Here's the tool you need to do the job right- - - -it's called a "bridge reamer". It's used to align holes in two or more pieces of metal before they're bolted or riveted together. I'd recommend the 3/8" diameter one, after drilling the hole to 11/32" or so and clamping the part to the frame for a final line-reaming.

http://www.victornet.com/alphabetic/Reamers-Bridge/267.html

The tapered shank would need to be machined straight so the reamer could be used in a 1/2" capacity variable speed drill motor. Use lots of lubricant and as slow a cutting speed as possible.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!