As the type of cutter used determines, in a large measure, the design of the machine itself, it will be better at this point to take up a description of some of the different cutters, in order that the adaptation of the machine to the cutter may be clearly seen.
Cutters are classified according to their form or the use to which they are put, some of the more common types of these devices being as follows:
Nicked-tooth spiral mill
Straight end mill
Spiral end mill
Fly or single-tooth cutter
This classification does not include any of the cutters used in cutting gears, racks, spirals, helical gears, ratchets, sprocket-wheels, and similar work, which is usually considered as gear-cutting work. However, ratchet teeth may be cut with an angle cutter; brass gears, with a single-tooth or fly cutter, properly formed; and some others may be applied to a variety of uses, the cutter, in fact, not infrequently displaying a remarkable adaptability to the varying conditions of work and material.
Fig. 200. Details of Ordinary Milling Cutter.
The several details of an ordinary milling cutter are shown in Fig. 200. A is the outside diameter;
B, the thickness (or in mills such as shown in Fig. 201, the length);
C, the diameter of the hole; D, the width of keyway; E, the depth of keyway; F, the pitch of the teeth; G, the top of the teeth or land; H, the backing-off or clearance, either on the lands or on the side of the cutter; J, the depth of the teeth; K, the face of the teeth; L, the relieving recess made for the purpose of reducing the surface to be ground; and M, the hub. The direction of revolution is indicated by the arrow.
Fig. 201. Milling Cutter with Spiral Teeth.
Courtesy of Brown and Sharpe Manufacturing Company, Providence, Rhode Island.