Patent ID: 6889742

Claim:
A method for making a gear case by metal casting, said method comprising the steps of: (a) providing an in situ destroyable pattern to form an integral one-piece gear case casting of a desired shape, said pattern having a hollow body including a circumferentially continuous substantially tubular central wall section and axially spaced side wall sections adjacent to opposite ends of said central wall section, said central and side wall sections forming an internal cavity within said hollow body, wherein one of said axially spaced side wall sections comprises a flange portion radially extending away from said central wall section and provided with a plurality of bolt apertures having a shape of a bolt hole; and (b) embedding said pattern in an unbonded sand so that said unbonded sand is at least partially introduced into said cavity in said pattern; wherein each of said plurality of bolt apertures having a chamfer edge on at least one side of said flange portion.