A tool bit generally refers to a plain High Speed Steel (HSS) tool. It usually takes the form of a simple square bar of HSS. Some part of which is ground to suit an operation. The ground tool bit is then held solidly by a tool holder while it is cutting. By confining the expensive hard cutting tip to only the part doing the actual cutting, the cost of tooling is reduced. The supporting holding mechanism is made of cheaper tougher steel and does not wear and so does not have to be replaced. High Speed Steel (HSS) is a material usually used in the manufacture of machine tools. ...

Various tool bits, carbides and holders

Not all tool bits are HSS. Many are carbide, ceramic or diamond tipped bars with changeable tips(or inserts).

The term tool bit is sometimes used to refer to other high speed cutting tools such as slot drill, end mill or carbide tipped tool.