Armengaud, Jacques Eugène; Leblanc, César Nicolas   [Hrsg.]; Armengaud, Jacques Eugène   [Hrsg.]; Armengaud, Charles   [Hrsg.]
The engineer and machinist's drawing-book: a complete course of instruction for the practical engineer: comprising linear drawing - projections - eccentric curves - the various forms of gearing - reciprocating machinery - sketching and drawing from the machine - projection of shadows - tinting and colouring - and perspective. Illustrated by numerous engravings on wood and steel. Including select details, and complete machines. Forming a progressive series of lessons in drawing, and examples of approved construction — Glasgow, 1855

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ENGINEER AND MACHINIST’S DRAWING-BOOK.

holder, for pricking off distances, the positions of lines,
&c., upon the paper. It is so used in conjunction with
portable scales, the edges of which, being graduated, are
applied to the sheet, and measure off the required dis-
tance. The pricker to this extent supersedes the dividers,
and may be so employed with facility and accuracy. It
is also used in copying drawings, by placing the drawing
on the top of the sheet upon which the copy is to be
made, and pricking through upon the vacant sheet the
positions of the lines, angles, and centres of the drawing ;
thus the copying process is expedited.

Drawing Paper.

Drawing paper, properly so called, is made to certain
standard sizes, as follow :—

Demy,

... 20

inches hy 15J

inches.

Medium,

22f

m

)9

Royal. ...

... 24

„ 19i

9 9

Super Royal,

271

„ 19i

99

Imperial,

... 30

,, 22

9 9

Elephant,

28

„ 23

9 9

Columbier,

... 35

„ 23lr

9 9

Atlas,

34

„ 26

9 9

Double Elephant,

... 40

„ 27

9 9

Antiquarian,

53

,, 31

9 9

Emperor,

... 68

,, 48

9 9

Of these, Double Elephant is the largest in common use
by engineers, and it is the most generally useful size of
sheet. Demy and Imperial are the only other sizes worth
providing for a drawing establishment. Whatman's white
paper is the quality most usually employed for finished
drawings ; it will bear wetting and stretching without
injury, and, when so treated, receives shading and colour-
ing easily and readily. For ordinary sketching or working
drawings, where damp-stretching is dispensed with, cart-
ridge paper, of a coarser, harder, and tougher quality, is
preferable. It bears the use of indiarubber better, receives
ink on the original undamped surface more freely, shows
a fully better line, and, as it does not absorb very rapidly,
tinting lies better and more evenly upon it. For delicate
small-scale line-drawing, the thick blue paper, such as is
made by Harris for ledgers, &c., imperial size, answers
exceedingly well; but it does not bear clamp-stretching
without injury, and should be merely pinned or waxed
down to the board. With good management, there is no
ground to fear the shifting of the paper. Good letter-
paper receives light drawing very well ; of course it does
not bear much fatigue.

Large sheets, destined for rough usage and frequent
reference, should be mounted on linen, previously damped,
with a free application of paste.

Tracing paper is a preparation of tissue paper, trans-
parent and qualified to receive ink lines and tinting
without spreading. When placed over a drawing already
executed, the drawing is distinctly visible through the
paper, and may be copied or traced directly by the ink-
instruments; thus an accurate copy may be made with
great expedition. Tracings may be folded and stowed
away very conveniently; but, for good service, they should
be mounted on cloth, or on paper and cloth, with paste.

Tracing paper may be prepared from double double
crown tissue paper by lightly and evenly sponging over
one surface with a mixture of one part of raw linseed-oil
or nut-oil, and five parts of turpentine. Five gills of tur-
pentine, and one of oil will go over from IJr to 2 quires of
twenty-four sheets.

Tracing cloth is a similar preparation of linen, and has
the advantage of toughness and durability.

Drawing Boards.

Drawing boards are made truly rectangular, and for
common use may be of two sizes, 41 by 30 inches to carry
double-elephant paper, with a margin; and 31 by 24 inches
for imperial and all smaller sizes. Boards much smaller
than this are too light and unsteady in handling, and are
not worth having. They may be of mahogany, oak, or
yellow pine, well seasoned ; \ inch or -fz Rich thick for
mahogany, and 1 inch for pine, or say 1 h inch to allow
for dressing up. They should be barred and dowelled at
the ends, to stiffen them, and resist any tendency to twist,
as well as to afford a suitable edge for the working of the
drawing square. It would be an improvement to line the
working end of the pine board with a strip of mahogany
or other hard wood, as it is liable to wear slightly round
near the corner.

Boards are occasionally made as loose panels placed
in a frame, all flush on the drawing surface, and bound
together by bars on the other side.

Drawing paper may be fixed down upon the ordinary
board, either by damping and gluing its edges, or by
simply fixing it at the corners, and at intermediate points,
if necessary, with pins or with sealing wax or wafers.
The latter fixing is sufficient where no shading or colour-
ing is to be applied, and if the sheet is not too long a time
upon the board. It has the advantage, too, of preserving
to the paper its natural quality of surface. With mounted
paper, indeed, there is no other proper way of fixing. For
large, coloured, or tedious drawing, however, a damp-
stretched sheet is preferable; with colouring or flat tinting,
indeed, damp-stretching is indispensable, as the partial
wetting of loose paper by water-colour swells and distorts
the surface. Damp-stretcliing is done in the following
way: lay the sheet flat on the board, with that side under-
most which is to be drawn upon; draw a wet sponge freely
and rapidly over the upper side, damping the entire sur-
face, and allow the sheet to rest for a few minutes, till it
be damped through, and the surface-water disappears.
Those parts which appear to revive sooner than others,
should be retouched with the sponge. The damping
should be done as lightly as possible, as the sponge always
deprives the paper more or less of its sizing. The sheet is
now turned over and placed fair with the edges of the
board,—sufficiently clear of the working edges to permit
the free action of the drawing square. The square, or an
ordinary straight edge is next applied to the paper, and
set a little within one edge, which is then turned up over
the square and smeared all along with melted glue or
paste. The paper is then folded back and pressed down
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