I actually did tis too. I don't like this solution as well as replacing wheels but it worked pretty well. I just held the trucks at a slight angle on a grinding wheel and let them spin and grind at the same time. You have to be careful with this method. If you get the wheels spinning too fast, they can melt the truck side frame.
However, the wheels and plastic axle are split in the middle. You could pull one side off and chuck the other side in the drill press and file at them. The plastic is pretty soft and cuts easily. It is not engineering plastic (ie brand Delrin). you should be able to shape them pretty well and they will reassemble in the trucks
