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CHAPTER VIII
Milling Operations — Gear Cutting

We do not propose in this chapter to go deeply into the subject of gearing, for it would be impossible to properly treat it in so limited a space. Neither do we intend to describe the manner in which gears are cut on automatic gear cutting machines designed especially for that purpose. Our object is rather to give a few practical points applying to the cutting of different kinds of gears on a milling machine, and to show illustrations of how various gear cutting jobs and work of a kindred nature can be set up. Anyone desirous of making a detailed study of gears is referred to the many books now published that are devoted exclusively to the subject, among which are our "Practical Treatise on Gearing," and " Formulas in Gearing."

Cutting Spur Gears. The first things that are necessary to know in order to cut a spur gear, are the pitch, either diametral or circular, and number of teeth required. These must be had in order to select the correct cutter to use.

We make eight cutters for each pitch, as follows:

No. 1	cutter	will	cut	wheels	from	135	teeth	to	a	rack
No. 2	"	"	"	"	"	55	"	"	134	teeth
No. 3	"	"	"	"	"	35	"	"	54	"
No. 4	"	"	"	"	"	26	"	"	34	"
No. 5	"	"	"	"	"	21	"	"	25	"
No. 6	"	"	"	"	"	17	"	"	20	"
No. 7	"	"	"	"	"	14	"	"	16	"
No. 8	"	"	"	"	with	12	"	and	13	"

For those who require a finer division of the number of teeth to be cut with each cutter than can be cut with the regular numbers listed above, we can furnish half numbers in cutters from 2 to 8 pitch inclusive, as follows:

No. 1 1/2	cutter	will	cut	wheels	from	80	teeth	to	134	teeth
No. 2 1/2	"	"	"	"	"	42	"	"	54	"
No. 3 1/2	"	"	"	"	"	30	"	"	34	"
No. 4 1/2	"	"	"	"	"	23	"	"	35	"
No. 5 1/2	"	"	"	"	with	19	"	and	20	"
No. 6 1/2	"	"	"	"	"	15	"	"	16	"
No. 7 1/2	"	"	"	"	"	13	"