MARVELOUS accomplishments in the mechanical world have become so common in this day and age that we scarcely realize the slow process of evolution which machine shop work has been undergoing during the last century. Barely a hundred years ago Watt, the father of the steam engine, had to be satisfied with engine cylinders which were three-eighths of an inch out of true because neither the machines nor the workmen could do better. Our present day machinist, on the other hand, must make his error two hundred times as small to meet the requirements. He also must deal with machines and mechanical problems which would have staggered his untried and unskilled brother of the previous century.

And it is not only the workman who has progressed in accuracy. There are myriads of machines which have been built to facilitate the manufacture of all parts that go to make up a mechanical device-speed lathes, milling and stamping machines, die presses, and the jigs, tools, and dies which go with them-and all of these contribute mightily to the accuracy and speed of manufacture. One of our best known automobiles is made with such precision from radiator cap to differential that the parts are shipped "knocked down" to distant points and are assembled with practically no fitting-a truly marvelous performance and one which necessitates an exactness in the duplication of parts which would have been impossible even ten years ago.

¶ The tale of this development of machine shop work is an interesting one and should appeal not only to the technically trained man who desires the best advice on the correct mechanical process to follow, but also to the man who wants to know how to "do things" or at least how things are done. It is the hope of the publishers that this book will satisfy a real demand and prove of sterling value in its field.

VIEW OF BECKER CONTINUOUS MILLER MILLING CONNECTING-ROD FIXTURE.

Courtesy of Becker Milling Machine Company, Hyde Park, Massachusetts

MAKING ACCURATE MEASUREMENTS WITH MICROMETER CALIPER.