Drill bit shank shaft and shank, is usually of the same diameter. It is held usually in a three-jaw drill chuck. Bits of diameter too small to grip firmly can have straight shanks of larger diameter than the drill, which can be held firmly in a standard size collet or chuck. Large drill bits can have straight shanks narrower than the drill diameter so that they can be fitted in chucks not able to chuck the full diameter. Such a drill bit is called a reduced-shank or blacksmith's drill. For example, this allows a bit to be used in a pistol-grip drill's chuck.
Drill bit (well) by the American Society of Mechanical Engineers. Fixed cutter bits were the first type of drill bit employed in rotary drilling, and they are mechanically much simpler than rolling cutter bits. The cutting elements do not move relative to the bit; there is no need for bearings or lubrication. The most common cutting element in use today is the polycrystalline diamond cutter (PDC), a sintered tungsten carbide cylinder with one flat surface coated with a synthetic diamond material. The cutters are arranged on the blades of the bit in a staggered pattern with the diamond coated cutter surface facing the