strains. The size of the dish will
determine the depth of the hardening. When one
piece is hardened the dish may be emptied and filled
with cold water for the next.

The writer has seen this scheme used with excel-
lent results, not only on milling cutters, but on
broaches, small dies, etc., that showed a tendency to
crack when dipped in a large bath of cold fluid. Of
course, it should be borne in mind that the dish
selected for the bath must be large enough to hold a
sufficient amount of liquid to harden the piece the
necessary amount before it becomes too hot, but it is
also essential that it should not be so large that the
contents Vs^ill not heat, because then there is no differ-
ence in its action from that of a large bath.

Generally speaking, however, it is advisable to use
a large bath, having the contents at a temperature of
about 60 degrees Fahr., as then the process of con-
traction, which takes place when the piece is cooling,
is uniform.

Delicate articles, however, require a bath having
the contents heated somewhat above the temperature
mentioned, the temperature depending on the character
of the article and the nature of the steel.

It should be borne in mind that a tank or dish of
dirty water makes a very undesirable bath; neither
should one be used having dirt in the bottom, because
as the contents are agitated, the dirt rises, preventing
the liquid acting in a satisfactory manner.

n

Baths for Hardening.

The Lead Bath.

When comparatively small pieces of work are to
be hardened in large quantities, as, for instance, the
various small parts of bicycles, sewing machines and
guns, red-hot lead furnishes an excellent means of
uniformly heating in a very economical manner. It
is a speedy, and at the same time a very reliable
means to use, as the heat can be maintained so uni-
formly, it can be applied safely. By using a proper
amount of precaution, there is no danger of burning
the outside of the article before the center is heated.
Large and small parts are heated alike, and quite a
number of pieces can be heated at the same time, thus
making it a cheap, rapid, yet reliable way of heating.
It is necessary to have a uniform heat under and
around the crucible that can be maintained for quite a
length of time.

A furnace burning illuminating gas as fuel, gives
the most satisfactory results, although excellent results
may be obtained by the use of a furnace burning gaso-
line or crude oil. If it is not found possible to obtain
any of these, good results can be obtained by the use
of one burning charcoal, hard coal, or coke; but in
order to obtain uniform results, a great deal of atten-
tion must be paid to the fire.

If but a few pieces are to be hardened at a time,

96

About lead and crucibles.

and it is not considered advisable to purchase or make
a furnace especially adapted to this kind of work, a
crucible may be placed in a fire on an ordinary black-
smith's forge. Build up around it with bricks, placed
far enough away from the crucible to have a fire all
around it, and fill this space with charcoal. It will be
found necessary to raise the crucible occasionally and
poke coals under it.

The most satisfactory crucible is one made of
graphite, especially for this purpose. A cast iron one
is sometimes used, but as a rule is not as satisfactory
and is more costly, as it burns out very quickly.

The graphite crucible should be annealed before
using, as this toughens it, reduces the liability of
cracking and makes it longer lived. In order to anneal
the black lead crucible, place it in any oven or furnace
where a uniform heat can be obtained, heat it to a red,
take it out and place it where it can cool off slowly
without any drafts of air striking it.

It is very essential that the proper quality of lead
is used. Red-hot steel is very susceptible to the action
of certain impurities. Many brands of lead contain
sulphur in such quantities that it is very injurious to
the steel. Nothing but chemically pure leads should
be used. It is the custom in some shops to use lead of
any kind, and when unsatisfactory results are obtained,
the method, instead of the material, is condemned, be-
cause the operator does not understand the cause of
the trouble.

If the lead contains sulphur, even in small quanti-
ties, it will ruin the steel. The article will have a
honeycomb appearance, and portions of the outside
stock will be eaten away. When using lead that is

97

Mixture for hardening small tools.

chemically pure, this difficulty will not be encountered.
Many hardeners are averse to the use of the lead
bath in hardening on account of the tendency of the
lead to stick to the work. To prevent this trouble,
different compounds are used.

The writer has had excellent results with a solu-
tion of cyanide of potash in water. Dissolve one
pound of powdered cyanide and one gallon of boiling
water. Let it cool before using. If this should not
prove to prevent the lead sticking, put in a larger
portion of cyanide. Some use a strong solution of salt
and water. Dip the articles in the solution; place
them where they can dry, preferably in a hot place
where they will dry more rapidly. It is not safe to
put them in the lead when damp, as any moisture
would cause the lead to fly.

The writer has used the following mixtures with
very gratifying results when hardening such work as
small milling cutters, taps, reamers, broaches, cherries,
rotary files and similar tools having fine teeth likely to
hold the lead. This formula is taken from the report
of the Chief of Ordinance of the War Department, and
is used in the U. S. Government shops when harden-
ing files. The following is a copy of the report:
* 'Before hardening, the files are treated with a mixture
of salt and carbonaceous material to protect the teeth
from decarbonization and oxidation. The kinds and
proportions of the ingredients are exhibited in the fol-
lowing table :

Pulverized charred leather i ft).

Fine family flour 1% ft)S.

Fine table salt 2 ibs.

The charcoal made from the charred leather should

98

The hardening of files.

be titurated until fine enough to pass through a No. 45
sieve. The three ingredients are thoroughly mixed and
incorporated while in a dry state, and the water is then
added slowly to prevent lumps, until the paste formed
has the consistency of ordinary varnish. When ready,
the paste is applied to the file with a brush, care being
taken to have the teeth well filled with the mixture.
The surplus paste is then taken off the file by the
brush, and the file is pl&ced on end before a slow fire
to dry. If dried too quickly the paste will crack or
blister. If not dry enough, the remaining moisture
will be transformed into steam when dipped into the
hot lead bath, and cause an ebullition or sputtering of
the lead, throwing out minute globules of the latter,
which may endanger the eyes of the operator. The
fusing of the paste upon the surface of the file, indi-
cates the proper heat at which the file should be
hardened."

File makers have methods of hardening files that
differ very materially from the above process, but it
has proved particularly valuable when applied to the
tools mentioned. Small articles, if of an even size or
thickness throughout, may be put into the lead when
they are cold and left until red-hot, although they
should be turned over occasionally. But pieces, such
as shank mills and similar articles of irregular contour,
having large and small parts in connection with each
other, should be heated nearly to a red before putting
into the lead, as the sudden expansion of the large
thin parts would tear them from the more solid por-
tions that could not heat and expand so quickly.

The purpose of putting such pieces into the lead is
for the uniform heat that can be finally obtained on the

99

Reasons for heating in lead.

unequal sizes and thicknesses, making them much less
liable to crack when dipped in the bath. If an irregu-
lar shaped piece were plunged suddenly into the red-
hot lead, and thereby cracked, it probably would not be
noticed until it was hardened, and the natural inference
would be that it had cracked in the cooling bath ; but a
careful examination of the fracture would show the
walls to be black, proving it to have been subject to
heat after it was cracked. If it were sound until dipped
in the bath, the walls w^ould have a brighter appear-
ance, although it might be somewhat stained by the
contents of the bath, yet they would not be black.

The following question may suggest itself. If the
piece of work is to be partly heated in another fire, why
not heat to the hardening heat? The reason for this is,
that a much more uniform heat can be obtained in the
lead crucible than in an ordinary open fire. When it is
necessary to harden a portion of the piece, leaving the
balance soft, it need only be dipped in the lead the re-
quired distance, moving it up and down to prevent a
fire-crack. It is likely to crack at the point where the
heat leaves off, just as a piece of red-hot steel will
crack if dipped into water in such a way that some of
the red is out of the bath and the piece held in that
position. It then cracks at the point where the con-
traction ceases, while in the first case it cracks where
the expansion ceases.

If impossible to do the first heating in an open fire,
or if it is considered advisable to heat it in red-hot lead
altogether, the piece may be immersed in the lead, left
there for a moment and withdrawn. It may then be
immersed again, leaving a little longer than the first
time and withdraw it again, repeating the operation

100

How to handle lead for heating.

until the steel is heated to a point where the intense
heat will not cause it to crack from the sudden change
of temperature.

To prevent dross from forming on the lead, keep
the surface covered with broken charcoal. This not
only has a tendency to prevent dross forming, but the
charcoal, catching fire and burning, keeps the surface

v *

Figure 39. Mould for casting lead.

of the lead at a more uniform heat, than if not used.
But despite all these precautions, more or less dross
will form in the surface of the lead. This should be
skimmed off occasionally, in order that it may not stick
to the work.

When no longer using the crucible, the lead should
be emptied out, as if left in the crucible until it cools
and solidifies, the crucible will probably crack when the
lead is heated again. It may be removed by means of
a ladle and emptied into small moulds. When the cru-

Caution about too hot lead.

cible is nearly empty, it may be lifted from the fire and
the balance of the lead poured out. As it is necessary
to put the lead into the crucible in small pieces, it is
best to use a mold of the form shown in Fig. 39, as this
makes a very convenient size to put into the crucible
again. To get good results when hardening, the lead
should be stirred up from the bottom occasionally in
order to equalize the heat, as it will be hotter at the
bottom than it will be toward the top.

When heating pieces with fine projections or teeth,
it is well to use a stiff bristle brush to remove any lead
that may stick in the bottom between such projections.
This should be done before dipping into the bath, to
prevent soft spots. Steel will not harden where lead
adheres to it, as the liquid in the bath cannot then
come in contact with the steel.

There is no one method of heating steel which is
so generally used that is a source of more annoyance
than the one under consideration, because attention is
not paid to a few simple points. But if a chemically
pure lead is used in the crucible, the contents of the
crucible is stirred occasionally, and as low a heat as
possible is maintained, excellent results will follow.

A serious mistake, which is made many times, is
to heat the lead too hot, leaving the piece of work in
just long enough to bring the surface to the desired
heat, then removing and quenching. The objection to
this method is, the heat is not uniform throughout the
piece, consequently poor results follow. If the article
is left in the lead long enough to become uniformly
heated throughout, it will become too hot. If the lead
becomes too hot, it is best to plunge a large piece of
iron or scrap steel into it, allowing it to absorb the

Cyanide solution before heating.

extra heat, thus reducing it to the proper temperature.
It is then safe to go ahead with the heating, and not
until then. Do not neglect this precaution.

It will readily be seen that the lead should be of

about the same temperature as the steel should be

heated, and the articles left in it

long enough to become uniformly

heated throughout.

The hardener should
bear in mind that the
amount of heat given
steel affects the struc-
ture rather than the
method of applying the
heat. In order to use
this method to advan-
tage when hardening
large quantities of small
articles, quite
a number of
pieces may be
heated at a
time in the
lead. This
may readily
be accom-
plished by

Fisurc 40. Dr/ins steel before heating. dipping a

number of pieces in the cyanide solution, laying them
on the top of the furnace as shown in Fig. 40. When
these are thoroughly dried, place them in the lead, dip
another batch in the solution, and lay on the furnace
as described. By this time the pieces in the lead will

103

How to handle work in lead furnace.

be hot enough to dip in the bath. As one is taken from
the lead, another may be taken from the top of the
furnace and put in its place, another should be dipped
in the solution and placed on the furnace. In this
way a rotation may be kept up, which insures the
maximum amount of work in a given time.

Before taking a piece of work from the lead, it
should be plunged below the surface and held there
long enough to equalize the heat. Articles being
heated in lead should be turned over occasionally, in
order that they may heat uniformly. If long articles
are to be heated by this means, it is necessary to stir
the lead from the bottom frequently, or the piece will
be the hottest at the end nearest the bottom of the
crucible.

When heating certain tools, as long reamers,
broaches, etc., it is sometimes advisable to place a
piece of cyanide of potassium on the surface of the
lead. It will fuse and remain for some time in a body
around the steel. The tool may be raised and lowered
in the lead through this melted cyanide occasionally,
and especially just before quenching in the bath.

If the article is dipped in a bath of water, heated
as hot as it is possible to hold the hand in, the teeth
will be found very hard and the tendency to spring or
crack will be reduced very materially. If it is desirable
to have the tool extremely strong, that is, able to stand
strains, as would be the case if a broach used for draw-
broaching were being hardened, the tool could be
heated as described and quenched in a bath of raw
linseed oil, or into a bath of sperm oil and tallow, to
which is added a small quantity of resin. The amount
of resin added should be very small, as it has a ten-

104

Cyanide of potassium bath.

dency to crystallize the steel if too great a proportion
is used. Generally speaking, one part resin to loo
parts of oil, or oil and tallow, will be sufficient, and
generally it will not be found necessary to use it, if
tallow is added to the oil.

Although red-hot lead furnishes an excellent means
of heating small articles, and a very satisfactory method
of heating certain kinds of tools, yet for most cutting tools,
the writer has found cyanide of potassium, melted and
heated red-hot in a crucible, or a mixture of salt and
cyanide of potassium, to give more satisfactory results.

Cyanide of Potassium Bath.

Cyanide of potassium, if placed in a cast iron cruci-
ble and heated red-hot, furnishes a method of heating
steel that gives very excellent results in many shops.
This method is employed very extensively in heat-
ing articles whose
shape betokens soft
spots when hard-
ened by the ordinary
methods. It is also
used in hardening
dies for transferring
impressions onto
plates used in print-
ing bank notes and
similar work.

The articles heat-

Figurc 41. Method of suspending work in
cyanide of potassium.

ed by this method are not subject to oxidation from
the action of the air on the surface. The cyanide does
not have a tendency to stick to the work, and the action

[05

The action of cyanide.

of the cyanide tends to increase the surface hardness,
thereby making the tools more durable than when
hardened by ordinary methods.
Many dies with finely engraved
working surfaces are heated by
this method and
the best of re-
sults obtained.
In order to get
satisfactory re-
sults, it is neces-
sary to use chem-
ically pure cya-
nide of potas-
sium.

It is different
from red-hot
lead in that iron
will not float on
its surface, but
sinks to the bot-
tom, conse-
quently it is
necessary to
suspend the
pieces being
heated with
wires which
pass over the
edge of the cru-
cible in the form
of a hook, as
showninFig. 41.

Figure 42. Cyanide hardening furnace,
also shown in Figure 1 8.

106

About attention to heat.

As cyanide of potassium is a violent poison, the
greatest care should be exercised wlien using it. The
fumes of this chemical are very injurious to the work-
man, consequently a furnace should be used having
some means of conveying the fumes into a chimney or
ventilating shaft.

A furnace may be procured of the pattern shown
in Fig. 42, using illuminating gas as fuel. A is the
pipe furnishing fuel to the burners, B the crucible, C
the hood, D the door, E the pipe which conducts the
products of combustion to the pipe F, the pipe which
conveys the fumes and products of combustion into
the chimney. The lighting holes are stopped by the
fire clay plugs G G.

If it is considered advisable to make a furnace
burning hard coal or coke, the same design may be
used as illustrated in Fig. 19. For a lead hardening
furnace, a hood must be added to prevent the poison-
ous vapors getting into the room. This hood must be
connected with the chimney.

The operator must bear in mind that in order to
get satisfactory results, attention must be paid to the
amount of heat given the piece of steel, as previously
explained. The strength of the hardened piece depends
in a greater measure than mechanics generally realize,
on the amount of heat given when hardening. In
order to get the best results possible, it is necessary to
have the steel at the refining heat.

It is easy to be deceived when heating by the
method under consideration, as the effect of the cyanide
is to cause the surface of steel to harden at a tempera-
ture lower than the ^ refining heat. Consequently the
portion beneath the surface may not be hardened at all

107

How to obtain colors.

when the surface shows hard, if tested with a file. It
matters not by what method steel is heated for harden-
ing, there is a temperature at which it should be
quenched. If not heated to that temperature, it is not
as hard as it should be to accomplish the maximum
amount of work possible. If heated to a higher tem-
perature, the pores are opened, the steel made brittle
and it is unfitted to do the amount of work it should.

Not only is this method valuable because it fur-
nishes a means of heating steel uniformly without
danger of its sur-
face becoming
oxidized, but if
certain points are
observed, the
most beautiful
colors imagin-
able may be ob-
tained. It is nec-
essary, in order
to procure nice
colors on the

hardened product, that it be nicely polished, and free
from dirt and grease. While grease will bum when
subjected to a red heat, yet it leaves a stain on
the work.

When colors are wanted, articles made of tool steel
may be suspended in the molten cyanide by means of
wire hooks, which pass over the edge of crucible, as
shown in Fig. 43. When the article becomes heated
to a uniform heat, it may be removed and plunged in a
tank of water, working it around well until cold, when
it may be removed and dried. If it is desirable to draw

108

Tlie Derry CoUard Co.

Figure 43. Heating in cyanide for colors.

Hardening gun frames in colors.

tlie temper and yet retain the colors, it may be done
by heating in a kettle of oil, guaging the heat by a
thermometer. The work must be left in the oil, away
from the action of the air, until it is cooled below the
point where temper colors are visible.

This method of hardening is used very extensively

in gun shops to
harden gun
frames, and at
the same time
procure the beau-
tiful colors often
seen on them. It
works equally
well on machin-
ery steel or mal-
1 cable iron. It
is accomplished
by attaching a
piece of wire bent
in the shape of
a hook to the
frame, the other
end of the hook
hangs over the
upper edge of the
crucible. It is
necessary to have
the article entire-

Mm

The Derry Collard Co.

Figure 44. Method for obtaining vine
effect on tempered work.

ly under the surface of the cyanide. When it is
heated for a sufficient length of time, which must be
determined by experiment, it may be removed and
plunged in a tank of water. In order to produce the

109

Hardening malleable iron.

beautiful vine-like effect often noticed, the inlet pipe
may be situated about two feet above the tank, as
shown in Fig. 44. The end of the pipe may be made
to spray the water. The articles when taken from
the cyanide crucible should be passed through the
spray into the bath. Wherever the fine spray strikes,
it produces the vine-like effect mentioned. The colors
may be guaged by the heat given the contents of the
crucible, also by the temperature of the bath.

After using, a hook must be thoroughly dried be-
fore putting in the molten cyanide, as the presence of
moisture, even in the most minute quantities, will cause
the cyanide to fly. If it strikes the flesh, it produces a
bum, which, on account of the poisonous nature of the
chemical, is liable to be very sore, but by avoiding the
presence of any form of moisture, this need not occur.

Articles made of malleable iron, as cutters for
paper, and wood, may be hardened by heating in this
manner. If only a few pieces are to be hardened, the
cyanide may be heated in an iron dish of suitable size,
the articles suspended in the dish until heated suffi-
ciently, when they may be quenched in a bath of cold
water, or warm water, according to the nature of the
work to be done. Should this prove to make them
too hard, a bath of tallow or oil may be used.

Articles made of machinery steel may be heated in
the cyanide crucible for hardening, the amount of
hardness and depth which it penetrates depending on
the amount of heat given and the length of time the
article is left in the cyanide.

If the articles are of a size that warrants it, they
may be suspended in the cyanide by means of wires,
as previously explained. If they are small and there

no

To harden throughout.

are many of them, they may be placed in baskets made
of wire cloth and suspended in the molten mass.
These baskets should not, however, be made of gal-
vanized wire, or have any solder used in their con-
struction, or the articles will be coated with lead.
Care must be exercised when placing- the articles in the
basket, not to put in too many, especially if the basket
is to be dipped into the hardening bath, as the pieces
would touch each other when in the water ; consequently
they would not be hard at these points.

When it is desired to make articles other than cut-
ting tools, and harden them throughout, it may be
done by procuring a low grade steel, sufficiently high
in carbon to produce the desired result. The steel
may be either Bessemer or open hearth. If hearth
steel, the temper must be suited to the particular pur-
pose it is to be used for. When the article is ready for
hardening, it may be suspended in the molten cyanide ;
when it has heated for a sufficient length of time, it is
removed and plunged in the bath. If hardness is the
only quality desired, use a bath of water. If a hard
surface is desired, and a very tough, strong interior,
use a bath of oil and tallow.

Malleable iron may be hardened by heating in
cyanide of potassium, as is the case with machinery
steel, the depth of hardening depending on the length
of time it was left in the cyanide. If colors are desired,
the surfaces must be polished, and a bath of clean
water used. If a strong, tough effect is desired,
quench in oil.

It is sometimes desirable to color a piece of work
in imitation of case hardening, yet leaving the article
soft. If the piece is made of machinery steel of low

Uniform heat necessary to hardening.

carbon, or of malleable iron, this is accomplished by
using a cyanide made especially for the purpose. This
is known as ** 50 per cent, fused cyanide of potassium."

Hardening Steel.

CO

Having considered the nature of steel, methods of
heating for different purposes, and the means of cooling
by the various baths, we will proceed to the considera-
tion of hardening articles of various types. As it would
be impossible to consider all the articles that require
hardening in the various shops throughout the country,
such examples have been selected as are representative
of the articles that are commonly hardened.

Uniform heats are the secret of success when hard-
ening steel. A greater part of the trouble experienced
by men not skillful in this branch of the business arises
from this fact not being observed. The writer cannot
resist the desire to caution the reader against trouble
arising from this cause, and hopes he will be pardoned
if he apparently repeats this warning oftener than may
seem necessary.

When hardening steel, avoid too rapid cooling of
the surface, as it is then rigid and inflexible, while the
inside of the piece is still undergoing the change in
structure incident to hardening. As a consequence, if
the outer surface is hard and inflexible, and the internal
portion is undergoing changes in size and structure, the
outer surface will crack from the enormous strain
brought to bear on it. It is advisable when hardening

How to heat to avoid strains.

small articles to heat the contents of the bath somewhat,
to avoid the sudden cooling mentioned.

As stated, when the surface becomes hard before
the center has ceased changing its size and structure,
there is a tendency to crack the surface from the in-
ternal strains.

To overcome this tendency, the piece should be
heated to a degree that allows the surface to yield some-
what and conform to the strains in the piece. The
amount of heat necessary to produce this result has
been ascertained
to be at the tem-
perature of boil-
ing water (212 de-
grees). An ex-
perienced hard-
ener can deter,
mine the necessary
amount of heat
very nicely by the
sense of feeling,
heat the steel until,
when touched with
the moistened
finger, the peculiar
snapping sound is
heard. This is the
same as the house-

r

Perforated Catch Pan

Y<'^<'<'^<'<'<'<'^<'i^///////<'^<'?<'///^?<'<'<'<'<'<'<'?<'i'/<^

i

=3^

The Derry Collard Co.

Figure 45. Bath for hardening in hot water.

wife tells when her irons have reached the proper
temperature for ironing linen.

When pieces are hardened in large quantities, it
becomes very costly practice reheating each piece over
the fire, guaging the heat by the sense of feeling. A

13

Cold baths not usually advisable.

good plan in such cases is to have a tank of the descrip-
tion shown in Fig. 24. A steam pipe is connected with
the tank, as by this means it is possible to heat the
water to any desired degree to the boiling point. A
perforated pan is provided to catch the work as it is
dropped into the tank. Occasionally the pan may be
removed from the tank by means of the wires shown,
the pieces emptied out and the pan returned.

As the pieces are removed from the hardening bath,
they may be dropped into this tank, and the tendency
to crack overcome. For certain articles the brittleness
is reduced sufficiently, making it unnecessary to draw
the temper any more.

The use of extremely cold baths is not as a rule
advisable. Results fully as satisfactory so far as the
hardened surface is concerned, are obtained if th-e bath
is warmed somewhat, and the danger of cracking is
greatly reduced.

It is claimed that when articles made of steel and
heated red-hot are plunged in a cooling bath, the out-
side surface becoming chilled and consequently con-
tracted, causes by this process of contraction an
immense pressure on the internal portion of the steel
which is red-hot ; this pressure has the effect of raising
the temperature of the interior of the steel still higher,
with the result that it expands still more. This extra
expansion is, of course, communicated to the hardened
(and consequently unyielding) surface, and this being
unable to stand the immense strain, either cracks or
bursts.

If the contents of the bath are heated to some
extent, the surface is not chilled below a temperature
that allows it to yield somewhat, allowing it to con-

114

How to straighten hardened work.

form in a measure to the internal pressure, which is
relieved as that portion cools and contracts.

The pliability of steel when warmed is illustrated
in the case of such tools as taps, reamers, or drills,
which become crooked when hardening. In order to
straighten, it is necessary to apply a certain amount
of heat. Place the tool between the centers of a
lathe, with the convex side toward the operator, a
piece of stock
is then put in
the tool post
of the lathe,
having one
end against
the bowed
side, as shown

Figure 46.
Method of straight-
ening work bent
in hardening.

Fig. 46.
The article is now heated
until oil placed on the sur-
face commences to smoke;
pressure is applied by means

of the cross feed screw and until the article is slightly
bowing in the opposite direction.

The piece should now be suddenly cooled while in
this position. If it is not straight, the process should
be repeated. Now, it is safe to spring the steel when
warm, but when it is cooled, even after heating, as de-
scribed, it will break if any great amount of pressure
is applied. Should it spring somewhat when cold, it
will return to its original shape when the pressure is
removed, thus proving that hardened steel, when
heated to a certain degree, is somewhat pliable. It is
for this reason the surface of a hardened piece is
reheated to ** remove strains," as it is familiary termed,

"5

Drawing the temper.

or it is made pliable by heat, and in this condition con-
forms to the immense strain incident to hardening.

In the case of the article heated and straightened
by pressure, it is necessary to cool the piece uniformly.
Should one side be cooled and the opposite side left
hot, the piece would probably crack from the unequal
contraction. By carefully following this plan it will be
possible to save many tools that would otherwise have
to be thrown away — or which, if used, would not be
satisfactory.

Drawing the Temper
after Hardening.

CO

When a piece of steel is hardened it becomes brit-
tle. When the design of the piece is such that the
working surface has sufficient backing, it is safe and
advisable to keep the article as hard as when it comes
from the bath. But in the case of tools having slender
cutting edges, as taps, screw threading dies and mill-
ing machine cutters of the ordinary styles, it becomes
necessary to reduce the amount of brittleness in order
that it may stand up when in use. This is done by re-
heating the piece somewhat.

The process of reheating also has the effect of soft-
ening the steel to a considerable degree. It is not gen-
erally desirable to soften it, but it is necessary to do so in

ii6

The amount of heat necessary to temper.

order to reduce the brittleness. This reheating is gener-
ally termed "drawing the temper." Unfortunately,
the word temper is understood as having more than one
meaning, and as a consequence people are sometimes
puzzled to know exactly what one means when the term
is used. By some it is understood as the double pro-
cess of hardening and drawing the temper. To others
it simply conveys the idea of drawing the temper of a
hardened piece, and will be so used by the writer in
connection with treating steel by heat, although the
steel maker's definition of the word temper will be used
occasionally to designate the percentage of carbon the
steel contains.

When steel is heated, the amount of heat it absorbs
may be determined by the surface colors, provided it
has been brightened previous to heating. It is custom-
ary after hardening to brighten the surface with a stick
whose surface has been coated with glue arid then cov-
ered with emery, or a piece of emery cloth may be
attached to a stick or held on a file. After brightening,
the piece may be subjected to heat. As the steel be-
comes heated various colors will appear on the bright-
ened surfaces. The first color visible is a faint straw
color, then straw color, light brown, darker brown,
brown with purple, light blue, darker blue. If heated
to a black, the hardness is reduced to a point that
makes the steel practically soft.

The amount of heat necessary to give steel in
tempering, depends on the make of the steel, how hot
it was heated when hardening, and for what purpose it
is to be used. The method ordinarily practiced has
been briefly described above.

When work is done in large quantities, the temper
117

Methods of drawing temper.

is sometimes drawn by placing the articles in a pan
having a long handle, as shown in Fig. 47. A quantity
of clean sand is put in and the pan held over a fire,
moving it back and forth, thus keeping the sand and
work in motion. The surface colors can be closely
watched and excellent results obtained. If there are
any sharp edges or cutting teeth that will be harmed
by striking against the other pieces, it is not advisable
to use this method unless extreme care is exercised,
but a pan of sand may be placed over the fire and a
few pieces of work, having edges as described, placed
in it and kept in motion by a stick, being careful not
to hit them together.

An excellent furnace, which is illustrated in Fig.

The Derry CoUard Co.

Figure 47. Pan for drawing temper.

48, can be procured, which gives very satisfactory
results. The pieces to be tempered are placed in the
pans, D D, which rotate at the speed of two or three
revolutions per minute, the pans being hung loosely
from rods connected with spokes around the driving
block in the center, which receives motion from the
worm and gear, A B, connected with power. The
door, C, is closed and the furnace is charged with
work, and may be opened for observation. When
opened, the door forms a shelf or rest for the pans.

Xlg

Revolving furnace for tempering.

The thermometer indicates a degree of temper some-
what different from the actual heat in the furnace, but
if the temperature indi-
cated is observed when
the desired temper is ob-
tained, the operation may
be repeated
with satisfac-
tory results.

This furnace
is designed for
tempering small
articles, but the
writer has used
it with excel-
lent results on
punches used
for punching
rectangular
holes 2 inches
by ^ inch, the
shanks being
i^ inches in
diameter and 5
inches long.
The action of
the furnace de-
pends on the

heated air, with Figure 48. Revolving furnace for

temperature so tempering small pieces.

regulated that articles of irregular shape can be exposed
to it long enough to impart the proper temper to the
heavier parts without drawing the temper too low on

119

Tempering lathe tools.

the lighter parts of the same piece. By means fur-
nished of regulating the heat generated, the injection
of the heat evenly throughout the furnace is easily
secured, and the overheating of any part of the piece
prevented.

A common method when drawing the temper of
articles which are of a uniform thickness, is to heat a
flat piece of iron to a red heat, lay the pieces on this,
moving them around and turning
them over occasionally to insure
uniform heating. When the desired
temper color shows, the piece is
immediately immersed in oil to
prevent its softening more
than is desired.
This method is
open to objec-
tions when arti-
cles having
heavy and light
portions, which
must be heated
alike, are to be
tempered, be-
cause the lighter
parts, heating
more quickly than the heavy ones, will become too soft
before the heavier portions reach the desired temper.

When tools having heavy parts adjoining the cut-
ting portion are to be hardened, and it is not necessary
to harden the heavy parts, as a diamond point lathe
tool or similar article, it is the general practice to heat
the tool for a distance on the shank — say as far back as

Figure 49.

The Derry CoUard Co.

Hardening a diamond pointed
lathe tool.

Tempering in oil.

the dotted line in Fig. 49 — to a red heat. Plunge the
cutting blade into the bath, being careful not to dip the
portion marked a into the bath. Work up and down to
prevent a water line, and move around to avoid steam.
When the cutting part is sufficiently hardened, remove
from the bath, and allow the heat from
the heavy portion to run into the
hardened part until the desired color
shows, when it may be quenched to
prevent its running any lower.

When work is tem-
pered in large batches,
a very satisfactory
method consists in put-
ting the articles in oil
and heating to a proper
degree, gauging the
heat by means of a
thermometer.

A very satisfactory
tempering furnace is
shown in Fig. 50. Illu-
minating gas is used as
fuel. The burning gas
circulates around the
kettle holding the oil,
thus heating it very

Figure 50. Oil tempering furnace.

uniformly. The work is held in a perforated pail or
basket, somewhat smaller than the inside of the kettle.
The degree of heat to which the oil is brought is
shown by the thermometer.

If not situated so that a furnace of this kind is
accessible, a kettle may be placed on a fire in a black-

121

Oil tempering in a kettle.

smith's forge and built up around with bricks, leaving
a space up around the kettle for coals. Now fill the
space with charcoal. As this catches fire, it heats the
oil in the kettle. The articles to be tempered may be
placed in the perforated sheet iron pail, at least two
inches smaller than the inside of the kettle. The pail
should have a flange at the bottom, as shown in Fig.

o o o o o o
o o o o o o o
o o c o o o o
ooooooooj
oooooooo
oooooooci

lOOOOOOOC

to o o o o o o o Oi

Perforated Pail

Figure 51. Oil tempering In a kettle.

51, or it should be blocked up i^ inches or 2 inches
from the bottom of the kettle, to allow the oil to cir-
culate freely beneath it.

If the pail were to rest directly on the bottom, the
pieces of work at the bottom of the pail would soften
too much from coming in contact with the kettle,
which is acted on by the direct heat of the fire. The
thermometer should be placed between the pail and the

Temperature of temper colors.

kettle, as shown. It is advisable to stir the oil in the
kettle occasionally, in order to equalize the heat.
When the thermometer shows the desired degree of
heat, the pail containing the work may be removed,
set to one side, where no current of air can strike it,
and allowed to cool off.

When pieces of hardened steel are placed in a
kettle of oil and heated, the temper colors do not show,
so it becomes necessary to gauge the heat by a thermo-
meter. The temper colors are significant of a certain
amount of heat which the steel has absorbed.

Faint straw color 430 degrees Fahr.

Straw color 460 " "

Light brown. 490

Darker brown 500

Brown with purple spots. .510

Light purple 530

Dark purple 550

Light blue 570

Darker blue 600

Blue, tinged with green ... 630

((

Knowing the proper degree of heat to which a
piece of steel should be subjected, it becomes possible
to draw the temper on any number of pieces exactly
alike, and much more uniformly than though they were
gauged by color. As stated, 430 degrees of heat repre-
sents a faint straw color, while 460 degrees a full straw,
a difference of only 30 degrees, yet when tested with a
file by one accustomed to this work, there is a vast
difference in the hardness of the two. While the differ-
ence in the two colors is slight, yet difference in the
ability of the tv/o pieces to resist wear in the case of

123

The necessity for proper temperatures.

cutting tools is quite noticeable. The average man
does not detect a difference of lo degrees by observing
colors, consequently he is liable to have a product vary-
ing in efficiency if he attempts to draw the temper by
observing the color. But if he gauges the temper by a
thermometer he can get his product within a limit of i
degree or 2 degrees every day, and at a much less cost
than if he were to draw to the color, provided the work
is done in large quantities.

At times a tool as it comes from the bath is too
brittle to stand up well, yet when the temper is drawn
to the first color discernible, /. e. , a light straw — it is
too soft to do its maximum amount of work. Now, in
a case of this kind the temper may be drawn to 200 to
250 degrees, or any temperature that proves exactly
right.

The writer has in mind tools which, if left dead
hard, would crumble away on certain projections when
used; but if they were heated to the faintest straw
color, would not do the amount of work required of
them. But if they were taken from the hardening
bath and placed in a kettle of boiling water (212 de-
grees) and left there about five minutes, would show
excellent results when used. Other tools showed best
results when heated to 300 degrees and some to 350
degrees. These facts are given the reader in order
that he may understand that there is a method whereby
the amount of brittleness in a piece of steel may be re-
duced to a point where it will stand up to its work and
yet not soften it as much as is necessary when it is
drawn to the first temper color discernible.

The colors visible on the brightened surface of a
piece of heated steel are supposed to be due to a thin

124

Reasons for colors on brightened surface.

coating of oxide, formed by the action of the air on
the heated surface. If a piece of steel is heated in oil
away from the air, these colors will not present them-
selves, provided the steel is left in the oil until the
temperature is below the point necessary to show the
faint straw color (430 degrees).

It is necessary, in order to gauge the temper to
which steel is drawn if gauged by temper colors, not
only to have the piece bright, but it must be free from
grease or oil, as the presence of oil will cause the
colors to show differently than if the surface were
clean.

It is the custom in some shops to polish the
hardened pieces and then draw the temper leaving the
temper color as a finish. Now, if the work has been
polished on a greased wheel, a certain amount of the
oil is taken into the pores of the steel. When it is
heated in tempering, this oil comes to the surface of
the steel and produces a peculiar appearance. The
surface appears streaked. If it is wiped with an oily
piece of waste or cloth, this streaky or mottled look
disappears. Many hardeners always wipe a piece of
steel being tempered with some substance having oil
or vaseline on it ; the appearance of the temper color
is slightly changed by so doing, but allowance is made
for this.

When drawing the temper of articles which are
small or thin, it is not advisable to heat by rapid
methods, heating until the desired color appears and
then quenching in cold water to keep it from running
too low. The cold water, on account of the sudden
chill which it gives an article heated to 430 to 500 or
more degrees, has a tendency to make it more brittle

1*5

Always harden at the lowest heat.

than it would be if it were drawn to the proper temper
color and allowed to cool off slowly, or plunged in
warm oil or hot water. In the case of large, heavy-
pieces, or where brittleness would do no particular
harm, this precaution need not be observed so closely.
But on the other hand, if brittleness did no harm, it
would not be necessary to draw the temper, because
few tools are ever too hard for the purpose for which
they are intended. For, as previously explained, the
process of hardening makes them too brittle to stand
up well when they are in use, consequently they are
tempered to reduce the brittleness to a point where
they will stand up. But the process of tempering is also
(unfortunately for cutting tools) a process of softening.

It should be the aim of the hardener at all times
to harden steel at the lowest heat that will give the
desired result, because in this condition the steel is the
strongest possible, and consequently will not need the
temper drawn as much as though it was given a higher
heat and made brittle. Many times the writer has
seen hardeners heat a diamond point turning tool to a
temperature much hotter than was necessary when
hardening, then draw it to a full straw color in order
to reduce the brittleness so it would be able to cut and
not flake off, or the surface cave in when the tool was
cutting.

Now, the tool in this condition could not do any-
where near its maximum work in a given time.
Neither would the life of the tool be as long as though
it were hardened at the proper heat, and in this case it
is doubtful if it would be necessary to draw the temper
at all, provided it had not been improperly heated
when forging. Many times tools of this description

ia6

Examples of hardening.

can have the temper drawn sufficiently by immersing
the tool after hardening in a dish of boiling water and
leaving there a few minutes.

Examples of Hardening.

CO

When hardening articles made of tool steel, it is
necessary to consider, first, the nature of the steel used,
the construction of the article, next the shape of the
article, and the use to which it is to be put. It is also
necessary to take into consideration the means of heat-
ing furnished by the shop, and the bath to be used in
quenching the article after it is heated.

The operator should adapt himself so far as possi-
ble to circumstances as he finds them, although it is not
advisable to attempt the impossible, because a failure
is generally counted against the man making it, rather
than to any lack of apparatus necessary to do a job suc-
cessfully. By this is meant that it is not policy to at-
tempt to heat a piece of steel for hardening in a fire
that cannot be made to heat the piece the entire length
under any conditions — that is, if it is necessary to
harden it the entire length — ^because such an attempt
must end in a manner disastrous to the steel. It is,
however, the best plan to attempt to find some means
whereby the piece may be heated properly by means
of the apparatus at hand.

The writer remembers, when a boy, seeing a tool

117

How a long reamer was heated.

maker heating a long taper reamer. The only means
of heating furnished by the shop was an ordinary black-
smith's forge. By building a large, high fire he was
not able to do a job satisfactory to himself, so he cleaned
the fire out of the forge, and then took some fire brick,

Figure 52. How a long reamer
was heated.

The Deny Collard Co,

placing two rows on the forge, as shown in Fig. 52.
On these he placed pieces of wire, about one-half inch
apart, built two rows of bricks on top as shown, thus
forming an oven, and then built a fire of charcoal on
the wires between the bricks. By standing bricks up
at the openings at the ends, he was enabled to get a
very good fire in which he heated the reamer in a very
satisfactory manner.

While it would not have been wise to have pursued
this method of heating, if there had been many pieces
of the kind mentioned to be hardened, yet the fact that
this man was able to adapt himself to circumstances
and devise a way of doing a seemingly impossible
thing, made him a valuable man in the estimation of
his employers. It is the man who can do the seem-

128

The preference of some hardeners.

ingly impossible things about a shop that is looked
upon as the invaluable man, and it generally counts,
as would be seen if his pay envelope was examined.

While it is advisable, whenever possible, to study
up some way of doing the work, do not attempt the
impossible unless some one over you in authority
assumes the responsibility. It is better to acknowledge
your lack of ability than to spoil a costly piece of work,
when it would have been considered advisable by those
in authority to have sent the article to some one having
the necessary equipment, had their attention been
called to the matter.

Cases like this may often be used to good advan-
tage in pointing out the advisability of securing better
facilities for hardening and tempering. As long as it
is possible to get along without any equipment but a
common blacksmith's fire, it is often very hard to
obtain anything better.

Hardening Dies.

If it is necessary to heat a large die in an
ordinary blacksmith's forge, it can be done. It is
done right along by men who have had years of ex-
perience, and very satisfactory results are obtained.
The writer knows a man who is considered a very suc-
cessful hardener. He does very little else but harden-
ing large drop forging dies. He heats them in an open
fire and has very good success. He could have, were
he to ask for it, the very best equipment that money
could buy, but he prefers heating by the method men-
tioned.

The writer also knows of an old man who lives

129

Poor scheme to heat in blacksmith's forge.

four or five miles from the city. The electric cars run
within five hundred feet of his house, but rather than
ride on ** them air new f angled devil's contraptions,"
as he calls them, he walks to the city, unless some of
his neighbors give him a ride in their carriage. It
may not seem to be a parallel case. If it isn't, the odds
are in favor of the farmer, as there may be a certain
danger in riding in the trolley cars.

Now, it is possible to heat a large piece of steel,
such as a drop forging die, in a blacksmith's forge by
building a large, high fire of charcoal, placing the die
on this, making certain that the face is buried in the
live coals to a depth of several inches. It would be
necessary to raise the die occasionally and work the
coals under it, as it would not do to allow the air from
the blast to strike the face. It is very necessary to
heat the face uniformly. In order to do this it may be
found necessary to move the die, so that some part
that is heating slowly may be placed in a position
where it will get more heat.

Now, while it is possible to heat work of the descrip-
tion mentioned by the method described, it is not policy
to do it, provided any other means is at hand, or can be
procured — that is, if there are many pieces to be hard-
ened. If there are but one or two pieces, it is possible
by using extreme care to get good results ; but if there
are many of them it is folly, speaking from a commer-
cial standpoint, to heat by this method.

A furnace which gives very good results may be
made, if it is not considered advisable to purchase one
especially adapted to this class of work. Fig. 53 repre-
sents a muffle furnace burning hard coal as fuel,
although charcoal or coke may be burned ; but it will

130

"Home-made" furnace for die work.

be found easier to maintain a uniform heat by the use
of hard coal, and as the products of combustion do not
come in contact with the piece being heated, they cannot
in any way harm it. A represents the muffle which
receives the work. This is located directly over the

Figure 53.

The Dorry Collard Co.

** Home-made" furnace for die work.

fire box B. The heat and gas from the fire pass up the
sides and back of the muffle, thus insuring a very strong
heat. The ash box C is provided with a door which has
a sliding damper to furnish a draft for the fire. The
smoke pipe is connected with the chimney. This is
also provided with a damper to use in controlling the fire.
The die may be blocked up from the bottom by

131

r

A

Z

■•:••

Boxes for heating dies.

means of several pieces of iron or fire brick to prevent
the face coming in direct contact with the floor of the
muifle. The door of the muffle should have an open-
ing, which should be covered with a piece of mica in
order that the heat may be readily observed without
cooling the die.

When many very large, heavy dies are heated it is
advisable to have the bottom of the muffle on a level
with the floor,
sinking the fire
box and ash box
in the ground.
By having the
muffle on a level
with the floor
it is not neces-
sary to raise the
die in order to
get it into the
muffle. When
it is not consid-
ered advisable

to do this, an iron platform may be built on a level
with the bottom of the muffle. The heated die may
be run out on this and then taken with tongs or grap-
pling hook and carried to the bath.

Other forms of furnaces which may be used for
this purpose are illustrated under the section showing
Methods of Heating.

It is customary with some manufacturers who make
a great many dies to harden them in the following man-
ner : Take a box 2 or 3 inches longer and wider than
the die, and 4 or 5 inches deeper. Put in about 2 inches

^WZ/Z/Z/Av^'^^^^^

The Derry Collard Co.

Figure 54. Box for heating dies in
charred leather.

132

Proper methods for heating dies.

of granulated charred leather, place the face of the die
on this, as shown in Fig. 54, then fill the box with
leather.

Some hardeners use a box large enough to take in
the whole die and allow for a cover on top. It is then
entirely removed from the action of the fire, even if
heated in a furnace where the work is placed directly
in the fire. But as it is not possible to get a test wire
down through the center of the die, and a wire at the
sides of the die would not show the amount of heat the
die contained, and as there would be no means of
observing the heat, the operator would have no means
of knowing whether the die was too hot or not hot
enough, or whether it was heating uniformly. And as
the decarbonization of the surface of the upper part of
the die is of little consequence, the plan suggested by
Fig. 54 will be found the most satisfactory, as the
heats can be watched and the die moved occasionally
in order to equalize the heat, which is apt to be greater
in one part of the furnace than in another. The furnace
should not be heated much above the temperature
desired for the die. It is better to take a longer time
in heating than to heat unevenly, thereby setting up
strains which are bound to manifest themselves when
a piece is hardened, or if they do not at that time they
will shortly afterward.

When the proper heat has been obtained, the box
may be removed from the furnace and the die taken
out and plunged into the bath. The form of bath
used for this class of work differs, some hardeners pre-
ferring one with a jet of water coming up from the
bottom, as shown in Fig. 55. This works very nicely
if the impressions are not too deep, in which case the

133

I

L

Die

Bath for hardening dies.

steam formed has a tendency to rise in the impressions
and keeps the water from going to the bottom. When
dies of this description are to be hardened, a bath may
be constructed with an overhead pipe, as shown in Fig.
56. By this means the die is placed on the rods shown,
and when the water is turned on it will go to the bot-
tom of any im-
pression that
would be likely
to be in any die.
This form has
the further ad-
vantage that a
cupful of strong
solution of salt
and water, pot-
ash and water,
or cyanide of
potash and
water may be
dashed on the
face and into
the impression
just ahead of the
jet of water. This has the effect of starting any scale
that may have been formed after the die was exposed
to the air.

Some hardeners have rods in the bath for the face
of the die to rest upon, as shown in Fig. 55, then allow
the jet to play against the face, while others claim bet-
ter results if the die is worked up and down somewhat
in the bath as described.

It is customary with many manufacturers who

Supply

Ovecflaw

Figure 55. Bath for hardening dies.

»34

Baths for hardening dies.

have many dies of this character to harden, to use a
bath having an inlet pipe coming up from the bottom,
as just shown. When the die is properly heated,
it is placed on the rods with the dovetailed tongue
down ; the stream of water is allowed to play against
this side of the die until it is
somewhat cooled ; this not only (C>1
prevents this portion springing
when the face is hardened, but
it allows the heat to run to the
face of the die.

/Imk

Figure 56.
Bath for hard-
ening dies.

After the
tongue side is
sufficientl}'-
cooled, the die
is turned over
and the stream
of water is di-
rected against
the face; the
o V er flo w is
checked suffi-
ciently to allow
the water to
rise several

inches above the face, on the sides of the die ; that is,
it is immersed several inches in the bath; the depth
of immersion depending on the character of the die and
the custom in the individual shop.

When dipping large, heavy dies in the bath, it is
advisable to hold the die with a pair of grappling
hooks, as shown in Fig. 57. These should be attached
to a rope or chain and operated by a pulley, in order

The Deny Collard Co.

Overflow

135

Tongs for handling heavy dies.

that the die may be raised and lowered somewhat in
the bath. Then again, it would not be advisable for
the workman to dip so large a piece of steel with tongs
that necessitated holding his hands and arms over the
bath, as the im- ^^ Excellent results

mense volume of vw/ may be had by the

steam would be // \ ^^^ ^^ ^ furnace built

liable to burn // >\ expressly for this

him; neither /^ \V\ class of work (see
could he properly \ I / / Fig. 58). The die A
support the die \ \ / I is supported on a

in the bath.

Figure 57.

Tongs for

handling

heavy dies.

platform B, and is
raised mechan-
ically, so that
the amount
which it is nec-
essary to hard-

en is in the furnace, while the rest of the die is below
and removed from the action of the heat. The heat-
ing chamber is on top, with burners entering opposite
sides and projecting the flame against the top lining
and distributing it evenly. The die should not be
placed on the platform until the furnace is evenly
heated, when it may be raised by means of the lever
D, until the face enters the furnace the desired amount.
The face of the die can be observed through the open-

136

Heating dies with a gas furnace.

ing- C. When heated to the desired degree, the plat-
form is lowered, the die withdrawn and quenched.
The weight of the die is counterbalanced
by the weight shown, which can be shifted
as occasion requires.

Dies used in
making molds
for hard rub-
ber and similar
work, whose
faces are en-
graved, may-
be packed as
described and
represented in
Fig. 54, and
run until the
required heat
is attained.
After the heat
becomesequal-
ized — /. e.y the
same through-
out— the die
may be dipped
in the bath of
brine, using
the arrange-
ment shown in

Fig. 57. It is necessary to get the die in the bath as
soon as possible after removing from the packing
material in order to prevent oxidation of the face
containing the engraved work.

Figure 58. Gas furnace for heating dies.

137

Punching press dies.

Dies for punch press work, especially those used
for blanking — that is, punching blanks from sheet or
other stock — occasion a vast amount of trouble in many-
shops when they are hardened. Observation has led
the writer to believe that most of the trouble is caused
by uneven heats. The corners and edges of the block
and the edges surrounding the openings will heat much
more rapidly than the balance of the die block unless
extreme care is used.

Before putting the die in the fire, all screw and
dowel pin holes and holes for guide pins (stops) should
be filled with fire-clay, mixed with water to the consis-
tency of dough. This prevents the contents of the bath
entering the holes, and reduces the tendency to crack.
The die should, if possible, be heated in a muffle fur-
nace, not heating the furnace much, if any, hotter than
the desired heat for the die. When it is to the proper
heat and uniform throughout, remove from the fur-
nace, catch by one end with a pair of tongs and lower
into a bath of brine. Swing slowly back and forth in
the bath, in order that the contents of the bath may
pass through the openings. This insures the harden-
ing of the walls, as otherwise the steam generated
would force the contents of the bath away from the die
until it had cooled to a point where it would not harden.
When the die ceases to sing, it may be removed and
plunged into a tank of oil.

There is not much danger of a die cracking when
dipped in a bath, provided it was annealed after the
blank had been machined all over and the openings
blocked out somewhere near to shape. But it is ex-
tremely essential that the utmost care be taken when
heating for hardening. Be sure that no part of the die

138

How to prevent cracking of dies.

block is heated any hotter than it should be. The heat
must be uniform throughout the piece. If the shape is
one that betokens trouble, it is advisable to heat the
contents of the bath considerably. Generally speak-
ing, it is not advisable to use an extremely cold bath
on this class of work.

The writer prefers using a tank of generous pro-
portions, so the contents would not be materially
affected by the heated piece, and heating the liquid to
a degree that does away with any tendency to crack
the piece. An excellent method to prevent the ten-
dency to crack from internal strains, consists in placing
the die, after hardening, in a kettle of boiling water,
keeping the die in the water at this temperature for
one or more hours, according to the size of the die.

If the temper is to be drawn immediately after the
die is taken from the bath, a flat piece of cast iron or
scrap steel may be heated while the die is being heated,
and quenched. It is customary with some hardeners
to heat the piece red-hot. Brighten the face of the
die and lay it on the heated iron. The die should be
moved around on the heated piece and turned over
occasionally to heat both sides alike. When the temper
has been drawn the desired amount, the die may be
immersed in oil, thus preventing the temper being
drawn too much.

While it is the custom of many hardeners to heat
the drawing plate red-hot, as explained, before placing
the die on it, the writer considers it better practice to
heat the plate somewhat^ leaving it over an open fire.
Place the die on the plate and gradually raise the heat.
It is rather rough treatment for a piece of unyielding
hardened steel to be brought in direct contact with

139

Don*t bring steel to sudden heat.

extreme heat, and is liable to crack the surface of the
steel in innumerable places, especially if the operatoi
is not thoroughly experienced in this line of work.

The amount necessary to draw the temper of a
blanking die depends on the steel used in its construc-
tion, the temperature it was heated to when hardened,
and the nature of the work to be performed by it.

Generally speaking, it is advisable to refer the
matter of how hard the die or punch should be to some
one familiar with the requirements of the work to be
done. In some cases it is desirable to have the punch
the harder of the two, although, generally speaking, the
die is left harder than the punch. In some shops, the
one that requires the greater expense in making is left
the hardest, in order that it may be the least injured in
case they strike together when in use. In such cases
it is necessary to draw the one that is desired softest
considerable lower than the other.

But as the circumstances must govern the relative
hardness of the two, no hard and fast rule can be given.

It is customary to draw to a temperature varying
from that which produces a faint straw color, to a
brown with purple spots.

Probably no one class of tools used in machine
shop work requires greater care on the part of the
hardener than the hardening and tempering of punches
and dies ; and probably no class of tools involves a wider
range of methods of hardening and degrees of hardness
essential to produce desired results in the individual
shop.

The hardener who is desirous of giving satisfac-
tion will study the conditions in the shop where the
tools are to be used. He will also consider the steel

140

Hardening the punch.

used in the construction of the tools and the nature of
the stock to be machined. It will be necessary also to
get the experience of men familiar with the work to be
done, because a die and punch hardened and tempered
in a manner that insured satisfaction in one shop would
not meet the requirements in some other shop.

When hardening the punch, use extreme care in
heating. If the punch is strong and is to be used for
punching comparatively light stock, it is not necessary
to harden it the entire length. Take, for instance, the
punch shown in
Fig. 59, to be

used for punch-
ing sheet steel
■^Q inch thick.
This will work
satisfactorily if
hardened to
the dotted line
shown.

When, how-
ever, it is neces-
sary to harden a
piercing punch of
the design shown
in Fig. 60, it will
be found neces-
sary to harden
the entire length
of the end a^ if
the punch is to be
used on heavy
stock. Should

J ' ■ =

Figure 59. Punch for ^ inch steel plates.

)

141

Kind of steel to use for punches.

the hardness extend only to the dotted cross line, it
would buckle, as shown in Fig. 6i, when punching
stock as thick as the diameter of the punch.

When making punches that are heavy and strong,
and which must retain a good edge, it is advisable to
use a steel of comparatively high carbon. But if

Figure 60. Piercing punch for heavy work.

punches are made of the form shown in Fig. 60, best
results will follow if a comparatively low carbon steel
is used, as it is not as liable to crystallize as if a higher

The Derrjr CoUard Co.

Figure 61. Result of hardening only as far as the dotted line,
as shown in Figure. 60.

Steel were used. As a rule, drill rod does not give
good results when used in making tools of this de-
scription.

When punches are sufficiently strong, it is advis-
able to apply the heat at the shank end when draw-
ing the temper. A block, as shown in Fig. 62, having
several holes a trifle larger than the shanks of the
punches may be heated red hot and the punches placed
in these holes. When the desired temper color is visi-

144

How to heat slender punches.

ble at the cutting end, the punch may be taken from
the block and dropped in oil to prevent its becoming
too soft. The upper end of punch will, of course, be
softer than the cutting end.

When a long, slender punch, of the design shown
in Fig. 60, is to be tempered, and the punch is to be

The Derry CoUard Co.

Figure 62. Heating block for tempering long, slender punches.

subjected to great pressure, it must be hardened the
entire length, and the temper drawn equally the whole
length. This can be accomplished by heating in a
heating machine of the design shown in Fig. 48, or the
punches may be placed in a pan containing sand and
drawn over a fire. Or they may be placed in a kettle
of hot oil, gauging the heat by means of a thermometer.

If intended for piercing a heavy, tough stock, they
will be found to work very satisfactorily if drawn to
a full straw color, 460°.

Many hardeners and others look askance at ther-
mometers and always associate them with theory
rather than practice, with the laboratory rather than

143

Forming and ring dies.

the workshop. In reality they are just as practical a
tool as a steel scale or a micrometer, and, like them,
enable us to measure rather than to guess.

Forming Dies.

When hardening forming dies or dies for compres-
sion work, if a great amount of pressure is to be exert-
ed in order to perform the necessary work, the dies will
not stand up as well if hardened at a low heat as though
heated somewhat hotter. The outside surface will be
hard, but under pressure this surface will be forced or
crushed in, the interior not being hard enough to resist
the pressure on the outer surface. It is, as stated,
sometimes necessary in such cases, to heat the block
somewhat hotter than if it were a cutting tool, yet care
must be exercised that the piece be not overheated.
But while it may be advisable to heat somewhat hotter
than is the case with most tools, the heat must be uni-
form throughout the die.

It is not, generally speaking, advisable to draw the
temper very much on tools of this description, but it is
necessary to remove the tendency to crack from in-
ternal strains. This is done by heating the die over a
fire until it is at a temperature that makes it impossible
to hold the hand on it, yet not hot enough to percep-
tibly start the temper, or it may be boiled in a kettle
of water for several hours.

Ring Dies.

When hardening large ring dies or pieces of a cir-
cular shape, whose size and weight make it impracti-

144

Furnace for ring dies.

cable to harden by ordinary methods, it is a good plan
to heat in a furnace made especially for this class of
work. Such a furnace is seen in Fig.
63, which shows a circular block A in
position for heating. It is resting on
strips of iron C supported by pieces
of fire-clay B. The circular piece be-
ing heated should be in the center
of the furnace — i. e.y evenly dis-
tant from the inner
walls. The cover D
is attached to
the mecha-
nism for rais-
ing the cover,
and held by
the chains EE.
It is possible,
by using prop-
er care, to heat
work very uni-
formly in a
furnace of this
description.

A method
the writer has
used with ex-
cellent results
when harden-
ing work of this character, consists in placing the
ring or circular die in an iron box two or three inches
larger each way inside than the circular piece. A cir-
cular box gives better results than a square one, as

The Ocrry ColUird (

Figure 63. Gas furnace for ring dies
and similar work.

»4S

Box for heating ring dies.

Figure 64.

Method of removing ring

dies when heated

in boxes.

more uniform heats may be obtained. Place i>^
inches of a mixture of equal parts granulated charred
leather and charcoal in the bottom of the box. Place
the piece of work on this, cover with the mixture
to a depth of an inch or so, put the cover on the box
and place in the furnace.

When the piece is of a uniform red heat, the box
may be removed from the furnace and the piece of

work taken out by
grasping it with
tongs on opposite
sides, as shown in
Fig. 64. Place it
on a device which
consists of a ring
having three han-
dles, as represented
in Fig. 65. Have
the ring (which
should be made of
iron or machinery
steel) considerably
thinner than the
thickness of the piece to be hardened, but wide enough
to screw the handles in as shown. The handles b b
are threaded on one end and bent; they are then
screwed into the ring, as shown. A stud c having a
tapped hole is screwed in also. The third handle is
screwed into this. The object of making it by this
method is, the handle may be unscrewed from the stud
c and the piece to be hardened put in place. The
handle may then be screwed into the hole in stud. If
the piece of work is very large and heavy, a man may

146

Device for handling large ring dies.

be stationed at each handle. If not very heavy, two
men can handle it all right. The operators should
protect their hands and arms in some manner to pre-
vent being burned by the steam generated when the
red hot piece comes in contact with the water.

It will be necessary to use a bath having a jet of
water coming up from the bottom, so as to cool quick-
ly, when harden-
,b ing work of this

description. Be-
fore immersing,
the water should
be turned on, and
at the minute the
piece is dipped, a
quantity of table
salt (about a pint)
should be thrown
into the water.
The ring should be
worked up and
down in the bath.
When the * * sing-
ing" ceases, the
supply valve may be closed. The water in the bath
may become somewhat warm, but it will reduce the lia-
bility of cracking. As soon as the piece of work is
reduced to the temperature of the bath, it may be re-
moved, placed over a fire and heated to prevent crack-
ing from internal strains. If it is necessary to draw
the temper, the piece of steel may be brightened while
heating and the temper drawn at this time.

It is advisable when drawing the temper of articles

Th* Denry ColUrd Co.

«47

Forms of screw cutting dies.

of this description to heat very slowly^ so as to have all
parts of an equal temperature. If possible, have the
heat so uniform that it will not be necessary to quench
the article when the desired heat is reached. Should
the temper colors, however, run so fast that it seems
necessary to quench in order to keep it from becoming
too soft, it should be dipped in oil or hot water, as, if
dipped in cold water, it would have a tendency to cause
brittleness.

Screw Threading Dies.

There are several forms of the die under considera-
tion. They are sometimes made square, then again
they are made round in shape, with no means of ad-
justment. They are then termed solid dies. Most
square dies are made solid.

The Derry OoUard Co.
Figure 66. Various styles of screw
threading dies.

When it is necessary to cut a screw to size or to
gauge, it is generally considered advisable to make the
finish die of a form known as an adjustable die. The
forms referred to are shown above, in Fig. 66.

The solid square die, being used mostly for thread-
ing bolts and similar work where accuracy is not
essential, are usually made to cut small enough, and no
particular pains taken when they are hardened. How-

148

Holder for hardening screw dies.

ever, if a die of this form is hardened all over, the con-
traction from the outside edges is very unequal, on ac-
count of the corner containing more stock than the
portion between. Owing to the unequal contraction,
the cutting edges do not have an equal amount of
work to do, so one cutting edge dulls more rapidly
than the other. Every tool maker knows the secret of
success in making a screw threading die that will work
satisfactory, lays in having each cutting edge cut its
proportional amount. It will readily be seen that any
unequal contraction or wear, which causes an upsetting
of this equality in cutting, must reduce the usefulness
of the tool.

Too often no account is taken of the amount of work
a tool will do after it is hardened. If it survives the
ordeal of going through the fire and water, and will
cut, it is considered a successful job of hardening.

From the preceding it will be seen that it is neces-
sary, in order that best re-
sults may follow, that the
die be in (as near as possi-
ble) the same shape, and
the location of the cutting
edges be the same as be-
fore hardening. Now, in
order to accomplish this
result, it is necessary to
treat the die in a manner
that will cause the cutting
portion to harden ^/-j/. By
so doing, the contraction

Figure 67. Device for cooling screw ^^ the OUtcr portioU doeS
threading dies. UOt SCrioUSly aff CCt the CUt"

'^%

How to prevent "twist" in screw dies.

ting qualities of the tool. When hardening a square
or a solid round die, it is sometimes considered advis-
able to place the die in a fixture, as shown in Fig.
67. It is then immersed in the bath and swung slowly-
back and forth in
order that the liquid
may readily pass
through the opening,
thus insuring the
hardening of the cut-
ting teeth. The por-
tion near the circum-
ference is, of course,
soft. This is rather
to be desired than
otherwise in the form
of die under consid-
eration.

When adjustable
dies are hardened, it
is generally consid-
ered necessary to harden the outer portion in order
to furnish a certain amount of elasticity, in order
that the die may open
uniformly when ex-
panded. The necessity
of this depends on the
design of the die. If
stock enough is left at
the portion where the die is supposed to spring, the
stiffness of the stock will give it sufficient tension.
Should it be necessary to harden the outer portion
somewhat, the fixture may be cut away in a manner

Figure 68. Method of preventing "twist'
in screw threading dies.

Figure 69. Example of "twist*
in screw die.

ISO

Cooling dies for screw cutting.

that allows the contents of the bath to come in contact
with the steel nearer the outer edge.

Adjustable dies of the description shown should not
be cut entirely through at the point where pressure is
applied to open them, but may be cut nearly through,

Figure 70. Method of cooling dies for thread cuttmg.

commencing at the inside and cutting toward the out-
side, leaving a thin partition, as shown in Fig. 68.
This partition holds the die in shape, preventing the
tendency to twist, shown in Fig. 69.

When it is not considered advisable to make or use
a fixture as described, the die may be grasped, after
being heated, with a pair of tongs, as shown in Fig.
70, and quenched in a bath of lukewarm water or
brine, swinging it slowly back and forth, as repre-
sented. When hardening any tool of this description,

Drawing the temper of a "spring" die.

bear in mind the fact that the article should never be
heated in a manner that allows the cutting teeth to
become oxidized by exposure to the air while heating.
Best results are obtained by heating in a muffle or a
piece of pipe. If the surface of the teeth become
covered with a scale of oxide, this raises, and keeps the
contents of the bath from acting, thus causing soft
spots, which render the tool practically useless.

An excellent plan consists in heating the dies in an
iron box having a half inch of charred leather in the
bottom. Fill the opening in the die with the same
material. When the die reaches a uniform tempera-
ture which is right to produce the desired result,
quench in the bath.

When hardening ** spring" dies, or, as they are
familiarly termed in some shops, *' hollow mill dies,"
best results are obtained by dipping in the bath with
the cutting end up-

permost, as de-
scribed under Hard-
ening Hollow Mills.

Figure 71.
Drawing the temper of
' 'spring'

Generally speaking, it is not necessary to heat the die
much beyond the length of the threads.

152

Tempering small dies.

The temper may be drawn by placing the die on a
hot plate, as shown in Fig. 71, drawing from the back
end. On account of the shape of the cutting edge,
which makes it stronger than the ordinary form of
screw threading die, it is not necessary to draw the
temper as much. A faint straw color making them
about right, unless the cutting tooth is long and weak,
in which case it may be drawn to a full straw color.

If many dies are to be tempered at a time, the cost
may be reduced very materially by heating in a kettle
of oil, drawing them to a temperature which varies
from 460° to 500°, according to the conditions pre-
viously mentioned.

When but one or two are to be done, it is advisable
to brighten the sides and draw the temper by laying
them on a flat plate, moving around on the plate, and
turning them over occasionally. The temper color
should be from a straw to a brown color. If it is con-
sidered advisable to draw the temper of a large batch
of dies by the hot plate method, the plate may be
placed over a fire, in order to maintain a uniform heat.
Quite a number of dies may be placed on the plate at
a time. It is necessary to turn them occasionally, as
mentioned. As one shows the proper temper color, it
may be removed and placed in a dish of warm oil. By
this method a skillful operator can temper a large batch
of dies in a comparatively short space of time, but the
results will not be as satisfactory as though heated in oil.

The amount of work to be done will always deter-
mine the most economical method of doing it, but it is
better to err on the side of having too many convenien-
ces. A few spoiled tools will pay for several improve-
ments.

«53

Cracking of dies from internal strains.

Larg-e pieces of steel are more liable to crack as a
result of internal strains than smaller pieces. On ac-
count of the weight of the piece there is a tendency on
the part of some hardeners to neglect reheating the
piece to overcome this tendency to crack, due to various
uneven heats the steel may have received.

In order to overcome this tendency, the die should
be reheated in a uniform manner to a temperature that
allows the various portions to conform to any strains
in the piece. This may be accomplished by placing the
die in the fire, turning it occasionally, in order that it
may be uniformly heated, and heating until moisture
applied to the surface forms steam. This method when
applied to large pieces is not apt to result in the center
of the piece being heated as hot as the outside. Con-
sequently better results will follow if the die is placed in
a kettle or tank of boiling water (212°) and left there
until heated uniformly throughout. If the die is large
this will necessitate leaving- it in the water at the boil-
ing point for several hours, as it takes longer to heat
a large piece of steel throughly than we realize. It
pays to be very careful about these little points, as these
dies are often expensive.

Hardening Long Articles.

Most hardeners dread hardening long, slender
articles, on account of the uncertainty attending the
operation, so far as results are concerned. If the
article is a reamer or similar tool, having teeth on the
outer surface, it will not require as great an amount of
heat as though it were a solid piece. In any case,
however, do not heat any hotter than is necessary to

154

Proper way to harden long articles.

accomplish the desired result, always remembering
that even heats are the secret of success when heating
steel for hardening. If the tools are hotter on one side
than the other, unequal contraction must take place ;
consequently, the article will be crooked.

When hardening long reamers and similar tools, it

is necessary that the

Wrong

Right

heat should be uniform
and as low as possible.
It must be the same
on each side. If one
side be a low red and
the opposite side a
bright red, and it is
quenched in the bath,
it is sure to come out
crooked. A piece of
this description must
be dipped in the bath
in as nearly a vertical
position as possible, as
shown in Fig. 72, in
order to cool both
sides uniformly. If
it be dipped at very
much of an angle, as
shown in example marked * 'wrong, " it will surely spring,
on account of the uneven contraction of the two opposite
sides. It is necessary to work such pieces up and
down in the bath, changing the location occasionally in
order to avoid the effects of the steam generated.

These may seem like unnecessary precautions, but
the results obtained will show that it is worth while

Figure 72.

The Derry CoUatd Co.

Proper method for dipping
long articles.

155

Advantages of heated baths.

observing them as thorouglily as possible. It's the
little things that count in successful hardening and
tempering.

Condition of the Bath.

If the tool is of a design that makes springing a
possibility when the article is quenched, it will be
necessary to warm the contents of the bath consider-
ably, the degree to which it should be heated depend-
ing on the shape of the tool and the temper of the steel
used. Excellent results are many times obtained with
a bath heated to a temperature of ioo° to 150°.

The writer has had excellent results when harden-
ing articles of this description by placing them in
tubes one inch larger inside than the piece to be
hardened. It should be placed in the center of the
tube, the space between the article and the tube being
filled with charred leather. The ends should be stop-
ped and sealed with fire-clay. The tube is then placed
in the fire and given a uniform heat for a period that
insures the article being evenly heated to the desired
temperature, when it may be removed from the tube
and plunged in a warm bath of brine or the citric acid
solution.

Hardening Taps.

It is necessary to take into consideration the design
of the tool, the steel used, and the nature of the work
to be done by the tap. If the tool is very long and it
is necessary to harden but a small portion of the length,
it is not necessary to heat it any farther up than the

156

The hardening of taps.

length wliicli requires hardening. In such cases it is a
comparatively simple job.

When a long tap requires heating and hardening
its entire length, it is necessary to devise some way of

uniformly heat-

i-5^2Z%r:*L^^_

The Derry Collard Co.

ing the piece.
It is also neces-
sary to quench
in such a man-
ner that all por-
tions will cool
as uniformly as
possible, to
avoid unequal
contraction,
thus preventing
springing or
cracking.

When hard-
ening taps, care
should be exer-
cised that the
teeth are heated no hotter than the refining heat,
or they will be brittle. If heated hotter than nec-
essary, it must have the temper drawn very low, or
the teeth will snap off when used. If the temper is
drawn low, as described, the tap is too soft to perform
its full share of work. When hardening tools having
teeth or projections, it is essential that the heat be the
lowest possible. It is advisable to heat in a muffle
furnace or enclosed in some receptacle to remove it
from the products of combustion in the furnace and
from oxidation by the action of the air. When it

Supply Pipe

Figure 73.

Bath for hardening taps.

157

Bath for hardening taps.

reaches a low, uniform heat, dip in the bath of water
or brine, preferably the latter. Work up and down
rapidly, to bring" the contents of the bath in contact
with the teeth; or, better still, use a bath as shown
in Fig. 73, having inlet pipes on opposite sides of the
tank, these pipes being perforated, as shown. It is
advisable to have the piping so designed that the
upright perforated pipes may be placed against the
side of the tank or moved toward each other, in order
that the jets coming out of the holes may strike the
object with sufficient force to drive the steam away,
thus allowing the liquid to act on the steel.

Long taps give best results if packed in a tube
with carbon, in the form of charred leather, as de-
scribed in hardening reamers. When it has reached
the proper uniform hardening heat, it may be hardened
by immersing in the form of bath represented in Fig.
73. If a bath of this description is not at hand, very
satisfactory results may be obtained by dipping in an
ordinary bath of the desired temperature, and revolve
the piece rapidly in the bath to insure uniform results.
This will in a measure imitate the bath mentioned.

A bath of brine, or the citric acid solution, give
excellent satisfaction for hardening tools of this descrip-
tion. Unless the tap is of large diameter, do not use
a cold bath.

Hardening Small Taps, Reamers,
Counterbores, Etc.

When small articles of this description are hardened
in great quantities, it is necessary to devise means

158

Muffle furnace for heating taps.

whereby they may be hardened cheaply, yet the work
must be done in a satisfactory manner. Various
methods are employed to accomplish this, and one of
the most successful methods that has come to the
writer's attention consists of a furnace made with a

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Muffle

b

ml

Fire Box

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Ash Box

Smoke
Pipe

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^

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=o

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The Derry Collard Co.

Figure 74. Muffle furnace for heating taps.

muffle. The heat was furnished by burning illuminat-
ing gas, or it may be designed to bum coal. The
muffle was made as shown in Fig. 74. Cleats are cast
on to the walls of the muffle, which in this case was
cast iron. On these cleats shelves were placed, and
on these shelves the pieces to be hardened were heated.
It was necessary to turn the pieces over occasionally to
insure uniform results.

When a piece was heated to the proper tempera-
ture, it was taken by means of a pair of tongs and
dropped into a bath, which consisted of a tank having

159

Bath for hardening taps and reamers.

several tube-shaped pieces of wire netting, as shown in
Fig. 75. The tubes were slightly larger inside than
the diameter of the largest part of the tool being
hardened. Tubes of various sizes were used, the
size depending on the diameter of the tools to be
hardened. The tank had a supply pipe coming up

fam\\\\\^^^^^^

Tlw-Detry CoUard Co.

Figure 75. Bath for hardening taps and reamers.

from the bottom. This was connected with a supply
tank overhead. A pump was used to force the water
into the supply tank. It was possible to use a bath
of clear water, brine, or any favorite hardening
solution. In this case, the bath consisted of the citric
acid solution, described under ** Hardening Baths."
It was kept at a temperature of about 60°. As fast
as the pieces were heated to the desired temperature,
they were taken with tongs and dropped into one
of the tubes, the cutting end being down. They

160

How to brighten taps to show color.

passed down through the tubes on to an incline, and
then into a catch pan, as shown. The distance the
pieces traveled in the bath was considered when
designing it. It was found by experiment that the
largest piece to be hardened would cool below a red
heat in falling a distance of two feet in the bath. To
make satisfactory results a certainty, the depth of the

part of the tank
through which the
pieces passed was
made 36 inches. If
the tools had struck
the bottom and

Figure 76.

Grinding to show

temper color.

turned on their side before the red had disappeared
from the surface, they would have, in all probability,
sprung ; but, as it was, excellent results were obtained.
When taps are brightened, in order that the temper
colors may be visible, it is not advisable to use a piece
of emery cloth on a stick or round file, as is often done,
because unless the operator is extremely careful, he is
apt to cut away the cutting edge of the teeth, thus
rendering the tool unfit for use. If possible, use an
emery wheel of the shape of the groove, as shown in
Fig. 76. It is not absolutely necessary to use a fixture,
as the tap may be held in the hands for brightening.

161

Other ways of heating taps.

In this way, not only is the steel brightened, so the
colors may be readily seen, but the cutting edges are
ground sharp, and any burrs thrown up between the
teeth are ground away.

When but a few taps are to be tempered, it is pos-
sible to heat them sufficiently in a gas jet or the flame
of a Bunsen burner ; sometimes the flame of a candle
is used when the article is very small, as in Fig. 77.
With a blowpipe, a hot flame can be produced.

When the taps are made in quantities suffi-
ciently large, it is much more economical to
draw the temper by placing in a kettle of oil,
gauging the temperature with a thermometer.

The amount necessary to draw the temper
of a tap in order to get desired results, de-
pends, as with most
other cutting tools, on
the steel used, the heat
given when hardening,
and the use to which they are to
be put. Very small taps that are
to be used by hand may be left
harder than those intended for The oerry' couard co.
use in a screw machine. Taps Figure 77. One way to
used by hand should be drawn ^^^ ^"^^ ^^^^'

to deep straw or brown color, while those used on
screw machine work need drawing to a deep brown,
and in some cases to a purple.

Half Round Reamers.

These should be heated very carefully in a pipe or
muffle furnace to the lowest heat possible to harden.

162

Method for cooling half-round reamers.

When dipping in the bath, the reamer should be in-
clined somewhat from a perpendicular position, the
heavier portion being on the lower side, as shown in
Fig. 78, to avoid a tendency to spring. The contents
of the bath should be heated as warm as is consistent
with good results, as this will help keep it straight.

Should the ream-
er spring somewhat
in hardening, it
may be straight-
ened by reheating
and exerting a
pressure on the
convex side.

If the projection
has been left on the
end, as shown in
Fig. 79, the reamer
may be placed be-
tween centers and
straightened, as
represented else-
where.
Should it be a reamer having no center at the
small end, it may be placed on two V blocks, as shown
in Fig. 80. Apply heat by means of a gas jet, spirit
lamp, or any other means to the lower side, heat until
oil placed on the surface commences to smoke. Now
apply pressure at P, on top side. When it has been
sprung the proper amount, cool by means of wet
waste.

The possibility of straightening reamers and sim-
ilar work means such a saving in many shops that it

163

Figure 78. Proper method for cooling
half-round reamers.

Hardening milling cutters.

will pay to have special attention paid to it, as crooked
tools of any kind cannot do accurate work. It will
pay to rig up fixtures especially for this, as the saving
is far greater than the cost.

Small, half-round reamers should be drawn to a
full straw, or a brown color for most work.

Hardening Milling Machine Cutters.

As most shops have at least one milling machine,
and many shops hundreds, there are probably more
cutters hardened for this class of work than for any
other.

In hardening this class of tools, it is necessary to

The Derry CoUard Co.

id

Figure 79. Half-round reamer.

have them hard enough to cut the metal being
machined, yet tough enough to stand up under the
strain to which it must be subjected.

Milling machine cutters should be hardened at a
lower heat than a solid piece of the same size. The
teeth, being slender and projecting from the solid
body, take heat very readily. When possible, tools of
this description should be annealed after a hole some-
what smaller than the finished size has been drilled
and the tool blocked out to shape in order to overcome
the tendency to crack from internal strains. If it has
not been possible to do this, or if for any reason it has

164.

Care in heating milling cutters.

not been considered advisable, the cutter may be heated
to a low red and laid to one side and allowed to cool
until the red has disappeared, when it may be reheated
and quenched. It is always better, however, to anneal
after blocking out if it can be planned so as to take
the time necessary to do this. The results are more
satisfactory in every way.

It may be well to again caution the reader in regard
to the heats. The teeth of this form of tool being thin,
are apt to absorb heat faster than one realizes, and as
a consequence, they become too hot. If a cutter is

The Derry Collard Co.

Figure 80. Straightening a half-round reamer.

overheated, it will not do as much nor as satisfactory
work as though properly heated ; but should the teeth
by any carelessness become overheated, do not quench
at that heat, thinking no one will know the difference.
While it is possible to misrepresent the condition of
the heat when describing it, the texture of the steel
always tells the truth in regard to what the operator
has done with it when in the fire. Neither is it a good
plan to hold it in the air and let it cool until the color
shows about right, because it is hotter inside than on
the outside ; and then again, the grain will be as coarse

165

How to cool milling cutters.

as thougli it were dipped at the higher heat. It should
be allowed to cool off and then heated to the refining
heat and quenched.

When this form of tool is ready to harden, place it
on a wire, bent as shown in Fig. 8i. The wire should
be large ^ enough to hold the cutter without
bending, ^,^ but not much larger, as it should
not impede ^^ the circulation of the fluid through
the hole of the ^^ cutter. Neither should any con-
siderable sized ^^ piece of steel rest against the
side of the cutter, ^^ as the action of the bath
would not be uni- ^^ form if it were kept away
from some portions ^^ of the piece. The cutter
should be worked ^^^ around well in the bath
until the teeth are hard, ^^^ when it may be re-
moved and plunged in oil ^^^ and left until cold.
It should then be taken and ^^ held over a fire
and heated sufficiently to re- ^. move any ten-
dency to crack from internal ^ strains. The
temper may now be drawn the re- quired amount.

A method in use
in many shops, con-
sists in dipping the
cutter in a bath of
water having one or
two inches of oil on
the surface. The
cutter is passed down through the oil into the water.
Fig. 82 shows a bath of this description. The oil does
away with the first sudden shock, which results when
hot steel is plunged into cold water, and as a small
portion of the oil adheres to the teeth, especially in the
comers where the teeth join the body of the material,

166

liM-Drnj CoUard Co.

Figure 81. Proper way to cool
milling cutters.

Drawing temper of milling cutters.

the action of the water is not as **rank" as would
otherwise be the case. Where the teeth are long or
the mill is of irregular contour, it is advisable to heat
the water somewhat. Water or brine, heated luke-
warm, works fully as well as though cold on tools of
this description and is not as likely to crack them.
When the outline is very irregular and the tool is made
of high carbon steel, the writer has had excellent suc-
cess using a bath of brine heated to 80° Fahr. The
idea that a bath must be as cold as possible has prob-
ably ruined more steel than we realize.

Drawing Temper of Milling Machine
Cutters.

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III I !i i:i.!!i!

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niTg

r^ri^-zznWatec:

A method in very general use for drawing temper
of milling machine cutters, consists in placing the
hardened cutter on an
iron plug of the form
shown in Fig. 83, the
plug having been pre-
viously heated suffici-
ently to draw the tem-
per of the cutter.

The plug, when
heated, should not fill
the hole in the cutter.
In order to heat the
cutter uniformly, it
should be turned con-
stantly on the plug.

It is, of course, necessary to brighten the backs
167

7////////////////////////////////^////////////^^^

TTut T>errv Collard Co.

Figure 82. Oil and water bath for
milling cutters.

Heating milling cutters on a plug.

of the cutter teeth in order that the temper colors
may be readily discerned.

The writer has had best results by holding the
cutter over a fire, or a hot plate, and warming the
circumference to a degree that made it impossible to

Figure S3. Plug for heating milling cutters.

hold the hand on it, previous to placing the cutter on
the plug. It was then placed on the plug and turned
constantly until the proper temper colors showed,
when it was plimged in oil to prevent its getting too
soft.

The object attained in heating the outer surface
first, was that the heat given was sufficient to make
the steel at this point somewhat pliable; whereas, if
the cutter had been placed when cold on the red hot
plug, the cutter absorbing the heat would tend to
expand the steel toward the outer, rigid surface. If
this expansion should prove, as it does many times, to
be greater than the steel could stand, cracks would
result.

The amount of heat necessary to give a milling
machine cutter when drawing temper can not be stated
arbitrarily. It is desirable to leave it as hard as possi-

168

Hardening shank mills.

ble, and yet not have it too brittle to stand up when
in use ; consequently, it should not be heated any hot-
ter than necessary when hardening. It should not be
plunged in a bath of extremely cold fluid, neither
should it be checked in cold water when the temper
has been drawn sufficiently.

While it is not considered advisable by many
mechanics to make cutters of this description of a high
carbon steel, the writer's experience has convinced
him that better results are obtained by using a high
carbon steel extremely low in phosphorus, and using
extreme care in the heating. Then quenching in a bath
of warm brine, 80° to 100° Fahr.

For ordinary work, a faint straw color (430**) gives
best results, although it may be necessary at times to
draw to a full straw color, 460°.

A kettle of oil, heated to the desired temperature,
furnishes an ideal method of tempering cutters of this
description. This method has been ftdly described
under the proper section on pages 121 and 122, and
should be carefully considered in connection with tools
of this character

Hardening Shank Mills,

The percentage of carbon necessary to give the
best results, depends on the make of steel. For ordin-
ary work, however, a steel having i % per cent, gives
good results.

The methods employed in heating and quenching
shank mills when hardening, depend in a measure on
the form of the mill and the custom in the individual
shop. Mills of the form shown in Fig. 84, may be

169

Best way to harden shank mills.

heated to a uniform low red heat for a short distance
above the teeth, stopping the heat in the necked portion,
marked a. In some shops it is the custom to leave
the shank quite a little larger than finish size in order
that it may be turned to size in the lathe and fitted to

Figure 84. How to harden shank mills

the collet or spindle after hardening. In such cases it
is necessary to leave the shank soft its entire length.
In other shops it is the custom to turn the shank nearly
to size before hardening, leaving on just enough to
allow for grinding to a fit and remove any untruth
resulting from springing in hardening. If it is neces-
sary to leave the shank soft its entire length, care
should be exercised in heating and dipping in the bath
that the shank is not hardened in the least. If it is to
be ground to a fit, the same care is not necessary,
although greater care must be exercised in grinding if
the shank is hard for a short distance and the balance
is soft ; but if careful when taking the finishing cuts on
the grinder, no trouble need be experienced. If the
cutter is made as represented in Fig. 85, it will be
necessary, in order to harden the teeth the entire length
in a satisfactory manner, to harden the shank for a
short distance.

When hardening a cutter of the description shown

170

Treatment of holes in shank mills.

in Fig. 86, having a recess of considerable depth in the
end, much better results will be obtained if it is dipped
in the bath with the hole uppermost, as shown in Fig.
87 — that is, provided it is necessary to harden the walls
of the hole. If this were not desirable, then it would
be safest to fill the hole with fire-clay, mixed with
water, to the consistency of dough, and the cutter
dipped as shown on next page. If the hole was not
filled and the cutter was dipped in the bath with the
hole down, the steam generated would drive the water
away from the teeth at end; and furthermore, the
steam would very likely cause the thin walls to crack.

TtM Shrry C«lUrd Co.

Figure 85.

Figure 86. Shank mills.

When hardening cutters of the form shown in Fig.
88, known as T slot cutters, it is necessary to harden
the entire length of portion necked below size of
shank for several reasons. When the neck portion is
slender, this is necessary, in order to strengthen this

171

Treatment of T slot cutters.

portion so it will not spring or twist off when the cutter
is in operation. If the cutter is of a size that makes
the necked portion large and strong enough to resist
the cutting strain, it might not appear at first thought
necessary to harden this. But as it ^ is g e n e r
ally made but a few thousandths of an inch

smaller than the slot it travels in, it will, if left

soft, become roughed up by the fine cast iron

chips, which are liable to get between the walls

of the slot and
the stem. Con-
sequently, it will
be readily seen
that in most cases
it is advisable to
harden the entire
length of the
necked portion.

If there is
considerable dif-
erence between
the size of the
cutting portion
and the shank
of the tool, the
cutter should be
made, if possible,
with a fillet in the
comer, as shown at a^ in sectional view of Fig. 89. If,
however, this precaution has not been taken, or it has
not been possible to do it, a piece of iron wire may be
wound around, as shown at 5. This wire being red-
hot when the cutter is dipped in the bath, has the effect

Figure 87. Proper method for
treating shank mills.

172

Tlie Derry Collard Co.

Figure 88. T slot cutter.

Fillets for T slot cutters.

of keeping the contents of the bath away from the
sharp comer until the larger and smaller portions of
the mill have become hardened to a degree, thus reduc-
ing the liabil-
ity of cracking
at this point.
When the cut-
ter has been
heated to a low
red, it should
be plunged into a bath of water or brine from which
the chill has been removed ; work around well in the
bath until it is of the same temperature as the bath,
when it may be removed and the temper drawn.

If it has not been possible to heat the cutter in a
muffle or in a piece of pipe or other receptacle, it will
be found an excellent plan to have a strong solution of
potash and water, which should be heated quite warm.
Before the cutter is heated,
it may be plunged into the
potash solution. Place it
in the fire and heat to the
proper hardening temper-
ature and plunge in the
hardening bath. The
effect of the potash is to
cause any thin scale of oxide which may have formed on
the surface to drop off the instant the tool touches the
bath. If this scale adheres to the piece, it has a tend-
ency to rise in the form of a blister when in contact
with a cool liquid, and consequently it keeps the con-
tents of the bath from acting on the steel directly
underneath.

Figure 89. Fillets for
T slot cutters.

173

Drawing temper of T slot cutters.

When drawing the temper of a tool of this descrip-
tion it is necessary, in order that the necked portion be
as strong as possible (especially if it is slender), to
draw it to a purple or even a blue color, while the cut-
ting teeth need drawing to a straw color.

It is surprising to one not thoroughly posted in the
effects of different degrees of heat on steel to find how
hard a cutter of this kind may be left if it was properly
heated when hardened. This is best seen by compar-
ing with one that was heated a trifle too hot, yet not to
a degree that is generally considered harmful to the
steel. In the case of the cutter properly heated — that
is, to the refining heat — it may be left when tempering
at a faint straw color, while if given a trifle more heat,
it is necessary to draw it to a full straw, a difference
of 30° of heat, and a vast difference in the amount of
work it will do between grindings. In order to suc-
cessfully draw the temper, the necked portion may be
placed in the flame of a gas jet, a Bunsen burner, the
flame of a spirit lamp ; or, if none of these are avail-
able, and it is necessary to use a blacksmith's forge for
all work of this description, a piece of sheet iron having
a hole in it may be placed over the fire. A jet of flame
will come through the hole, which may be made to
strike the necked portion. In this way the desired
temper may be obtained.

Hollow Mills.

When articles having a hole running part way
through them, as, for instance, the hollow mill shown
in Fig. 90, are to be hardened, it is advisable to dip

174

Hardening hollow mills.

them in the bath, with the opening uppermost, as re-
presented in Fig. 91. If the mill were dipped with the
opening down, it would be almost impossible to get
water to enter the hole for any considerable distance,

Figure 90. A hollow mill.

as the steam generated would blow the water out. As
a consequence, the walls of the hole would not harden,
and the steam would in all probability cause the steel
to crack.

Then again, best results will follow if the frail end
is not chilled until after the heavier, solid portions have
contracted somewhat. If the lighter portions are chil-
led and contracted before the heavier ones, the tend-
ency is for the heavier parts, which are stronger than
the lighter, to pull them into conformity with them-
selves, and as the steel is hard and rigid, it must crack.
While this principle is explained elsewhere in this
work, it seems wise to show the adaptability of this
peculiarity of steel to pieces of this description.

When making articles having holes, as shown, if
the piece is to be hardened, the liability of cracking
will be lessened if the stock at the end of hole is left,
as shown in Fig. 92. If, however, the piece is made

»7S

Tepid water for hardening hollow mills.

with a sharp comer, as shown in Fig. 93, it is advisable
to fill in this sharp comer with fire clay, or graphite,
in order that there may be no pronounced difference in
the contraction of the two portions.

When hard-
ening pieces of
this character, it
is, generally
speaking, good
practice to use a
bath of tepid
water or brine.

When it is con-
sidered desirable
to harden a piece
a certain dis-
tance, and no far-
ther, and the fa-
cilities for heat-
ing do not allow
of heating ex-
actly the right
distance, it is
necessary to dip
in the bath with
the teeth down.
In order to over-
come the tendency of the steam to blow the water
from the hole, a small vent hole is drilled through the
wall of the piece, as shown in Fig. 94. If this hole is
large enough to allow the steam to escape, good re-
sults will follow if a bath is used having a jet of water
coming up from the bottom, as, by this means, water is

176

The Derry Collard Co»

Figure 91. Method for hardening
hollow mills.

Various types of hollow mills,

forced into the hole. However, the operator should
bear in mind that it is never good practice to have

Figure 92.
Hollow mill with
rounded corners.

The Derry CoUard Co.

the hardening stop at a shoulder, either inside or out-
side of a piece of steel. Where possible, stop the

Figure 93.

Hollow mill with

sharp corners.

hardening somewhat short of the shoulder, but if
this does not meet the requirements, harden a trifle

Figure 94.

Hollow mill with hole

to allow escape

of steam.

beyond the shoulder. This may seem like a little
thing to bother about, but it generally means the dif-
ference between a good job and a poor one, and it's

177

Hardening thin articles.

one of the little points that count in making a success-
ful hardener.

Thin Articles.

Thin articles, as screw slotting saws, metal slitting
saws, etc., may be hardened between two plates whose
faces are covered or rubbed with oil. If reasonable
care is exercised in the operation, they will be very
straight.

It is essential, in order to get good results, to heat
the pieces on a flat plate. They should be heated no
hotter than is necessary to accomplish the desired result.
When at the proper heat, the saw may be taken by a
pair of tongs, of the form shown in Fig. 95, and placed
on a plate whose face is covered with lard, sperm
or raw linseed oil. The advantage derived from using
tongs of this description is, the saw is held by the por-
tion near the hole, rather than by the teeth, as would
be the case if a pair of the ordinary style were used.
In that case, the teeth grasped by the tongs would not
be of the same temperature as the balance of the saw ;
and, as a consequence, the hardening would not be
uniform. Another plate, whose face has been treated
in a similar manner, may be placed on top of the saw
and held there until the saw is cold. It is necessary to

Figure 95.
The Derry Coiiard Co. Tongs for holding flat plates.

place the top plate in position as quickly as possible,
after the saw has been placed on the lower plate.

If the saw should become chilled before the upper

178

Method of cooling flat plates.

plate is placed on it, it will spring somewhat, and the
upper plate cannot straighten it. Should it be sprung

II II II II

II II II II II

y/////f//^^/^/^////j//Mf/^//wj,j//:r//f/.

Figure 96. Device for cooling
thin, flat work

'The Derry Coltard Co.

very much, the pressure applied to the upper plate
will, in all probability, break the saw, as it would be
hard and unyielding.

If many pieces of the description mentioned are to
be hardened, it is advisable, for the sake of economy, to
make a special device for chilling the work, as when
two plates are used, it is necessary to have the services
of tvv^o men, one to handle the saws, and one to work
the movable plate. If the number of pieces to be
hardened does not warrant an expensive apparatus,
two flat plates may be used, drilling two holes in each
plate, as shown in Fig. 96. The holes in the lower
plate should be a driving size for ^ inch wire, while
those in the upper plate should be -^ inch larger than

179

Devices for hardening thin plates.

the size of the wires. A cord should be attached to
the upper plate, as shown. This cord should pass
over a pulley and return to a treadle. The operator,

a

u

Qel

r: r.z: i x*>

'.-.:

O Q:

lerffjri <D\

0=0=;

de Dsrry Collani Co.

Figure 97. Device for hardening between plates.

by using this device, can handle the saws and operate
the plate very nicely.

In Fig. 97 a device is shown for hardening thin
pieces between plates, which consists of the base a,

I go

Necessity for keeping jaws of plate holders cool.

and slide ^, to which are attached jaws cc. Through
the jaws are several wires for the work to rest on when
it is placed between the jaws. The side is operated by
the treadle <?, which is connected to the base and slide
by the brackets ff. The device is supported by the
legs as shown. The advantage derived from using a
fixture having the jaws standing in a vertical line, as
shown, is, the piece of work is not as liable to chill while
closing the jaws, as would be the case were the jaws
in a horizontal position.

If the work is hardened in large quantities and the
jaws show a tendency to get hot, they may be cast hol-
low and a water pipe connected with each, providing
an outlet on the opposite side. In this way a circula-
tion of water may be kept up through the jaws, thus
keeping them cool at all times. In order to insure a

The Derry Collard Co.

Figure 98. Cooling plate mounted on springs.

uniform circulation of the water, it will be necessary
to have the inlet pipe at the lower edge, on one end of
the jaw, and the outlet pipe on the upper edge at oppo-
site end. The outlet pipe should be carried far enough
to do away with any liability of any of the water get-
ting on the surfaces of the jaws that were to come in
contact with the pieces being hardened.

J8i

Cooling gun springs.

When saws or other pieces of considerable thickness
are hardened between plates, it is sometimes necessary
to provide for a supply of oil around the teeth when
the plates are in position. In order to do this, it is
necessary to use
plates in a horizontal
position, as shown in
Fig. 98, having the
lower plate resting on

^ ° Figure 99. Gun spring.

Springs, or other ar-
rangement to keep its upper face above the surface of
the oil in the pan, until the work has been placed on
it. The pressure applied by the upper plate must

Th« Derry CoUard Co.

Figure 100. Method for cooling gun spring shown above
or other irregular pieces.

submerge them in the oil in pan to a depth that
insures the teeth being well covered with oil.

Drawing temper of slitting saws.

When drawing the temper of tools of this descrip-
tion best results can be obtained by putting the pieces
in a kettle of oil, gauging the heat by a thermometer.
While the degree of heat necessary to produce the
desired result can not be given arbitrarily, as very
much depends on the steel used, the amount of heat
given when hardening, and the use to which it is to be
put. But ordinarily, metal slitting saws for general
jobbing purposes should be drawn to 460 degrees.
Screw slotting saws, -^ inch thick and under, 525 de-
grees. If thicker, do not draw as low.

The method of hardening between plates may be
applied to pieces having other than flat forms. Take,
for instance, springs which, in order to maintain a
given tension, must be of a certain shape ; for example,
the main spring of a gun, as represented in Fig. 99.
The form of spring is shown at a, while dd is a pair of
plates, having their faces formed to harden the spring
and keep it in the proper shape. It is not generally
desirable or advisable to use a form when hardening
springs of this character, but is sometimes necessary.
The method and amount necessary to draw the temper
of springs is given under Spring Tempering, and to
avoid repetition the reader is referred to that section.
It has seemed necessary to repeat some statements in
order to show their different applications and to im-
press them on the mind.

Screw-Drivers.

There is probably no one article so generally used
as the screw-driver that gives so much trouble. In the
first place, not more than one man in ten understands
how to properly make the tool, and then but a small

183

How to make a proper screw-driver.

percentage of this one-tenth can harden and temper it
properly after it is made.

A screw-driver is better for having been forged to
shape, provided it is forged properly ; that is, heated
properly and hammered in a scientific manner. Unless
one understands these operations well enough to do a
good job, it is advisable to file or machine one from
the bar.

A screw-driver should be made with the end that
enters the screw

ir

a

V

Figure

Tlie Derry CoUard Co.

Styles of screw-driver points.

slot of an equal
thickness through-
out, and to nearly
fill the slot. At
times, this precau-
tion is observed,
and the portion
immediately ad-
joining is made
much heavier and

with square comers, as shown at a, Fig. loi. Now, on
account of the unequality of size of the adjoining por-
tions, it is a difficult matter to harden and temper
it uniformly throughout. Then again, the shape is
such that it must break where the heavy and light por-
tions adjoin, on account of the unequal strength of
the two portions.

Now, a screw-driver, or any tool which must resist
a bending or twisting strain, must be made in such a
manner that the tension will be taken up for a con-
siderable portion of the length of the article, thus
doing away with a tendency to break at any one point.
In Fig. loi, ^ represents a screw driver made in a man-

184

More about screw-drivers.

ner that apparently, according to some meclianics'
minds, will just fill the bill. It is symmetrical, that is,
there are no breaking points ; but look at the end that
enters the screw slot — it looks more like a chisel than a
screw-driver. Now, when pressure is applied to this
form, it, on account of the inclined sides,
slips out of the slot. It will not hold, so

^

Figure 102.

One way of testing

a screw-driver.

The Deri-y CoUard Cd,

a stick or piece of iron is
placed on top of it in the
form of a lever, and one or
two men hold down on the end
of this, as shown in Fig. 102,
and the fellow
doing the job gets
a wrench on, and
yanks. Now, the
screw-driver is
subjected to two
strains instead of
one. It tries to
get out of the
slot, and cannot,

on account of the power applied above. It is also
subjected to torsional strain from the direct pull of
the wrench, and it breaks. Now, if it is made of the
form represented at <:, Fig. 10 1, and hardened and tem-
pered properly^ there will be very little danger of it
breaking from any ordinary usage.

When heating for hardening, give it the lowest heat
that will produce the desired result. Remember, hard-

185

Hardening taper mandrels.

ness is not the desired quality ; it will not be called on to
cut metals, it must simply resist strain or pressure,
consequently toughness is the quality to be sought.
Articles hardened in cold water do not show this
quality to "such a degree as those quenched in oil, so
it is advisable to use oil as the cooling medium when it
will answer. If oil will not answer, then heat the
water. If it is a comparatively small screw-driver,
heat the water nearly to the boiling point. The larger
the article, the less heat it will be found necessary to
give the water ; but in no case, unless the steel is low
in carbon and the screw-driver very large, should cold
water be used.

The amount necessary to draw the temper varies
with the percentage of carbon the steel contains. If it
is made of ordinary tool steel, it may be heated until
hardwood sawdust catches fire from the heat in the
steel, or until a fine shaving from a hardwood stick,
made by drawing the stick across the edge of the screw
driver, catches fire, as noted before. When the proper
temper shows, it may be quenched in warm oil or hot
water, never in cold water.

While screw-drivers may seem like a small affair,
hardly worth while thinking much about, the frequency
with which they are used and the time lost in regrind-
ing after breakage, make them quite an important tool
in any shop. Then, too, the damaged screw heads
must be counted against them.

Tap

er Mandrels,

When it is necessary to harden taper mandrels
made of tool steel, it is necessary to provide some means
of uniformly heating the article. One end, being of a

i86

Hardening counterbores.

greater diameter than the other, has a tendency to heat
slower. Owing to this fact, it will be necessary to
heat slowly. When it has reached the desired heat,
which should be uniform throughout, grasp by the
small end with a pair of tongs and immerse in a bath
of water or brine, which has a jet coming up from the
bottom. When it ceases singing, remove and plunge
in a tank of oil, allowing it to remain until it is cooled
to the temperature of the bath. It should then be
reheated to remove the tendency to crack from internal
strains.

Counterbores.

The toolmaker or designer should, when designing
tools that are to be hardened, avoid, as far as possible,
sharp corners between portions of different sizes. If
a count erbore is made as shown in Fig. 103, the presence

5^'-t- %

=\-

The Derry Col lard Co.

Figure 103. Counterbore with square corners.

of sharp comers is an invitation for the steel to crack
from unequal contraction at these points. If the
comers are rounded (filleted), as shown in Fig. 104, the
tendency to crack is almost entirely eliminated.

Many times serious trouble arises from countersink-
ing center holes too deeply in articles that are to be
hardened. Fig. 104 represents a sectional view of
countersinking in pilot, which is deep enough for all

187

Proper temper for counterbores.

practical purposes, while in Fig. 103, the countersink-
ing is so deep that there would be a great tendency to
crack when hardening. When articles of this de-
scription are countersunk too deeply, it is advisable to
fill the hole with fire-clay before placing it in the fire.
This plan, of course, would not work satisfactorily in
the case of mandrels, arbors, and similar tools, whose
centers must be hard in order to resist wear.

Heat to the lowest uniform red that will cause the

%^%

Figure 104. Counterbore with filleted corners.

article to harden, dip in a bath of lukewarm brine,
hardening part way up the portion necked below size
of shank.

When drawing the temper of counterbores, apply
the heat at shank end, allowing it to run toward the
cutting end of teeth.

The proper amount to draw the temper depends on
the character of the work to be done, the design of the
counterbore, etc. It was formerly the custom to draw
the temper to a degree that made it possible to sharpen
the cutting edges by filing with a sharp, smooth-cut
file. If the counterbore is made of the design shown
in Fig. 104, it may be sharpened by grinding on the
face (a) of cutting tooth with an emery wheel, thus
making it practical to leave the tool much harder than
would otherwise be the case.

A very common mistake when making tools of this

188

Hardening mandrels, arbors, etc.

description is to stamp any distinguishing marks on the
tool when finished, thereby springing it; and unless
this fact is noticed, the hardener will be blamed for it.
All stamping should be done before the important portions
are to size.

When hardening counterbores having inserted pi-
lots, it is advisable to fill the pilot hole with fire-clay, in
order to prevent the water entering. If the design is
such that the tool is liable to crack when quenched, it
should be dipped in the bath with the teeth uppermost.
The contents of the bath should be warmed to reduce
the liability of cracking.

Hardening Mandrels, Arbors, Etc.

Mandrels, arbors, and similar articles, which are to
be hardened, are generally made of any piece of tool
steel which comes handy. Now, it is a fact that tools
of this description give a great deal of trouble when
hardened, unless the operator is quite skillful. As the
only reason for hardening a mandrel is to give it a hard
surface and make it as stiff as possible, the desired
result may be obtained by using a steel that is not high
in carbon. Take, for instance, a steel containing ^
per cent, or one per cent, carbon. As good results can
be obtained as if a steel containing i ^ per cent, carbon
were used, while the article would not be as liable to
crack or spring as if a high carbon were used.

When making articles of this description, steel
somewhat larger than finish size should be selected.
The outside should be turned off and the piece annealed.
After annealing, it may be machined to grinding size
and then hardened.

When hardening, a fire large enough to heat the

189

Caution about small fire.

piece uniformly should be used, and the piece turned
frequently to insure good results. A mistake some-
times made in heating pieces of this description con-
sists in using a fire too small to accomplish the desired
result. One end and the center is heated, the end is
reversed and the opposite end is heated. The first
end, in the meantime, has cooled to a degree that
makes it unsafe to quench the piece in the bath. So
the second end is heated hotter than it should be, with
the idea in view that the piece will again be reversed
and the over-heated end will cool to the proper harden-
ing heat, while the temperature of the opposite end is
being raised to the desired heat. When it is taken
from the fire, it is in the worst possible condition to
harden; the center is too hot, one end is apparently
about the right temperature, but the interior is not hot
enough. The opposite end is possibly at about the
right heat, but the interior is too hot. In this condi-
tion it is immersed in the bath and violent strains are
set up, which result in the piece being cracked or
sprung out of shape. Now, this is not at all right, yet
it is so commonly practiced that the writer feels it
necessary to caution the reader against a practice which
is so radically wrong.

If obliged to use an ordinary forge, build a fire
large and high enough so the piece may be uniformly
heated ; turn frequently ; keep the piece well buried in
the fire to prevent oxidation of the surface. When the
steel reaches a low red heat, take it from the fire,
sprinkle some pulverized cyanide of potassium on the
surface. Place in the fire and bring to a uniform red
heat, which must be a trifle higher than if there were
teeth or projections on the surf ace, as, these being light,

190

Mandrel centers must be very hard.

would cool more quickly than a solid piece. If possi-
ble, use a bath having a jet of liquid coming up from
the bottom. If it is a mandrel, it should be grasped
by one of the ends with a pair of tongs of the descrip-
tion shown in Fig. 86. This insures hardening the
body of the mandrel, and also allows the contents of the
bath to have free access to the upper center, which
would not be the case if a pair of tongs of the ordinary
description were used.

It is essential that the centers of a mandrel be very
hard. For this reason a method of quenching in the
bath should be used that insures the centers in both
ends hardening.

If it is considered best to draw the temper of the
ends in order to avoid the comers chipping or the ends
breaking, it is not advisable to make them as soft as
the dead center of the lathe, which is usually drawn to
very deep straw or brown color. The object attained
in having the ends of a mandrel harder than the lathe
center is that in case of wear, the center, being the
softer of the two, will probably wear rather than the
centers of the mandrel.

The piece should be worked up and down in the
bath until it is of the same temperature as the contents
of the bath, when it may be removed and heated some-
what to overcome the tendency to crack from internal
strains. It should be held in a vertical position when
dipping, in order to avoid springing.

Better results will follow if the piece is placed in a
piece of pipe or tube when heating.

A very excellent method consists in placing the
article in a piece of gas pipe, which is closed at one
end. The hole in the pipe should be about one inch

291

Hardening grooved rolls.

larger in diameter than the piece to be hardened. Fill
around it with granulated charred leather, having the
mandrel in the center of the hole in the pipe, and the
ends should not be within ^ inch of the ends of the
pipe. Fill the pipe with the charred leather ; place a
loose-fitting piece of iron in the open end of pipe, and
seal with fire-clay. When this is dry, the pipe may be
placed in the fire and remain until the article is uni-
formly heated to the proper temperature, when it may
be taken from the pipe and quenched, as described.

Still better results may be obtained if the piece is
kept at a low red heat for a period of several hours,
the time depending on the size of the piece. If j^ inch
diameter or under, i ^ hours will be found sufficient.
If larger, run correspondingly longer. When it has
run sufficiently long, the piece may be removed from
the tube, grasped by the tongs, as shown, and plunged
in a bath of raw linseed oil, working up and down
rapidly in the bath. This method receives further
consideration in section on Pack Hardening.

Hardening Grooved Rolls.

When grooved rolls or similar articles are to be
hardened, it is necessary to heat very uniformly. The
projections, as shown in Fig. 105, have a tendency to
heat faster than the balance of the roll. Should they
become hotter, the projections will be very liable to
crack or break off when quenched. As it is necessary
to heat slowly in order to get uniform heats, the piece
would be liable to oxidation on its outer surface, which
is exposed to action of the products of combustion in

19a

Cooling in vertical position.

the fire and the air, if heated in an open fire. If small,
it may be heated in a tube ; if too large for this, it may
be covered with the carbonaceous paste described in
section on Methods of Heating. When the article has

Th« Derry CoUard Co.

Figure 105. A grooved roll.

reached the desired uniform heat, it should be plunged
in the bath in a vertical position. On account of the
peculiar shape of the piece and the tendency of the
steam generated, the contents of the bath should be
agitated from the outside toward the center of the bath.

A method that gives very excellent results when
hardening articles of this description is to use a bath
having pipes coming up at the sides of the tank, as
shown in Fig. io6. There should be a sufficient number
of openings in these pipes to supply a generous quantity
of water in order to produce the desired result. The
water should be under sufficient pressure to project the
contents of the bath against the piece being hardened,
with enough force to drive the steam away, so the
water can readily come in contact with the heated
surface.

If the pieces are short and not too large, they may
be heated in red-hot cyanide, dipping in a bath of the
form described.

If it is not necessary to harden very deeply, the

193

Hardening bath for grooved rolls.

article may be removed from the bath when hardened
sufficiently and placed in a tank of oil, leaving them in
the oil until the steel is uniformly cooled to the tem-

a

Q

W///////M

Pump

Q

The Derry CoUard Co.

Figure io6. Bath for hardening grooved rolls.

perature of the oil. It is extremely important when
hardening pieces of this description that they be
reheated as soon as possible after removing from the
bath to overcome the tendency to crack from internal
strains. The longer they remain under strain, the

194

Hardening the walls of holes.

more likely they are to crack later without any apparent
cause. Every mechanic can recall cases of this kind.

Hardening the Walls of Holes.

A peculiarity of a cylindrical piece of steel is that,
when hardened, it is liable to become oval in shape.
This is especially true of pieces having holes running
through their centers, as shown in Fig. 107. When it

is possible, or is
considered advis-
able to grind the
piece inside and
outside after hard-
Figure 107. Piece with hole through center. f^^^^' ^^® amOUUt

it goes out of shape
need not in any way interfere with the utility of the
tool, provided there has been a sufficient allowance of
stock made for grinding.

If, however, there
is no means at hand
for grinding the piece
after hardening, it be-
comes necessary to
harden in a manner
that does away with
the tendency of the
piece going out of
shape or the hole con-

Figure 108. Gauge with hole
through center.

tracting very appreciably. This may be accomplished
in the case of such articles as ring gauges, reducing

«95

No

necessity to "season

for

year.

Figure 109.
Method of

cooling
ring gauges.

dies, and any tools which do not require hardening
on their outer circumference, if proper care is taken.

When gauges of this description (as shown in Fig.
108) are hardened by the ordinary methods, it is neces-
sary to rough-grind them to within a few thousandths

of an inch of finish size and
lay them away to "season"
or "age." After laying for
a few months or a year, they
are finished to size by grind-
ing and lapping. It is not
necessary to observe this
precaution except in the case
of gauges that are to be used
in making very accurate meas-
urements.

Now, it is not always de-
sirable to wait a
year after a piece
of work is hard-
ened before
grinding to size
and using. In
order to o v e r -
come the tend-
ency of altera-
tion of sizes and
shapes as the piece ages, it may be hardened in a
manner that gives the walls of the hole sufficient
hardness to resist wear, yet leaving the circumfer-
ence soft. This can be accomplished by heating
the piece very carefully to the required heat and
placing in a hole a trifle larger than the outside of the

196

mii

How to close a worn die.

piece. Now place a piece of metal having a hole some-
what larger than the hole in the gauge on top of the
piece, as shown in Fig. 109. A stream of water may
now be turned on in such a manner as to readily pass
through the hole, thus cooling the walls and hardening
them. The balance of the stock, being protected, does
not harden. The walls of the hole being hard and in-
flexible do not yield as the piece grows cold. And as
the outside portion of the piece is hot and yielding, it
does not necessarily contract in the direction of the
hole, thus reducing the tendency of alteration of size
of the hole.

Dies used for re-
ducing the size of
gun cartridges. Fig.
no, and similar

pieces.

are hardened

Figure no. Die for reducing cartridges.

by this method, and
give excellent re-
sults, because the
outside, being soft,
v\rill have no tend-

ency to break from the pressure exerted when the
die is in use.

As there is very little tendency of alteration of size
and shape of the hole, it can be lapped to size without
grinding. In case it is not to be ground, there need
be but a small allowance for lapping, provided the hole
is smooth and straight.

As is customary when dies of this description be-
come worn, they may be closed by heating red-hot and
being driven into a taper hole. This diminishes the size
of the hole in the die, which may then be reamed to size

197

Hardening where holes are near edge.

and rehardened. In order to get good results, it is ad-
visable to anneal the steel after closing in, or the mole-
cules of steel will not assume their proper relations
when hardened.

Articles with Holes Near One Edge.

When hardening articles having holes near the edge,
extreme care must be observed, as the unequal con-
traction occasioned by the form of the piece will make
it very liable to crack. A piece of the form shown in

Fig. Ill, represents an
example of the form
mentioned. While
such a piece could be
hardened by the pack-
hardening process
with no liability of its
cracking if it were
quenched in a bath of

Rgurc III. Piece with hole near edge, ^-^^ j^ ^^^^^ ^^^ ^^^^^^

be considered advisable to use this method, so it be-
comes necessary to heat the article in some form of fire,
and quench in water.

The piece should be heated very carefully and no
hotter than is necessary to accomplish the desired re-
sult. It will be necessary to use the utmost care in
heating, because if the thin portion of stock between
the hole and the circumference of the ring were heated
any hotter than the balance of the piece, it would
surely crack at this point.

When dipping in the bath, the heavy portion should
198

How to cool pieces with holes near edge.

enter the bath first, the thin portion should be upper-
most in order that it may enter last.

If it is not essential that the walls of the hole be
hard, it may be filled with fire clay, previous to placing
in the fire. If treated according to this method, the
danger of cracking is reduced to the minimum.

A method employed very successfully in some shops
when hardening articles of this description, consists in

Figure 112. Method for

holding piece with

hole near edge.

7

bending a piece of wire in the form of a hook. This
hook is heated red hot on the bent end, and when the
article is at a uniform heat, the red hot end of the hook
is inserted in the hole near the edge, as shown in
Fig. 112, and the article immersed in the bath. The
heavy portion will, of course, enter the bath first, the
wire being red-hot will prevent the thin portion cooling
as rapidly as it otherwise would. The size of the wire
must be determined experimentally; that is, if many
pieces are to be hardened, the size of wire that gives
best results should be used, but in no case should it
fill the hole when the pieces are cold.

The bath should be warmed somewhat in order to
reduce liability of cracking.

Wood -Working Tools.

There are many methods used in hardening tools
used for cutting wood, the different methods varying

199

Hardening wood-working tools.

according to the nature of the steel used and the use to
which the tool is to be put when finished. The more
common method is to heat in an open fire and plunge
in water, drawing the temper until the brittleness is
reduced to a point that makes it possible for the tool
to stand up when in use. By this method, it is neces-
sary to draw the temper quite low in order to get a de-
gree of toughness that enables the tool to stand up well.

A method that is practiced in many shops is to heat
in a muffle furnace or in a tube, hardening in a bath
of water having oil on its surface, as shown in Fig. 82,
the depth of oil depending on the desired amount of
hardness. Some hardeners claim to be able to gauge
the amount of hardness by the depth of oil to a nicety,
that makes it unnecessary to draw the temper after
hardening. The writer cannot vouch for this claim,
as he has never seen it done when hardening wood-
working tools, but has been able to accomplish it when
certain kinds of iron-working tools were hardened.

Another method consists in heating the tool in a
crucible of red-hot lead, or in a crucible of red-hot
cyanide of potassium, dipping in a bath of oil, to which
has been added a quantity of alum. The exact amount
cannot be stated, as he has found it to vary when
applied to hardening steels of various percentages of
carbon. The use to which the tool is to be put when
hardened, has a great deal to do with the composition
of the bath.

As brittleness is not a desirable quality in wood-
working tools, it is necessary to harden in a manner that
insures toughness in the hardened product. For this
reason it is not advisable to use a bath of cold liquid
of any kind.

Mixture for hardening wood-working tools.

If the cutters are light on the cutting portions, the
bath may be heated considerably, the temperature de-
pending on the shape and size of the tool and the steel
used in its construction.

Various animal or vegetable oils are used for quench-
ing tools of this description, either separately or mixed
with varying proportions of tallow. Melted tallow is
many times used with success, heated to a temperature
that gives good results when applied to the individual
piece of work. The amount necessary to draw the
temper depends on circumstances and can not be arbi-
trarily stated, but it is generally found to be between
a brown and a dark blue color.

A method employed in some shops when hardening
wood cutting tools consists in heating to a low red
and plunging in a mixture of molten lead and tin in
the following proportions : Lead, 7 parts ; tin, 4 parts,
which melts at about 440° Fahr.

The cutters are heated to a low red and plunged in
this mixture at the temperature mentioned, allowed to
cool for a short time, then removed and cooled in water.
They will be found to be exceedingly tough, and capa-
ble of holding their edge in a satisfactory manner.

Unless this method is used in a painstaking manner,
it had better not be tried, as anything but satisfactory
results will follow.

If many cutters are to be hardened, it will be found
necessary to gauge the heat of the bath by use of a
thermometer.

Fixtures for Use in Hardening.

In order to attain certain results, it is necessary at
times to make fixtures for holding the work. These

An example of hardening fixtures.

fixtures are designed to protect certain portions of the
piece of work from the action of the contents of the
bath.

The writer was at one time in charge of work in a

]

The Derry Collard Co.
Figure 113. A hard piece to harden.

shop manntacturing bicycles. In order to accomplish
a desired object, the axle cones, which had formerly
been made of machinery steel, were made from a high
grade of tool steel. The front axle cone was of the

^

The Derry Collard Co.

Figure 114. Device for hardening piece shown in Figure 113.

shape shown in Fig. 113. It was necessary to harden
the beveled portion extremely hard, in order to resist
wear. It was found very difficult to harden this
portion without hardening the flange. If this were
hardened, it showed a tendency to break when in the
wheel, as it was very thin.

In order to harden the bevel and leave the flange

The Genesis of pack hardening.

soft, a fixture was made, as shown in Fig. 114. The
cone was heated in a crucible of red-hot lead. When
it reached the desired temperature, the cover of the
fixture was raised and the cone taken from the lead by-
means of a wire hook made for the purpose. It
was placed in the fixture, as shown, the cover lowered,
and the fixture immersed in a bath of water, working
it around well until the cone was cold, when the fixture
was inverted over a tank of boiling water, and the cone
dropping into this and remained until a sufficient
quantity was in the catch pan. Fig. 45, to warrant
emptying it. This tank was found very valuable, as
it furnished a means whereby the strains incident to
hardening could be removed, and at the same time the
temper was drawn sufficiently.

Pack Hardening.

When articles which are small or tkln are heated to
a red and plunged in oil, they become hard enough for
most purposes, but not as hard as if immersed in water.
Articles hardened in oil seldom crack from the effects
of cooling, as the heat is not absorbed as quickly as if
water were used, neither are they as likely to spring.

The fact that articles quenched in oil showed no
tendency to crack, and very little liability to spring,
has led the writer to make exhaustive experiments in
perfecting a method whereby articles which gave
trouble when hardened by ordinary methods might be

Pack hardening prevents cracking.

hardened in oil and produce a surface as hard as if it
were heated red-hot and plunged in water. The re-
sults have been more gratifying than were ever dream-
ed of before trying. It is not claimed that this method
was originated by the writer. It was suggested by a
man in his employ, who had seen it practiced with
varying results in a shop where he formerly worked.

The fact that milling machine cutters, punch press
dies, and similar articles, could be treated in such a
manner that they might be hardened in oil without
danger of cracking, led to experimenting, which re-
sulted in a method whereby tools could be hardened
with absolutely no danger of cracking. The tendency
to spring was also reduced to the minimum. Unexpected
results were accomplished in some ways, for it was
found by experience that milling machine cutters could
be run at a periphery speed, two, and in some cases four,
times as great as when a similar cutter made from the
same bar was heated red-hot and plunged in water.
Punch press blanking dies would do from six to ten
times the amount of work as when hardened by meth-
ods formerly used.

It was also found extremely satisfactory when ap-
plied to taps and screw thread dies, because the tendency
to alteration of pitch was reduced to the least possible
amount. Neither would they change so far as diametri-
cal measurements were concerned. Gauges hardened
by this method gave results fully as satisfactory as other
articles hardened in a similar manner. Long reamers,
stay-bolt taps, and similar tools, have been hardened
by the thousands and shown results more than satis-
factory.

Tool steel is made with a sufficient quantity of

ao4

Never use bone in pack hardening.

carbon to harden in a satisfactory manner and accom-
plish the results intended when the tool is made. To
make steel with a higher percentage of this hardening
element, and put it on the market, would be folly, as
the average man hardening steel would treat it the
same as the ordinary tempers are treated, with the re-
sult that the tools made from it would be ruined when
hardened.

Now, tool steel may be treated with carbonaceous
materials when red-hot, with the result that the sur-
faces will be extremely hard if the article is quenched
in oil. The depth of the hardened surface depends on
the length of time the article is subjected to the car-
bonizing element. In order to accomplish the desired
result, the piece of work must be packed in a hardening
box with the carbonaceous material; the top must be
closed with a cover slightly smaller than the opening
in the box, and the space between the cover and sides
of the box covered with fire-clay. This operation is
familiarly known as sealing. Sealing the box has the
effect of preventing the gases escaping. It also pre-
vents the direct heat of the fire from entering the box,
as that would be very injurious to the steel. Then
again, the oxygen in the air is excluded from the box,
or, if present in a degree, does not oxydize the surface
of the piece, as it is taken up by the packing materials
in the box.

It is very necessary when charging steel by the
process under consideration, that a carbonizing ma-
terial be used which contains no elements injurious to
tool steel. For this reason no form of bone should
ever be used, as bone contains a very high percentage
of phosphorus, and phosphorus, when present in tool

205

About boxes for pack hardening.

steel, has the effect of making it extremely brittle. The
processes the steel maker puts the steel through in
order to remove injurious impurities is one reason of
its high cost as compared with the ordinary cheap
grades of steel. The lower the percentage of phos-
phorus, the more carbon it is safe to have in the steel ;
so it will readily be seen that any process which results
in an addition of this harmful impurity should never
be used. The writer has used a mixture of equal parts,
by measure, of granulated charcoal and granulated
charred leather in most of his work for the past nine or
ten years with the best results ; although in exceptional
cases, where extreme hardness was desired, charred
leather alone was used.

The work is packed in a hardening box. This box
may be either wrought iron or cast iron. Best results
are claimed by some when wrought iron boxes are used.
But the writer has never in practice been able to notice
any difference, so he has used cast iron boxes altogether
for the past eight years, as they are cheaper and more
readily obtained. The work should be placed in the
box in a manner that does not allow any of the pieces
to come within i }^ inches of the bottom or top of the
box, or within 1% to i^ inches of the sides or ends, for
two reasons. If they are placed too near the walls of
the box, they are affected by every change of tempera-
ture in the furnace. Then again, cast iron has a great
affinity for carbon, and will extract it from a piece of
tool steel if it comes in contact with it. If one end of
an article, packed as described, comes in contact with
the walls of the box, the piece will not harden at that
point, or, if it does, it will not be as hard as the balance
of the piece. And, as a chain is no stronger than its

»o6

How to pack for hardening.

weakest link, so a hardened tool is no better than its
softest spot, provided it is on any cutting- portion, be-
cause, when that dulls, the whole tool must be ground.

This method of pack hardening is not only a means
of getting good results, but when work is hardened in
large quantities, it is a much cheaper method than that
ordinarily used, because quite a number of pieces may
be packed in the box at a time. Or, if the furnace used
is of sufficient capacity, several boxes may be heated at
the same time.

When packing work in the hardening box, place
about i>^ inches of packing material in the bottom, then
lay a row of work on this, being careful that no pieces
come within ^ inch of each other, or within i Yz inches
of the walls of the box. Cover this row of work with
packing material to the depth of ^ inch, put in another
row of work, and continue in this way until within i %
inches of the top of the box. After covering each row
of work with the packing material, it should be tamped
down lightly to insure its staying in place. When the
box is filled to within the distance of top mentioned
(i}^ inches), the balance should be filled with packing
material, the cover put in place and sealed with fire-
clay mixed with water to the consistency of dough,
and allowed to dry before placing in the furnace.

Before the articles are packed in the box, a piece of
iron binding-wire should be attached to each piece of
work in such a manner that the article may be removed
from the box and dipped in the bath by this means,
unless the piece is too heavy to be handled in this man-
ner, in which case it must be grasped with a pair of
tongs. The wires should extend up the sides to the
top of the box and hang over the edge, in order

ao7

Figure 115. The wrong way to
pack harden.

Pack boxes with similar articles.

that the operator may readily see them when removing

the articles from the box. If several rows of work are

placed in the box, it is necessary to place the wires in

a manner that allows the different rows to be readily

distinguished. As it is necessary to draw the pieces on

the top row first, each succeeding row should be drawn

in its order, because if an article were drawn from the

bottom row first, it would probably draw one or more

of the pieces located above along with it. As a conse-

quence they

would lay on

the top of the

box exposed to

the action of the

air, and would

cool perceptibly

while the first

piece was being

quenched in the

bath. For this reason it is advisable to draw the

pieces in the top row first, as described.

As the length of time a piece of steel is exposed to
the carbonaceous packing material after it is red-hot
determines the depth of hardening, articles packed in
a box should all be of a character that need carbonizing
alike, or some pieces will not receive a sufficient depth
of carbonizing and others will receive too much. Know-
ing this, one may select the articles accordingly, pack-
ing those requiring charging for one hour in one box,
those requiring two hours in another, and so on. A
little experience will teach one the proper length of
time to give a tool of a certain size to accomplish a
given result.

The Derry-Collard Co.

ao8

Boxes for pack hardening.

Attention must be paid to the shape of the piece
when packing in the box. If it is long and slender, it
should not be packed in such a manner that it will be
necessary to draw it through the packing material, as
shown in Fig. 115, or it will surely spring from doing
so, it being red-hot, and consequently easily bent. If
but a few pieces of this character are to be hardened,
it would not be advisable to procure a box especially

Figure Ii6. Box for pack hardening.

adapted to it. In that case the articles could be packed
two or three in a box. When they have run the proper
length of time, the box should be removed from the
furnace, turned bottom side up on the floor, provided
the floor is of some material that will not catch fire.
The piece of work may be pulled out lengthwise from
the mass, and in that way all danger of springing is
done away with.

If, however, quite a number of pieces are to be
hardened, it is advisable to procure a box adapted to
pieces of this description. This may be done by adopt-
ing a design opening at the end, as shown in Fig. n6.
This may stand on end with the opening uppermost
while packing the pieces. If a furnace of the design

209

How to tell when heated.

shown in Fig. 1 1 7 is available, it should be used, as the
box can stand on end. If this form of furnace is not
at hand, the box may be placed on its side in any fur-
nace large enough to receive it. If necessary to use a
furnace where the box must lay on its side, it will be
advisable to provide some way of fastening the cover
in place. This may be done
by drilling a j^ inch hole on
opposite sides of the box and
running a rod at least -jV of
an inch smaller than the hole
across the face of the cover,
Fig. 118, before sealing with
fire-clay. This rod can easily
be removed when the articles
are ready for immersion in
the bath.

In order that the exact
time at which the work be-
comes red-hot may be ascer-
tained, it will be necessary
to use test wires. Several %
inch holes may be drilled
near the center of the
cover, a -f^ inch wire
run through each of
these holes to the bot-
tom of the box, as

The Derry Collard Co.

Figure 117. Furnace for use in
pack hardening.

shown in Fig. 26. When
the work has been in
the furnace for a sufficient length of time to become
heated through, according to the judgment of the
. operator, one of the test wires may be drawn and its

The length of time work should be run.

condition noted. If it shows red-hot the entire length,
note the time. If not, wait a few minutes (say, 15
minutes) and draw another wire. When one is drawn
that shows the proper temperature, time from this.
The length of time the pieces should be run cannot

The Derry Colliwd Co.

Figure 118. Method of fastening cover in place.

be Stated arbitrarily, as the character of the work to be
done by the tool must, in a measure, determine this.
However, if the pieces are ^ inch diameter, and are to
cut a soft grade of machinery steel, one hour may be
found sufficient. If a harder surface is required, it is
necessary to run somewhat longer (say, 1% hours).
When the work has run the required length of time, the
box may be removed, the cover taken off, and the ar-
ticles taken out one at a time and dipped in a bath of
raw linseed oil. When the articles are long, it is ad-
visable, if possible, to use a bath having a perforated
pipe extending up two opposite sides of the tank, as
shown in Fig. 119. A pump should be connected with
the oil in the bath, pumping it through a coil of pipe
in a tank of water and forcing back into the tub through
the upright perforated pipes shown. This method
insures evenly hardened surfaces, as the jets of oil
forced against the sides of the article drive the vapors
away from the piece, thus insuring its hardening. It
is necessary to move the work up and down and to turn

How to treat milling cutters.

it quarter way around occasionally in order to present
all sides to the action of the oil.

When milling machine cutters, or similar tools
having projections, are to be hardened by this method,
they should be packed in the box, using the packing

Figure 119. Bath for use in
pack hardening.

Tbe Deny Collard Co.

material mentioned. Previous to placing the cutters
in the hardening box, a piece of iron binding- wire should
be attached to each cutter and allowed to project over
the edge of the box. Test wires should be run down
through the holes in the cover, as shown in Fig. 26.
The length of time the cutters should run is determin-
ed by the character of the work they are to do ; but for

Milling cutters needing no tempering.

ordinary milling, a cutter 3 inches diameter, if of the
ordinary design, should run about 3 hours.

If the teeth are heavy, of the style known as form-
ed mills, Fig. 120, they should be run 4 hours after they
are red-hot. When the box is removed from the fur-
nace, the cutters may be removed one at a time, placed
on a bent wire of the form shown in Fig. 81, and im-
mersed in the oil, working them around well until all
trace of red has disappeared, when they may be dropped
to the bottom of the bath and left until cold.

A milling machine cutter of the form shown in Fig.
120 will not as a rule require tem-
pering. The teeth may be left
as hard as they come from the
bath, but those of the ordinary
form of tooth should have the tem-
per drawn. This may be done by
the method described under Hard-
ening and Tempering Milling
Machine Cutters, or, if there are

. . The Derry ColUrd Co.

many cutters, a savmg of time

will result if the articles are igure 12,0. orme

-1 • -I 1 f '^ 11 milling cutter.

placed m a kettle of oil and the

temperature gauged by a thermometer, drawing them

to 430 degrees.

Punch press blanking dies give excellent satisfac-
tion if hardened in this manner. The die is packed in
a box. Test wires are run down through the opening
in the die to the bottom of the box. "When drawing the
wires to test the heat, do not draw them way through
the cover. After observing the heat, place the wire
back in its original position. A wire can be raised from
time to time, the amount of heat observed and the wir^

213

Treatment of blanking dies.

returned. In this way the operator can tell from time to
time the exact temperature of the piece being heated,
and as the same laws governing the heating of steel in
the open fire apply when heating to harden by this
method, it is advisable to keep the heats as low as pos-
sible ; for steel treated by this method will harden in
oil at a lower heat than if treated in the ordinary way
and hardened in water.

Blanking dies for the class of work usually done
on punch presses (if they are i inch to i j^ inches thick)

Figure 121. Bath for
blanking dies.

vx/i>)<;>./^y/yyyyx^z^xy^^^y^yyy^///yy/x^^^^^

Tlie Perry Collard Co.

should run about four hours after they are red-hot.
At the expiration of that time the box may be removed
from the furnace, the die grasped by one end with a
pair of tongs and immersed endwise down into a bath
of raw linseed oil. It is a good plan to have the bath
rigged as shown in Fig. 121. A pipe is connected with
the tank near the top, and runs in a coil through a tank
of water. A pump draws the oil from the tank through
the coil, and forces it back into the bath, as represented.

214

Handling of dies and taps.

The inlet pipe may be so situated as to cause the oil to
circulate with considerable force through the bath. This,
striking the face
of the die, passes
through the
opening, insures
good results. If
no means are pro-
vided for the cir-
culation of the
oil, the die may-
be swung back
and forth in the
oil, and it will
harden in a satis-
factory manner.
Forming and
bending dies, if
hardened by this

The Derry Collard Co.

Figure 1 22. One method of packmg
snap gauges.

method, must be run longer, and heated somewhat
hotter, yet not hot enough to injure the steel.

Pack hardening fur-
nishes a method
whereby taps may be
hardened without
altering the pitch very
perceptibly; neither
will the diametrical
measurements be
changed, provided the
blanks were annealed after blocking out to shape, and
by this method the teeth are made exceedingly hard
without being brittle. A tap from one to two inches

Figure 123.

Another method of packing
snap gauges.

215

Pack hardening for gauges.

in diameter should be run about two hours. It should
be worked around rapidly in the bath, in order that the
teeth may be hardened. For general machine shop
work, taps do not require the temper drawn as low
as if they were hardened by heating red-hot and
plunging in water. Generally speaking, 430 degrees
(a faint straw color) is sufficient, provided a low heat
was maintained in the furnace.

This is an ideal method of hardening gauges and
similar work, as the liability of cracking is eliminated
and the danger of springing is reduced to the minimum.
If the gauge is of the plug or ring form, it is not neces-
sary to allow as great an amount for grinding as would
otherwise be the case, as there is little danger of
springing.

When hardening snap gauges, especially if they
are long, it is advisable to pack as represented in Fig.
122, provided a box deep enough is at hand. If obliged
to pack in a box so that the gauges lay lengthwise in
the box, they should be so placed as to have the edges
up and down, as shown in Fig. 123, thus doing away
with the tendency to spring when they are drawn
through the packing material.

Articles of a form which betokens trouble when
hardening can, if proper precautions are taken, be
hardened by this method in a very satisfactory manner.
Take, for instance, the shaft shown in Fig. 124. This
was made of ^ per cent, carbon crucible steel, and turned
within a few thousandths of an inch of finish size. It
was packed in a mixture of charred leather and char-
coal, and subjected to heat for i^ hours after it was
red-hot. It was then dipped in a bath of raw linseed
oil, heated to a temperature of 90°. It was found

zi6

Treating difficult subjects.

upon being tested between centers to run nearly-
true.

The designer does not always take into consideration
the difficulties which may be encountered when a piece
of irregular contour is hardened, consequently we some-
times run across articles which call for serious study
on the part of the hardener when the article reaches
him. Then again, such articles are many times made

The Derry Collard Co.

Figure 124, A peculiar piece to harden.

of a high carbon tool steel, when a low grade steel would
answer the purpose as well, and not cause nearly as
much trouble.

At one time the writer was called to a shop where
they were experiencing all kinds of trouble in an attempt
to harden a gauge of the description shown in Fig. 125.
As it was not practical to grind the interior of this gauge
with a grinding machine, it was necessary that it should
retain its shape when hardened. In order to accom-
plish this, the gauge was surrounded with a mixture of
fire-clay, to which was added sufficient hair (obtained
from a plasterer) to hold it together. It was moistened
with water to the consistency of dough. The hole in th e
gauge was filled with finely granulated charred leather.

It was then placed in a small hardening box, in the
bottom of which was placed 2 inches of granulated wood

ai7

How the "teaser" was hardened.

charcoal. The box was filled with charcoal, the cover
placed in position, and sealed with fire-clay.

The box was subjected to heat for one hour after
the contents were red-hot, this being ascertained by
means of the test wires, as described. The gauge was

then taken from

the box, the leather
removed from the
hole, and a jet of
raw linseed oil

Figure 125.

A "teaser" for

hardening.

TheDerry CoUard Co.

forced through the hole until the piece had cooled off.
The walls of the hole were very hard, and the gauge
was found by test to have retained its shape. The
coating of fire-clay prevented the exterior hardening
of the piece, thereby eliminating the tendency to
spring or go out of shape. The walls of the hole,
hardening first, retained their shape, and the balance,
being red-hot, conformed to this portion.

While it would be impossible to enumerate the
various articles of irregular contour that may be hard-
ened by applying this principle — namely, protecting
the portions that do not require hardening, by the use
of a mixture of fire-clay and water, adding sufficient
hair to hold it together — it can safely be said that many
thousand dollars' worth of tools are ruined annually,
which might have been saved had this precaution been
observed.

zi8

Pack hardening for mandrels and arbors.

As this process of charging the surface of the steel
with carbon is a process of cementation, it is necessarily-
slow. When extremely high carbon steel is used in
making tools, it is considered advisable by some to use
hoofs and horns as packing material rather than leather.
At times it is not considered desirable to subject
the articles to heat for so great a length of time. In
such cases it is necessary to treat the surfaces to be
hardened with some material that will act more quickly
than charred leather. In fact, at times it is necessary
to prevent any portion other than the ones to be hard-
ened from becoming red-hot.

This can be effected by covering the parts with the
fire-clay mixture to a considerable depth, applying heat
to the portions that need hardening. When it is not
desirable to subject the article to heat for a length of
time sufficient to charge the steel with the necessary
amount of carbon to cause it to harden (if it was to be
carbonized by means of charred leather), excellent re-
sults may be had by the use of a mixture of 5 parts of
rye flour, 5 parts table salt, 2 parts yellow prussiate of
potash, filling the hole or covering the portions to be
hardened with this.

Mandrels, or any form of arbor which it is consid-
ered advisable to harden, will harden in a more satis-
factory manner by this method than by any that has
come to the writer's notice. If the article is long and
slender, do not pack in the box in such a manner that
they will spring when drawn out ; but if the shape of
the box is such that this cannot be avoided, the box
may be turned bottom side up on the floor when the
articles are ready for hardening, as previously explained.
If, however, the mandrels are made of the proportions

119

How to dip mandrels and arbors.

tisually observed when making for general shop usd,
there is very little liability of springing when drawing
them through the packing material. The mandrel may
be wired as represented in Fig. 126, or it may
be grasped with a pair of tongs of a form that
allows the contents of the bath to have ready
access to the end of piece ; but as tongs of this
form are not in general use, the wires will
answer unless the pieces are very heavy. In
this case it is advisable to procure tongs of
a suitable shape rather than to have an un-
satisfactory article when it is finished. As
stated under Examples of Hardening, it is
never advisable to hold a mandrel with any
form of tongs that in any way interfere with
the hardening of the walls of centers in the
ends of a mandrel.

If the work is wired, it should be done
in a manner that makes it possible to dip
the mandrel in the bath in a vertical position,
to avoid any tendency to spring. The wires
may be grasped by means of tongs which
close together very nicely, as shown in Fig.
126, in order that they may not lose their
grip and the piece fall to the bottom of the
bath before the red had disappeared from
the surface. It should be worked up and
down in the oil until all trace of red has
disappeared, when it may be lowered to the bottom
and left until cooled to the temperature of the bath.

Circular forming tools, especially those having
long, slender projections and sharp comers, as shown
in Fig. 127, are safely hardened by this process, as they

n r

Stay-bolt taps and the like.

can be given any degree of hardness desirable without
making them brittle. Being solid in form, they must
be heated for a longer period of time than if there were
teeth on the surface — as a milling machine cutter. As
with other cutting tools, the length of time a tool of
this form should be subjected to heat depends on the

nature of work to
be performed by
it. A tool 4 inches
in diameter and 2
inches wide for
ordinary work
should run about
4 hours after it is
red-hot. If there
are slender projec-
tions from the face of the tool, it will be found
necessary to draw the temper somewhat ; but as a rule
it should not be drawn as low as if it were hard-
ened by the methods ordinarily employed.

The writer has in mind a forming tool of the
same general outline as the one represented in Fig. 127,
which gave excellent results when drawn to 350 degrees
after hardening by the method under consideration.
It was hard enough to stand up in good shape, and yet
tough enough to stand very severe usage.

If the formed surface is of a shape that insures
strength — that is, if there are no projections — the cut-
ter should be left as hard as when it comes from the
bath.

Stay-bolt taps and similar tools may be packed in
a box of the proper shape and run for a length of time,
depending on the size of the piece. They should then

Tlw Derry Collard Co,

Figure 127. A forming tool.

221

Precautions to be taken on large work.

be taken one at a time and immersed in a bath of raw
linseed oil and worked up and down in a vertical man-
ner, moving to different parts of the bath, unless there
is a jet of oil coming up from the bottom. Or, better
still, having perforated pipes coming up the sides of
the bath, as represented in Fig. 119. In either case it
is advisable to work the articles up and down, to avoid
the vapors which always have a tendency to keep the
contents of the bath from acting on the heated steel.

If the articles are long, a deep tank should be used
for the bath. If the taps are 24 inches long, there
should be a depth of 40 inches of oil. If the articles
are longer, the tank should be proportionally deeper.

A precaution that should always be observed when
hardening large pieces of work, when they are to
be quenched in a bath of oil, consists in protecting the
hands and arms of the operator to prevent burning
from the fire, which results when a piece of red-hot
steel is immersed in oil. This is, of course, simply a
burning of the surface oil as the steel passes through
it, but it is liable to flash high enough to bum the
hands and arms unless they are protected in some
manner.

When hardening long articles, it is found much more
convenient if the tanks containing the cooling liquid
are so located that the tops of the tanks are nearly on
a level with the floor — say 12 or 15 inches above it.

The toolmaker should, when making adjustable
taps, reamers, etc., of the description shown in Fig. 128,
leave a portion on the end solid, as shown in Fig. 129,
to prevent the tool springing out of shape. The hole
for the adjusting rod should be filled with fire-clay,
the article packed with the mixture of charcoal and

How to harden an adjustable reamer.

charred leather, and subjected to a very low red heat,
and dipped in raw linseed oil, warmed to about 90
degrees Fahr. The length of time it should be sub-
jected to heat after it is red-hot depends on the size,

§

Figure 129

of reamer.

The Derry CoUard Co.

Solid portion

Figure 128. An adjustable reamer.

quality of steel used, and the work it is to do. It
will vary from i to 2^ hours. The temper may be
drawn to a light straw or a full straw color. The
shank, and ends of flutes nearest the shank, should be
drawn to a blue. When drawing the temper, the
reamer or tap may be placed
in a kettle of oil heated to
the proper degree for the
cutting edges. The shank
may be drawn lower in a
flame, or heat may be ap-
plied at the shank end by
means of a flame from a gas jet, Bunsen burner, or
any other means, allowing the heat to run toward the
cutting end. After the reamer has been hardened and
ground to size, the extreme end may be ground off
enough to allow the slots to extend to the end.

Dies used for swaging tubing are a source of an-
noyance when hardened by methods usually employed,
as the unequal sizes of the different portions cause
them to spring out of shape, and their shape is such
that it is next to impossible to grind them in a manner
that insures satisfaction when they are used.

Pack hardening furnishes a method whereby this

aa3

Box for heating swaging dies.

class of work can be made hard enougli to do the work
required of them, and they do not alter in shape enough
to require grinding. For this reason the extremely
hard surface, which comes in contact with the contents
of the bath, need not be removed by grinding.

When making swaging dies of the description
mentioned, best results will follow if they are made of
tool steel of i^ to I }4^ per cent, carbon. . Block to shape,
anneal thoroughly, and finish to size. When harden-
ing, the dies should be wired and packed in a box,
as shown in Fig. 130, placing charred leather all
around the die for a distance of % inch to i inch. The
balance of the box
may be filled with ^^^ ^'^"'"^ ^3°-

packing mixture ^8\i Box for hardening

that has previously 1 V* swaging dies. ^v

been used. Run

for about 4 hours

after they have

reached a medium

red heat. It is

necessary to give

articles of this description a trifle higher heat than

if hardening cutting tools made from the same stock.

As hardness is the required quality, the dies should
be left as hard as when taken from the bath, which
should be raw linseed oil at a temperature of about 60
degrees Fahr.

A careful study of the pack hardening method
will help every one handling steel. It often makes
possible the use of lower grade steels, and it enables
pieces to be made of any desired shape with the knowl-
edge that they can be hardened without cracking.

Tke Derry Collard Co.

224

Case Hardening,

6--^=^ .^=^=^>©

CO

When wrought iron or machinery steel — especially
the latter — will answer the purpose as well as tool steel,
they are generally used. The first cost is less, and it
can be machined much more cheaply, and in many cases
it is better adapted to the purpose.

Machinery steel is made by two entirely different
processes, namely: the Open Hearth and the Bessemer
processes. Each method produces steel adapted to
certain classes of work. There are many grades of
steel made by each of these processes, these being de-
termined by the amount of carbon or other elements
present in the steel. Machinery steel is not only valu-
able to the manufacturer on account of its low first cost,
as compared with tool steel, and the ease with which
it may be worked to shape, but it possesses the quality
of toughness, and is not so susceptible to crystalliza-
tion from the action of shocks and blows. A very
valuable feature is, that by subjecting it to certain
processes, the surface may be made extremely hard,
while the interior of the steel will be in its normal
condition, thereby enabling it to resist frictional wear
and yet possess the quality of toughness.

The hardening of surfaces of articles made of
wrought iron and machinery steel is generally termed

225

Case hardening a few pieces.

**case hardening," and consists in first converting the
surface of the article to steel, then hardening this steel
surface. In order to convert the surface to steel, it is
necessary to heat the piece red-hot, then treat it while
hot with some substance which furnishes the necessary-
quality to cause the steel to harden when plunged in a
cooling bath.

Most machine shops have some means whereby
they can harden screws, nuts and similar articles.
Where there is only a limited .number of pieces to
harden, it is customary to heat the work in a black-
smith's forge, in a gas jet, or in any place where a red
heat can be given the piece. When hot, sprinkle with
a little granulated cyanide of potassium, or some yel-
low prussiate of potash, or a mixture of prussiate of
potash, sal ammoniac and salt. If cyanide of potassium
is used, it is advisable to procure the chemically pure
article, as much better results may be obtained. The
reader should bear in mind that this is a violent poison.
Re-heat to a red and plunge in clear, cold water. When
there are large quantities of work to harden, this is an
expensive as well as a very unsatisfactory way. To
case harden properly, one must understand the ma-
terial of which the article is made and the purpose for
which it is to be used — whether it is simply to resist
friction or wear, or to resist sharp or heavy blows, a
bending or twisting strain, or whether it is merely de-
sired to produce certain colors.

We will first consider the case hardening of work
that simply needs a hard surface, with nothing else to
be taken into consideration. Pack the articles in an
iron box made for this purpose, as shown in Fig. 131.
The size and shape of the box used depend, as a rule,

226

Case hardening in a gas pipe.

on what can be found in the shop. But when results
are to be taken into consideration, it is advisable to
procure boxes adapted to the pieces to be hardened.
It is not policy to pack a number of small pieces,
which do not require a deeply hardened portion, in a
large box, especially if it is desirable to have a uni-
formity in the hardened product, as the pieces which

Figure 131. Box for case hardening.

are near the walls of the box will become red-hot long
before those in the center. And as steel or iron
absorbs carbon only when red-hot, the pieces nearest
the outside would be hardened to a greater depth
than those near the center of the box.

For small articles, where but a few pieces are to
be hardened at a time, a piece of gas-pipe may be used.
Screw a cap solidly on one end or plug the end with a
piece of iron, using a pin to hold it in place. The
outer end may be closed by means of a piece made in
the form of a cap to go over the end, or it may be a
loose-fitting plug held in place by a pin, as shown in
Fig. n8. When a hardening box of the description
shown in Fig. 131 is used, the heat may be gauged
nicely by running test wires through the cover to
bottom of tube, as shown in Fig. 126. Pack the pieces
of work in a mixture of equal parts, by measure, of

az7

How to pack for case hardening.

granulated raw bone and granulated charcoal mixed
thoroughly together. Cover the bottom of the harden-
ing box to a depth oi 1% inches with the mixture,
pack a row of work on this, being sure that the arti-
cles do not come within X ^^ ^ i^^^ of each other,
or within i inch of the walls of the box. Cover this
with the packing material to a depth of half an inch.

Test wire!
Test wire I

QL

The Deny Collard Co.

Figure 132. A method of using test ynttz.

Tamp down, put on another layer, and so continue
until the box is filled to within i inch of the top.
Fill the remaining space with refuse packing material
left over from previous hardenings, if you have it.
If not, fill with charcoal or packing material, tamp
well, put on the cover, and lute the edges with fire-
clay to prevent as much as possible the escape of the
gases. This is necessary, as the carbon is given off
from the packing material in the form of a gas. Then
again, if there are any openings, the direct heat will
penetrate these and act on the work in a manner that
gives unsatisfactory results.

If the articles are so large that they would not cool
below a red heat before reaching the bottom of the bath,
they should be wired, as shown in Fig. 130, before put-

228

Figure 133.

Bath for case hardening

small pieces.

o o
000

To case harden many small pieces.

ting in the hardening box. Use iron binding wire, suf-
ficiently strong to hold the piece when it is worked
around in the bath. If the articles are too heavy for
wiring, we must devise some other way of holding —
either tongs or grappling hooks. If the pieces are
small, they can be dumped directly from the box into
the tank, sifting the work out of the box somewhat
slowly, so that the
articles will not go <^
into the bath in a
body. If the tank
is large enough, it
is a good plan to
have wires across
from side to side,
about 4 inches
apart in horizontal
rows. Have the
rows 3 or 4 inches
apart. Do not put
any two consecu-
tive rows of the wires underneath each other, but in such
a manner that the work will strike the wires as it passes
to the bottom of the tank. In striking these wires, the
work will be separated, and any packing material ad-
hering to it will be loosened by the jar. The work will
also be turned over and over, thus presenting all sides
to the cooling effects of the bath as it passes through.
These wires can be arranged as shown in Fig. 133 by
taking two pieces of sheet metal, a little shorter than the
inside length of the tank, drilling holes in them as de-
scribed in the arrangement of wires, and wires can be
passed through these holes and riveted, thus making a

.-"hS^

W<'<<yMMMWWi<!M \M/WMWWM//W/<^

The Derry Collard Co,

229

Details of tank for hardening small work.

permanent fixture that can be placed in the tank and
taken out at will. The distance the wires are apart can
be varied to accommodate the particular kind of work
that is to be done. They must be far enough apart so
that the work cannot become lodged on them.

This simple device does away with the liability of
soft spots in pieces of work that are case hardened. Do
not have any wires within 8 or lo inches of the bottom
of the tank. Have a coarse screen or a piece of sheet
metal drilled full of holes somewhat smaller than the
piece we are to harden. Block it up about 4 inches
above the bottom, to allow a free circulation of water
underneath it. This also allows the water to pass
through it around the work, and the packing material
will pass through it, giving the water a better chance
to get at the work. The water inlet should be at the
bottom of the tank, and we should have an outlet about
2 inches from the top to allow the surface water to
escape. The cold water coming up from the inlet at
the bottom should be turned on before we dump the
work, allowing it to run until the work is cold. In
heating the work, any form of furnace that will give
the required heat and maintain it evenly for a sufficient
length of time will do.

The cover of the boxes should have several % inch
holes drilled in the center, as shown in Fig. 26. After
putting the cover in place, put pieces of ^ inch wire
through these holes down to the bottom of the boxes,
allowing them to stick up an Inch above the cover, to
enable us to get hold of them with the tongs. The
boxes may now be put in the fire, and subjected to a
heat which should vary according to the character of
the work. The work should be heated to a red, and

230

Unsatisfactory to gauge heat by total time.

for some classes of work it may even be brought to a
bright red. When it is thought that the work has been
in the fire long enough to heat through, draw one of
the wires with a long pair of tongs. If the wire is red
the entire length, time from then. If not, wait a few
minutes and draw another, and so on until one is drawn
that is red the entire length.

The writer considers this the proper method to
employ in timing all work being heated in the fire,
whether it is to be annealed or case hardened, charging
for hardening by the Harveyizing method, or when we
are pack hardening tool steel. If the work is timed
from the time it is put in the fire, the results will be
uncertain, as the fire is hotter one day than it is another.
Sometimes the fire acts dead, another day lively, so the
box is longer in heating at one time than at another;
but if it is timed from the period when the work com-
mences to take carbon, the results will be as nearly-
uniform as it is possible to get them, provided the heat
is uniform, which can be gauged quite closely by the
eye. Better results can be obtained by the use of the
pyrometer, although for ordinary work this is not
necessary. After running the work the proper length
of time, which varies according to the nature of the
steel and the purpose for which it is intended (small
articles, % inch or less, which do not require anything
but a hard surface, should be run one or two hours
after they are red-hot), dump into the water.

If it is desired to have them colored somewhat,
hold the box about a foot or i8 inches above the tank,
allowing them to pass this distance through the air be-
fore striking the water. If we are hardening small
screws having slots for screw-drivers, and are harden-

231

Advice as to use of packing material.

ing simply to keep the screw-driver from tearing the
slot, we can use expended bone as packing material —
i. e. , bone that has been used once before. It will make
the work hard enough for all practical purposes, yet
not hard enough to break. If we wish to harden deeper,
we must run about five hours after the work is red.
By running sixteen or twenty hours, we can harden to
a depth of y& inch. In the case of small articles, it is
best to use a bone not coarser than what is known as
No. 2 granulated raw bone. When we are to run for
a long period of time in the oven, we should use a
coarser grade.

When it is necessary to harden very deep, it is ad-
visable to pack the work with coarse bone, letting it run
from 15 to 20 hours in the fire, then taking out and re-
packing with fresh material. Work that is allowed to
run for too long a time with the same packing material
is very liable to be not only insufficiently carbonized,
but to be in a measure decarbonized and highly charged
with phosphorus, which is very injurious to the ma-
terial we are using. The charcoal used in the mixture
should, if possible, be the same size granules as the bone.
The commercial article is much superior to anything
we can pound and sift, so it is policy to buy it. The
first cost may seem a trifle stiff, but if account is taken
of the time it takes to pound and sift a barrel of char-
coal, it will be found the cheaper article.

There are many special preparations used in case
hardening, some of which are excellent for special
work, while some are good for all kinds of work.
When we wish to harden deep in a short space of time,
it is advisable to use bone black in place of granulated
raw bone. Bone black, or animal charcoal, as it is

232

Mixture for use on color work.

commercially called, is prepared by burning bones in a
special furnace. It comes in tbe form of a powder. It
leaves a finer grain in the work hardened, and it will
make it stronger than if hardened with raw bone.
Another form of bone which gives excellent results is
called hydrocarbonated bone, a form of bone black
treated with oil so that it gives off its carbon more

readily than
bl either form
mentioned be-
fore. It is not
generally used,
but for nice
work it is very
satisfactory.

If we wish to
give a nice color
to our work, it is
necessary to
first polish it
and be sure it is
clean when
packed in the
hardening box.
Use the follow-
ing mixture
when packing:

Figure 1 34. Bath having an air inlet with water,
for obtaining colors.

10 parts No. i granulated raw bone.
2 parts bone black.
I part granulated charred leather.
Mix thoroughly before using. The results will be
much more gratifying, if a pipe which is connected with
an air pump is run up into the water inlet pipe, as shown

a33

How to cool case hardened work.

in Fig. 134. By this means a jet of air is forced into the
water at the bottom of the tank in stich a manner that
it will be distributed through the whole bath, in order
that each piece of work may come in contact with it as
the work passes through the water.

When articles are hardened by the first process
mentioned, heating in the fire and treating with cyanide
of potassium, very nice colors can be obtained by taking
a piece of gas pipe, putting one end in the bath and
blowing through it, passing the work through the air
in the water when we dip it. When the articles are thin,
and must be very hard, yet tough, it is best to use a
bath of raw linseed oil.

If this bath is used, it is advisable to attach a piece
of iron binding wire to each piece when we pack the
work, allowing the wires to hang over the sides of the
box. When we take the box from the fire, the articles
can be removed from it and immersed in the oil by
means of the wires. They should be worked around
well in the bath until the red has disappeared, but in
such a manner that broad sides are not moved against
the cool oil, or the articles may spring. By taking this
precaution, there will be no difficulty in obtaining satis-
factory results in practically all cases.

The advent of the bicycle opened the eyes of me-
chanics to the fact that a low grade steel could be used
to advantage for many purposes, where formerly it
would have seemed necessary to use tool steel under
similar conditions.

As competition made it necessary to produce a
machine weighing less than one half of what it originally
weighed, and capable of standing up under greater
strain, methods were devised whereby low grade steel

234

Hardening bicycle parts.

could be hardened in a manner that insured its standing
as well as if the article was made of the more costly-
tool steel.

Crank axles were made of 40-point carbon open
hearth steel, which was given sufficient stiffness by-
heating red-hot and plunging in hot oil. When the
percentage of carbon was lower than that mentioned —
40-point^it was sometimes found necessary- to pack
the axles in a box with granulated wood charcoal, sub-
jecting them to a red heat for a period of from 2 to 6
hours; they were then dipped in hot oil. If the per-
centage of carbon was too low to insure hardening by
this process, they were packed in a box with equal
parts of charred leather and charcoal, run for a suffi-
cient length of time, and quenched as described.

It was found necessary to make handle bar binders
very light. When made of tool steel, hardened and
tempered, the cost was too great, and if made of ordi-
nary machine steel, case hardened, they were elastic,
but stretched when strain was put on them. By using
a 30-point carbon steel packing in charcoal, and running
I hour after they were red-hot, then plunged in hot oil,
they gave as good satisfaction as though made of tool
steel, while the cost of machining was not one-quarter
as much.

Hardening bevel gears for bevel gear chainless
bicycles caused a great many anxious moments in shops
where it was attempted. One prominent manufactur-
ing concern lost at one time 75 per cent, of all gears
hardened, according to their own statement.

At the time mentioned the writer was connected
with a concern manufacturing a high-grade chainless
wheel. The gears were of the design represented in

ass

Case hardening bicycle parts.

Fig"- 135- They were made of 40-point carbon open
hearth steel, which was extremely low in phosphorus.
When hardened, they were packed in a hardening box

Crank Axle Gear

Pinion Gear

Figure 135.

Bicycle parts case

hardened.

Cerry ColUrd Co,

with a mixture of granulated charred leather and char-
coal, run at a red heat for a sufficient length of time to
make the teeth hard enough to resist wear, yet not
brittle enough to break when in action. This was the
reason it was necessary to use a steel of a very low
percentage of phosphorus.

The crank axle gear, as shown above, was run
I ^ hours after it was red-hot, then dipped in a bath of
raw linseed oil at a temperature of loo degrees Fahr.

236

DifFerent case hardening results.

The surfaces of the teeth were extremely hard ; the gear,
being made light to reduce weight, necessarily had to
be very stiff, yet tough. They gave the best of satis-
faction. Another concern in the same line of business
packed their gears in granulated raw bone, with the re-
sult they were so brittle it was found impossible to use
them. Still another packed their gears in raw bone, run
them for one hour after they were red-hot, then allowed
them to cool, reheated and hardened. The gears were so
brittle the teeth would break when the surfaces were
not sufficiently hard to resist wear. Both concerns
adopted the method in use in our factory and had
excellent results.

While bone is an excellent hardening agent, it is
not good practice to pack steel in it for case hardening,
if brittleness is objectionable in the hardened product,
because, as previously stated, raw bone contains phos-
phorus, and phosphorus when present in steel, es-
pecially in combination with carbon, causes the steel to
be brittle.

The pinion gear, shown in Fig. 135 on preceding
page, was hardened in the same manner as the one
mentioned, with the exception of the temperature of
the bath, which was about 60 degrees. When hard-
ening the small gears, it was found possible to wire
several on the same wire, being careful to have suffi-
cient space between them to insure good results.
The advantage of this method of wiring was that a
great amount of time was saved when dipping in the
bath. While it was necessary to dip the large gear
in the bath in a vertical position, working it up and
down, the small gears were dipped in any position, as
their shape prevented their springing.

237

Case hardening small screws.

The gears, shown in Fig. 136, were used on the rear
end of the gear shaft and rear hub, and were hardened
in the same manner as the crank axle gear.

Th« Derry Collard Co,

Hub Gear

Geai Shaft Rear End Gear

Figure 136. Bicycle parts
case hardened.

While the critic might
claim that some of the ex-
amples given do not prop-
erly belong under the head
of case hardening, it has
seemed advisable to group
them under this head, be-
cause they are, as a rule, so classified in most shops.

It is generally advisable when case hardening
screws made of Bessemer steel wire, to pack in expended
bone. In this way the extreme brittleness incident to
the use of raw bone is done away with in a great
measure. The writer has seen batches of small screws
(^ inch and under) made of Bessemer screw stock,
which was packed in raw bone and hardened, so brittle
that they would break from the necessary power ap-
plied to a screw-driver to screw them into the hole. At
the same time, when annealed, they filed easier, and
were apparently softer than a piece of the rod they were
made from. They had been heated to the different
temper colors in order to toughen them, but it did no

*38

Charred leather toughens.

good. They were so brittle, even when annealed, that

they were useless.

Yet screws made from stock out of the same batch,

packed in expended bone and run for the same length

of time, were apparently all right. Had charred leather

been used, it
would have made
them tougher, but
the expended bone
made them tough
enough for all
practical purposes.
As it is much
cheaper and more
readily obtained,
it is generally used
for work of this
class.

When case hard-
ening small pieces,
which do not re-
quire a deeply
hardened portion,
but which must be
uniform, as bicycle
chain links, it is
advisable to use
boxes made espe-
cially for them, in
box may become
The writer has in

Thu Derry CoUard Co

Fig. 137. Another form of box
for case hardening.

order that all the pieces in the

heated at about the same time.

mind a certain stock used for making bicycle chain

block links, which was packed in a box of the de-

239

How to pack snap gauges.

scription shown in Fig. 137, using as packing
mixture equal parts animal charcoal, wood char-
coal and charred leather. The work was run 45
minutes after it became red-hot, then dumped in cold
water, and gave excellent results. The links tested
showed up well, and the chains gave the best of satis-
faction when on the wheels. A different stock was
procured, and it was found by experiment that links
made from the new stock could be run only 25 minutes
after they became red-hot. If run the same length of
time as those made of the first stock used, they would
break very easily, but when run only 25 minutes gave
very good satisfaction.

In many shops it is customary to make snap gauges
of machine steel. They are much easier made, the
cost of material is less, and, if hardened properly, they
will wear well. It is best, in cases of this kind, to use
open hearth steel rather than Bessemer, as the latter
runs more uneven. The best results will be obtained
if we use as packing material granulated leather instead
of bone. When packing, mix with an equal amount
of granulated charcoal, run five or six hours, if the
gauge is % inch thick or more. Run at a very low
heat, and dip in the oil bath. It will be found to be
very hard, and probably straight. If hardening small
pieces, it is advisable to use smaller boxes than when
large pieces are being treated, as it takes some time to
heat a large box through. Pieces near the walls of the
box will become hot quicker than those in the center,
and consequently will be hardened deeper.

Many pieces of work are made of tool steel when
machine steel would answer the purpose as well, or
better, were it not for the coarseness of the grain when

040

Machine steel used as tool steel.

the piece is case hardened. The fine grain may be
necessary to resist pressure and wear on some small
part of the surface, or possibly it is to be subjected to
the action of blows, and the grain being coarse, the
surface has no backing and is soon crushed in. The
causes of the open grain are : first, that it is the natural
condition of the stock ; second, the pores are open when
heated, and the steel is absorbing carbon. The higher
the heat to which the pieces are subjected, the coarser
the grain.

It is possible to heat machine steel in such a man-
ner as to produce a fine grain — in fact, as fine as that
of the nicest tool steel. While the writer would not be
understood as advocating the use of machinery steel in
the making of nice tools, as so good an article cannot
be produced as if made of tool steel, yet for certain
purposes cutting tools are made of a good grade of open
hearth steel, case hardened very deep, with fine compact
grain, which gives excellent results. This is particu-
larly the case where the cutting part is stubby and
strong. Cams made of low grade steel, and hardened
by this method, will resist wear as well as though made
of tool steel and hardened, and they are not as liable to
flake off or break. Punch press dies that are to be used
for light work, cutting soft metals where there are no
projections, will do very satisfactory work. Gauges,
whether they be snap, plug, ring or receiving, are
hardened with much less liability of their going out of
shape, are easier to make, and will wear as long as
though made of tool steel. Then, too, the necessity of
allowing them to ''age" after hardening, before grind-
ing to size, as is the case when gauges are made of tool
steel for accurate work, is done away with.

Z41

What is needed in case hardening.

Many bicycle parts, formerly made of a good grade
of tool steel, are now made of machine steel, and the
best of results are obtained. Such is not apt to be the
case if they are simply case hardened by the ordinary
method, as the grain is too coarse to resist the peculiar
action of the balls, particularly on the cones and ball
seats. Spindles of machines, where there is considera-
ble tendency to wear, also a pounding or twisting mo-
tion to resist, where tool steel would be liable to break
and ordinary case hardening would yield to such an
extent as to make the bearings out of round, can be
treated very successfully by this method.

All that is needed is a good hardening furnace,
large enough to receive as many boxes as we may need,
a plentiful supply of boxes, some granulated raw bone,
a good supply of charcoal and a small amount of hydro-
carbonated bone, and some charred leather for our
nicest work. We should also have a suitable supply of
water in a large tank, and a smaller tank arranged so
that we can heat it to any desired temperature, and a
bath containing raw linseed oil. The work should be
packed in the hardening boxes as for ordinary case
hardening, run about the same length of time, and left
in the oven to cool the same as for annealing.

When cool, the articles may be heated in the
open fire, muffle furnace or in the lead crucible, and
hardened the same as tool steel ; or, if the articles are
small, and there are many of them, they can be re-
packed in the hardening box with charcoal. But do
not use any carbonizing substance, as that would have
a tendency to open the grain, and the object of the
second heat is to close the grain. The lower the hard-
ening heat, the more compact the grain will be, as is

242

Case hardening metal cutting tools.

the case with tool steel. This method not only gives a
close grain, but a very strong, tough surface, and, the
center being soft, the piece is very strong.

When hardening tools whose office it is to cut
metals, it is always best to use a packing mixture of
equal parts of charred leather and charcoal. The
kernels should be fine and of about the same size, if
possible, for if the kernels of the leather were large,
and those of the charcoal were small, the tendency
would be for the finer to sift to the bottom of the box.
Leather gives a stronger, tougher effect than bone, it
being practically free from phosphorus, while bone
contains a large percentage. The presence of phos-
phorus in steel makes it brittle, especially when com-
bined with carbon. Yet for most purposes where there
are no cutting edges bone works very satisfactorily in
connection with machinery steel, and is much cheaper
than leather. When using either bone or leather, mix
with an equal quantity (by measure) of granulated
charcoal. Being well' mixed, the particles of charcoal
keep the kernels of bone or leather from adhering to
each other and forming a solid mass when heated.
Then again, the charcoal has a tendency to convey the
heat through the box much more quickly than would
be the case were it not used.

If small pieces are to be hardened that do not need
carbonizing more than -^ of an inch deep, it is best to
use No. 2 granulated raw bone. If the pieces require
a very deep hardened section, it will need a coarser
grade, as they must run longer in the fire. When
hardening bicycle cones and similar articles, where it is
necessary to carbonize quite deeply, it is best to pack
with No. 3 bone and charcoal, equal parts, or better

»43

To case harden thin pieces.

yet, with two parts raw bone, two parts charcoal and
one part bone black or animal charcoal. Pack in the
hardening box, as previously described, run in the fur-
nace lo hours after the box is heated through, using
the test wires to determine the beginning of the heat.
After the work is cold, it can be reheated as described
and hardened. It is advisable to occasionally break a
piece of work and examine the grain, noticing how
deep the hardening has penetrated. If not deep enough,

The Derry Collard Co.
Figure 138. Piece to be hardened, leaving the center soft.

repack in the boxes with fresh material, and run again ;
but if directions given are followed closely, results will
in all probability be found satisfactory. The grain, as
far in as the carbon has penetrated, should be as fine
as that of hardened tool steel.

In hardening thin pieces, where it is necessary to
resist wear or blows, it is advisable to use leather as a
packing material, hardening in a bath of raw linseed
oil. The pieces will be found extremely tough and
hard. It is sometimes desirable to harden the ends of
a piece of work, leaving the center soft. Take, for in-
stance, the piece shown in Fig. 138. The surface of the

»44

Case hardening thin pieces.

ends marked a needs hardening, while the portions
marked b should be soft. Pack the ends inside and out
with hydrocarbonated bone and charcoal, having pre-
viously filled the center with expended bone. Cover
the outside of the center with expended bone, run in
the oven 7 or 8 hours after the box is
heated through. Allow the work to
cool as described, remove the pieces
from the box, heat the ends separately
in the lead cruci-

Figure 139.

How to dip thin

pieces.

ble, dip in a bath
of lukewarm
water, dipping
with the heated

end

up, as

shown in Fig. 139.
Otherwise the
steam generated
from contact of
the hot steel with
water would pre-
vent the water
from entering
the end where it
dipped with the
heated end down.
If the water can-
not enter the
work and get at the portions necessary to be hard,
they certainly will not harden. If the piece is dipped
with the heated end as described, the water readily
enters. The ends will be found extremely hard, and
the grain will be very compact. Not only is this so,

The Derry GoUard Co.

Case hardening bicycle axles.

but the piece will be much less liable to crack than
if the extreme ends were dipped first and hardened, as
would be the case with the heated end down.

Tke Dairy Collard Ck>.

Figure 140. Bicycle axle.

Another method employed when hardening the
ends of a piece of work and leaving the center soft, can
be illustrated by the bicycle axle shown in Fig. 140.
The ends are machined to shape, the center being left
large, as represented at a. The axle is packed in the
hardening box and charged with carbon, as described.
The center is then cut below the depth of charging
shown at d. The piece is ready for hardening. This
can be accomplished by heating in an open fire, muffle
furnace or lead crucible, and dipping in the bath.

When it is necessary to harden the center of a
piece and leave the ends soft, it can easily be accom-
plished. If the ends are to be smaller than the center,

246

How to harden bicycle chain studs.

the pieces may be packed in the hardening box with
raw bone and charcoal. Run for a sufficient length of
time to carbonize to the desired depth of hardening.
Allow the pieces to cool off. When cool, machine the
ends, as shown by lower cut in Fig. 141, the upper cut

The Derry Collard Co.

Figure 141. Method of treatment for chain studs.

representing the piece of work before charging with
carbon; the lower, after machining the carbonized
portions at the ends. It may now be heated red-hot
and dipped in the hardening bath in the usual man-
ner. The center will be found hard.

A method employed in making bicycle chain studs
that are hard in the center at the point of contact with
the block link and soft on the ends, in order that they
may be readily riveted in the side links, consists in
taking screw wire or special stud wire of the desired
size, packing it in long boxes with raw bone and char-
coal and running 3 or 4 hours after it is red-hot. Then
allow it to cool off. The stock is now placed in the
screw machine and cut to shape — that is, the ends are
cut down to proper size. The center, being of the
proper size, is not machined. The studs may be heated

H7

An interesting experiment.

in a tube in any form of fire and dumped in a bath of
water or brine. The center will be hard enough to re-
sist wear, while the ends will be soft, the carbonized
portion having been removed.

An interesting experiment can be tried, which in
itself is of no particular value, except that it acquaints

a & a b a b q

The Derry Collard Co.

Figure 142. An interesting experiment.

one with the manner in which carbon is absorbed by-
steel. Take a piece of open hearth machinery steel,
turn it in the lathe to the shape shown in Fig. 142, neck-
ing in every half inch to the depth of }i inch, leaving
the intervening spaces }4 inch long. Pack the piece
in the hardening box with raw bone and charcoal.
Run five or six hours after the box is heated through.
AVhen cold, turn the shoulders marked d to the size of
a, leaving a the same size as before charging. Heat to
a low red and dip in the bath. The portions marked
a will be found hard, while the balance of the piece
will be soft.

When pieces are to be case hardened, and it is con-
sidered desirable to leave a certain portion soft, it is
accomplished many times by making tongs of the
proper form to effectually prevent the contents of the
hardening bath coming in contact with the portion men-

248

Case hardening to leave soft places.

tioned Suppose, for example, a piece of the design
shown in Fig. 143 is to be case hardened, and itisde-

< PORTION-G^StRtD-SOFl

The Derry Collard Co.

Figure 143. Piece with portion desired soft.

sired to leave the central portion marked soft. Make a
pair of tongs to grasp the piece, as shown in Fig. 144.

It will be seen that
tioned is eff ect-
the tongs. The
in the bath, and
until the red has
it may be dropped
tank and left until
desirable to leave a

the portion men-
ually protected by
piece may be dipped
worked around well
disappeared, when
to the bottom of the
cold. When it is
portion of an article

i

^

P

Tba Dtfiry Collard Co,

Figure 144. Tongs for handling piece shown above.

soft, as shown in Fig. 145, it is sometimes accomplish-
ed by covering the portion to be soft with fire-clay, as
shown in lower view. The fire-clay may be held in
place by means of iron binding wire ; sometimes the
fire-clay is held in place by means of plasterers' hair,

249

The use of fire-clay for soft places.

whicli is worked into the mass when it is mixed with
water. The fire-clay prevents the carbon coming in
contact with the stock where it is desired soft.

The Derry Collard Co,

Figure 145. The use of fire-clay for soft spots.

A method employed in some shops consists in
wrapping a piece of sheet iron around the article over
the portion de-
sired soft, as
shown in Fig. 146.
The sheet metal is
held in place by
means of iron
binding wire, as
shown.

The Derry Oollard Co.

Figure 146. Using sheet iron to
prevent hardening.

A very common method, which is costly when
many pieces are to be treated, consists in forcing a

250

The use of a collar in case hardening.

collar on to the piece over the portion desired soft, as
shown in Fig. 147. The collar is removed alter the
article is hardened.

Piece to be hardened

Collar

The Derry Collard Co.

Collar In position
Figure 147. A collar for keeping portions soft.

When machine nuts are to be case hardened, and
for any reason it is desirable to have the interior
threaded portion soft, it is accomplished by screwing
a threaded piece of stock in the hole before the nuts
are packed in the hardening box.

As carbon can not penetrate a nickeled surface,
articles are sometimes nickel-plated at portions desired
soft; this, however, is, generally speaking, a costly
method of accomplishing the desired result.

It is sometimes considered necessary to harden the

251

Mow to produce toughness.

Surfaces of pieces quite hard and leave the balance of
the stock stiffer than would be the case where ordinary-
machinery steel is used. In such cases many times an
open hearth steel is selected, which contains suf-
ficient carbon, so that it will become very stiff when
quenched in oil. The writer has in mind a gun frame
which, on account of the usage to which it was to be
put, must have a hard surface, while the frame itself
must be very stiff. They were packed in a mixture of
charred leather and charcoal, placed in the furnace and
run for a period of ij4 hours after they were red-hot.
They were then quenched in a bath of sperm oil. The
stock used was 30 -point carbon open hearth steel. Were
the articles heavier or a greater degree of stiffness de-
sirable, a steel could be procured having a greater per-
centage of carbon.

When toughness or strength is wanted in the case
hardened product, a steel having much phosphorus
should not be used ; in fact, the percentage of phosphorus
should be the lowest possible, as steel containing phos-
phorus, in connection with carbon, is extremely brittle.
For this reason, articles which must be extremely tough
should not be packed in raw bone, as this contains a
very high percentage of phosphorus.

At times a job will be brought around to be case
hardened, and one particular part will be wanted quite
hard, while the balance of the piece will not require
hardening very hard or deep. In such cases, if the por-
tion mentioned be a depression, it may be placed upper-
most in the hardening box, and some prussiate of
potash or a small amount of cyanide of potash placed
at this point, the piece being packed in granulated raw
bone or leather, and run in the furnace a short time.

Furnaces for case hardening.

The article may be quenched in the usual manner. The
portion where the potash was placed will be extra hard.

The 'Deny CoU«rd Co,
Figure 148. Gas furnace for case hardening.

The furnace used in case hardening should receive
more consideration than is many times the case; an
even heat that can be maintained for a considerable
length of time is essential if desi results are desired.

A very satisfactory form of furnace is represented
in Fig. 148; it bums illuminating gas as fuel.

When it is considered desirable to use hard coal as

aS3

A "home-made" case hardening furnace.

fuel, the furnace made by the Brown & Sharpe Co. , of
Providence, R. I., gives excellent results.

When it is considered advisable to construct on the

Figure 149. ** Home-made" fiiinace
for case hardening.

premises a furnace burning charcoal or coke, the form
shown in Fig. 149 will be found very satisfactory.

However, the form and size of furnace depend in a
great measure on the character and amount of work to
be hardened.

Baths for Case Hardening.

The bath that is to be used for cooling work being
case hardened must be suitable to the work being

254

Various styles of case hardening baths.

hardened. Where work is case hardened in large
quantities, it is customary in most shops to harden in
iron boxes. When the work is in the proper condition,
the box is inverted over a tank of water or some fluid,
and the contents dumped into the bath. If the pieces
of work are large or bulky, and the tank is shallow,
they reach the bottom while red-hot, and, as a con-
sequence, the side of the piece that lays on the bottom
will be soft. In order to overcome this trouble, the
tank must be made deep enough so that the pieces will
be sufficiently chilled before reaching the bottom. If
it is not considered advisable to have an extremely deep
tank and the pieces are large, various ways are taken
to insure their hardening.

One method which the writer has used with excel-
lent results is to have a series of rows of wire rods
reaching across the tank, no two consecutive rows being
in the same vertical plane, as mentioned in the previous
section. The work as it descends into the bath strikes
these wires, which turns them over and over, bringing
all portions in contact with the contents of the bath.
These wires also separate the pieces from each other
and from any packing material which may have a
tendency to stick to them. The wires also retard the
progress of the articles, giving them more time to cool
before reaching the bottom of the bath.

In order to insure good results, it is necessary to
have a jet of water coming up from the bottom of the
tank. An outlet is provided near the top for an over-
flow. The overflow pipe, of course, should be larger
than the inlet pipe, and should be located far enough
below the top edge of the tank, so that the contents will
not overflow when a box of work is dumped into it.

Bath with catch pan,

I

Perforated Catch Pan

W//f^//^/y'^/^/^/////^////^///^/M^/7/?///.

In order to get tlie hardened pieces out of the bath
easily, it is necessary to provide a catch pan, as shown
in Fig. 150. The bottom of this pan should be made of
strong wire netting or a piece of perforated sheet metal,
preferably the former. The holes in the pan allow the
packing material to fall through to the bottom of the

tank, and also
allow the water
from the supply
pipe to circulate
freely around the
work and to the
top of the bath.
This catch pan
should be provided
with strong wire
handles, as shown,
in order that it may
be readily raised.

I was at one time
requested to call at
a shop where they
were having very
unsatisfactory re-
sults with their
case hardening. An examination showed they were
dumping their product into a barrel of water to harden.
The box containing the work was inverted over this
barrel, and the work and packing material went into
the water in a lump. Some of the pieces that hap-
pened to get out of this mess were cooled sufficiently
to harden somewhat, but the majority of the pieces were
soft, or else they were hard on one side and soft on the

256

=s^

Tha Dtsrry Col lard Co.

Figure 150. Case hardening bath with catch
pan and steam pipe.

How a temporary bath was arranged.

other. An examination of the bottom of the barrel
showed it to be considerably charred. In places the
outline of the pieces was plainly visible. These pieces
had reached the bottom red-hot, and had burned their
way into the wood. It is needless to say that the side
of the piece of work which was down did not harden.

As those in charge of the work did not think it ad-
visable, considering the limited amount which they had
to case harden, to get a tank of the description shown
in Fig. 150, we made a catch pan as described, blocked
it up about 6 inches from the bottom of the barrel
by means of bricks. We then bored a hole into the
bottom of the barrel, screwed in a piece of pipe, and by
this means were able to connect an ordinary garden
hose, so as to get a jet of water coming up from the
bottom. As the barrel was out of doors, we simply
bored a two -inch hole about two inches from the top of
the barrel for an overflow, and let the water run on
the ground. When the work was ready to dump, we
sifted it out of the box into the water gradually, rather
than to dump it in a body. As soon as the box was
emptied, we grasped the wire connected with the catch
pan, and raised and lowered the pan in a violent man-
ner, in order to separate any pieces that might have
lodged together. The result was very satisfactory, and
I think they are still using that barrel.

Baths are made, when large quantities of work are
hardened, with some means of keeping the work in
motion after it reaches the bottom of the bath. This
is sometimes done by mechanically raising and lower-
ing the catch pan, and at the same time turning it
around. Then again, it is done by means of several
sweeps, which are attached to the lower end of a verti-

257

Baths with air pumps or perforated pipes.

cal shaft, the shaft resting in a bearing in the center of
the catch pan. These sweeps, or arms, revolving, keep
the pieces in motion, turning them constantly, but un-
less arranged
properly, they
have a tendency
to gather the
work in batches,
thereby acting
exactly opposite
from what they
are intended to
do. Then again,
they have a ten-
dency to scratch
the surface of the
work, which is a
serious objec-
tion, if color

Supply Pipe

Figure 151.

Bath for cooling slender
case hardened articles.

work is wanted.
When it is de-
sirable to get nice colors on case hardened work, an
air pump may be connected with the bath, as shown in
Fig. 134, the water and air entering the bath together.
While it is not advisable to let air come in contact with
the pieces to be hardened for colors while passing from
the box to the water, yet the presence of air in the
water would have the effect of coloring the work nicely.
When hardening long slender articles or those
liable to give trouble if a bath of the ordinary descrip-
tion is used, excellent results may be obtained by the
use of a bath with perforated pipes extending up the
sides of the tank, as shown in Fig. 151.

258

Spring Tempering,

G^<^ .^=^n9

CO

When it is necessary to give articles made of steel a
sufficient degree of toughness, in order that when bent
they will return to their original shape, it is accom-
plished by a method known as spring tempering.

The piece is first hardened, then the brittleness is
reduced by tempering until the article, when sprung,
will return to its original shape.

Generally speaking, it is not advisable to quench
pieces that are to be spring tempered in cold water, as
it would not be possible to reduce the brittleness suffi-
ciently to allow the piece to spring the desired amount
without drawing the temper so much that the piece
would set. Steel heated red-hot and plunged in oil is
much tougher than if plunged in water ; and as tough-
ness is the desired quality in springs, it is advisable to
harden in oil whenever this will give the required result.

For many purposes a grade of steel made especially
for springs gives better results than tool steel ; for in-
stance, bicycle cranks made of a 40-point carbon open
hearth steel will temper in a manner that allows them
to stand more strain than if made of the finest tool
steel, and the stock does not cost more than one-quarter
the price of tool steel.

When springs are to be made for a certain purpose,
259

How to harden clock springs.

it is generally safer to state the requirements of the
spring to some reliable steel maker, allowing him to
furnish the stock best suited for the purpose, than to
attempt to specify the exact quality wanted — unless, of
course, the operator or manufacturer has, either by ex-
perience or by study, acquired the knowledge necessary
to qualify him to judge as to the quality needed.

As previously stated, the hotter a piece of steel is
heated for hardening the more open the grain becomes ;
and as hardened steel is strongest when hardened at
the refining heat, it is always advisable to heat no hot-
ter than is necessary to accomplish the desired result.
But as springs are generally made of a steel lower in
carbon than ordinary tool steel, and as low carbon
steel requires a higher heat to harden than is the case
when tool steel is used, it is necessary to experiment
when a new brand of steel is procured, in order to as-
certain the proper temperature in order to produce the
best results.

When steel is heated to the proper degree, it may be
plunged in a bath of oil or tallow and hardened, the
character of the bath depending on the size of the piece
to be hardened and the nature of the stock used. For
ordinary purposes a bath of sperm oil answers nicely.
In some cases tallow will be found to answer the pur-
pose better. It is necessary sometimes to add certain
ingredients to the bath in order to get the required de-
gree of hardness.

The following is used by a concern when hardening
clock springs: To a barrel of oil add lo quarts of
resin and 13 quarts of tallow. If the springs are too
hard, more tallow is added. If, however, the fracture
indicates granulation of the steel rather than excessive

»6q

Mixture for hardening springs.

hardness, a piece of yellow bees'- wax of about twice
the size of a man's fist is added to the above.

The following mixture has been used by the writer
with success in hardening springs which, on account of
the thickness of the stock or a low percentage of carbon,
would not harden in sperm oil :

Spermaceti oil 48 parts.

Neat's foot oil 46 ' ' I

Rendered beef suet 5 ' '

Resin i * '

The proportion of the different ingredients may be
changed to meet the requirements of the particular
job. Resin is added to the oil to strike the scale. As
the scale or oxidized surface of the steel, when subjected
to heat, is liable to raise in the form of blisters, and as
these are filled with gas, the contents of the bath can
not act readily on the steel. A small proportion of
spirits of turpentine is sometimes added, to the oil for
the same purpose, but as it is extremely inflammable,
it is somewhat dangerous to use unless great care is
observed. The presence of resin in a hardening bath
has a tendency to crystallize the steel, and on this ac-
count is sometimes objectionable.

A very good method, when neither resin nor turpen-
tine are used to strike the scale, consists in having a
dish of soft soap ; or, if that can not be procured, dis-
solve some potash in water, dipping the steel into this
before heating. It has the effect of preventing oxida-
tion of the surfaces, and helps to strike any scale that
may have been on the stock previous to hardening.

When small springs are to be hardened, which, on
account of their size, cool quickly, they can, if there
are many of them, be placed in tubes and heated in a

261

Furnace for heating springs.

furnace of the description shown in Fig. 152. When
the pieces are heated to the proper temperature, a tube
is removed and inverted over a bath. The contents
should go into the bath in a manner that insures uni-
form results, that is, the pieces should be scattered in
the bath. If the tube was held in the position shown

Figure 152. Furnace with removable tubes for
heating springs.

0000

000
0000

Jht D«nry ColUrd Co.

at Uy in Fig. 153, the pieces would go into the bath in a
lump; but if it were held as shown at ^, the pieces
would become scattered, thus insuring good results.

When springs larger than those previously con-
sidered are to be hardened, an oven having some means
of heating the articles in a manner that keeps them
from coming in contact with the products of combus-
tion should be used. Any form of a muffle having

%6%

An oil bath for spring hardening.

Figure 153.

How tubes shown ia

Figure 152 should

be emptied.

sufficient capacity will do, or the pieces may be placed
in a hardening box, having ^ inch powdered charcoal
in the bottom, and a cover placed on the box — which
need not be sealed. The box may then be placed in a
furnace and subjected to heat. The cover may be
raised from time to time and the contents of the box
noted. This makes an excellent way of heating large
coil springs and similar articles.

If the oven is sufficiently large, several boxes may
be heated at a a

time. When a
spring shows the
proper tempera-
ture, which
should be uni-
form through-
out, it may be re-
moved, placed on
a bent wire and
immersed in a
bath of sperm oil,
having a jet of
oil coming up
from the bottom,
as shown in Fig.

154, A repre- | ^EiEp-EZIr^
senting the outer
tank containing
water, B the bath
of oil, C the pump used in drawing the heated oil from
the bath through the pipe D ; it is then forced through
the coil of pipe in the water and back into the bath
through the inlet E. F is the catch pan. The jet of

263

The DeiTy CoUardi €••

Oil bath for spring tempering.

oil is forced toward the top of the tank, as shown at G.
The spring should be worked up and down in the
bath until all trace of red has disappeared, when it
may be lowered to the bottom of the tank and left
until the temperature has been reduced to that of
the contents of the tank, or until a convenient time
comes for their removal.

As previously explained, it is not advisable to re-
move articles being quenched from the bath until they

"The J)erry Collwd Co.

Figure 1 54. Oil bath for spring tempering.

are of a uniform temperature throughout. While this
procedure might not make as much difference with a
piece of work hardened in oil as one hardened in water,
yet it is not a good plan to remove articles from the bath
until they are reduced throughout to the temperature of
the bath.

In order that the contents of the bath may be kept a
uniform temperature, the pump shown in accompany-
ing cut may be connected with the tank, as represented,
the oil to be taken from near the top and pumped

264

How to heat heavy springs.

through the coils of pipe in the outer tank, which
should be supplied with running water.

When steel contains carbon of too low a percen-
tage to harden properly in oil or any of the mixtures
mentioned, the writer has used a bath of water at, or
nearly at, the boiling point (212°) with very gratifying
results. It may be found necessary with certain steels
to reduce the temperature of the water somewhat.

Various methods are employed when drawing the
temper. The one more commonly used than any other
is to heat the spring until the oil adhering to the sur-
face catches fire and continues to burn, when the piece
is removed from the fire, burning until all the oil has
been consumed. If this method is used, it will be
found necessary to provide some means whereby a
uniform heat may be obtained, or one part of the spring
will be found to be too soft by the time the balance is
rightly tempered.

If the spring is of heavy stock, it is necessary to bum
the oil off three and sometimes more times, in order to
bring it to the proper degree of elasticity. The process
of drawing the temper by heating the spring until the
oil catches fire from the heat contained in the steel is
familiarly known as "flashing." Hardeners say that
it is necessary to flash oil off this spring three times,
or it is necessary to flash tallow off this spring twice,
some using the oil the piece was quenched in, while
others prefer some other kind of oil or tallow.

Springs hardened in boiling water may be coated
with oil or tallow and the temper drawn as described,
if it be found necessary. It is not policy to use a fire
having a forced draft or blast when drawing articles
to a spring temper. An open fire burning wood or

265

The thermometer in spring tempering.

charcoal gives excellent results. A gas flame having
no air blast also works very satisfactorily.

Springs of unequal sizes on the various portions re-
quire a very skillful operator, in order to get uniform
results, if the above method is used. The thinner
portions, heating faster than the heavier parts, be-
come too soft before the other parts are soft enough.
Consequently, it is advisable to temper these by a dif-
ferent method. The spring may be placed in a per-
forated pail, which in turn is set into a kettle of oil or
tallow. This kettle is placed where a sufficient amount
of heat may be obtained to draw the temper to the
proper degree.

The amount of heat given is gauged by a ther-
mometer, and varies according to the nature of the
steel and the character of the spring. It ranges from
560° to 630°. The exact amount of heat necessary must
be ascertained by experiment. This method furnishes
a very reliable way of tempering all kinds of springs.
The kettle should be so arranged that a cover may
easily be placed on it in case the oil catches fire, as
otherwise the operator, or the building, might be burned,
or the work in the oil spoiled, or the thermometer
cracked. The cover should be made high enough to
take in the thermometer.

The cover should be provided with a long
handle, in order that the operator may not be burned
when putting it on the kettle. If it is not considered
necessary to provide the cover mentioned, a piece of
heavy sacking should be kept conveniently near for
use. If this is placed over the top of the kettle, it will
generally extinguish the flames.

The thermometer should not be taken from the hot

266

Heating watch springs.

oil and placed where any current of air can strike it, or
the glass will crack. It is advisable to leave it in the
oil, letting it cool down with it. If the furnace
where the oil is being heated is located where any cur-
rent of air will strike the thermometer, it must be pro-
tected in some manner, or it will crack.

If it is considered advisable to remove the pail of
work from the oil before the pieces are cool, it may be
done, and the pieces dumped into a wooden box, cover-
ing the opening, so that the air will not strike the
pieces. The pail may now be filled with fresh pieces
requiring tempering. The pail of work should be
placed in the kettle of oil. The kettle should not be
placed in the fire again until the pieces of work have
absorbed considerable of the heat that was in the oil,
when the kettle may be placed in the fire and the
operation repeated.

When work is hardened in large quantities, it is
generally considered advisable to devise methods that
allow of handling the work cheaply, at the same time
keeping the quality up to the standard. Watch springs
are sometimes heated in a crucible containing melted
cyanide of potassium or salt and cyanide of potas-
sium heated to the proper degree. The springs
are immersed in the mixture until uniformly heated,
then quenched. It is stated, however, that this
mixture will not do when heating the hair springs,
as it causes the nature of the steel to change
slightly. These springs are heated for hardening in a
crucible of melted glass.

When a make of steel is found that gives satisfac-
tory results when made into springs and tempered, it is
folly to exchange it for another make, unless convinced

267

The "second blue."

that the other is better. A saving of a few cents, or
even dollars, on an order of steel is quite often very-
costly economy, as many times springs do not give out
until in actual use, and in that case they are often-
times many miles from the factory where they were
made.

When large numbers of springs that must receive
severe usage are made, it is advisable to give them a
test — at least, test an occasional spring. Give them a
test somewhat more severe than they will be liable to
get in actual use. By so doing it is possible to detect
an improper method of hardening or tempering before
the whole batch is done.

"Second Blue-"

When all springs were made of tool steel and
hardened, and the temper drawn one at a time, it was
customary with some hardeners to draw the temper to
what is known as the * 'second blue." After harden-
ing, the springs were polished, then placed in a pan of
sand and held over the fire until the temper colors
commenced to show, the pan in the meantime being
shaken to keep the sand and springs in motion and
insure uniform heating. The tempers will show in
order as set forth in the color table given under
Drawing the Temper. After the] colors had all
appeared, the surface of the steel assumes a grayish
appearance. When heated a trifle above this, it as-
sumes a blue color again, which is known as the
"second blue." When this color appears, the spring
should be dropped in a tank of hot oil, leaving it to
cool off with the oil.

a68

Colors for springs — how obtained.

Another method sometimes used when drawing the
temper of heavy springs made from high carbon steel
consists in heating the article until sawdust dropped
on it catches fire, or a fine shaving left from a hard-
wood stick, such as a hammer handle, being drawn
across a comer of it, catches fire at the proper temper-
ing heat.

Mechanics are sometimes surprised when they ob-
serve a spring in some conspicuous place which is drawn
to a straw color, a brown or a light blue. It does not
seem possible to them that a spring drawn to the tem-
per represented by the color visible should be able to
stand up to the work. The temper color shown is
simply for appearance. The articles are first hardened
and tempered to give them the necessary elasticity.
This is ordinarily done by heating in a kettle of oil,
gauging the heat with a thermometer. After heating
to the proper temperature and cooling, they are
polished. Any desired color can be given by placing
the articles in a pan of sand and shaking over a fire
until the desired color shows, when they may be
dumped in warm oil to prevent running. This second
operation does not affect the hardness or elasticity,
provided they were not heated as hot as when the
temper was drawn.

Many times it is impossible to harden and temper a
spring in a manner that gives satisfactory results, be-
cause the spring was bent to shape when cold. Now,
it is possible to bend most steel somewhat when cold,
and yet have it take a good spring temper ; but it is
impossible to bend it beyond a certain amount, which
varies with the steel.

The writer has seen large safety valve coil springs

269

Caution about annealing sheet steel.

rendered unfit for use by coiling when cold. If a
piece of the same steel was heated red-hot and coiled,
excellent results were obtained.

Many times it is necessary to anneal steel one or
more times between operations in order to obtain good
results. It was found
necessary to anneal
the spring shown in
Fig. 155 after punch-
ing the blank and
before bending at all.
The first operation of
bending brought the
spring nearly to
shape ; it was then an-
nealed, and the finish-
ing operation taken.
If it was bent to shape
without annealing
the second time, it
would break in the
comers when in use, if not in the operations of bending.

When annealing sheet steely whether it be for springs
or cutting tools, the utmost caution should be exercised.
If the steel is allowed to stay in a red-hot condition for
too great a length of time, the stock is rendered unfit
for hardening. If heated red-hot and laid aside to cool
slowly^ much better results will follow than if it were
packed in an annealing box with charcoal and kept red-
hot for a considerable length of time. These long
heats apparently have the effect of throwing the carbon
out of its proper combination with the iron. It will
harden, but can never be made elastic or strong.

Tlw Derry C«ll»rd Co.

Figure 155. A peculiar case.

ayo

Making Tools of Machine
Steel.

6^?=^ ^?=^s£)

CO

While it is considered advisable in most shops to
make articles whose bearing surfaces must be hard, in
order to resist frictional wear, of some form of machine
steel, and give the surfaces sufficient hardness by case
hardening, it is generally considered necessary to make
cutting, forming and similar tools of tool steel.

It is practical, however, to make cutting tools for
certain classes of work of machine steel, and harden the
cutting edges sufficiently to produce very satisfactory
results.

Steel is, as previously explained, a combination of
iron and carbon. The grade of iron used in making
tool steel is, however, vastly superior and much more
expensive than that used in the manufacture of the or-
dinary machine steel. Being much purer, it is much
stronger when carbonized and hardened, and conse-
quently can do many times the amount of work of tools
made of the lower grades of steel, even when these are
charged with the satnc percentage of carbon. It is also
less liable to crack when hardened, as the impurities
contained in the lower grades make it, when combined
with carbon, very brittle when hardened.

But notwithstanding the facts just presented, it is
471

How phosphorus affects steel.

possible to make tools for cutting paper, wood, lead,
brass and soft steel of a low grade of steel, and harden
it by a process that gives results much more satisfac-
tory than would be thought possible by one who had
never tried it. This method recommends itself on ac-
count of the comparatively low cost of the steel, and it
can be worked to shape more cheaply than if tool steel
were used. But it is usual, when the experiment is
tried, to use any piece of low grade steel laying around
the shop that will machine to shape in a satisfactory
manner, not realizing that it is necessary, in order to
get satisfactory results, to use steel adapted to the pur-
pose. As phosphorus, when present in steel, and es-
pecially when in combination with carbon, causes it
to be extremely brittle when hardened, a grade should
be selected that has the least possible percentage of this
harmful impurity.

If it is not necessary to have the hardened surface
very deep, a steel having a low percentage of carbon
may be used. If, however, the tool is to be subjected
to great strains, it is advisable to use a steel containing
sufficient carbon to cause the tool to harden enough to
furnish the necessary stiffness or internal hardness.
The extra amount of hardness necessary to insure the
cutting portions standing up when in use, must be fur-
nished by the process of hardening.

The writer has seen reamers, counterbores, punch
press blanking, forming and drawing dies, and many
other forms of tools made of low grade steel, which,
the parties using them claimed, gave the best of results.

As before stated, when making tools which are not
to be subjected to a very great amount of strain, or
which will not be called upon to resist a great amount

^^^

Steel for slender tools.

of pressure, a steel low in carbon may be used. Any
desired amount of surface hardness may be given the
piece. If, however, the tool will be subjected to tor-
sional strain, as in the case of a long, slender reamer,
or if it may have to resist a crushing strain, as in the
case of a punch press forming die, it is necessary to use
stock containing sufficient carbon to furnish the desired
result when hardened. If the tool is not to be subjected
to very great strain, almost any low grade stock that is
practically free from impurities will do.

If a long, slender reamer, or similar tool, is to be
made, excellent results are claimed by using a low
grade steel of 40-point (.405^) carbon. In the case of a
forming die, or similar tool, use a steel of 60 to 80-point
carbon. If, however, it was to be subjected to great
pressure or very severe usage, the writer's experience
leads him to advocate the use of tool steel specially
adapted to this class of work.

As it is necessary, in order to get satisfactory re-
sults, to have the percentage of impurities as low as
can be obtained, in order to have the hardened steel as
strong as possible, do not allow it to come in contact
with any form of bone when heating. The articles should
be packed in a hardening box with a mixture of equal
quantities (volume) of charred leather and granulated
charcoal in the same manner as described under Pack
Hardening. It will be necessary to subject the articles
to heat for a longer period of time than if hardening
tool steel. The length of time the articles are sub-
jected to the action of the carbonizing element depends
on how deep it is necessary to have the hardened portion.
The test wires previously mentioned should be used
to determine when the contents of the box are heated.

a73

When in doubt about steel.

If you are reasonably sure the steel used was prac-
tically free from injurious impurities and is low in car-
bon, it may be dipped in a bath of water or brine.
Should there be any doubt as to this, dip in raw lin-
seed oil.

If the article being hardened is a cutting tool, or
something requiring a fine, compact grain, better re-
sults will follow if it is left in the box after being sub-
jected to the action of carbon, the box removed from
the fire, and the whole allowed to cool. When cold,
the article may be reheated to a low red, and hardened.

While the writer has used a low grade steel in
making various forms of tools, and had excellent re-
sults when they were put to the use for which they
were intended, he cannot recommend its use, unless the
parties doing the work select stock suited to the pur-
pose and exercise due care when hardening.

While this subject might properly be classed under
the heading of Case Hardening, it has not seemed wise
to the writer to do so, because case hardening, according
to the interpretation usually given it by mechanics, is
simply a process of transforming the surface of the
article into a condition that allows it to become hard if
plunged red-hot into water. Hardness is apparently
the only object sought, but such is not the case when
the subject is considered in its proper light.

When applying this principle to tools, it is neces-
sary to consider the requirements of the tools. Know-
ing this, it is necessary to proceed in a manner that
will give the desired results.

If it is considered advisable to make certain tools
of a low grade steel, treating it as described, it is
necessary to select steel adapted to the tool to be made.

274

special steels.

It is never advisable to use Bessemer steel bought in
the open market, because it does not run uniform.
Always use open hearth steel, procuring it, if possible,
of a quality that will give satisfactory results. Steel,
with a very small percentage of phosphorus and other
impurities, may be obtained from any reliable maker,
if the purpose for which it is to be used is stated when
ordering.

Special Steels.

To one interested in working steel, the history of
the development of this industry furnishes a remarka-
bly interesting study.

Steel may be grouped under four general heads,
the name given each class being selected on account of
the method pursued in its manufacture.

Probably the oldest of all known steels is the
cemented or converted steel. This steel is made by
taking iron in the form of wrought iron bars, packing
them in a fire-brick receptacle, surrounding each bar
with charcoal. This is hermetically sealed, and heat
is then applied until the whole is brought to a degree
of heat that insures the penetration of a sufficient
quantity of carbon. Experience proves that carbon
will penetrate iron at about the rate of one-eighth of
an inch in twenty-four hours; and as bars of about
three-quarter inch thickness are generally used, it re-
quires three days for the carbon to penetrate to the

»75

Crucible cast steel.

center of the bar (^-inch). The furnace is then al-
lowed to cool, and the iron bars, which are converted
to steel, are removed. They are found to be covered
with blisters, hence the name. Blister Steel.

When examined, the bars are found to be highly-
crystalline, brittle steel. When this form of steel is
heated and rolled directly into commercial bars, it is
known as German Steel.

If blister steel is worked by binding a number of
bars together, heating to a high heat, and welded under
a hammer, it is known as Shear Steel, or Single- Shear.

If single-shear steel is treated as above, the finished
product is known commercially as Double- Shear Steel.

Until within a comparatively few years these three
classes of converted steel were practically the only
kinds known in commerce.

Crucible Cast Steel.

As this is the standard steel used for fine tools, a
brief study of the methods used in its manufacture
may be of interest to the reader. Benjamin Huntsman,
a clockmaker, is supposed to have been the inventor of
this process. It occurred to him that he might pro-
duce a more uniform and satisfactory article than was
to be had at that time for use in manufacturing springs
to run his clocks. The method he had in mind con-
sisted in charging into a crucible broken blister steel,
v^^hich was melted to give it a homogeneous character.

While Huntsman thus founded the crucible steel
industry, which has been of incalculable value to the
mechanic arts, he met with many difficulties. These
have been overcome by later inventions, notably those

276

Alloy steels.

of Heath and Mushet, until to-day it is possible, with
skill and care, to produce a quality of steel which, for
strength and general utility, has never been equaled,
despite the claims of some blacksmiths that the steel of
to-day is not as good as that produced 25 to 50 years ago.
Competition has rendered it necessary to run cut-
ting tools, or stock, as the case may be, much faster
than was formerly the case, which made it necessary to
make steel containing a higher percentage of carbon
than was formerly the case. As stated in a previous
chapter, when high carbon steels are used, it is neces-
sary to exercise great care in heating for the various
processes of forging, annealing and hardening. As
high carbon steels are more easily burned than those
containing a lower percentage, it is necessary to put
them in the hands of skilled workmen, for, unless the
steel is to be worked by men understanding its nature,
it proves to be a very unsatisfactory investment, and
is often condemned because it will not stand as much
abuse as a steel of lower carbon; but if properly
treated, will do many times the amount of work.

Alloy Steels.

In order to accomplish certain results, steel is made
containing other metals. To distinguish them from
steels, which depend on the quantity of carbon present
for their hardening properties, they may properly
be termed "alloy" steels, the amount of the hardening
property present determining the quality of the
steel. As these steels can generally be run at a higher
periphery speed and cut harder metals than carbon
steels, they are very valuable at times, and in some

277

Self-hardening steel.

shops are used altogether. As a rule, they are more
easily injured by fire than carbon steel, and, conse-
quently, extreme care must be exercised when working
them.

When high carbon steel is alloyed with other hard-
ening properties, a steel is produced which will be found
more efficient for machining chilled iron than the
regular high carbon steels. However, as the nature of
steel of this character depends entirely on the amount
and kind of the alloy used and the amount of carbon
present, no fixed rule can be given for the treatment.
It is always best to follow as closely as possible direc-
tions received with the steel.

The writer has seen milling machine cutters, punch
press blanking dies, and other tools, which were to cut
very hard, "spotty" stock, give excellent results, when
made from a reliable alloy steel, where carbon steels
would not stand up.

If the amount of certain hardening elements be
increased to a given point, the steel hardens when
heated red-hot, and is exposed to the air. It is styled
**Air Hardening Steel," more generally known, how-
ever, as Self-Hardening Steel.

Self-hardening Steel.

It was not originally the intention of the writer to
mention self -hardening steel, because there are so many
different makes of the article, each differing from the
other to an extent that the method employed to get sat-
isfactory results, when using one make, would prove
entirely unsatisfactory when applied to another.

Self-hardening steel has a field of its own, and is
very useful when made into tools for certain work. It

278

A common error.

is used very extensively in cutting hard metals, and
can be run at a high periphery speed, because the heat
generated does not soften the tool, as is the case when
carbon steels are used.

No general instructions can be given for working
the steel, because the composition of the different makes
varies so much that the treatment necessary, in order
that one brand may work satisfactorily, would unfit
another for doing the maximum amount of work pos-
sible for it to do.

A very common error in shops where a make of
this steel is used, and another brand is to be tried, con-
sists in attempting to treat the new brand in the same
manner they have been treating the other, regardless
of instructions furnished.

As previously stated, the treatment suited to one
brand would render another unfit for use, and as the
reputation of a brand depends on the results attained,
the makers are very careful when selling steel to state
plainly the treatment it should receive. The buyer
should see that the directions are followed implicitly.

When purchasing self-hardening steel, it is advisa-
ble to investigate the merits of the different makes. In
practice, certain brands prove best for cutting cast
iron, while another brand, which will not do as much
work when cutting cast iron, proves to be more desira-
ble when working steel. Other brands, which give sat-
isfaction when made into lathe and planer tools, prove
useless when made into tools having projecting cutting
teeth, as milling machine cutters, etc.

As previously stated, the different makes of self-
hardening steel require different methods of treatment.
One gives best results when worked (forged) at a full

279

A few don*ts.

red heat, while another requires a much higher heat.
As the steel is less plastic when red-hot than most
carbon steels, it is necessary to use greater care in re-
gard to the manner in which it is hammered. A heavy
hammer should be used, if a large section is to be forged,
as it is necessary to have it act uniformly on the entire
mass, or the surface portion will be drawn away from
the interior, and, as a consequence, a rupture will be
produced. Small pieces should be forged with lighter
blows, or the steel will be crushed.

Do not attempt to forge when the temperature is
lowered to a point where the steel loses its malleability,
or it will be injured.

It is very necessary that a uniform heat be main-
tained throughout the piece. Do not think, when work-
ing a small section, that it is safe to forge when it has
cooled to a low red, because some heavier portion has
not cooled below a full red.

Do not allow the steel to cool off from the forging
heat. After forging, place the piece in the fire again,
and allow it to come to a uniform bright red. Do not
allow it to **soak" in the fire, but it should be heated
at this time without the aid of the blast. When it has
reached a uniform red heat, remove from the fire, and
allow it to cool in a dry place, not exposed to the action
of any draft.

While most self -hardening steels will become hard
enough when cooled in the air, it is sometimes necessary
to have the tool extra hard. In such cases, it may be
cooled in a forced blast. Some steels give better re-
sults if cooled in oil, others require cooling in hot oil,
while others may be cooled in hot or cold water. Gen-
erally speaking, however, it is not advisable to bring

280

Different steels need different treatment.

most brands of this steel in contact with water when
red-hot.

While it is generally admitted that self-hardening
steels are principally valuable for lathe, planer, and
similar tools, when cutting hard metals or running at
high speeds, there are makes which give excellent sat-
isfaction when annealed and made into such tools as
milling machine and similar cutters.

When it is necessary to have the stock in an an-
nealed condition, it is advisable to procure it in this
state, as the manufacturer, understanding the composi-
tion and nature of the steel, is in a position to anneal
it in a more satisfactory manner than the novice. How-
ever, if it is considered advisable to anneal it in the
factory where it is to be worked, it may be accom-
plished. Different makes of steel require treatments
differing from each other, the treatment depending on
the element used to give it its hardening qualities.
Some brands may be annealed sufHciently to work in
the various machines used in working steel to shape
by heating to a bright red and burying in green pine
sawdust, allowing it to remain in the sawdust until cool.

Most brands may be annealed by keeping the steel
in an annealing furnace at a bright red heat for from
twenty- four to forty hours, then covering with hot sand
or ashes in the furnace, and allowing to cool. It should
be about the same length of time cooling as it was ex-
posed to the heat. It is necessary many times to
machine it with tools made of the same quality of steel,
on account of the natural hardness and density of the
stock. It is claimed that tools made of certain brands
of self-hardening steel give better results when cutting
chilled iron than tools made of high carbon alloy steels.

28X

Get reliable steel.

The writer cannot substantiate this claim, as he has
never been able to get as good results as when using an
extra high carbon alloy steel, properly treated.

However, it is safe to say that used for machining
(roughing) work in the lathe, planer, and similar
machines, can be made to do many times the amount
of work in a given time than would be the case were
ordinary carbon steel tools used.

Much better results may be attained, however, than
is usually the case, if makers* instructions are implicitly
followed.

On account of the rapidly growing popularity of
certain makes of this class of steel, many swindles
have been perpetrated by unscrupulous parties, claim-
ing to be representatives of a reliable house. A tool
made, as they claim, from the steel they were selling
is submitted for trial. It proves to be all that could
be asked for, and a quantity of steel is ordered sent
C. O. D. When this is received and paid for, it is found
to be of no use. Parties purchasing steel of any but
known and reliable steel concerns do so at a great risk, as
a number of manufacturers have found to their sorrow.

Steel for Various Tools.

There is no one topic connected with this work that
caused the writer so much anxiety as the one under
consideration, because a temper of steel that gives en-
tire satisfaction when used in one shop, would not
answer when made into tools intended for the same, or

282

Phosphorus in steels.

similar purposes, in a shop situated on the opposite
side of the street. This is simply because in one case
the operator who forged or hardened the tools under-
stood handling the steel, and in the other case a man
totally incompetent was entrusted to do the work.

Then again, steels of certain makes are more free
from harmful impurities than others. A steel contain-
ing a low percentage of these impurities can safely have
a higher percentage of carbon. Certain steels which
are low in their percentage of phosphorus can have a
greater amount of carbon than other steels which con-
tain more of this harmful impurity.

A tool made of 1.4 per cent, carbon steel low in
phosphorus will not cause as much trouble as if made
of a 1.25 per cent, carbon steel containing a greater
amount of phosphorus, but its capacity for cutting hard
metals, and holding its edge when running at high
speeds, is much greater.

Knowing the tendency in many shops to use a high
carbon steel, and realizing the advantages of so doing,
the writer would advocate the use of such steels, were
it not for the fact in many cases the results have been
anything but satisfactory, because men totally unfit for
such work were employed to forge and harden the tools
made from them.

But it has seemed wise to give the tempers of tool
steel suited for certain purposes, the reader bearing in
mind that in many cases it is safe and advisable to use
a higher carbon, provided due care is exercised when
working it during the various operations of forging,
annealing and hardening. As previously stated, steel
of a certain make and temper giving excellent results
in one shop does not always give satisfactory results in

Z83

The degrees of hardness.

some other shop on the same class of work. Knowing
from experience that the variable factor is the man
working the steel, rather than the steel itself, the writer
has deemed it wise to quote the experience of various
steel makers, rather than results of his own personal
experience.

Degree of Hardness

Percent-
age of
Carbon

Should be used for

Very hard

1-5

Turning and planing tools for
hard metals, small drills,

gravers.

Hard

1.25

Tools for ordinary turning and
planing, rock drills, mill
picks, scrapers, etc.

Medium hard

1.

Taps, screw thread dies,
broaches, and various tools
for blacksmiths' use.

Tenaciously hard

•85

Cold sets, hand chisels, ream-
ers, dies, drills.

Tough

•75

Battering tools, cold-sets, shear
blades, drifts, hammers, etc.

Soft

•6s

Battering tools, tools of dull
edge, weld steel for steeling
finer tools, etc.

While the foregoing table gives the tempers of
steel that can safely be used for the purposes specified,
it is many times advisable to use steel of a higher per-
centage of carbon.

Then again, it is sometimes best to use a low carbon
steel of good quality, in order to get the maximum
amount of toughness in the interior portions, packing
the finished tool in a box containing charred leather, as

284

How to make steel extremely hard.

explained under Pack Hardening, and running for a
sufficient length of time to get an extremely hard sur-
face when hardened. By adopting this method, it is
possible to get a cutting surface that will stand up when
running at a high rate of speed, and yet be strong
enough to resist extremely rough usage.

When it is desirable to get the steel extremely hard
and very deep, in order to allow for grinding, and yet
have the tool sufficiently tough to stand up, use a high
carbon steel, pack in a box as described, running in the
iire at an extremely low heat ; quench in a bath of raw
linseed oil.

In order to provide a guide for use in selecting
steel suitable for various purposes, the following list
is given. It is the result of the writer's experience, and
information picked up here and there. A very notice-
able fact, however, must be taken into consideration,
namely: mechanics in the same class do not advocate
the use of steel of like tempers, even when making tools
of the same kind, to do the same class of work under
the same, or similar circumstances, so no rule can be
given arbitrarily.

The reader should, however, bear in mind that
steels, which contain impurities to any considerable de-
gree, cannot safely be used with the percentage of
carbon mentioned. But as most of the leading steels
on the market have received their standing because they
are practically free from these impurities, it is safe
when using them to use the percentages of carbon
mentioned.

There are several makes of crucible tool steel
on the market, which are exceptionally low in their
percentage of impurities, and when using these, it is

285

About cast steel.

safe to use a higher carbon than the one mentioned,
provided due care is used when heating for the various
operations of forging, annealing and hardening.

In the following pages the term crucible steel is
intended to denote crucible tool cast steel.

The term cast steel is often misunderstood by me-
chanics, and many are of the opinion that any cast steel
is tool steel. Such, however, is not the case, for the
products of the Bessemer and open hearth processes
are cast steel in the same sense that crucible steel
is, yet they are not understood as tool steels, although
products of both processes which were highly carbon-
ized have been sold to parties as tool steel.

Arbors for saws.
Saw arbors, and similar articles, when made from
crucible steel are made from a stock containing .60 to
.70 per cent, carbon. When made from open hearth
steel the percentage of carbon is about the same,
although some manufacturers claim good results when
a lower percentage is used.

Arbors for milling machines.
Milling machine arbors when made from crucible
steel give good satisfaction if a steel of .70 to .80 per
cent, carbon is used. Unless they are to be hardened,
better results are obtained if the steel is worked to
shape without annealing, as it is much less liable to
spring when subjected to strain in use. In shops where
great numbers of these arbors are used crucible steel
is considered very costly. In such cases open hearth
steel containing .40 to .60 per cent, carbon is often
used. Many times a stock containing a higher per-
centage is used.

Augers.
Augers for wood-work are made from crucible
steel of .70 to .80 per cent, carbon.

Axes

are made from crucible steel containing i.oo to 1.20
per cent, carbon.

Barrels for Guns

are made from crucible steel containing .60 to .70 per
cent, carbon, while some manufacturers use an open
hearth steel containing .50 per cent, carbon, and others
claim to use the same steel with . 60 or even . 70 per cent.

Centers for Lathes

are made of crucible steel containing .90 to i.io per
cent, carbon.

Chisels for Working Wood
are made from crucible steel containing 1.15 to 1.25
per cent, carbon.

Chisels for Cutting Steel,

where the work is light, give good satisfaction when
made from crucible steel containing 1.25 per cent,
carbon.

Cold Chisels,

for chipping iron and steel, work well if made from
crucible steel containing .90 to i.io per cent, carbon.
Trouble with cold chisels is more often the result of
poor workmanship than an unsatisfactory steel.

Chisels for Hot Work

may be made of crucible steel of .60 to .70 per cent,
carbon.

a87

Chisels for Cold Work,

for blacksmiths' use, are made of crucible steel con-
taining .70 to .80 per cent, carbon.

Chisels for Cutting Stone
are made from .85 per cent, carbon crucible steel.

Cutters for Milling Machine Work

are probably made from a greater range of tempers than
almost any other tool used in machine shop work,
some manufacturers never using a steel containing over
1. 00 per cent, of carbon, on account of the liability of
cracking. Cracking is, however, a result of careless
working, and as much more work can be done in a given
time with a cutter made from a high carbon steel, it
is, generally speaking, advisable to use such steels.
Cutters, 2 inches and smaller, may safely be made from
crucible steel containing 1.25 to 1.40 per cent, carbon.
Cutters, 2 to 3 inches, 1.15 to 1.25. Larger than 3
inches, or if of irregular contour, 1. 10 to i. 20 per cent,
carbon. There are several alloy steels on the market
which give excellent results when made into cutters of
this character, provided extreme care is taken in
heating.

Cutters for Pipe Cutting

may be made from crucible steel containing 1.20 to
1.25 per cent, carbon.

Cutters for Glass

are made from crucible steel containing 1.25 to 1.40
per cent, carbon.

288

Dies (Threading) for Bolts

and similar work, made from stock having rough, un-
even surfaces, may be made from crucible steel con-
taining . 70 to . 80 per cent, carbon. However, when the
dies are hardened by the process described under Pack
Hardening, steel containing i.ooto i.io percent, works
nicely, stands well, and holds a good edge.

Dies for Screw Cutting,

to be used by hand or in screw machine, may be made
from crucible steel containing i.oo to 1.25 per cent,
carbon.

Dies for Blanking or Punch Press
work are made from crucible steel containing .90 to
I.IO per cent, carbon. When the articles to be punched
are small, and the stock to be worked is hard, steel con-
taining 1.00 to 1.25 stands better than the lower carbon
steel for small dies. Some manufacturers use a steel
containing 1.25 to 1.40 per cent, carbon, provided it is
low in percentage of impurities. When the work is
not of a shape that requires great strength on the part
of the die, open hearth steel containing .40 to .80 per
cent, carbon is used. The die in this case should be
hardened according to directions given for hardening
tools made from machine steel.

Dies Used for Swaging

metals are made from crucible steel, the percentage of
carbon varying according to the character of the work
to be done. When the die is not to be subjected to
very severe usage, a steel containing .90 to i.io per
cent, of carbon may be used. Where a deeply hard-
ened portion is desirable, a steel containing 1.20 to 1.25
per cent, works nicely.

289

Drawinrr Dies

o

are made of crucible steel containing 1.20 to 1.25 per
cent, carbon.

Dies for Drop Forging.

As the product of different steel manufacturers
varies so much, and the requirements are so varied for
work of different kinds, it is advisable to submit the
article to be made to some reliable steel manufacturer,
letting him furnish a steel especially adapted to the
work to be done. Ordinarily a crucible steel is used
containing .40 to .80 per cent, carbon. However, many
manufacturers consider it best to use a good quality of
open hearth steel containing the proper percentage of
carbon. Small dies, or those having slender portions
requiring great strength, are made of the higher carbon.

Drills— (Rock Drills),

for quarry work, are made of crucible steel containing
1. 10 to 1.25 per cent, carbon.

Drills— (Twist).

Sma// drills are made of crucible steel of 1.25 to
1. 50 per cent, carbon, while larger drills require a steel
of 1. 00 to 1.25.

Files

are made of crucible steel of 1.20 to 1.40 per cent, car-
bon. Files of inferior quality are made of open hearth
steel.

Hammers for Blacksmiths

use are made from crucible steel of .65 to .75 per cent,
carbon.

S90

Hammers for Machinists'

use are made from crucible steel of .85 to 1.15 per
cent, carbon. For the ordinary sizes steel containing
1. 00 per cent, works nicely.

Hardies for Blacksmiths
are made of crucible steel of .65 to . 75 per cent, carbon.

Hobs for Dies

are made of crucible steel of .90 to i.oo per cent, carbon,
when they are to be used for cutting a full thread in a
die. If they are to be used for sizing only, a steel
containing 1.20 to 1.25 may be used, as it will hold its
size and form longer than if made of steel containing
less carbon.

Jaws for Bench Vises

are made from crucible steel of .80 to .90 per cent,
carbon. Open hearth steel is, however, extensively
used for this purpose.

Jaws for Chucks

are strongest if made of crucible steel containing .85
to 1.00 per cent, carbon, although many times they are
made from a good quality open hearth steel.

Jaws for Cutting Pliers

are made from crucible steel containing i.io to 1.25
per cent, carbon. When they are to be used for cutting
piano or other hard wire, they are made from steel
containing 1.40 to 1.50 per cent, carbon.

291

Jaws for Gripping

work in various fixtures are made from crucible steel
of . 80 to . 90 per cent, carbon.

Jaws for Pipe Machines

are made from crucible steel containing i.oo to 1.20
per cent, carbon.

Jaws for Screw Threading Dies,

having inserted jaws or blades, are made of crucible
steel of 1.00 to 1.20 per cent, carbon.

Jaws for Wire Pullers

are made from i.oo to 1.20 per cent, carbon crucible
steel.

Knife Blades.

When crucible steel is used, a stock containing .9
to I.oo per cent, carbon is selected.

Knife Blades,

to be used for whittling and general wood- working, are
made from i.io to 1.25 per cent, carbon crucible steel.

Knives — Draw Knives

are made from crucible steel of 1.20 to 1.25 per cent,
carbon. Many times, however, they are made of open
hearth steel.

Lathe Tools

for ordinary work are made of crucible steel containing
1.25 per cent, carbon. For turning hard metals or
running at high rate of speed, use steel containing
1.40 to 1.60 per cent, carbon.

Lathe Tools.

For turning chilled iron, a high carbon alloy steel
works better than a straight carbon steel.

When it is desirable to run at very high speeds,
use a self -hardening steel.

Machinery Crucible Steel
contains .55 to .65 per cent, carbon.

Mandrels.

Custom differs in various shops. Some mechanics
consider it best practice to make mandrels up to and
including i inch of crucible steel, and for sizes above i
inch advocate the use of machine steel, case hardened.
Others claim best results from crucible tool steel for
all sizes. Mandrels, however, do not require a steel
containing as high a percentage of carbon as cutting
tools. Small mandrels give good satisfaction when
made from steel of from i.oo to i.io carbon, larger
sizes made of steel containing .80 to i.oo per cent.

When mandrels are hardened by the process known
as Pack Hardening, a steel containing .75 to .90 per
cent, will give excellent results.

Mowers.

Lawn mower knives, .90 to i.oo per cent, crucible
steel, although in many instances they are made from
open hearth steel.

Planer Tools for Stone,
•75 to .90 per cent, carbon crucible steel.

Planer Tools for Wood-working
machinery are made of crucible steel containing from
I.IO to 1.25 per cent, carbon.

293

Planer Tools.

If the tools are large and the metal to be machined
is comparatively soft, crucible steel containing 1.25
works nicely. If, however, high speeds are desired or
the metal to be cut is hard, a steel containing 1.40
to 1.50 per cent, carbon gives better results, provided
care is exercised in heating for forging and hardening.
If the stock to be cut is extra hard or it is desirable to
run at speeds higher than is practical when using tools
made from carbon steels, it is advisable to get a reliable
self -hardening steel.

Punches for Hot Trimming,

. 85 to 1 . 00 per cent, carbon crucible steel. Some mechan-
ics claim as good results if the punch is made of open
hearth steel of . 60 to . 80 per cent, carbon, while others
make both punch and die of open hearth steel. These
tools may be hardened in the ordinary manner or they
may be hardened according to directions for hardening
tools made of machine steel.

Punches for Blanking Work

in punch press. The percentage of carbon desirable
depends on the stock to be cut and the skill of the
operators doing the hardening If crucible steel is used,
a range of .90 to 1.25 per cent, carbon is allowable, de-
pending on the character of the work. Many times,
however, such punches, if of a shape and size that in-
sures strength, are made of . 40 to . 80 per cent, carbon
open hearth steel, and hardened as explained under
Making Tools of Machine Steel.

Punches for Blacksmiths
should be . 80 to . 90 per cent, carbon crucible steel.

294

Punches for Railroad Track Work,
about .85 per cent, carbon crucible cast steel is advis-
able.

Reamers.
Small reamers, which are to be used continuously,
should be made from crucible steel of 1.25 to 1.50 per
cent, carbon. When they are to resist great strain,
steel of 1. 00 to 1.25 per cent, may be used. Excellent
results will follow if steel containing .90 to i.io per
cent, carbon is used, and the reamer hardened by the
method described under Pack Hardening. This is es-
pecially true if the reamer is long or slender, or of a
shape that betokens trouble when it is hardened.

Saws (Circular) for Wood,
about .80 to .90 per cent, crucible steel.

Saws for Cutting Steel
are made from 1.25 to 1.50 per cent, crucible steel.

Scrapers for Scraping Surfaces,
1,50 carbon crucible steel. Although many scraper
hands claim best results from using a high carbon alloy
steel.

Screw-Drivers,
small, .90 to 1. 00 per cent, crucible steel; large, .65 to
.80 per cent.

Stamps for Stamping Steel,
1.25 to 1.50 per cent, carbon crucible steel.

Shafts for High Speed Machinery
are many times made from crucible steel, containing
.65 per cent, carbon.

Spindle Steel,
same as shafts.

295

Springs for Ordinary Purposes

are made from i.oo to i.io per cent, carbon crucible
steel. For many purposes, an open hearth steel is used
with satisfactory results.

Springs for Locomotives

are made by some manufacturers of crucible steel con-
taining .90 to 1. 10 per cent, carbon, and by others of a
steel containing .80 to .90 per cent., while in many
cases very satisfactory results follow if open hearth
steel, made especially for the purpose, is used.

Springs for Carriages

are made from crucible steel containing .80 to .90 per
cent, carbon, but many more springs of this character
are made from open hearth and Bessemer stock than
from crucible, because it answers the purpose and is
much cheaper.

Taps

are made of crucible steel containing i.io to 1.25 per
cent, carbon in many shops, while others claim better
results from steel containing 1.25 to 1.40 per cent.

Taps for Tapping Nuts,

generally called machine taps, give best results if made
from steel containing i.oo to i.io per cent, carbon.

196

Causes of Trouble,

CO

While most of the causes of trouble when steel is
hardened have been considered under the various
topics presented, it has seemed wise to group together
the more common causes, in order that they may be
referred to more readily by the reader.

Uneven Heats.

Probably the most common cause of trouble is un-
even heating of the piece in forging, annealing or
hardening. As a consequence, violent strains are set
up which cause the piece to crack or, in the case of
heavy pieces, to burst. The different parts of the piece
being unevenly heated, must, when cooled, contract
unevenly; and when two portions of a piece adjoining
each other attempt to contract unevenly — that is, one
contracting more or faster than the other — and both
being rigid to an extent that makes it impossible for
them to yield one to the other, there must be a separa-
tion at the point where the uneven temperature occurs.

High Heats.

A very common. cause of trouble consists in heat-
ing steel too hot for the purpose. High heats open the
pores of the steel, making the grain coarse and causing
the steel to be weak. When the piece is broken, it has

497

Too rapid heating.

a honeycomb appearance — looks full of holes, so to
speak. Now, as there is but a very thin layer of steel
over these holes, when pressure is applied the surface
over the holes caves in, and the steel is unfitted for
doing the maximum amount of work.

Steel which has been overheated may be restored
— unless the heat was high enough to burn or disinte-
grate the steel — by reheating carefully to the refining
heat and quenching ; but it can never do the amount of
work possible, had it not been overheated. Yet, it will
be much better than if left in the condition the high
heat placed it.

Then again, high heats have a tendency to cause
the steel to crack when hardened. This is especially
true if the piece be cylindrical in shape. Cylindrically
shaped pieces will not stand the amount of heat that
may safely be given a piece of almost any other shape
without cracking, although the effect on the grain and
the ability of the steel to stand up and do the maximum
amount of work possible would be the same in any case,
regardless of the form of th e piece or the method of
applying the heat.

Too Rapid Heating.

While it is advisable to heat steel as rapidly as
possible consistent with good results, it should not be
heated too rapidly, as corners and edges will become
overheated before the balance of the article has reached
the proper heat ; and even if they are allowed to cool
down to the proper heat (apparently), the grain has
been opened at these portions, and violent strains are
set up. This is one of the places where experience
seems to be the only guide and where the instructor

298

Fire cracks — how to avoid.

can only give suggestions, wliicli should be heeded
and worked out by each hardener.

Heating Too Slowly.

In attempting to avoid heating too rapidly, do not
go to the opposite extreme and allow the steel to
**soak" in the fire, or soft surfaces will result, and the
steel is not as good as if heated properly.

Fire Cracks.

There are a number of causes for steel cracking in
the fire. Among the more common are, first, the cold
air from the blast, if the work is heated in a black-
smith's forge. Then again, it may be heated in a gas
flame having an air blast. The air may be turned on
too much, resulting in cold air jets striking the heated
steel. If a charcoal fire is used, it is the custom of
some hardeners to throw cold water on the fire. Now,
if the steel is red-hot, the water has a tendency to cause
it to crack in the same manner as if the air from the
blast came in contact with it.

Large articles plunged in a crucible of red-hot
lead, cyanide of potassium, or any substance where they
are exposed to violent heats, are very liable to crack,
especially if there are heavy and light portions adjoining
each other. The unequal expansion tears the steel
apart at the point where the unequally heated portions
adjoin each other. This may be avoided by heating
the articles nearly to a red in some form of fire where
it would heat more slowly, then plunge in the lead to
bring to the desired heat ; or, the article may be im-
mersed in the red-hot contents of the crucible, left for
a moment and withdrawn, immersed again, leaving a

299

Improper forging.

trifle longer, and so continue until it reaches the
desired heat.

If a piece of steel is immersed in a crucible of red-
hot lead or similar material for a certain distance so
that part of the piece is out of the red-hot material, it
should be moved up and down in the molten mass, or
the part below the surface will expand more rapidly
than the adjoining metal. If the article were im-
mersed and withdrawn, repeating this operation until
the desired result is obtained, the heat being applied
gradually, the expansion is more uniform, and the heat
is imparted to the adjoining stock so it can yield to an
extent that does away with any tendency to crack.

Cold Baths.

Extremely cold baths are the cause of a great deal
of trouble when pieces of irregular contour are harden-
ed. It is nearly always advisable, when hardening
articles made of high carbon steel, to warm the con-
tents of the bath somewhat. Many hardeners claim
that oil heated to a temperature of loo degrees to 120
degrees will harden steel harder than if it were ex-
tremely cold. It will certainly cause it to be tougher.

Improper Forging.

This is the cause of a great amount of trouble
when steel is hardened. While the writer claims best
results from steel properly forged, he is aware that
much better results are obtained from steel machined
to shape than if the articles were heated or hammered
in any but a proper manner.

Steel to be made into tools whose cutting edges
are on or near the end should not be nicked with. a chisel

300

A few more don*ts.

and broken, as the portions at the end are rendered
unfit for cutting purposes.

Do not straighten steel that is to be hardened
without heating it red-hot.

Do not attempt to harden a tool of irregular shape
unless it has been annealed after blocking out to some-
where near to shape.

Do not take it for granted that because you have
held a piece of steel in the fire and stuck it into water,
it is necessarily hard. Try it with a sharp file before
brightening the surface preparatory to drawing the
temper, as much valuable time may be saved if the
piece should prove not to have hardened.

When you get a piece of steel that you are in doubt
about, it is advisable to cut a small piece of it from the
bar and harden it, noticing the amount of heat neces-
sary to produce desired results. If this is not done,
trouble may follow when the article is hardened. It is
better to experiment with a small piece of steel than
with a costly tool.

Do not use any but chemically pure lead in a crucible
intended for heating tools, or you will not get as good
results as you might otherwise have.

Do not think that because the surface of red-hot
lead appears to be at about the proper heat, that the
contents nearer the bottom of the crucible are neces-
sarily of the same temperature; because, generally
speaking, the deeper you place a piece of steel in the
contents of the crucible the hotter it becomes. Being
ignorant of this fact, workmen spoil many valuable
articles, and then think the lead has an injurious effect
on the steel, not knowing that it is the amount of heat
given rather than the method used in applying it that

301

Things to remember.

caused the trouble. Impure lead will injure the sur-
face of the steel, but will not alter the appearance of
the grain if the temperature is right.

Remember that steel heated for annealing should
not be subjected to heat for a longer period of time
than is necessary to produce a 7iniform heat of the de-
sired temperature. Steel overannealed does not work
as well in the various operations of machining, neither
will it harden and temper as satisfactorily as though
properly treated.

Remember that heating is a process of softening
steel, and cooling is a hardening process. The slower
the process of cooling is carried on the softer the steel
will be; consequently, it is never advisable to place
red-hot steel that needs softening in cold or damp lime
or ashes.

Always use a clean fire. Dirty slack fires are a
source of a great amount of trouble, as they cause the
surface of the steel to be covered with a sulphurous
oxide.

A fire of new coals should be used (when using a
charcoal fire) for heating steel. Dead coals require
more blast than is good for the steel.

Ten pieces of steel are cracked as a result of
uneven heating to every one that is the result of a
defect in the steel.

Do not think that because the surface of a hardened
piece of steel is not scaled that it is not overheated.
Every degree of heat given it above that necessary to
produce the desired result unfits the steel for doing the
maximum amount of work possible for it to do.

Always harden on an ascending heat. Never heat
a little too hot and allow to cool down to the /r^<?r heat,

302

About carelessness.

as the grain of steel remains in the condition the last
heat leaves it. To refine, it is necessary to allow it to
cool off, and then reheat to the proper hardening heat.

It often happens that the hardener is blamed for
things he is entirely innocent of. A man in this posi-
tion is liable to have enough spoiled work to account
for that is the result of his own carelessness or ignor-
ance without being obliged to shoulder the short-
comings of others. It may be that some careless
blacksmith has forged a tool at heats which unfitted the
steel for the purpose for which it was intended. He
may have heated the steel too hot, and opened the
grain, causing brittleness, or he may have had uneven
heats when he was forging, thus setting up internal
strains which would cause the steel to crack when
hardened. Then again, the tool maker may have at-
tempted to straighten the piece without heating it red-
hot, in which case it is almost sure to spring when
hardened. Or, in the case of a long reamer or tap, the
flutes may have been milled with a dull cutter, which
would, of course, get duller the longer it was used, with
the result that by the time the last flute was milled the
tool would have been stretched very materially. This
is especially true on the side where the last cuts were
taken, as the cutter would be duller than when the
flutes on the opposite side were milled, and the uneven
stretching of the stock would, of course, spring the
reamer.

Another difficulty would also present itself. The
dull cutter would glaze the surface of the tooth that
came in contact with the dulled portion of the mill, and
any surface of steel which is glazed, whether it be from
the action of cutting tools or grinding wheels, will not

303

The effect of not paying attention.

harden in a satisfactory manner. This difficulty is
more pronounced in the case of a piece glazed from the
action of grinding- wheels. While a glazed surface
might not be considered objectionable, if it was to be
ground away after hardening, yet it is not always con-
sidered advisable to grind the cutting faces of reamer
and milling machine cutter teeth. There is no good

.The Derry Collard Co.

Figure 156. The spring of a mandrel.

excuse for using dull tools when machining steel. Not
only does it lead to trouble when the pieces are hard-
ened, but it is a means of wearing the tools out much
faster than if they were kept sharp. Neither can as
much nor as good work be done with dull tools.

It is often the case that a careless workman will
mill the flutes in a long reamer, tap, or similar tool,
without supporting the work properly. In this way the
tool is sprung, first one way, then the other. This not
only results in a crooked tool, but there is no knowing
where it may go when hardened. Many times hard-
ened pieces are sprung by heating when grinding.
This is especially true with pieces that may have sprung
when hardened. Take, for instance, a long mandrel
which may have gone in the direction shown in Fig. 156.
Now, if this mandrel were placed in a grinder and
ground in a manner that caused it to become heated on
the side that is already curved out, as shown in cut, it
would spring still more.

Many times thin, flat pieces are sprung from the

304

What caused the cracks.

expansion of one side when ground in a surface
grinder. The side which comes in contact with the
wheel becomes heated, while the opposite side, from
contact with a mass of cold iron — the table — remains
cool. The side which heats must expand, with the re-
sult that the piece is curved in the direction of the heated
side.

When flat pieces which are hardened are ground
with a glazed wheel or one too fine for the purpose,
they are very liable to crack, commencing at the edge
or end where the wheel leaves the work. Fig. 157 re-
presents a rectangular gauge which cracked as a result

-@

The Derry Collard Co.

Figure 157. Cracked gauge.

of grinding. The fault was laid at the hardener's door,
and he, poor fellow, was doing his best to harden the
gauges in a satisfactory manner, so he said the steel
was no good. An investigation showed the cracks to be
from the end where the wheel left the gauge when
grinding in the surface grinder. The vise which held
the piece was turned one-quarter way around, and it
was found that the cracks were from one side^ instead
of the end of the piece. An examination of the wheel
revealed the fact that it was too fine for the purpose,
and that it was badly glazed. A coarse wheel, free from

305

Cracking from the wrong use of water.

glaze, was substituted and the gauges were found to be
sound after grinding.

Not only may hardened steel be sprung and cracked
from heat generated when grinding, but it may also be
cracked if water is run on it, unless due care is observed.
If the operation is hurried to the extent that it becomes
heated, even when the water is running on it, the water
cools the piece, which is instantly heated again and
then cooled. This sudden expansion and contraction
causes the steel
to become
cracked in
innumerable
places, these
cracks running
in all directions. -
This trouble
may occur when
grinding pieces
of almost any
shape. The
cracks may oc-
cur on the sur-
face of a cylin-
drical piece, on the flats of a square, or on the face of
an article being ground. Fig. 158 represents a disc
whose face was cracked, as represented, when ground,
with a stream of water running on the work. The fault
did not lay in using water, but in forcing the grinding
faster than the wheel could properly cut the metal.

These few facts are pointed out, because it often
happens that when these troubles arise, the party doing
the hardening is blamed, and unless he is sufficiently

306

Fig. 158. Disc cracked from being
ground too rapidly.

A proper emery wheel for cutter teeth.

versed in the action of emery wheels on surfaces of
steel, he naturally thinks the fault is either in the steel
or in his method of treating it.

Very often milling machine cutter teeth are soft-
ened when ground, the hardener being blamed as a con-
sequence. It is not good practice to use a very fine
wheel when grinding tools of this description, neither
should too hard a wheel be used. Ordinarly an emery
wheel made of 60 to 90 emery will be found about
right, and be sure the face of the wheel is not glazed.
Should it become glazed, use a piece of emery wheel
somewhat coarser than the one in use to remove the
glaze. This also makes the face of the wheel open,
and lessens the liability of heating.

Many times the writer has seen workmen using a
tool ground in a manner that made it impossible for it
to cut. It was forced into the stock, and broke it off.
The tool could not stand this treatment, and gave right
out, the workman in the meantime saying things about
the hardener. When the tool was properly ground, it
worked all right.

Some mechanics do not seem to realize that there
is a proper speed to run stock or cutting tools, in order
to get desired results. As a consequence, they either
run them much too fast, with the result the tools can
not stand up, or they are afraid they will exceed the
proper speed, and, as a consequence, do not produce
anywhere near the amount of work they might.

When cutting a key way or spline in a tool that
is to be hardened, the tool maker should avoid sharp
corners, as they are an invitation for a crack when the
steel is rapidly cooled in the bath. While an article
having sharp corners is not as liable to crack when

307

How tools are weakened by grinding.

hardened by the process termed Pack Hardening as
when treated in the ordinary manner, it is not advisable
to in any way weaken a tool, or give it an invitation to
crack. Consequently, avoid sharp comers as far as
possible, or cuts or deep scratches that tend to weaken
the article.

A milling machine cutter, made with light, weak
teeth, can not be made to stand up when in use ; the
teeth being slender and weak, break like pipe-stems.
Cutters with teeth of this description require greater
care when hardening, to avoid overheating. Being
slender, they spring and break. Do not blame the
hardener if they fail to give s-atisfaction when in use.

Another source of trouble is fine teeth in milling
cutters, reamers, and similar tools. The teeth, being
fine, fill with chips, and in the case of milling machine
cutters, the oil not being able to get to the teeth, can
not conduct away the heat generated, which has the ef-
fect of drawing the temper to a degree that makes it
impracticable to use them.

A short time ago the writer's attention was called
to a side tool for use in an engine lathe. The tool was
made from a well-known brand of steel, which is gen-
erally considered one of the best steels on the market.
It was claimed that the tool could not be made to keep
an edge on a mild grade of machine steel running at a
periphery speed of 30 feet per minute, taking a fair cut.

An examination of the tool revealed the fact that
it was ground in such a manner that the cutting edge
had no backing. It might possibly have stood up
if the material being machined had been wood in-
stead of steel. Because the tool would not stand,
the hardener was considered as being to blame. When

Why reamers, broaches, etc., break.

properly ground, it stood up all right without re-
hardening.

Milling machine cutter teeth are many times ground
with too great an angle, and the cutting edge, not having
backing, gives way. Or it may not be given as much
clearance as it should have. As a consequence, the heel
of the tooth rubs, and the friction resulting trom this
contact of the heel of the tooth with the material being
machined produces heat, which softens the tooth. It
is tried with a file, found to be soft, and the hardener
is blamed.

Many times the liquid supplied to keep cutting tools
cool, and to lubricate the cutting edges, can not reach
the cutting edges of the tool. As a consequence, it
becomes heated and the temper drawn. This is es-
pecially liable to happen to tools used on automatic
screw machine work, where heavy cuts are being taken.

Twist drills, used in drilling very deep holes in
steel, are very liable to receive insufficient lubrication,
unless supplied with oil tubes, because the oil which
is fed down the flute is forced back by the action of the
chips and the angle of the flutes.

Taps are allowed to become clogged with chips, and
break ; the hardener is blamed, because the tap, it is
claimed, is too hard. Broaches break from the same
cause, and the trouble is placed at the hardener's door.
Reamers are allowed to become clogged, the cutting
edge chips off, and it is said the steel is burnt.

Cases of this character might be enumerated by the
thousands, but it is needless. The tool maker should
bear in mind that a place must be provided for the chips
made when a tool is cutting, or roughly machined sur-
faces or broken tools (possibly both) must follow.

309

Welding.

G-<?=\ /=^

CO

When it is considered necessary to join two pieces
of iron, thus making them one, or when it is desirable
to join the two ends of a bar, thereby making a ring,
it is accomplished by the process called welding.

This is of inestimable value as applied to the
mechanic arts. Not only may iron be welded to iron,
but steel may be joined to steel by this process. Iron
may also be joined to steel.

It is accomplished by heating the metal to a tem-
perature that makes the surface of a pasty consistency,
which for soft steel should be a dark white, for iron a
scintillating white, while for tool steel it should be a
bright yellow. The formation of a soft pasty layer on
the surface of the steel is an absolute necessity, in order
to effect a union of the pieces of metal. This operation
is assisted by scattering fusible substances on the sur-
faces to be united, as these protect the work from
oxidation. These substances are termed /luxes.
Among those most commonly used are borax, clay,
potash, soda, sand and sal ammoniac. Ordinary red
clay, dried and powdered, is an excellent flux for use
when welding steel, and is one of the cheapest known.
Borax melted and powdered is called the best of known
fluxes, but it is so expensive when used in large

31Q

A good flux for welding.

quantities, that its use is confined to the finest tool
steels and alloy steels where it is not possible to heat
the metal as hot as a lower grade of steel.

A very good flux, whose cost is about one-half that
of borax, is a mineral barite, or heavy spar. It does
not fuse as readily as borax, however, but forms an ex-
cellent covering for the heated surface of the steel. It

is necessary to fur-
nish this coating for
the surface of the
steel, in order to pre-
vent oxidation; for
if any portion is
oxidized, no matter
how small the por-
tion may be, it fur-
nishes a starting
point for a break or

Figure 159. First operation on special
swaging die.

fracture when the piece is under heavy stress. Al-
though steel may be welded, it is a job to be avoided
when the welded piece requires hardening.

Pieces are welded and afterwards hardened which
remain intact, but it is not advisable unless the weld is
to be made by a smith skilled in this particular branch
of the business, and even then it is attended with vary-
ing results.

The writer was at one time connected with a
manufacturing concern who built 50 machines for
swaging wire. The operation of reducing the diameter
of the wire was accomplished by dies known as swag-
ing dies. These were actuated by hammers working
inside of a large ring. This ring was made of tool
steel, and in order to save expense, it was considered

311

Why the piece broke at the weld.

advisable to take flat steel of the desired size to allow
for finishing all over, bend in the form of a ring and
weld the ends. A very skillful smith was given the
job, but when finished and hardened, the rings broke
apart at the weld. When broken to examine the grain,

it was evident that
the smith had used
extreme care, yet
a small portion of
the welded surface
was found to be
oxidized ; c o n s e -
quently, it could
not unite at that
place, and a rup-
ture started from
that point.

The method of
procedure was
changed, stock
sufficiently large
was procured and
split, as shown in Fig. 159. It was then opened until
it resembled Fig. 160, and was afterward hammered
to shape. Before shaping by hammering, however,
the sharp comers were removed by means of a chisel.
After machining to the desired size to allow for grind-
ing, they were hardened as described under Harden-
ing Large Rings, with the result that not one was
lost.

While steel can be welded if great care is used, it
is very apt to result disastrously if the steel is to be
hardened. Not only has this been the writer's ex-

The De/ry CoUard Co,

Figure i6o. The special swaging die finished.

31a

Substitute for borax.

perience, but it seems to be the experience of most
practical writers on the subject.

Other Things,

CO

Substitute for Borax.

The following rule for preparing a substitute for
borax for use in welding high carbon tool steel was
given the writer several years ago by a blacksmith who
was considered as an expert in welding steel. He
claimed that steel could be welded by use of this flux
at a lower temperature than is required with borax :

Copperas 2 ounces.

Common Salt 6 *'

Saltpetre i ounce.

Black Oxide Manganese, i * *

Prussiate of Potash i **

All pulverized and mixed with 3 lbs. good welding
sand.

Charred Leather.

While it is possible to purchase charred leather of
a desirable quality, so much depends on the condition
of this article that it is always advisable to prepare it
in the shop where it is used, if possible.

Use heavy leather, as scraps left when shoe soles
are punched. Never use light leather, as there is little

313

Charred bone for colors.

goodness in it after charring. The very best article for
the purpose can be procured from shoe shops.

To char the leather, fill one or more hardening
boxes with small pieces, place the cover in position and
seal with fire-clay. Place in the furnace, leaving it
just long enough to char sufficiently, so it can be pounded
fine. Do not expose it to the action of heat long enough
to destroy the '•'• goodness'' of the leather.

A very satisfactory method is to fill boxes, 9x9x36
inches, with the leather scraps, sealing the covers as
described, and placing them in the furnace at night
after the work has been withdrawn. The remnant of
fire and the heat of the furnace are sufficient to char the
leather during the night. As previously stated, do not
overchar. It should be exposed to the action of heat
only long enough to break in pieces readily when
pounded. If smaller boxes are used, it is not advisable
to leave in the furnace over night. They must be
watched, and taken out when the leather is charred
sufficiently.

Charred Bone for Colors.

It is necessary, in order to obtain nice colors, that
the work be polished and absolutely clean ; unpolished
surfaces will not color. Grease also prevents the ob-
taining of satisfactory work.

Pack the work in boxes as previously described,
except that charred bone is used as packing material.
When it has run the proper length of time, remove the
box from the furnace, and dump into a tank of water
having a jet coming up from the bottom. Better colors
are obtained if a bath is used having an air pump con-

314

How to char bone.

nected with the inlet pipe, as illustrated in Fig. 134.
This shows an easy way of putting in an air pipe,
connected with inlet water pipe. Soft water in the
bath gives much better results than hard, although
very satisfactory results may be obtained with hard
water if the air pipe is connected as described.
When hardening for colors by the method under con-
sideration, it is essential that the box be held very close
to the top of the water when dumping the work ; the
box should be inverted quickly, to prevent the air
striking the work before it reaches the water. If the
air comes in contact with the metal, the surface as-
sumes a blue-black color. This is sometimes desirable,
but not in connection with work packed especially for
hardening for colors.

When the work is cold, it may be removed from the
bath and boiled in clean water. Dry in sawdust, and
oil the surface either with sperm oil or vaseline. This
has the effect of making the colors more prominent,
and it will also keep the steel from tarnishing or rusting.

To Char the Bone.

It is sometimes considered desirable to use bone
rather than leather, and it is thought that the expended
article would not give the necessary hardness. Yet it
may be necessary that the articles be tough. This may
be accomplished by taking raw bone, filling a small
hardening box with it, placing the cover in position,
and sealing with fire-clay. When the day's work of
hardening is taken from the furnace, the box may be
placed in it, the door shut, the fire extinguished, and
the box left until morning. If the furnace is one

315

How to preserve the bone.

having light walls, that would lose their heat rapidly, it
would be found necessary to apply the heat for a time.
The bone will be found charred when the box is opened.
Care should be observed that the charring is not over-
done^ however.

Charred bone may be used as packing material
either alone or with an equal quantity (in volume) of
granulated wood charcoal.

Preserving the Bone.

When the hardened articles are removed from the
bath, the water may be drawn off, and the packing ma-
terial taken out and dried. This may be done by
placing it on top of the hardening furnace, if that be of
sufficient size ; if not, it may be spread out thinly and
allowed to dry. This is the expended bone previously
mentioned.

Expended bone may be used for packing certain
classes of work in, or it may be mixed with an equal
quantity of granulated raw bone and used the same as
raw bone. Or it may be used for packing machine
steel forgings or small articles of cast iron for an-
nealing.

316

An Index to Contents

CO

Action of charcoal on steel 36

Cyanide 10

Aging of gauges 196

Steel 241

Agitated baths 90-91-93

Air annealing 71

Air blast for cooling 230

Should not strike steel 35-63

Air blasts cause cracks 299-302

Air hardening steel 278

Annealing 23 1

Air jet in case hardening 233

Alloy steels 277

Anneal at uniform heat 84

Annealing 271

After blocking out 301

Between boards 73

Methods of 71

Roughing out 78

Annealing in ashes 72

Cold water 73

Crucibles 97

Furnace — danger of 74-75

Gas furnace 74-75

Iron boxes 75-76-77

Lime 72

Machinery steel 81

Object of 71

Self-hardening steel 28 1

Sheet steel 270

Wrong way 81

Arbors and mandrels 219-220

317

Arbors for saws 236

Arbors — taper 187

Appliances for case hardening .242

Ashes for annealing 72

Attempting the impossible 127

Augers 287

Axes 287

Axles — case hardening of 246

Balls — case hardening of 242

Barrel for hardening bath 256-257

Barrels for guns 287

Baskets for hardening Ill

Bath for case hardening small pieces 229

Cooling mandrels, etc 191

Grooved rolls 194

Hardening taps 157-158-160

Springs 86

Toughening 87

Bath of oil for springs 263-264

Baths for case hardening 254

Baths for hardening.

Brine 86-89

Citric acid 87

Hardening 85-86-87-96

Hardening dies 133-135-136

Heated 66-92

Heat for best work 156

Lead 96

Mercury 85

Oil 86

Oil and water 88

Poisonous baths 87

Saltpeter 87

Springs 260-261

Sulphuric acid bath 87

Water 86

With liquid in motion 90-91-93

Bench vises — jaws for 29 1

Bessemer steel — case hardening of 238

Hardening 1 1 1

Not good for tools 275

^3.8

Best steel for mandrels or arbors 189

Punches 142

Bevel gears for bicycles 235

Bicycle axles 246

Chains 239

Cones— hardening 202

Crank testing 82

Parts— case hardening 234

Blacksmiths' chisels 287-288

Forge for hardening dies 129-130

Forge — heating in 35

Hammer 290

Hardies 29 1

Punches 294

Blades of knives 290

Blame — shifting of 80

Blaming the hardener 303

Blanking dies 214

Blanking press dies 289

Blanking work punches 294

Blister steel 276

Blocking out work for annealing 78

Blow pipe and candle for tempering 162

Blow pipe and spirit lamp 44-45

Boiling water for springs 265

Bolt dies 289

Bone 223

Black for case hardening 223

Cast iron in 316

Charred 314-315

Expended 316

Packing steel in 316

Preserving 316

Should never be used in pack hardening 250

Borax — substitute for 313

Boxes for heating dies 132

Pack hardening 206-209

Box for case hardening 227-239

Hardening springs 263

Heating swaging dies 224

Brine bath 86

Brittleness 66

319

Brittleness — due to phosphorus * 63

In wood-working tools 200

Bunsen burner 4445

Burns from cyanide — caution 110

Burnt steel — restoring 298

Bursting from internal strains 65

Cams of low grade steel 24 1

Candle and blow pipe for tempering 162

Carbonaceous'paste 46

Carbon and quality 22

Best for various tools 284

Necessary for good results 29

Penetrates iron 275

Percentage of 15-20-21-29-33

Surface 63

Careful hammering , 69

Carelessness 303

Careless workmen 17

Carriage springs , 296

Case hardening 225

Baths. 254

Bicycle parts 235

Furnaces 253-254

Gas pipe 226

Imitation of Ill

Machine nuts 251

Many small pieces 229

Portion of piece 248

To leave soft places 249-250

Cast iron bad for steel 206

In annealing 76-81

Cast steel 286

Catch pan in baths 229-256

Causes of trouble 297

Cautions about lead bath 100

Cemented steel 275

Centering steel 23-24

Centers for lathes 287

Of mandrels or arbors should be hard 191

Chain blocks 239

Chain studs 247

2^o

Charcoal 232

Action of on steel 36

Annealing 75-76-77

Prevents dross 101

Charred bone for colors 314

Leather for annealing 85

Leather for heating dies 132

Leather — making 313

Leather toughens steel 239

Charring the bone 315

Cheapening cost of production 8

Cheap steel 31

Chilled iron— steel for 28 1-282

Tools for 293

Chisels for cutting steel 287

Chisels for wood 287

Chisel temper 27

Choosing steel 28

Chuck jaws 29 1

Cigars — effect on steel 87

Circulation of water necessary 256-257

Citric acid bath 87

Clay for filling corners 176

Clean fires 302

Clock springs— hardening 260

Coals not always good 63

Coke for high carbon steel 37

Cold air blast cracks steel 35-63

Baths not usually advisable 1 14-300

Bending of springs 269

Causes cracks 299

Chisels 287-288

Water annealing 73

Water bad for springs 259

Work 287-288

Collars to prevent case hardening 251

Color blindness 11

Coloring gun frames 109

Colors denote temper 1 17-123

For springs 269

In case hardening 233

Obtained with cyanide 108

321

Colors on case hardened work 258

On malleable iron Ill

Reason for 124-125

Visible 117

Cooling case hardened work 234

Deep hole in die 94

Device for gauges 196

Dies for screw cutting 151

Flat plates 179

Grooved rolls 193

Gun springs 182

Half round reamers 163

In air blast 280

In bath 14

In small bath 94

Jaws of hardening device 181

Milling cutters 166

Pieces with holes near edge 199

Plate mounted on springs 181

Shank mill 94

Springs 262-263-264

The oil bath 263-264

Thin pieces 245

With dirty water 95

Commercial bars vs. hammering 70

Common error 279

Compounds for hardening 88

Cones for bicycles— hardening 202

Considerations in hardening 127

Continued heating 84

Continuous or agitated baths 90-9 1-93

Contraction and expansion 12-14

Converted steel 275

Correcting wrong annealing 82

Cost of production 8

Testing steel 33

Counterbores 158-187-188

Countersinking too deeply 187

Covering paste 46

Cracking in lead bath. 100

Liability of 271

Of hollow articles 175

322

Cracking of round pieces 62

Cracks 14-35-298-299

Cause of 305

Prevention of 203-204

Where they occur 100

Crank axles — hardening 235-246

Critical temperature 13

Crucible cast steel 276

Steel 286

Crucibles — annealing 97

Should always be emptied 101

Used for lead baths 97

Crushing grain in hammering 69-70

Cutters for milling machine 288

Glass 288

Pipe cutting 288

Cutting pliers 291

Point of tools 7

Tools— hardening 86-87

Tools of machine steel 241-243-272-274

Cyanide — action of 106

Bath best for cutting tools 105

Bath for watch springs 267

Coloring with 108

Hardening furnace 106

Hardens surface 107

Heated in open forge 50

Heating bath — advantage of 46-108

Of potassium a poison 107

Of potassium bath 105

Of potassium for case hardening 227

Of potassium furnace 51-52

Should be chemically pure 106

Solution prevents lead sticking 98-103

Dampers 39-40

Danger from small fire 190

Cracking removed 138-139

In steel welds 311

Of cast iron in annealing 76-81

Overheating in annealing 74-75-83

Decarbonized surface 23-28-35-45-61-64

3*3

Deep case hardening 232

Deep fire best 35

Defects in steel — lack of 302

Degrees of hardness 284

Depth of hardening 89

Detecting time of cracking 100

Device for cooling thin plates 179-180

Die or punch hardest ? 140

Dies— baths for hardening 133-136

Blanking press .• 289

Boxes for heating 132-224

Cracking from internal strains 154

Drawing 290

Drawing temper of 139

Drop forging 290

For cartridges and other work 197

Forming 144

For punching 241

Furnace for 130-131-137

Heating in charred leather 132

Hardening 149-204-215-221

Heating 40

Heating box for 145

Hobs for 291

Method of cooling 151

Methods of hardening 129

"Spring" 153

Starting scale before hardening 134

Tempering 153

Tongs or grappling hooks 135-136

To prevent cracking 138-139

Punch press work 138-143-249

Ring 144

Ring — furnace for 145

Screw cutting 289

Swaging 289

Threading bolts 289

Difference in steel 16

Different results in case hardening 237

Steels 26

Difficult pieces to harden 217-218

Dipping thin pieces 245

3H

Dirty water for cooling 95

Disc cracked in grinding 306

Dont's 280-301

Doubts about steel 274

Drawing dies 290

Forming dies 144

Milling cutters 167-168

Punches 142-143

Ring dies 147-148

Slitting saws 183

Springs 265-266

Temper 56-116

Temper of dies 139

Temper of T slot cutters 174

Draw knives 228

Drill rod not good for punches 142

Drills for rock 290

Twist 290-309

Prop forging dies 290

Dull cutters spring work 303

Eccentric centering 24

Holes in articles 198

Economy in heating 45

Of inspection, 33

Effect of continued heating 84

Heat on hammered steel 69

Oil on temper color 125

Slight changes in heat 123-124

Emergency annealing 74

Emery wheel— use proper 307

Equalizing heat of lead bath 106

Error — common 279

Even heating by lead bath 92

Exact tempering by thermometer 123

Examples of hardening 127

Expansion and contraction , 12

Expended bone for Bessemer steel 233

In annealing 83

Experience 16

Experiment in partial hardening 248

Extravagant economy 24

Extreme hardness 285

3*5

Falling heat 62

Files 290

Method of hardening 99

Fillets in counterbores 187

T slot cutters 172-173

Filling corners with graphite or clay 176

Fire-clay to prevent hardening 249-250

Fire cracks 299

Fixture for handling ring dies 147

Fixtures for use in hardening 201-202

Flashing springs 265

Flat plates— methods of cooling 179

Springs 270

Flexibility of hardened steel 66

Fluxes 310-311-313

Forging 68

And tempering at once 71

Dies (drop forging) 290

. Improper 300

Self-hardening steels 279-280

Troubles 68

Forming dies 144

Tools 221

Fuels 36-37-38

For hardening baths 96

Fumes from cyanide furnace 52-53

Lead baths 47-51

Furnace for case hardening 242

Case hardening 253-254

Dies 130-131-137

Heating baths 47-49-51-52

Heating springs 262

Heating taps 159

Heavy dies 136-137

Lead heating 96

Pack hardening 210

Ring dies 145

Furnaces — location of 54

Gas as fuel 37

Blast for heating 42-43-44-45

Furnace for dies 137

316

Gas pipe for case hardening 228

Gauges — aging of 196

Crack from grinding 305

Hardening ring 195-196

Packing for hardening 240

Snap and ring 215-216-218

Gear for chainless bicycles 235

Genesis of pack hardening 203

German steel 276

Glass bath for hair springs 267

Cutters 288

Hardening bath for watch springs 54

Heating baths 46

Government method of hardening files 98-99

Grain of tool steel 55-56-57-61

Granulated raw bone 243

Graphite for filling corners 1 76

Grinding cracks tools 305-306

Taps to show color 161

Tools right 307

Gripping jaws 292

Grooved rolls— hardening 192

Gun barrels 287

Gun frames — coloring 109

Hardening 252

Springs — cooling 182

Hair springs 267

Half round reamers 162-163

Hammer — blacksmiths' 290

Machinists' 291

Refining 69-70

Hammered steel 69

Handle-bar binders 235

Handling heavy dies 135-136

Maximum amount of work 104

Ring dies 146

Harden at lowest heat 126

Hardened work — straightening 1 15

Hardening 22

Arbors 189

A screw driver 184

327

Hardening baths 85-86-S7-96-105

Bessemer steel 1 1 1

Between plates 178

Bicycle parts 235

Compounds 88

Cutting tools 86

Depth of 89

Dies 129

Dies without " twist " 150

Eccentric pieces 198

Files 98-99

Fixtures 201-202

Grooved rolls 192

Half round reamers 163

High carbon steel 285

Holes 90-93

Hollow mills 175

Hot water 1 13

In baskets 1 1 1

Large pieces 35

Lead 96

Locally 252

Long tools , 30-104-154-155-258

Machine for thin articles 180

Machinery steel 1 10-1 1 1-225

Malleable iron 110

Mandrels, arbors, etc 189

Milling cutters 164-165

Places 243

Ring dies 144-145-147

Saws 178

Screw cutting dies 149

Shank mills 169-170

Small tools— mixture for 98

Springs 259-260-26 1-262-263-264-265

Steel 112

Taps and dies 53-156-160-202

Temperature of different steels 59

The punch 141

Thin pieces 178-244

Walls of holes 195

Watch springs 54

328

Hardening wood-working tools 200-201

Hardies for blacksmiths 29 1

Hard metals— steel for 277

Hardness— degrees of 284

Due to cyanide bath 51

Extreme 285

Heat depends on carbon 55

For welding '. 310

High 297

Necessary to draw temper 117

Of lead bath— care about 102

Rapid 298

Refining 13-56

Should be low as possible 13

Slow 299

Slowly for tempering 140-125

"Soaking" 299

Strength depends on 107

Uneven 297

Work — timing 231

Heated baths 66-92

Advantages of 156

Heath 277

Heating articles of irregular shape 67

At right speed 60-61

Box for ring dies 145

Cyanide in an open forge . ^ 52

Cyanide of potassium 46

Dies 40

Dies in boxes 132

Dies — proper method 133

For hardening with lead bath 96-100

Gas blast 42-43-44-45

Glass 46

Grooved rolls 192

In a forge 35

Lead 46-49

Tin 46

Tubes in open fire 63

Large work 45

Long tools in lead bath 104

Machine for slender punches 143

329

Heating mandrels 186-189

Screw dies in boxes 152

Slender punches 143

Small work in tubes 41-42

Steel — methods of 34

The baths 92

To avoid strains 113

Tool steel 55

Uniformly 14-60-62

Various substances 46

Water for hardening tools 104-1 13

Wood-working tools 201

Work in cyanide bath 105

Heavy and light portions 62

Blows when hot 69

Cuts 65

Punches 142

Springs 265

High carbon steel 30-278-283

Duty steels 277

For punches 142

Heats 297

Heats open grain 69-70

Speed steel 277

Hobs for dies 29

Holes— hardening 90-93

Hardening out of round 195

In dies — cooling of 93

In shank mills 171

Near edge 198

Stopped with clay 138

Hollow articles— to prevent cracking 175

Danger of steam forming in 175

Mills 174-175

Home-made furnace for dies 131

Furnaces 39-40-47-49-53

Gas blast oven 44

Lead heating apparatus 49-50"

Hot lead for hardening 96

Water bath for springs 265

Work— chisels for 287

How to case harden small quantities 226

330

How to pack harden 207

Huntsman, Benjamin 276

Hydrocarbonated bone 233

Identifying steel 33

Imitation case hardening Ill

Importance of cutting point 7

Improper forging 300

Heating and hammering 70

Impure lead injures steel 97

Increase in production 10

Indifference of some hardeners 64

Inspection of steel — economy of 33

Internal strains 65-79

Strains in dies 154

Iron boxes for annealing 75-76-77

Irregular shaped work 62-67

Jaws for bench vises 291

Chucks 291

Cutting pliers 291

Gripping 292

Pipe machines 292

Screw threading dies 292

Wire pullers 292

Jarolinech 13-59

Kettle for tempering in oil 122

Key ways 307

Knife blades 292

Knives — draw knives 292

Knowing it all 16

Labeling steel 33

Lack of ability 129

Large baths 95

Fire best for hardening 190

Tanks best 139

Work— caution about 222

Lathe centers 287

Tools 292-^09

Tools — tempering 120

Lead and crucibles 97

Bath for hardening 96

331

Lead bath sometimes unsatisfactory — why 97-102

Furnace — handling work in 104

Hardening furnace 47-48

Heating baths 46-49

Heating furnace 96

Should be pure 97

Sticking to work 98-102

Too hot — caution about 102

Leather — charring 313

Charred for annealing -. 85

For heating dies 132

Length of time to heat 23 1

Liability of cracking 271

Lighter blows when cooling 69

Lime for annealing 72

Local case hardening 249-250

Hardening 252

Location of furnaces 54

Locomotive springs 296

Long taps — best methods for 158

Tools— hardening 154-155

Loss due to poor hardening 9-10

Low carbon steel for tools 272-274

Heats best 13

Heats for tempering 124

Lowest heat best for hardening 126

Lubricating tools 309

Machine for hardening thin articles 180

Steel for tools 241-271-274

Taps '. 296

Machinery crucible steel 293

Case hardening 225

Hardening Ill

Steel 19

Machinists' hammer 291

Makeshift oven • 128

Making a screw-driver 184

Malleable iron — hardening 1 10-1 1 1

Mandrels 293

And arbors 219-220

Taper 186-189

33^

Men who harden 15

Mercury bath 85

Metcalf on " refining heat " 56

Method of cooling gun springs 182

Cooling for hardening 89-90-91

Drawing temper 118

Heating steel 34

Milling cutters 55-204-2 12-213-288-307-309

Arbors 286

Drawing temper of 167

Hardening 164-165

Machine 286

Reamers or taps 304

Mixing of different grades 28

Mixture for color work 233

Hardening small tools 98

Hardening springs 260-26 1

Heating wood-working tools 201

Machine steel tools 240-243

Mould for casting lead 101

Mowers 293

Muffle furnace for heating taps 159

Furnaces 37-4 1

Mushet 277

Mysteries — absence of 25

Nature of steel 1 1-80

Neat's-foot oil 261

New charcoal best 36

Nickel-plating prevents case hardening 251

Non-crackers 11

Nuts — case hardening 251

Oil affects temper color 125

And water bath 88-167

Bath 86

For case hardened work 234

Hardening 211-212-214

Hardening thin articles 181

Kettle 122

Long tools 104

Removing strains 67-68

333

Oil for hardening springs 263-264

Tempering furnace 121

Toughens springs 259

Wood-working tools 200-201

Overheated steel — restoring 298

Overheating 13

In annealing 74-75-83

Oxidized steel 63

Pack hardening 203

Arbors and mandrels 219-220

A "teaser" 218

Bath of oil for 21 1-212

Bicycle parts 236

Blanking dies 214

Boxes for 206

Danger in cast iron 206

Depth of hardened surface 205

Dies and taps 215-221

Difficult pieces 217

Don't use bone 205

Forming tools 22 1

Furnace for 210

Gauges 215-216-218

Heat of boxes 210

How to do it 207

Large work 222

Long articles 209

Mandrels and arbors 219-220

Method of packing 206

Milling cutters 212-213

Phosphorus to be avoided 205

Possibilities of 224

Reamers 222-223

Similar articles together 208

Swaging dies 223

Tanks should be convenient 222

Taps and dies 215-221

Time necessary 211

Wiring the work 207

Wrong way of doing 208

Packing for case hardening 228

334

Packing gauges for hardening 240

Material 232

Pan of sand for drawing temper 118

Partial heating 127

Paste for coating small tools 98

Covering work 46

Peculiarities of tool steel 22

Percentage of carbon 15-20-21-29-33

Carbons for tools 284

Penetration of carbon in iron 275

Phosphorus affects steel 272-283

Bad effects of .' 83

Makes steel brittle 252

Piercing punch 141

Pinion gear — hardening of 237

Pipe cutters 288

Machine jaws 292

Pipes in steel bars 32

Planer tools 293-294

Plates — cooling 179

Pliability of hardened steel 66

Pliers for cutting 29 1

" Points" of carbon 21

Poisonous fumes 47-52-53

Potash 261

Preventing decarbonization locally 46

Dross forming on top 101

Lead sticking to work 98-103

Local hardening 249-250

Springs in ring gauges 195

Prevention of cracking 138-139

Springing of long articles 30

Process of annealing in boxes 77

Production — cheapening cost of 8

Increase in 10

Prussiate of potash for case hardening 226

Punch — buckling of 141

Blacksmiths 294

Blanking work 294

Drawing temper of 142-143

Hardening of 141

Heating machine for 143

335

Punch for hot trimming 294

Sheet steel 141

Track work 295

Punch or die hardest ? 140

Punch press dies 133-143-241-289

Quality and carbon 22

Quantity of work to be case hardened 226

Rapid heating 60-61-298

Raw bone contains phosphorus 252

Razor temper 20

Reamer — heating a long 128

Reamers 158-162-222-223-295

Dull cutters may spoil 303-304

Half round 162-163

Heating in lead -bath 104

Reasons for temper colors 124-125

Using lead bath 100

Reducing worn dies 197

Refining— heat 13-56-60

By hammering 69-70

Temperature 13-56-60

Reheating to draw temper 116

Remove strains 65-66-67

Reliable steel 282

Removing lead from steel 102

Strains from grooved rolls 194

Rendered beef suet 261

Resin 261

Use of— caution 104-105

Restoring burnt steel 298

Results of case hardening 237

Revolving furnace for drawing temper 1 18-1 19

Ring dies 144

Drawing temper 147-148

Furnace for 145

Hardening 144-145-147

Ring gauges — hardening of 195-196

Rings without welds 311-312

Rising heat 62

Rock drills 290

336

Rotting of steel 88

Roughing out work 24-25

Safety valve springs 269

Sal ammoniac for case hardening 226

Salt and cyanide bath 53-105

Salt for case hardening 226

Satisfactory annealing 75-76

Saturated solution 86

Saw arbors 236

Saw-file temper 21

Saws for wood 295

Hardening of 179

Steel 295

Tempering 183

Scale formed in dies— removing 134

Scrapers 295

Screw cutting dies 289

Hardening 149

Method of heating 152

Preventing twist 150

Screw-drivers 183-186-295

Screws— case hardening 238

Screw threading dies 148-229

Seasoning of gauges 196

" Second blue " 268

Self-hardening steel 278

Annealing 28 1

Separating steel ... 33

Set temper 21

Shafts for high speed 295

Shank mill — cooling 94

Shank mills— hardening 169-170

Methods of making 170

With holes 171

Shapes of steel bars 28

Sharp corners to be avoided 178

Shear steel 276

Sheet steel — annealing 270

Springs 270

Shifting the blame 80

Singing of steel in bath 90

337

Slender articles — hardening 258

Slender tools 273

Slitting saws— drawing temper 183

Slotting saws — hardening of 176

Slow heating.. .. 60-61-299

Best for tempering 125

Small bath for cooling 94-95

Lots of case hardening 226

Pieces— method of case hardening 229

Taps, reamers, etc 158

Work — heating in tubes 41-42

Snap gauges 215-216-240

"Soaking" 299

Soft places on work 249-250

Portions— leaving 248

Soap 261

Spots where lead sticks to steel 102

Special preparations 232

Steels 275

Spermaceti oil 261

Sperm oil for springs 26 1

Spindles 242

Spindle steel 295

Temper 21

Spirit lamp for heating 44-45

Spoiled steel 9

Spring dies 152

Springing of mandrel 304

To prevent 155

Spring of work by dull cutters 303

Springs— bath for 86-260-261

Best steel for 259

Carriage 296

Clocks 260

Colors of 269

Danger of bending cold 269

Flat stock 270

Furnace for heating 262

Locomotive 296

Safety valves 269

Sheet steel 270

Method of cooling 262

338

Springs — toughened by oil 259

Tempering 259

Watches 54-267

Stamps for steel 295

Steam forming in hollow articles 175

Prevents cooling 93

Steel 19

Affected by phosphorus 272

Air hardening 278

Alloy 277

Bessemer 286

Better than ever 277

Blister 276

Cast 286

Cemented 275

Choice of 28

Converted 275-286

Crucible 279-286

Difference in 16

Different 26

Doubts about 274

For chilled iron 281-282

For hard metals 277

For mandrels or arbors 189

For slender tools 273

For various tools 282-285

German 276

Hammer refined 70

(Machine)— tools 271-274

Machinery 20

Nature of 11

None best for all purposes 30

Open hearth 286

Pliability of 66

Saws 295

Self-hardening 278

Shear 276

Spoiled 9

Stamps 295

Usually all right 27

Tool 20

To use for springs 259

339

Steels — special 275

Stiffness — how to secure 252

Stirring lead bath to equalize heat 102-104

Stock — keeping separate 28

Stone work 288

Chisels for 288

Working tools 293

Stop all holes in dies with clay 138

Straightening hardened work 115

Steel 66-301

Work 26-30

Work that is sprung 79

Strains in grooved rolls 194

Internal 65-79

Internal — in dies 154

Removed by reheating 65-66-67

Strength depends on heat used 59-64

Study of steel 11-18-80

Substitute for borax 313

Successful steel working ^ 18

Sudden heating is dangerous 140

Sulphur in lead — avoid it 97

Surface carbon 63

Square corners in counterbores 187

Supporting cutting edges 308

Swaging dies 223-289

Heating boxes for 224

Sweeps for moving pieces of work 258

Tallow for tempering springs 265

Tank for hardening small work 230

Reheating 66-67

Tanks for case hardening 255-256

Should be convenient 222

Should be large 139

Taps 296

Brightening for color 161

Furnace for heating 159

Hardening 156-160-204-215-214

Hardening bath for 157-158-160

Machine 296

Taper mandrels 186

340

Temper 20-21-28

Chisel 21

Milling cutters 213

Razor 20

Saw file 21

Set 21

Spindle 21

Tool 21

Tempers of tools 283-284

Temperature — critical 13

Colors 123-125

For drawing small dies 153

Grades of 20-21

Of counterbores 188

Of lead for hardening 103

Refining 13-56

Tempering 116

A screw driver 164

At very low heats 124

Heat necessary ' 117

In a revolving furnace 1 18-1 19

In oil 121

Is softening 1 16-126

Lathe tools 120

Milling cutters 167-168.

Ring dies 147-148-

Saws 18a-

Small dies 153-

Spoiled steel 82:

Springs 259-265-266.

Springs by thermometer 266

Taps 162

To "second blue" 268

Temporary bath for hardening 257

Furnace for oil 121

Tepid water for hardening 176

Test after hardening 30 j

Pieces 57-58-61

Wires in annealing 76-77

Wires when case hardening 227

Testing a screw driver 185

Bars in stock 32

341

Testing bicycle crank 82

Hardened work 82

Heat of boxes 210-212

Steel 33-57-58-61

Work occasionally 244

Thermometer — care of 266

For gauging heat 1 19-21 1

In spring tempering 266

Thin articles— hardening 180-244

Threading dies 148-289-292

Time for heating gauges 240

Needed for pack hardening 211

Timing heat of work 23 1

Tin heating baths 46

Tool steel 20

Heating of 55

Temper 21

Tools cut faster if pack hardened 204

For chilled iron 283

Hard work 33

Importance of cutting point 7

Lathes and planers 292-293-294

Of machine steel 241-243-271-274

Steel for 282-285

Stone 293

Weakened by grinding 308

Wood-working 293

Tongs for hardening mandrels or arbors .191

Hardening thin articles 178

Heavy dies 136

Preventing hardening 249-250

Toughening bath 87

Steel 239

Toughness — how to produce 252

In wood-working tools 200

Tubes for heating small work 41-42

Turpentine 261

Track work punches 295

Trimming punches 294

Trouble — causes of 297

Troubles from forging 68

T slot cutters 171-172-173-174

34^

Twist drills 290

In hardening dies 150

Types of furnaces 37-38

Hollow mills 177

Uneven hardening from small baths 255

Heating 14-26-60

Heats 297-302

Uniform annealing heat necessary 84

Heating 14-26-60

Heats the secret of success 1 12

Temperature necessary 264

Valuable men to have 128

Vent holes in hollow mills 176-177

Vine-like effect in coloring 109

Warm water for hardening 176

Waste through improper handling 9

Watch spring hardening 54-267

Water annealing 73

Bath 86

Cooled oil bath 214

May crack work 306

Welding 310

Heat for 310

Rings — how to avoid 31 1-312

Steel— don't 311

Wine suppers and steel 87

Wire pullers 292

Wires for testing heat 76-77

Wiring pieces to be hardened 207

Wood saws 295

Chisels 287

Tools 199-200-201-293

Working augers 287

Work done depends largely on tools , 7

Of tool depends on heat used 126

Workman 15

Wrong annealing 82

To anneal 81

Way of pack hardening 208

Wrought iron— case hardening 225

343

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