Abstract: A drill bit for cutting annular holes in medical casts without cutting into the covered skin surface. The drill bit includes, an elongated one-piece tubular body having a first end portion and a second end portion. The first end portion is closed except for a centered hole used to attach the drill bit to a driver. The second end portion incorporates a plurality of non-offset equilateral triangle shaped saw-like cutting surfaces machined into the circumference of the second end portion. When attached to a driver imparting a reciprocating motion, the drill bit responds with a self aligning bidirectional cut in the cast matrix obviating the need for a pilot bit. As a result, a cast core is safely cut without damage to the covered skin leaving a hole for aeration of the skin surface.