Tool bits are cutting tools that are commonly used in machine tools such as lathes, milling machines, and drill presses. They are made of various materials such as high-speed steel, carbide, and ceramic, and are available in a wide range of shapes and sizes to suit different machining applications.

Some common types of tool bits include:

1. Turning tool bit: Used for turning, facing, and chamfering operations on a lathe.
2. Boring tool bit: Used for boring holes in a lathe.
3. Threading tool bit: Used for cutting threads on a lathe.
4. Parting tool bit: Used for parting off workpieces on a lathe.
5. Milling cutter: Used for milling operations on a milling machine.
6. Drill bit: Used for drilling holes in a workpiece on a drill press.
7. Counterbore: Used for enlarging the diameter of a previously drilled hole.
8. Countersink: Used for creating a conical recess in a workpiece to accommodate the head of a screw.
9. Reamer: Used for enlarging and finishing existing holes in a workpiece.
10. Broach: Used for shaping and enlarging holes in a workpiece.

The selection of a tool bit depends on the specific machining operation to be performed and the material being machined. Different materials require different cutting speeds, feed rates, and cutting depths, which can affect the choice of tool bit.