flattening a bolt

I hope this isn't a stupid question, but here goes.... I need to replace a missing bolt in a casement window hinge. The way it works: The part of the hinge attached to the window frame has a 3/8 inch hole. The part of the hinge attached to the window has a rectangular slot (with the shorter sides of the rectangle rounded). So I need to flatten two sides of a 1 inch long, 3/8 inch stainless steel bolt (about 1/8 inch of the bolt body will remain round)...What is the best way to do this? A file? A belt sander? A grinding wheel? Thanks...Eric

Flat file or a milling machine. I'd use the mill because it's quicker for me.

......with the tools that your have on hand. A mill would do a nice job. A grinder would do the job. a file would work and give you a workout.

John

Sure it isn't some form of carriage bolt? Would be a whole lot easier knocking the corners off the square on a carriage bolt than trying to flat a regular bolt all the way down as well as being more secure, nothing for anyone on the outside to grab onto.

Stan