Feed is usually measured in inches per minute. It is the product of feed per tooth times revolutions per minute times the number of teeth in the cutter. Due to variations in cutter sizes, numbers of teeth and revolutions per minute, all feed rates should be calculated from feed per tooth. Feed per tooth is the basis of all feed rates per minute, whether the cutters are large or small, fine or coarse tooth, and are run at high or low peripheral speed. Because feed tooth affects chip thickness, it is a very important factor in cutter life.
Highest possible feed per tooth will usually give longer cutter life between grinds and greater production per grind. Excessive feeds may overload the cutter teeth and cause breakage or chipping of the cutting edge.
The following factors should be kept in mind when using the recommended starting feed per tooth.
| Heavy, roughing cuts |
| Rigid set-ups |
| Easy to machine work materials |
| Rugged cutters |
| Slab milling cuts |
| High tensile strength materials |
| Coarse tooth cutters |
| Abrasive materials |
| Light and finishing cuts |
| Frail set-ups |
| Hard to machine work materials |
| Frail and small cutters |
| Deep slots |
| Low tensile strength materials |
| Fine tooth cutters |
| Type of Cut | Feed Per Tooth |
|---|---|
| Face milling | .007 |
| Straddle milling | .005 |
| Slot milling (Side Mills) | .003 |
| Slab milling: | |
| Light duty | .004 |
| Heavy duty | .008 |
| End milling: | |
| 1-1/2" dia. and over | .002 to .003 |
| Under 1-1/2" dia. | .0002 to .002 |
| Sawing | .0005 to .001 |
| Thread milling | .0005 to .001 |
