WHILE WORKING IN THE INDEPENDENT SHOP, EMPLOYEE WAS USING A FREESTANDING GRINDER TO SMOOTH THE EDGE OF A PIECE OF METAL. WHILE GRINDING, THE METAL PIECE LURCHED OFF THE WHEEL AND FORCED EMPLOY EE'S HAND TO GET CAUGHT BY THE WHEEL. EMPLOYEE'SLEFT THUMB SUFFERED AVULSION TYPE INJURY. ALL SAFETY ITEMS CHECKED ON MACHINE AND WERE FOUND INTACT.