Tim, once they fill, they no longer cut. They cut when they're clean, just
like sandpaper. The metal worker keeps tapping to release, or uses a file
card (wire brush) to get the material out. I'm sure you've noticed that
loaded sandpaper heats and brightens the surface, leaving a background of
scratches, at one time or another. I even clean sandpaper with a file card
when sanding wet wood.

As the OP was thinking of trying it on a rotating piece, he had virtually no
chance of cleaning it. Ditto if the wood is damp.

A mill file is probably closer to 320 than 220 in "grit," and is meant for
non-fibrous material like steel. Fibrous material like wood responds best
to a self-cleaning rasp. If you keep it clean with a brush, you've got
sandpaper on a stick, if you don't keep it clean, you've soon got the stick.


"Tim Miller" wrote in message
oups.com...
I didn't want to argue but if they fill up quickly that means there is
wood in there and that means they are cutting not burnishing. They do
leave a nice glass like finish. I came across it by accident one day
after using a file to sharpen some things. I had some small branches
that I had cut off on some canes and was out of sand paper so I just
thought I'd try a file and see how it would work. Took em down pretty
good and didn't need any sandpaper. Couldn't get a better finish any
easier than this.