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MECHANICAL DRAWING SELF-TAUGHT:

COMPRISING

INSTRUCTIONS IN THE SELECTION AND
PREPARATION OF DRAWING
INSTRUMENTS,

_ELEMENTARY INSTRUCTION IN PRACTICAL
MECHANICAL DRAWING_;

TOGETHER WITH

EXAMPLES IN SIMPLE GEOMETRY AND ELEMENTARY MECHANISM,
INCLUDING SCREW THREADS, GEAR WHEELS,
MECHANICAL MOTIONS, ENGINES AND BOILERS.

BY JOSHUA ROSE, M.E.,

AUTHOR OF "THE COMPLETE PRACTICAL MACHINIST,"
"THE PATTERN MAKER'S ASSISTANT,"
"THE SLIDE VALVE"

ILLUSTRATED BY THREE HUNDRED AND THIRTY ENGRAVINGS.

PHILADELPHIA:
HENRY CAREY BAIRD & CO.,
INDUSTRIAL PUBLISHERS, BOOKSELLERS AND IMPORTERS,
810 WALNUT STREET.

LONDON:
SAMPSON LOW, MARSTON, SEARLE & RIVINGTON,
CROWN BUILDINGS, 188 FLEET STREET.
1887.




Copyright by
JOSHUA ROSE.
1883.

PHILADELPHIA.

COLLINS, PRINTER




PREFACE.


The object of this book is to enable the beginner to learn to make
simple mechanical drawings without the aid of an instructor, and to
create an interest in the subject by giving examples such as the
machinist meets with in his every-day workshop practice. The plan of
representing in many examples the pencil lines, and numbering the order
in which they are marked, the author believes to possess great
advantages for the learner, since it is the producing of the pencil
lines that really proves the study, the inking in being merely a
curtailed repetition of the pencilling. Similarly when the drawing of a
piece, such, for example, as a fully developed screw thread, is shown
fully developed from end to end, even though the pencil lines were all
shown, yet the process of construction will be less clear than if the
process of development be shown gradually along the drawing. Thus
beginning at an end of the example the first pencil lines only may be
shown, and as the pencilling progresses to the right-hand, the
development may progress so that at the other or left-hand end, the
finished inked in and shaded thread may be shown, and between these two
ends will be found a part showing each stage of development of the
thread, all the lines being numbered in the order in which they were
marked. This prevents a confusion of lines, and makes it more easy to
follow or to copy the drawing.

It is the numerous inquiries from working machinists for a book of this
kind that have led the author to its production, which he hopes and
believes will meet the want thus indicated, giving to the learner a
sufficiently practical knowledge of mechanical drawing to enable him to
proceed further by copying such drawings as he may be able to obtain, or
by the aid of some of the more expensive and elaborate books already
published on the subject.

He believes that in learning mechanical drawing without the aid of an
instructor the chief difficulty is overcome when the learner has become
sufficiently familiar with the instruments to be enabled to use them
without hesitation or difficulty, and it is to attain this end that the
chapter on plotting mechanical motions and the succeeding examples have
been introduced; these forming studies that are easily followed by the
beginner; while sufficiently interesting to afford to the student
pleasure as well as profit.

NEW YORK, _February, 1883_.




CONTENTS.


CHAPTER I.

THE DRAWING BOARD.

The T square                                                          18

The triangles                                                         19

Curves                                                                21

Selecting and testing drawing instruments                             22

Lead pencils                                                          23

Mixing India ink                                                      25

The drawing paper                                                     26

Tracing paper                                                         29

The ink                                                               30

Testing and selecting India ink                                       30

Draftsmen's measuring rules                                           33


CHAPTER II.

THE PREPARATION AND USE OF THE INSTRUMENTS.

Preparing the lining pen for use                                      34

The shapes of the lining pen points                                   35

Oil stoning pen points                                                36

Preparing the circle pen for use                                      38

The shape for circle pen points                                       38

Shaping circle pens for very small circles                            39

A form of pen point recently introduced; forming the pen point        39

The method of oil-stoning circle pen points                           40

The needle point and pen point                                        42

How to use the circle pen                                             43

German instrument to avoid slipping of a needle point                 44

How to use the lining pen                                             45

Applying the ink to the bow-pen                                       46

Using a straight line or lining pen with a T square                   47


CHAPTER III.

LINES AND CURVES.

Explanation of simple geometrical terms; radius; explanation of
    conventional dotted lines                                         48

A line at a right angle to another; a point; parallel lines           49

A line produced; a line bisected; a line bounding a circle; an arc of a
    circle; segments of a circle; the chord of an arc; a quadrant of a
    circle                                                            50

A sector of a circle; a line tangent to a circle; a semicircle; centre of
    a circle; axis of a cylinder; to draw a circle that shall pass through
    three given points                                                51

To find the centre from which an arc of a circle has been struck; the
    degrees of a circle                                               52

The protractor                                                        53

To find the angle of one line to another                              54

To find the angles of three lines one to the other                    55

Acute angles and obtuse angles                                        57

Triangles; right angle triangle; obtuse angle triangle; equilateral
    triangle; isosceles triangle                                      58

Scalene triangle; a quadrangle; quadrilateral or tetragon             59

Rhomboid; trapezoid; trapezium                                        60

The construction of polygons                                          61

The names of regular polygons                                         62

The angles of regular polygons; the ellipse                           63

Form of a true ellipse                                                69

The use of a trammel for drawing an ellipse                           72

To draw a parabola mechanically                                       73

To draw a parabola by lines                                           74

To draw a heart cam                                                   75


CHAPTER IV.

SHADOW LINES AND LINE-SHADING.

Section lining or cross-hatching                                      77

To represent cylindrical pieces one within the other; to represent a
    number of pieces one within the other                             78

To represent pieces put together and having slots or keyways through
    them.                                                             79

Effects of shading or cross-hatching                                  80

Lines in sectional shading or cross-hatching made to denote the material
    of which the piece is composed--lead, wood, steel, brass, wrought
    iron, cast iron                                                   81

Line-shading                                                          82

The shade line to indicate the shape of piece; representation of a
    washer                                                            83

A key drawn with a shade line; shade line applied to a nut; a German
    pen regulated to draw lines of various breadths                   84

Example of line-shading in perspective drawing, shown in a pipe threading
    stock and die                                                     85

A cylindrical pin line-shaded; two cylindrical pieces that join each
    other; a lathe centre; a piece having a curved outline            86

Line-shading applied to a ball or sphere; applied to a pin in a socket
    shown in section                                                  87

A piece of tube, where the thickness of the tube is shown; where the
    hollow or hole is seen, the piece shown in section; where the body is
    bell-mouthed and the hollow curve shown by shading                88

Example of line-shading to denote the relative distances of various
    surfaces from the eye                                             89

Line-shading to denote that the piece represented is of wood; shade-lines
    being regular or irregular                                        90


CHAPTER V.

MARKING DIMENSIONS.

Examples in marking dimensions                                        91


CHAPTER VI.

THE ARRANGEMENT OF DIFFERENT VIEWS.

The different views of a mechanical drawing; elevation; plan; general
    view; a figure to represent a solid cylinder                      94

To represent the different sides of a cube; the use of a cross to denote a
    square                                                            95

A triangular piece requires two or three views                        96

To represent a ring having hexagon cross section; examples; a rectangular
    piece in two views                                                98

The position of the piece when in its place determines the name of the
    view in the drawing                                              103

View of a lever                                                      105

Best method of projecting one view from another; the two systems of
    different views of a piece                                       106


CHAPTER VII.

EXAMPLES IN BOLTS, NUTS AND POLYGONS.

To represent the thread of a small screw                             112

A bolt with a hexagon head                                           113

United States standard sizes for forged or unfinished bolts and nuts 116

The basis of the Franklin Institute or United States standard for bolts
    and nuts; hexagonal or hexagon heads of bolts                    118

Comparison of hexagon and square heads of bolts; chamfers            120

Without chamfer; best plan for view of both square and hexagon heads 123

Drawing different views of hexagon heads                             125

To draw a square-headed bolt; to draw the end view of a hexagon head 125

Use of the triangle to divide circles                                129

Scales giving the length of the sides of polygons                    135

To find what a square body which measures one inch on each side measures
    across the corners; to find what diameter a cylindrical piece of
    wood must be turned to which is to be squared, and each side of which
    square must measure an inch                                      136

To find a radius across corners of a hexagon or a six sided figure, the
    length of a side being an inch                                   138

To draw a stud                                                       142

To pencil in a cap nut; pencilling for a link having the hubs on one side
    only                                                             145

Link with hubs on both sides; pencil lines for a double eye or a knuckle
    joint                                                            146

Double eye or knuckle joint with an offset; a connecting rod end     147

A rod end with a round stem                                          148

A bolt with a square under the head                                  149

Example in which the corner where the round stem meets the square
    under the head is sharp; a centre punch giving an example in
    which the flat sides gradually run out upon a circle, the edges
    forming curves                                                   150


CHAPTER VIII.

SCREW THREADS AND SPIRALS.

Screw threads for small bolts with the angles of the thread drawn in, and
    the method of doing this                                         152

A double thread; a round top and bottom thread such as the Whitworth
    thread; a left hand thread; to draw screw threads of a large
    diameter                                                         156

Drawing the curves for screw threads                                 157

To draw the United States standard thread                            160

To draw a square thread                                              162

Form of template for drawing the curves of threads                   165

To show the thread depth in a top or end view of a nut; to draw a spiral
    spring                                                           166

To obtain an accurate division of the lines that divide the pitch    167


CHAPTER IX.

EXAMPLES FOR PRACTICE.

A locomotive spring; a stuffing box and gland; working drawings of a
    coupling rod; dimensions and directions marked; a connecting rod
    drawn and put together as it would be for the lathe, vise, or erecting
    shop                                                             169

Drawings for the blacksmith                                          172

A locomotive frame                                                   174

Reducing scales                                                      175

Making a drawing to scale                                            177


CHAPTER X.

PROJECTIONS.

A spiral wound around a cylinder whose end is cut off at an angle    178

A cylindrical body joining another at a right-angle; a Tee for
    example                                                          180

Other examples of Tees                                               181

Example of a cylinder intersecting a cone                            186

A cylindrical body whose top face if viewed from one point would appear as
    a straight line, or from another a circle                        188


CHAPTER XI.

DRAWING GEAR WHEELS.

Names of the curves and lines of gear teeth                          193

How to draw spur wheel teeth                                         194

Professor Willis' scale of tooth proportions                         195

The application of the scale                                         197

How to find the curve for the tooth face                             198

To trace hypocycloides for the flanks of teeth                       200

Sectional view of a section of a wheel for showing the dimensions through
    the arms and hub                                                 202

To draw an edge view of a wheel; rules for drawing the teeth of wheels;
    bevel gear wheels                                                203

The construction to find the curves                                  204

To draw the arcs for the teeth                                       205

To draw the pitch circle of the inner and small end of the pinion
    teeth                                                            206

One-half of a bevel gear and an edge view projected from the same    207

A pair of bevel wheels shown in section; drawing of a part of an Ames
    lathe feed motion; small bevel gears                             208

Example in which part of the gear is shown with teeth in, and the
    remainder illustrated by circles; drawings of part of the feed
    motion of a Niles horizontal tool work boring mill               209

Three bevel gears, one of which is line-shaded; the construction of oval
    gearing; Professor Rankine's process for rectifying and subdividing
    circular arcs                                                    210

Various examples of laying out gear wheels                           214


CHAPTER XII.

PLOTTING MECHANICAL MOTIONS.

To find how much motion an eccentric will give to its rod            223

To find how much a given amount of motion of a long arm will move the
    short arm of a lever                                             224

Example of the end of a lever acting directly on a shoe; a short arm
    having a roller acting upon a larger roller                      225

A link introduced in the place of the roller to find the amount of motion
    of the rod; a lever actuating a plunger in a vertical line, to find
    how much a given amount of motion of the long arm will actuate the
    plunger                                                          226

Two levers upon their axles or shafts, the arms connected by a link and
    one arm connected to a rod                                       227

A lever arm and cam in one piece on a shaft, a shoe sliding on the line,
    and held against the cam face by the rod, to find the position of the
    face of the shoe against the cam                                 228

To find the amount of motion imparted in a straight line to a rod,
    attached to an eccentric strap                                   229

Examples in drawing the cut off cams employed instead of eccentrics on
    river steamboats in the Western and Southern States. Different views
    of a pair of cams                                                232

The object of using a cam instead of an eccentric                    234

Method of drawing or marking out a full stroke cam                   237

Illustration of the lines embracing cut off cams of varying limits of
    cut-off                                                          240

Part played by the stroke of the engine in determining the conformation
    of cut-off cams; manner of finding essential points of drawings of
    cutoff cams                                                      241

A cam designed to cut off the steam at five-eighths of the piston
    stroke                                                           244

Three-fourths and seven-eighths cams                                 246

Necessary imperfections in the operations of cut-off cams            247

Drawing representing the motion which a crank imparts to a connecting
    rod                                                              249

Plotting out the motion of a shaper link quick return                250

Plotting out the Whitworth quick return motion employed in machines  253

Finding the curves for moulding cutters                              257


CHAPTER XIII.

EXAMPLES IN LINE-SHADING AND DRAWING FOR LINE-SHADED
ENGRAVINGS.

Arrangement of idle pulleys to guide bolts from one pulley to another;
    representation of a cutting tool for a planing machine           264

Drawings for photo-engraving                                         267

Drawing for an engraver in wood; drawings for engravings by the wax
    process                                                          268

Engraving made by the wax process from a print from a wood engraving;
    engravings of a boiler drilling machine                          269


CHAPTER XIV.

SHADING AND COLORING DRAWINGS.

Coloring the journals of shafts; simple shading; drawing cast-iron,
    wrought iron, steel and copper                                   277

Points to be observed in coloring and shading;  drawings to be
    glued around their edges to the drawing board; to maintain an even
    shade of color; mixing colors                                    278

To graduate the depth of tint for a cylindrical surface              279

The size and use of brushes; light in shading; example for shading a
    Medart pulley                                                    280

Brush shading                                                        281

To show by the shading that the surfaces are highly polished;
    representation of an oil cup; representation of an iron planing
    machine                                                          282

Example in shading of Blake's patent direct acting steam pump        284

Example of shading an independent condenser                          288


CHAPTER XV.

EXAMPLES OF ENGINE WORK.

Drawings of an automatic high speed engine; side and end views of the
    engine; vertical section of the cylinder through the valve face  289

Valve motion; governor                                               292

Pillow box, block crank-pin, wheel and main journal                  294

Side and edge view of the connecting rod                             295

A two hundred horse power horizontal steam boiler for a stationary engine;
    cross sectional view of the boiler shell                         296

Side elevation, end view of the boiler, and setting                  297

Working drawings of a one hundred horse power engine; plan and side
    view of the bed plate, with the main bearing and guide bars; cross
    sections of the bed plate; side elevation of the cylinder, with end
    view of the same                                                 299

Steam chest side and horizontal cross section of the cylinder; steam chest
    and the valves; cam wrist plate and cut-off mechanism; shaft for the
    cam plate; cross head; side view and section through the centre of
    the eccentric and strap                                          301

Construction of the connecting rod                                   303

INDEX                                                                305




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|Transcriber's note: In this text $T$ indicates a larger capital letter.|
+-----------------------------------------------------------------------+




MECHANICAL DRAWING

SELF-TAUGHT.

CHAPTER I.

_THE DRAWING BOARD._


A Drawing Board should be of soft pine and free from knots, so that it
will easily receive the pins or tacks used to fasten down the paper. Its
surface should be flat and level, or a little rounding, so that the
paper shall lie close to its surface, which is one of the first
requisites in making a good drawing. Its edges should be straight and at
a right angle one to the other, and the ends of the battens B B in
Figure 1 should fall a little short of the edge A of the board, so that
if the latter shrinks they will not protrude. The size of the board of
course depends upon the size of the paper, hence it is best to obtain a
board as small as will answer for the size of paper it is intended to
use. The student will find it most convenient as well as cheapest to
learn on small drawings rather than large ones, since they take less
time to make, and cost less for paper; and although they require more
skill to make, yet are preferable for the beginner, because he does not
require to reach so far over the board, and furthermore, they teach him
more quickly and effectively. He who can make a fair drawing having
short lines and small curves can make a better one if it has large
curves, etc., because it is easier to draw a large than a very small
circle or curve. It is unnecessary to enter into a description of the
various kinds of drawing boards in use, because if the student purchases
one he will be duly informed of the kinds and their special features,
while if he intends to make one the sketch in Figure 1 will give him all
the information he requires, save that, as before noted, the wood must
be soft pine, well seasoned and free from knots, while the battens B
should be dovetailed in and the face of the board trued after they are
glued and driven in. To true the edges square, it is best to make the
two longest edges parallel and straight, and then the ends may be
squared from those long edges.

[Illustration: Fig. 1.]

THE $T$ SQUARE.

Drawing squares or T squares, as they are termed, are made of wood, of
hard rubber and of steel.

There are several kinds of T squares; in one the blade is solid, as it
is shown in Figure 5 on page 20; in another the back of the square is
pivoted, so that the blade can be set to draw lines at an angle as well
as across the board, which is often very convenient, although this
double back prevents the triangles, when used in some positions, from
coming close enough to the left hand side of the board. In an improved
form of steel square, with pivoted blade, shown in Figure 2, the back is
provided with a half circle divided into the degrees of a circle, so
that the blade can be set to any required degree of angle at once.

[Illustration: Fig. 2.]

[Illustration: Fig. 3.]

[Illustration: Fig. 4.]


THE TRIANGLES.

[Illustration: Fig. 5.]

Two triangles are all that are absolutely necessary for a beginner. The
first is that shown in Figure 3, which is called a triangle of 45
degrees, because its edge A is at that angle to edges B and C. That in
Figure 4 is called a triangle of 60 degrees, its edge A being at 60
degrees to B, and at 30 degrees to C. The edges P and C are at a right
angle or an angle of 90 degrees in both figures; hence they are in this
respect alike. By means of these triangles alone, a great many straight
line drawings may be made with ease without the use of a drawing square;
but it is better for the beginner to use the square at first. The manner
of using these triangles with the square is shown in Figure 5, in which
the triangle, Figure 3, is shown in three positions marked D E F, and
that shown in Figure 4 is shown in three positions, marked respectively
G H and I. It is obvious, however, that by turning I over, end for end,
another position is attained. The usefulness in these particular
triangles is because in the various positions shown they are capable of
use for drawing a very large proportion of the lines that occur in
mechanical drawing. The principal requirement in their use is to hold
them firmly to the square-blade without moving it, and without
permitting them to move upon it. The learner will find that this is best
attained by so regulating the height of the square-blade that the line
to be drawn does not come down too near the bottom of the triangle or
edge of the square-blade, nor too high on the triangle; that is to say,
too near its uppermost point. It is the left-hand edge of the triangle
that is used, whenever it can be done, to produce the required line.

[Illustration: Fig. 6.]


CURVES.

To draw curves that are not formed of arcs or parts of circles,
templates called curves are provided, examples of these forms being
given in Figure 6. They are made in wood and in hard rubber, the latter
being most durable; their uses are so obvious as to require no
explanation. It may be remarked, however, that the use of curves gives
excellent practice, because they must be adjusted very accurately to
produce good results, and the drawing pen must be held in the same
vertical plane, or the curve drawn will not be true in its outline.


DRAWING INSTRUMENTS.

It is not intended or necessary to enter into an elaborate discussion of
the various kinds of drawing instruments, since the purchaser can obtain
a good set of drawing instruments from a reputable dealer by paying a
proportionate price, and must _per force_ learn to use such as his means
enable him to purchase. It is recommended that the beginner purchase as
good a set of instruments as his means will permit, and that if his
means are limited he purchase less than a full set of instruments,
having the same of good quality.

All the instruments that need be used in the examples of this book are
as follows:

A small spring bow-pen for circles, a lining pen or pen for straight
lines, a small spring bow-pencil for circles, a large bow-pen with a
removable leg to replace by a divider leg or a pencil leg, and having an
extension piece to increase its capacity.

The spring bow-pen should have a stiff spring, and should be opened out
to its full capacity to see that the spring acts well when so opened
out, keeping the legs stiff when opened for the larger diameters. The
purchaser should see that the joint for opening and closing the legs is
an easy but not a loose fit on the screw, and that the legs will not
move sideways. To test this latter, which is of great importance in the
spring bow-pencil as well as in the pen, it is well to close the legs
nearly together and taking one leg in one hand and the other leg in the
other hand (between the forefinger and thumb), pushing and pulling them
sideways, any motion in that direction being sufficient to condemn the
instrument. It is safest and best to have the two legs of the bow-pen
and pencil made from one piece of metal, and not of two separate pieces
screwed together at the top, as the screw will rarely hold them firmly
together. The points should be long and fine, and as round as possible.
In very small instruments separate points that are fastened with a screw
are objectionable, because, in very small circles, they hide the point
and make it difficult to apply the instrument to the exact proper point
or spot on the drawing.

The joints of the large bow or circle-pen should also be somewhat stiff,
and quite free from side motion, and the extension piece should be
rigidly secured when held by the screw. It is a good plan in purchasing
to put in the extension piece, open the joint and the pen to their
fullest, and draw a circle, moving the pen in one direction, and then
redraw it, moving it in the other direction, and if one line only
appears and that not thickened by the second drawing, the pen is a good
one.

The lead pencil should be of hard lead, and it is recommended that they
be of the H, H, H, H, H, H, in the English grades, which corresponds to
the V, V, H, of the Dixon grade. The pencil lines should be made as
lightly as possible; first, because the presence of the lead on the
paper tends to prevent the ink from passing to the paper; and, secondly,
because in rubbing out the pencil lines the ink lines are reduced in
blackness and the surface of the paper becomes roughened, so that it
will soil easier and be harder to clean. In order to produce fine pencil
lines without requiring a very frequent sharpening of the pencil it is
best to sharpen the pencil as in Figures 7 and 8, so that the edge shall
be long in the direction in which it is moved, which is denoted by the
arrow in Figure 7. But when very fine work is to be done, as in the case
of Patent Office drawings, a long, round point is preferable, because
the eye can see plainer just where the pencil will begin to mark and
leave off; hence the pencil lines will not be so liable to overrun.

[Illustration: Fig. 7.]

[Illustration: Fig. 8.]

In place of the ordinary wood-covered lead pencils there may be obtained
at the drawing material