Great, thanks for all of the suggestions. I'll give it a try. the slot
is through so that should simplify things. I'll mill with a two flute
cutter first and square up the ends with a 0.25" bit. Problem will be
holding the bit but I think I can drill a hole in a piece of drill rod
and set a 0.25 bit at a 45 degree angle to the rod with a set screw
inserted along the axis to hold it in place. That way the tip can reach
the far side of the slot without the holder having to enter. I guess the
other option is to use a bit holder that will fit in the slot, mount the
bit perpendicular to the bar, and scrape one corner at a time with say a
0.125 bit. The slot dimensions are 0.25 wide by 0.5 long through a 5/8
round bar.

Additional suggestions welcome.

Thanks

Dan


Roger Shoaf wrote:

"Grant Erwin" wrote in message
...


Is this a through slot or a blind slot? If it's a through slot, then
you can use a 1/4" lathe bit and stroke the slot end square using a
mill quill or lathe carriage feed.




Even if it is a blind slot you can rig a lathe bit as a broach. To do this
you need to cut a slot in a piece of rod to retain the tool bit. The idea
here is to restrain the tool bit in the rod so you can stroke the quill and
the cutting edge of the tool bit can nibble away with each stroke.

You lock the brake on the spindle tale a small cut, advance the table a few
thousands and stroke, advance, stroke, advance etc.

This goes pretty fast.