Fig. 1928.
End mills or shank cutters are formed as in [Fig. 1928], the shank sometimes being made parallel with a flat place at a, to receive the set-screw pressure, and at others taper, the degree of taper being 1⁄2 inch per foot. The hole at the end facilitates both the cutting of the tooth in the making and also the grinding. Shank cutters may be used to cut their way into the work, with the teeth on the end face, and then carry it along, bringing the circumferential teeth into operation; or the end teeth may be used to carry the cut after the manner of a face cutter.
Fig. 1929.
Shank cutters are rarely made above an inch in diameter, and are largely used for cutting grooves or recesses, and sometimes to dress out slots or grooves that have been cast in the work, as in the case of the steam and exhaust ports of steam engine cylinders. In work of this kind the direction of the feed is of great importance and must be varied according to the depth of cut taken on the respective sides of the cutter. Suppose, for example, that the conditions are such as illustrated in [Fig. 1929], the cut being deepest on the side a of the slot, and the cutter must be entered at the end of the slot and fed in the direction of d, so that the pressure of the cut may tend to push the cutter back, it being obvious that on the side b the cutter has a tendency to walk or move forward too rapidly to its cut, and if the cut was heaviest on that side it would do, this increasing the cut rapidly and causing tooth breakage.
