Process to cut down file

I got a three corner file from Home Depot. I remember reading a post about shaving down the 3 corners and make them smooth. How do I make the corners flat the smooth so it doesn't mash the fretboard. Thanks

I used my bench grinder to do the roughing and a Diamond sharpening steel to smooth mine. A Dremel stone would also work if you don't have a grinder.

If you try and grind it, don't use anything softer than silicon carbide, and be careful. Long time ago, we used to use old files to "dress" silicon carbide lapidary grinding wheels, so you can really mess up the grinding wheel if you don't apply steady pressure, back and forth at about medium pressure, to avoid "scoring" the wheel.

I use a blue Norton 3X wheel on my grinder and it works great for hard steel tooling. Heat is you primary concern and you don't want to overheat the file and ruin the the hardness. You actually want the stone to wear away and keep a fresh surface and not glaze over. This glazing causes you to need to apply too much force to grind which increases the potential for overheating. If you don't have a diamond dresser for your grinding stones get one.

I used a belt sander. It may or may not have changed the hardness but I've been used it for three years to dress fret ends without issue. I bought the Stew-Mac file and am pleased with it. I use the old triangle file for filing my fret slots now.

Just glue a piece of "silcon carbide" sanding material onto a flat piece of board...Lay the file on a flat surface "pointy side up" ..and and sand down the file corners until smooth...by hand...after 5 min's the corners will be as smooth as a babies bum.