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 sizes same concept that names like "general-purpose" and "multipurpose" reflect. Extended-reach or long-series drills are commonly called aircraft-length from their original use in manufacturing riveted aluminum aircraft. For bits thicker than a minimum size such as 1/8 inch, they are available in fixed lengths such as 6, 8, 12, or 18 inches rather than the progressive lengths of jobber drills. The image shows a long-series drill compared to its diametric equivalents, all are in diameter. The equivalent Morse taper drill shown in the middle is of the usual length for a taper-shank drill. The lower drill bit is the "jobber" or