Knurled

Knurled describes a surface that has been patterned with a textured series of ridges to improve grip and handling. Knurling is a metalworking process that impresses these ridges into the surface of a cylindrical part by rolling hardened knurling tools against the rotating workpiece, typically on a lathe or dedicated knurling machine. The pattern depth and uniformity are influenced by wheel size, pressure, and feed rate.

Common patterns include straight knurling, which produces parallel ridges along the axis, and diamond knurling, which creates a crisscross, diamond-shaped texture. Circular or ring knurling is used to apply a pattern around a rounded surface for grip or seating purposes.

Materials used for knurling are primarily metals such as steel, stainless steel, aluminum, and brass, though certain plastics can be knurled with appropriate tooling. Knurled textures are frequently found on control knobs, hand wheels, thumb screws, gripped pull handles, and the heads of some fasteners where increased torque or slip resistance is needed without enlarging the finished diameter.

Advantages of knurling include improved non-slip grip, better tactile feedback, and the ability to increase effective diameter without additional machining steps. It is relatively fast and economical compared with other grip-enhancing processes. Limitations include potential weakening of the surface if the process is misapplied, and reduced surface finish quality. Knurling is not suitable for surfaces that must be perfectly smooth or for parts made from very brittle materials that could crack under rolling pressure. Proper setup and tooling maintenance are important to achieve uniform patterns and avoid tearing.