HSS bi-metal. The break-proof design of the keyhole saws makes them perfect for cutting round holes in practically all machinable materials, including cast iron, copper, bronze, aluminium and wood. All dimensions have a 4/6 combi-tooth and can be used for cutting depths of up to 38 mm.. The associated mounting shanks enable quick and easy clamping in hand-held and stationary drills Supplied without adapter shank