Both the increasing use of the gearing and the greater demands made for strength, effiviency, and quietness make it nessesary for the mechanic to be familiar with the latest methods used by gear makers. Only enough of the theory of gearing is given in this book to make the terms used clear to the reader without previous gear experience. All the data given have been secured from what are believed to be the best sources of information and the authorities are given, both as a source of reference and as an acknowledgment of the assistance received. The recommendations and the standarts of the American Gear Manufacturers Association are quoted freely as these represent standart practice in many shops, Automobile practice is also given, both in the selection and heat treatment of the steels used and in the methods used, because this represents advances methods of making gears that are strong and quiet. Small-shop gear cutting practice also receives careful attention, including the cutting of spur, bevel, and worm gears on the standart milling machine. Much of the general information as to catters and cutting coolants or lubricants will be found useful in shops of any size. The same is true of the tables of tooth parts and of feeds and speeds that hate been found satisfactory in well-known plants.