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An Introduction to Machine Drawing and Design

AN INTRODUCTION TO MACHINE DRAWING AND DESIGN

BY

DAVID ALLAN LOW

(WHITWORTH SCHOLAR), M. INST. M.E.

HEAD MASTER OF THE PEOPLE'S PALACE TECHNICAL SCHOOLS, LONDON AUTHOR OF 'A TEXT-BOOK ON PRACTICAL SOLID OR DESCRIPTIVE GEOMETRY' 'AN ELEMENTARY TEXT-BOOK OF APPLIED MECHANICS' ETC.

[Illustration]

_FOURTH EDITION_

LONDON LONGMANS, GREEN, AND CO. AND NEW YORK: 15 EAST 16th STREET 1890

PRINTED BY SPOTTISWOODE AND CO., NEW-STREET SQUARE LONDON

PREFACE.

It is now generally recognised that the old-fashioned method of teaching machine drawing is very unsatisfactory. In teaching by this method an undimensioned scale drawing, often of a very elaborate description, is placed before the student, who is required to _copy_ it. Very often the student succeeds in making a good copy of the drawing placed before him without learning very much about the object represented by it, and this state of matters is sometimes not much improved by the presence of the teacher, who is often simply an art master, knowing nothing about machine design. It is related of one school that a pupil, after making a copy of a particular drawing, had a discussion with his teacher as to whether the object represented was a sewing machine or an electrical machine. Evidently the publisher of the drawing example in this case did not adopt the precaution which a backward student used at an examination in machine design: he put on a full title above his drawing, for the information of his examiner.

Now, if machine drawing is to be of practical use to any one, he must be able to understand the form and arrangement of the parts of a machine from an inspection of suitable drawings of them without seeing the parts themselves. Also he ought to be able to make suitable drawings of a machine or parts of a machine from the machine or the parts themselves.

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_.


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