A Manual of Engineering Drawing for Students and Draftsmen

by Thomas Ewing French

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1918 Excerpt: ...angle less than 90) it will generate a cone and the curve made by the moving point will be a "conical helix." When the angle becomes 90 degrees the helix degenerates into a spiral. To Draw the Projection of a Helix.--Fig. 305. Divide the circle of the end view of the cylinder into a number of equal parts, Fio. 305.--The helix and its development. and the lead into the same number. As the point moves around through one division it will advance a proportional distance of the lead; when half way around the cylinder it will have advanced one-half the lead. Thus the curve may be found by projecting the elements represented by divisions of the circle to intersect lines drawn through corresponding divisions of the lead. If the cylinder be developed the helix will appear on it as a straight line inclined at an angle whose tangent is v The conical helix ITU is drawn similarly, the lead being measured along the axis. Screw Threads.--Threads are always understood to be single and right hand unless otherwise specified. A single thread has one thread of whatever section cut on the cylinder. When it is desired to give a more rapid advance without using a coarser thread two or more threads are cut side by side, giving double, triple, etc., threads, as illustrated in Fig. 306. A right-hand thread advances away from the body when turned clockwise. A left-hand thread is always marked plainly "L.H." and may be recognized also by the direction of the slant. The pitch of a thread is the distance from center to center of consecutive threads. The lead has already been defined as the distance advanced in one revolution. In a single thread therefore the pitch and lead are equal, in a double thread the lead is twice the pitch, similarly for other multiple threads...

66 pages, Paperback

First published January 1, 1929

Reviews

[Rossdavidh · Rating 4 out of 5]

My copy of this book was the first edition (ninth impression), from 1911. Reading it over 100 years after it was written, I am not surprisingly not the author's intended audience. There may be fields where the author has in mind a readership in future centuries, but Thomas French was unlikely to have had a 21st century reader in mind when discussing, say, the use of compasses.

It is a fair question as to what possible merit there could be for me in reading such a book. I have no excuse to give. It was, however, quite pleasant to do so. The language is dated, but precise, and the various illustrations of, say, the proper way to hold a pen when doing proper lettering, were (unsurprisingly given the topic) well done.

There is, to be sure, something impressive in seeing the evidence in this book of a previous generation's ability to focus relentlessly on the task at hand, given our own current inability to focus for more than 10 seconds on anything at all. Reading this book had a calming and focusing affect on me, too, although I cannot claim to be able, as a result of reading it, to execute in a proper manner any of the techniques described. If I were to have the book at hand when attempting it, though, I believe I would find it sufficiently clear to be a great help.

I suppose that, more than anything else, that was why I read this book: to get a glimpse into what a professional engineer's work life might have consisted of in a time before smartphones, internet distractions, email, Slack channels, and myriad other ways to keep yourself from the task at hand. Much as gardening is not, for me, primarily a way to acquire food, but mostly rather a way to remind myself (at conscious and subconscious levels) of how we came to have food, this book was for me a way to disconnect from my current way of life and connect instead (however tenuously) to an older one.

[Andrew Volpe]

Acquired from my High School Drafting class, 1996

1966 Edition, originally 1911.

One of my "oldest" books, one that I have had for a long time.