Add strength and a smooth finish to hole edges. Unique tools can be used to punch and flare new holes, or to flare existing holes. Starting with a small center hole, the punch halves bolt together to cut and flare at the same time. Note: This tool will cut a hole in up to 20 gauge (.0359″) steel or 18 gauge (.0403″) aluminum. Hole size is increased about 1/8″ when hole is flared.;.