A LITTLE more than a century ago our mechanical development had its beginning when the first prime movers were invented and developed. With the development of machines came the development of mechanics to run these machines, to fabricate the parts and assemble them into the finished articles. The evolution of both machines and mechanics has been marvelous, the accuracy of workmanship of today being easily two hundred times that of a century ago, and the speed of manufacture probably much more than this. Since that time one industry has helped to develop others until today the mines produce ore in large quantities to supply the iron, copper, and other metals; the great steel mills supply the raw or fabricated material; the foundries and forging shops fashion the many castings and forgings for the intricate machine to be built; the immense shops machine the parts and assemble them for the market. Everywhere we turn we find a manufactured article which has gone through these various changes from raw material to finished product.

"Production" methods have enormously increased the output of our shops and the machines which have made this development possible are of a diversified character - speed lathes, planers, multiple drillers, grinders, milling machines, stamping machines, die presses and the jigs, tools and dies which go with them - all of these have contributed to the accuracy and speed of manufacture. The demands of the automobile industry have done wonders in hastening this development as the manufacture of the parts in duplicate was absolutely necessary in order to cheapen the price of the assembled machines. The fact that many of the present-day automobiles are shipped "knocked down" to assembly points without ever having been put together is an eloquent testimonial to the accuracy with which the duplicate parts are built. Another contributing factor in modern production methods is the development of high speed steels which enable the operators to run the machines at speeds hitherto unattainable.

And yet with all this wonderful development of the machines themselves and the design of what are termed "automatics/' the workman has not lost his skill. In fact, one trip to a well-organized scientific machine shop will teach any skeptic that the intelligent workman who has contributed so largely to the mechanical developments of the past twenty years is more skilled, more intelligent, certainly better paid, and more interested in his work than ever.

But this same skilled mechanic is today a specialist. He has no opportunity to build a complete machine or even a small part of one; his active work is carried on along rather narrow lines. Consequently, it is all the more necessary for him to have a standard reference work to help him in other shop lines with which he is unfamiliar. "Modern Shop Practice" is such a work - one which has been tested through six editions - and the practical treatises on the various shop subjects have been supplied by well-known teachers and practical men and are strictly up-to-date. The authors have at all times kept in mind the practical nature of their subjects and numerous shop kinks and other helpful suggestions have been introduced. It is the hope of the publishers that this new edition will supply the needs of both the skilled mechanic and the layman who is interested in mechanical affairs.

In conclusion, grateful acknowledgment is given to the authors and collaborators - engineers and designers of wide practical experience and teachers of recognized ability - without whose co-operation this work would have been impossible.