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 certain loss of hole quality. If it is deemed necessary to chamfer a hole with a spot or center drill bit when a solid-carbide drill bit is used, it is best practice to do so after the hole is drilled. When drilling with a hand-held drill the flexibility of the bit is not the primary source of inaccuracy—it is the users hands. Therefore, for such operations, a center punch is often used to spot the hole center prior to drilling a pilot hole. The term core drill bit is used for two quite different tools. A bit used to enlarge