File (tool)

A file is a hand tool consisting of a steel shaft whose surface is cut with sharp parallel ridges made by a chisel before the file is hardened. It is used to smooth or cut materials by abrasion. The tool is usually fitted in a handle.

Files are classified according to several attributes. One is the cross-section of the shaft, which may be flat, round, half-round, square or triangular. Another is the size of the ridges, which can range from rough, coarse and bastard (meaning intermediate) to second-cut, smooth and dead smooth. A single-cut or mill file has one set of parallel ridges, while a cross-cut or double-cut file has a second set at an angle to the first. In Swiss-pattern files the teeth are cut at a shallower angle.

The rasp is a related, but different, hand tool that has sharp bumps on its surface rather than straight ridges.