Burnisher is a tool that looks like a file but has almost no bite. It is used to cold-work the material, to smooth it and harden it on the surface. It is a very hard tool. It is either made of hardened steel or tungsten carbide.

This tool is mainly used in watchmaking for two distinct techniques where the tool has a different appearance. One technique is the burnishing of pivots and the other is the polishing of angles.

For the burnishing of the pivots, this technique is used to harden the surface of the pivots and their faces. The burnisher is often made of tungsten carbide and has two different angles. One is used to polish cylindrical pivots and the other to polish conical pivots. Surface cold-working has the advantage of hardening and polishing the surface while keeping the core soft, thus keeping the breaking point low. The ends of the pivots of high quality watches are often also polished by cold-working with a burnisher.

A second technique where the burnisher is sometimes used is the polishing of the angles. The materials polished in this way are often brass, german silver and sometimes steel. To give the polishing a final shine, wood and diamantine are often used. The burnishers used for angle polishing are often old files where the bite is removed with india stone.