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 cutting fluid (either compressed air or a suitable liquid) to be injected through the drill's hollow body to the cutting face. Indexable drill bits are primarily used in CNC and other high precision or production equipment, and are the most expensive type of drill bit, costing the most per diameter and length. Like indexable lathe tools and milling cutters, they use replaceable carbide or ceramic inserts as a cutting face to alleviate the need for a tool grinder. One insert is responsible for the outer radius of the cut, and another insert is responsible for the inner radius. The tool