Drill bit shank

The cutting edges of the drill bit contact the workpiece, and are connected via the shaft with the shank, which fits into the chuck.

The straight shank is the most usual style on modern drill bits, by number manufactured.

Rotational drive uses the sliding keyways that open to the end of the shank, which mate with keys in the chuck.

The smaller indentations that do not open to the end are grasped by the chuck to prevent the drill bit falling out.

The shank must be lubricated with grease to reduce the friction of the sliding action in the chuck.

SDS-Top with 14 mm diameter has been largely phased out in North America and is not common except for older tools.

The SDS bit was developed by Bosch in 1975 improving on the TE system introduced by Hilti in 1960.

[1][2] The triangle shank is almost always made by machining three flats on round bar stock.

Sockets are also available to extend the effective length of the drill as well as offering a variety of taper combinations.

The detail image shows a Morse taper shank on a 16 mm diameter drill bit.

Small (about 1⁄4 inch or 6.4 millimetres diameter) threaded drill bits and countersinks are common in aircraft metal work.

Threaded drill bits may be held in drills meant to reach into very tight spaces, and threaded countersink cutters are widely used (along with finely adjustable depth stops) to create holes which put a matching rivet directly flush with the surface.