Steel Rotary Files, Ball, 1/2" x 1/2" Features Rotary files offer perfect solutions for the welding jobs: Trimming welds, grinding smooth fillets & preparation for welds. Repairs can be easily done because of a variety of shapes and sizes available. All rotary files have a standard shank of 1/4" (6mm) Note Use lower speeds when cutting harder ferrous materials and higher speeds for softer non-ferrous materials.