General Tools 4 Circle Cutter, Adjustable 7/8-Inch to 4-Inches General Tools circle cutters produce precision cricles in sheet metal, brass, copper, soft steel, aluminum, plastic, wood and composition materials The high-speed steel cutting blade adjusts to accommodate the thickness of your material; Features a replaceable cutting blade and a replaceable 1/4 inch pilot drill This quality cutting machine will make circles from 7/8 inch to 4 inches in diameter; Maximum safe speed is 500 RPM, for use with a drill press only This round shank circle cutter is great for making smooth cuts through most materials, including wood, composite, sheet metal and more; Shank is 3/8 inch round All adjusments are made with a hex wrench which is included; Replacement blade is General Tools Model # 4/5 Blade