BURNISHER
Made from hardened metal, sapphire crystal, or synthetic diamond, the burnisher is a hand-operated tool used to harden the surface of a component. Similar to a file, the burnisher is shaped to match the profile of the component being treated. However, unlike a file, the surface of the burnisher has no cutting edge. The cold-working process, also known as mechanical burnishing, compresses the material’s surface, reducing its roughness similar to polishing but without causing abrasion. This results in a polished appearance that also lowers the friction coefficient of the treated surface. The compression also makes the material denser and therefore harder on the surface, providing enhanced resistance to oxidation and corrosion.
Burnishing is sometimes used in the artisanal decoration (chamfering) of components. However, the most common and well-known application of this technique is in the burnishing of the pivots within a movement, a process specifically referred to as “pivot burnishing.” Nowadays, burnishers are used exclusively in artisanal work.