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 sizes rare to find a set on the market which does not contain every gauge. There are also Renard series sequences of preferred metric drill bits: Metric dimensioning is routinely used for drill bits of all types, although the details of BS 328 apply only to twist drill bits. For example, a set of Forstner bits may contain 10, 15, 20, 25 and 30 mm diameter cutters. Fractional inch drill bit sizes are still in common use in the United States and in any factory (around the globe) that makes inch-sized products for the U.S. market. ANSI B94.11M-1979 sets size standards