Recoil Rob,
I talk about grinding blades to fit, but in actual practice I file them(I may start off grinding if there is a lot of metal to remove).

Hammergun,
You seem to be a man "after my own heart".If you use old screwdrivers, you won't hesitate to file them to fit, but nobody wants to mess up an expensive set of screwdrivers, and as a result, mess up an even more expensive gun.
Mike