A knurled finish is a regular ridged or grid-patterned texture applied to the surface of a metal component to provide grip, decoration, or both. The finish is produced by rolling or cutting the metal against a hardened steel knurling tool whose surface bears the inverse of the desired pattern. In jewellery the knurled finish appears on watch bezels, ring shoulders, pendant cases, jeweller's tool handles, and on the outer surfaces of bezel-set mountings as a decorative contrast to polished or matte areas.

Patterns and production

The standard knurled patterns in jewellery and watchmaking are straight axial knurling, with ridges running along the length of the workpiece; helical or angle knurling, with ridges following a single twist around the surface; and diamond or cross knurling, with two opposed helices intersecting to form a regular grid of small pyramidal peaks. Each pattern is produced by rolling the workpiece against a knurling wheel under pressure, displacing the surface metal into the pattern's voids, or by cutting it on a lathe with a knurling tool. Cast components reproduce knurling from a master at scale and tend to be less crisp than rolled or cut work. Knurling depth typically runs between 0.1 and 0.4 millimetres, deep enough to be visible and tactile but shallow enough not to disturb the structural section of the part.

Wear and restoration

Knurled finishes wear with use, particularly on rings worn daily and on watch bezels. The high points of the pattern soften first; after extended wear the original knurl may be reduced to a faint trace. Restoration of a worn knurl on a finished piece is generally not undertaken at the bench, since re-knurling requires the workpiece to be remounted in a lathe or roller and the metal removed in the original knurling step is not recoverable. Replacement of the knurled component, where this is feasible, is usually the more practical approach.