In producing this work the author has aimed at placing before young engineers and others, who wish to acquire the skill and knowledge necessary for making the simpler working drawings such as are produced in engineers' drawing offices, a number of good exercises in drawing, sufficient for one session's work, and at the same time a corresponding amount of information on the design of machine details generally.
The exercises set are of various kinds. In the first and simplest certain views of some machine detail are given, generally drawn to a small scale, which the student is asked to reproduce to dimensions marked on these views, and he is expected to keep to these dimensions, and not to measure anything from the given illustrations. In the second kind of exercise the student is asked to reproduce certain views shown to dimensions given in words or in tabular form. In the third kind of exercise the student is required to make, in addition to certain views shown to given dimensions, others which he can only draw correctly if he thoroughly understands the design before him. In the fourth kind of exercise the student is asked to make the necessary working drawings for some part of a machine which has been previously described and illustrated, the dimensions to be calculated by rules given in the text.
The illustrations for this work are all new, and have been specially prepared by the author from working drawings, and he believes that they will be found to represent the best modern practice.
As exercises in drawing, those given in this book are not numbered exactly in their order of difficulty, but unless on the recommendation of a teacher, the student should take them up in the order given, omitting the following:—26, 27, 28, 35, 40, 42, 43, 45, 49, 50, 54, 60, 61, as he comes to them, until he has been right through the book; afterwards he should work out those which he omitted on first going over the book.
In addition to the exercises given in this work the student should practise making freehand sketches of machine details from actual machines or good models of them. Upon these sketches he should put the proper dimensions, got by direct measurement from the machine or model by himself. These sketches should be made in a note-book kept for the purpose, and no opportunity should be lost of inserting a sketch of any design which may be new to the student, always putting on the dimensions if possible. These sketches form excellent examples from which to make working drawings. The student should also note any rules which he may meet with for proportioning machines, taking care, however, in each case to state the source of such information for his future guidance and reference.
As machine drawing is simply the application of the principles of descriptive geometry to the representation of machines, the student of the former subject, if he is not already acquainted with the latter, should commence to study it at once.
D. A. L.
Glasgow: March 1887.
PREFACE TO THE THIRD EDITION.
To this edition another chapter has been added, containing a number of miscellaneous exercises, which it is hoped will add to the usefulness of the work as a text-book in science classes. The latest examination paper in machine drawing by the Science and Art Department has also been added to the Appendix.
D. A. L.
London: August 1888.
AN INTRODUCTION
TO
MACHINE DRAWING AND DESIGN.
I. INTRODUCTION.
Drawing Instruments.—For working the exercises in this book the student should be provided with the following:—A well-seasoned yellow pine drawing-board, 24 inches long, 17 inches wide, and 3⁄8 inch or 1⁄2 inch thick, provided with cross-bars on the back to give it strength and to prevent warping. A T square, with a blade 24 inches long attached permanently to the stock, but not sunk into it. One 45° and one 60° set square. The short edges of the former may be about 6 inches and the short edge of the latter about 5 inches long. A pair of compasses with pen and pencil attachments, and having legs from 5 inches to 6 inches long. A pair of dividers, with screw adjustment if possible. A pair of small steel spring pencil bows for drawing small circles, and a pair of small steel spring pen bows for inking in the same. A drawing pen for inking in straight lines. All compasses should have round points, and if possible needle points. A piece of india-rubber will also be required, besides two pencils, one marked H or HH and one marked HB or F; the latter to be used for lining in a drawing which is not to be inked in, or for freehand work.
Pencils for mechanical drawing should be sharpened with a chisel point, and those for freehand work with a round point. Do not wet the pencil, as the lines afterwards made with it are very difficult to rub out.
Drawing-paper for working drawings may be secured to the board by drawing-pins, but the paper for finished drawings or drawings upon which there is to be a large amount of colouring should be stretched upon the board.
The student should get the best instruments he can afford to buy, and he should rather have a few good instruments than a large box of inferior ones.
Drawing-paper.—The names and sizes of the sheets of drawing paper are given in the following table:—
| Inches | |
| Demy | 20 × 15 |
| Medium | 22 × 17 |
| Royal | 24 × 19 |
| Imperial | 30 × 22 |
| Atlas | 34 × 26 |
| Double Elephant | 40 × 27 |
| Antiquarian | 52 × 31 |
The above sizes must not be taken as exact. In practice they will be found to vary in some cases as much as an inch.
Cartridge-paper is made in sheets of various sizes, and also in rolls.
Hand-made paper is the best, but it is expensive. Good cartridge-paper is quite suitable for ordinary drawings.
Centre Lines.—Drawings of most parts of machines will be found to be symmetrical about certain lines called centre lines. These lines should be drawn first with great care. On a pencil drawing centre lines should be thin continuous lines; in this book they are shown thus — - — - —.
After