Drill bit shank A hex shank can be grasped by a 3-jaw drill chuck or held in a chuck specifically for hex shanks. Quarter-inch hex shanks are common for machine screwdriver bits and have spread from that application to be used for drill bits that are compatible with screwdriver machinery. The diameter of an SDS and SDS Plus shank is 10 millimeters. (The SDS Max is 18 millimeters.) The SDS shank has the advantage of fitting into a simple spring-loaded chuck, so that bits are simply pushed into the chuck without tightening. This shank and chucks made for it are especially suited to
Drill bit shank hammer drilling with masonry drills in stone and concrete. The drill bit is not held solidly in the chuck, but can slide back and forth like a piston; it does not slip during rotation due to the non-circular shank cross-section, matching the chuck. The hammer of the drill acts to accelerate only the drill bit itself, and not the large mass of the chuck, which makes hammer drilling with an SDS shank drill bit much more productive than with other types of shank. Rotational drive uses the sliding keyways that open to the end of the shank, which mate with