from The Century Dictionary and Cyclopedia
- n. A cylindrical bit, terminating in a truncated cone, the oblique surface of which is cut into teeth. It is often used for enlarging holes of considerable depth in metals and hard woods.
Sorry, no etymologies found.
It is caused by using screws of which the heads are too large for the countersunk holes in the hinge, and may be avoided by slightly sinking the holes in the brasswork with a countersink or rose-bit.