High speed cutters can be used for shaping, hollowing, grooving, slotting, making tappered holes in soft metals, plastics and woods. Ideal for detail engraving, carving and routing. Not for use with hardened material. Use higher speeds for hard woods, slower speeds for metals and very slow speeds for plastics. Shank diameter: 3.2mm. Working diameter: 7.8mm. Maximum RPM: 30000/min.