Drill bit shank The name comes from the German "Stecken – Drehen – Sichern" (Insert – Twist – Secure). In German-speaking countries the back-formation "Spannen durch System" (Clamping System) is used, though Bosch uses "Special Direct System" for international purposes. The triangle shank is almost always made by machining three flats on round bar stock. It is intended as a minor modification of a straight shank, still allowing it to be held in a 3-jaw drill chuck, but allowing higher torque transmission and limited slipping. The Morse taper twist drill bits pictured right are used in metalworking. The full range of tapers is
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