[Bud]

A cross-drilled hole in a shaft will introduce a stress riser of 3 or more times the nominal stress--see any machine design textbook. You better know what you are doing. The shaft is subject to not only bending but torsional loads. The combined stress plus the stress riser will promote a crack to form. If the shaft looks like it cracked on a 45 degree angle it was primarily a torsional failure, probably aggravated by bending stress. You have to know where to drill, how much section you need, the expected loading, and know the capability of the crank material.