On Apr 24, 10:32*am, DC wrote:
I have a project where I need to cut a 0.188" radius fillet for about
16" in aluminum. *Unfortunately, the cut is at the bottom of a 4.5"
deep channel. *I haven't been able to find a cheap ($20) ball/radius
mill that is long enough to do the job.

However I can get a .75x6" HSS two flute for about $7. *Could I get
away with just grinding a radius on the end of the flutes? *I don't
have a grinding jig so I'd have to do it by hand. *I'm thinking that
it might be wise to grind it such that only one flute is cutting.
That way they don't have to be the same. *Obviously, this is a hack
--- I realize that. *That said, my tolerance is loose and my budget is
low.

Thanks for any advice,
-DC

I would drill a 3/16" hole in thin aluminum and cut it out to make a
template, then try to fit both flutes to it. I've hand-ground a
smaller less precise radius on both flutes when the end mill started
to dull, to keep it cutting, and couldn't see a difference.

You could drill a larger hole in a piece of stock an inch or two long,
slice it in half lengthwise, line it with fine SiC sandpaper and hone
the edge to shape.

If you cut too far you can shorten the end of the flutes to save the
job.

Jim Wilkins