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Download or read book Screw Thread Cutting (Classic Reprint) written by Erik Oberg and published by . This book was released on 2015-06-30 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excerpt from Screw Thread Cutting The terms pitch and lead of screw threads are often confused, and particularly in the case of multiple-threaded screws does this confusion cause difficulties. Before we therefore enter upon the subject of calculating change gears for the lathe for cutting screw threads, it may be well to make clear the real meaning of the words "pitch" and "lead" and their relation to the number of threads per inch. The pitch of a screw thread is the distance from the top of one thread to the top of the next, as shown in Fig. 1. No matter whether the screw has single, double, triple, or quadruple thread, tho pitch is always the distance from the top of one thread to the top of the next. Often, though improperly, the word "pitch" is used In the shop to denote "number of threads per inch." We hear of screws having 12 pitch thread, 16 pitch thread, etc. This is not correct usage of the word pitch, and only tends to cause unnecessary confusion. The lead of a screw thread is the distance the screw will move forward in a nut if turned around one full revolution. It is clear that for a single-threaded screw the pitch and the lead are equal, as the screw would then move forward the distance from one thread to the next if turned around once. In a double-threaded screw, however, the screw will move forward two threads, or twice the pitch, so that in a double-threaded screw the lead equals twice the pitch. In a triple-threaded screw the lead equals three times the pitch, and so forth. The lead may also be denned as being the distance from center to center of the same thread, after this thread has made one turn around the screw. In the single-threaded screw the same thread is the next thread to the one first considered. In a double threaded screw there are two threads running side by side around the screw, so that the same thread here is the second one from the one first considered. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.