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 as the bit is either establishing the "center" of a hole or making a conical hole for a lathe "center". However, the true purpose of a center drill bit is the latter task, while the former task is best done with a "spotting drill bit" (as explained in detail below). Nevertheless, because of the frequent lumping together of both the terminology and the tool use, suppliers may call center drill bits "combined-drill-and-countersinks" in order to make it unambiguously clear what product is being ordered. They are numbered from 00 to 10 (smallest to largest). Center drill bits are meant to