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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