If you can get hold of some good locksmiths warding files 4” & 6” which used to be got in various cuts ( bastard, second cut and smooth etc.) you’ll find you will be able to remove very small amounts quite accurately. My choice of brand was Nicholson files but I think they are hard to get or not made anymore. I always ground one edge off as a safety edge so to get a nice square edge and this was always useful to polish off the top radius of the key for a nice smooth edge, especially on safe keys.
I do find file these days files are not so precisely made and the edges f