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 (well) direction of bit rotation to provide full coverage of the borehole bottom. Other fixed cutter bits may employ natural industrial-grade diamonds or thermal stable polycrystalline diamond (TSP) cutting elements. There is also currently available, a hybrid type of bit that combines both rolling cutter and fixed cutter elements. Regardless of type, drill bits must satisfy two primary design goals: maximize the rate of penetration (ROP) of the formation and provide a long service life. The reason for this is a direct consequence of the rotary drilling method. Modern oilfield drilling operations require substantial capital and operating expense. It might cost