How to clean up an INT50 taper

[Bob Shaw]

Hi All,

Whats the best way to clean up an INT50 (CAT50, BT50) taper socket?

The socket on my old horizontal mill has taken a pasting over the years and has many dings from careless use (not mine I might add!). The tool holders no longer run true due to areas of raised metal in the socket.

What can you get to true these up? Reamers? Hones? Special scrapers?

I had considered either scraping the bore to get rid of the high spots or putting some 500 grade on a taper and using it as a form to hand sand the high spots.

What is done industrially to recondition sockets? Precision grinding?

TIA,

Bob.

[underthetire]

Yep, everyone in Nor CA. uses a guy out of Oregon to come in and re-grind the taper. Works well.

[HuFlungDung]

Is the taper hardened? If not, you could scrape the high spots off. I would probably use a triangular file to give two lines of contact. Lay the file in the taper and file with a bit of a swirl and sweep motion. Turn the spindle a little bit and file some more. Don't dwell in any particular spot for too long. The file should cut pretty good on the high spots and have a tendency to skate when it gets down to the nominal taper surface. Pay attention to the feel.

When the file doesn't seem to be finding any grab spots, then switch to a straight steel dowel wrapped with adhesive backed fine grit paper and file with that. This should impart a different sheen to the surface and you can start to get an idea of how much of the contact you are getting.

Clean up the spindle frequently, take a good tapered shank tool, and run a few streaks lengthwise up the shank with a felt marker. Put the tool in the taper and give it a twist and look for the rub off marks. Obviously you'll have to have the drive lugs removed from the spindle for this twist inspection.

If the rub marks show a distinct tight end to the taper, once you've gotten the high spots levelled, then you can run the spindle at a couple of hundred rpm and work the tight end of the taper with a flap wheel in a die grinder. If it is a new flap wheel (which is best to start with) it can be pretty aggressive. 60 or 80 grit is sufficiently fine. Do not dwell with the flap wheel, move in and out and cross the paths you make. Use light pressure to begin with. A new flap wheel is what I would recommend so that it is straight and cutting evenly along its width. Probably 1" width at minimum. A new flap wheel can remove .001" very quickly so be careful with it.

At some point when the taper shank tool feels like it fits solidly without rocking in the taper, then you can check the runout and see if you're flogging a dead horse. You cannot actually fix runout without a regrind, once the humps and bumps are smoothed off.