A mechanical process of cold-working welds to improve mechanical properties, primarily fatigue resistance, by correcting surface and near-surface defects, introducing a compressive residual stress at the surface of the weld, and work-hardening the weld metal.

The roll planisher is a machine consisting of two rollers, diametrically opposed, which exert pressure at a small contact area on the weld. The top roller is a driver and the lower roller is an idler.

Extremely high or low loads may be exerted on contact. Magnitude of output load can be adjusted pneumatically, from 0 to 9000 kg (0 to 20 000 pounds).