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Full text of "Modern Mechanical Engineering Vol-I"



a sectional elevation, an outer end, and a sectional end elevation, and simi-
larly with the plan. Half-sections are very common. It is common practice
to draw the plan, looking down on the article, immediately below the side
elevation. The end elevations are usually drawn on the left and right hands
respectively of the plan and side elevation. The end elevation on the left-
hand side is the end view when looking from right to left; and the end
elevation on the right-hand side is the end view looking from the left to
the right.

The aim of a drawing should be to portray the article drawn simply,
exactly, and completely. All the necessary instructions for manufacture
should be given on the drawing. Sometimes this information is given in
the form of notes, but it is better to give it in tabular form. It is usual to
give overall dimensions to assist the shop foreman to understand at once

Looking Oft B

Lookiruj ot\ A

Looking On, C

Fig. 5 — Disposition of Views on Drawing

the size of piece he will be called upon to handle, and to make his arrange-
ments accordingly.
Dimensions.—Dimensions should be written in large bold figures,
and where, as in an arrangement drawing, there are a number of similar
parts, each should have a distinguishing mark, such as capital letters of the
alphabet. Thus the ground plan for a large works would have the columns
marked A, B, C, D, &c., and the different piping systems might be lettered
H!, H2, H3 for hydraulic pipes, Sj, S2, S3, &c., for steam pipes, &c. These
distinguishing marks are of very great assistance in the identification of
pieces in the shop, where they will be painted on if wrought iron or steel,
and probably cast on if cast iron or gun-metal.
The practice in many offices now is to give all dimensions in a drawing
up to 2 ft. in inches, i.e. 23 in., but after 2 ft. in feet and inches, as 2 ft. 7 in.
At least one standard, whether it be this or another, ought always to be
adhered to. It is usual in large firms to give each part a cost number, so
that the actual cost of every detail as it passes through the various shops may
be known. This cost number should be shown on the piece, and an arrow
should indicate precisely its location. This cost number will also be given
in the table at the foot of the drawing, with the location, material, " number
off ", &c. In some cases a refinement is made on the cost system, so that