To machine a hole using a drill, cutting forces are experienced. The forces that act upon a drill are:
- A force in the opposite direction to the actual drill rotation direction (torque)
- A force in the opposite direction to the direction of feed (thrust).
These forces vary accordingly to the workpiece characteristics and the cutting conditions applied.
For milling and turning the cutting edge is subjected to 3 forces (principal, back, and feed force).
For drilling only 2 forces are experienced.
Torque and thrust vary with drill diameter and the feed rate.
For example, a 10mm drill with a feed rate of 0.3mm/rev will experience a torque of 15Nm and a thrust of 2500N (250kg).
Note that the thrust and torque are not really influenced by the variation of cutting speed (RPM).
A: Rotation direction
B: Feed direction