A lathe knurling tool is primarily used to create a textured surface on a workpiece, typically made of metal. This process, known as knurling, serves multiple functions. Firstly, it enhances grip by adding ridges to the surface, making it easier to handle or manipulate the workpiece. Holder Size : 3/8 x 7/8 x 5-1/2" Inches ( 9.5 x 22 x 140 mm ). Knurl Size : 3/4" x 3/8" x 1/4" (Bore) (16 x 7.9 x 5.5 mm).