Keep these knurls whirling to form a wide grip, like on a barbell. Also known as axial feed knurls, they have a convex face that runs along your workpiece more smoothly than standard knurls. This curvature means less force on the edge of the knurl, for less friction and a longer life. To create a diamond pattern—common for tool handles—machine your material with both a right- and left-hand spiral.

Made of M42 high-speed tool steel, these knurls—also known as carbon steel knurls—are ideal for hard material such as stainless and carbon steel. A ferritic nitrocarburizing (FNC) coating hardens the surface to protect against wear, corrosion, and warping. However, the hardness may damage brittle materials (such as cast iron and ceramics) and soft materials (such as plastic and brass).

Teeth per inch (TPI) determines how fine your pattern is. The higher the number, the smoother, more closely spaced your pattern will be. A tool handle is usually knurled with around 30 TPI. A precision instrument knob would require around an 80 TPI.