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 on an unprepared surface. Once a bit wanders off course it is difficult to bring it back on center. A center drill bit frequently provides a reasonable starting point as it is short and therefore has a reduced tendency to wander when drilling is started. While the above is a common use of center drill bits, it is a technically incorrect practice and should not be considered for production use. The correct tool to start a traditionally drilled hole (a hole drilled by a high-speed steel (HSS) twist drill bit) is a "spotting drill bit" (or a "spot drill bit",