The Mini Punch Grinder can process from dia. 0. 5mm to 10mm. If the diameter of workpiece is over than 6mm. Please use the Punch Grinder , Right pressure must be put on the screw to avoid Overpressure . Easy operation and high precision make it to be thebest grinding tool for small workpiece , the material of the Rollers: Tungsten steel. the lifetime is over 10 times of the mormal steel . The accuracy: 0. 004mm