Just bought a 14" four jaw chuck that just fits my nominally 14" Celtic Mondiale lathe with an L0 spindle. The chuck is used, and it looks like the previous owner didn't bother to clean the spindle and bore many times. The chuck body is a one piece casting. The L0 taper bore has lots of compression divots from compressing chips between the bore and spindle. I suspect that if one had a "master" L0, some dykem to expose high spots, a little judicious scraping would make the thing right. The chuck is VERY heavy or I would try removing the key on the spindle and using that, but the chuck body with all the moving parts removed still weighs 80 lbs. Too much for this 78 yo. to handle. I have a home built articulated boom crane I use for mounting my chucks and mill vise.
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Truing a L0 chuck spindle bore
- Thread starter Ian Moss
- Start date
You have a few years on me. I sympathize with your challenges. Not sure what I would do if my lathe was that big.
Regarding the surface mating marks, have you evaluated just how much they interfere? Sometimes such things look much worse than they are. A little judicious stoning might be all that is needed.
Or perhaps a long nose dial indicator. It would take some setup but I think it could be done. This might allow you to check the whole taper top to bottom.
Ian, If decided it had to be done, I'd scrape as you suggest, and do so to remove the high spots around the dings inside the bore. Turn a piece of CI and spot from that, aside from the weight issue, harden steel prints poorly. Possibly done in conjunction with regrinding the spindle.
I'd have to be really really convinced though that it was worth it. My DSG and D16tooling has the battlescars of use by sloppy hands, but I popped a rubberflex chuck on it the other day, 2 tenths runout in two planes about 3 inches apart. Just saying, if you are not seeing real performance negatives, might ok to leave it
I'd have to be really really convinced though that it was worth it. My DSG and D16tooling has the battlescars of use by sloppy hands, but I popped a rubberflex chuck on it the other day, 2 tenths runout in two planes about 3 inches apart. Just saying, if you are not seeing real performance negatives, might ok to leave it
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Former Member
Guest
Dremel tool, a stone, spinning chuck and a touch of cross slide feed......what could go wrong except a perfectly center jaw faces.
Dabbler
ersatz engineer
@Ian Moss How about a very easy test: Chuck a 2" or so bar into your normal chuck. if it is uneven, turn it to round... Then mount your new chuck onto the arbor, dialing it in closely - tenths aren't needed but +/- one thou might be nice)
Spin your chuck assembly by hand, feeling with your finger the contours of the taper. Your fingers can easily discern .001 imperfections, and this 'map' will tell you just how much work you have to do.
You can also radially stone using this setup, using an ultra fine round stone, to nick off any really bad high spots, if you can gear down to below 60RPM...
A similar setup, dialed in to tenths, can also be used to refresh the taper using a TPG...
Personally I wouldn't get too agressive using this technique, but getting the worst of the volcanoes off the taper will preserve your lathe's L0 taper.
Spin your chuck assembly by hand, feeling with your finger the contours of the taper. Your fingers can easily discern .001 imperfections, and this 'map' will tell you just how much work you have to do.
You can also radially stone using this setup, using an ultra fine round stone, to nick off any really bad high spots, if you can gear down to below 60RPM...
A similar setup, dialed in to tenths, can also be used to refresh the taper using a TPG...
Personally I wouldn't get too agressive using this technique, but getting the worst of the volcanoes off the taper will preserve your lathe's L0 taper.
Dabbler
ersatz engineer
It just occurred to me that you might not have tried ablative die stones: they take the general shape of the thing you are stoning. I used to have several, but I think they are all used up now. To stone a concave surface with one, you stone the high spots lightly, which knock off the edges, and you slowly mold the stone to the shape you need, while taking down the high spots. Once it has the general curve, you preserve it by moving the high spot across the curved surface of the stone.
Excellent idea. I will have to give it a quick try to see how true I can get it to run. Tried to Google "ablative die stones" but Google has no matches.
Dabbler
ersatz engineer
try
gesswein.ca
product # 405-2065, a selection of 8 stones in various sizes and grits for 55$
These stones are soft for stoning tapers.
You set the approximate shape on your belt sander, and lightly stone your high areas, and the stone will slowly adopt the curvature required. in a large taper like a L0, I start at 45 degrees, at the large end and slowly work my way in to the small end.
-- the are now called 'moldmakers' stones...
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gesswein.ca
product # 405-2065, a selection of 8 stones in various sizes and grits for 55$
These stones are soft for stoning tapers.
You set the approximate shape on your belt sander, and lightly stone your high areas, and the stone will slowly adopt the curvature required. in a large taper like a L0, I start at 45 degrees, at the large end and slowly work my way in to the small end.
-- the are now called 'moldmakers' stones...