Special Fret Files
Fret Tools
Here are some simple file modifications I've used to make files for fret work.
This is the one I use to trim the fret ends flush with the fingerboard:
It's a mill bastard with the tang end broken off. I ground the edges to a rounded safe surface, and tapered the ends slightly so they don't "bump" as I slide along the frets. I use four sizes, from four to ten inches in length. I'm not so interested in the length as much as the spacing of the teeth on the files. If I make "chatter" marks with one file, I'll switch to a different size because the different spacing of the teeth will quickly eliminate the problem.
I use mill bastards because they are the cheapest, and I can have a supply of nice, sharp files if I buy them a dozen at a time.
For rounding the fret ends, there's nothing like my cant saw file:
It has just the corners ground safe, and provides three different angles of attack.
I also use the standard 60 degree triangular file with safe corners for rounding frets
For making a tiny bevel at the top edge of the fret slots, I like my very thin taper six inch triangular file:
As you can see, I've ground one face completely flat. That leaves the corners very sharp so I can file one side of the fret slot at a time.