tight fitted top jaws

The top jaws on the 6" 6-jaw CME (Sanou) chuck I received are VERY tight in
the main jaws, enough to need a plastic hammer to remove. I've been sanding
them down with a square backing bar as the guide but the silicon carbide and
aluminum oxide paper I tried cuts extremely slowly. A 1/4" carbide bit in
the mill wouldn't touch the hardened steel and a larger one doesn't fit the
groove. My belt sander is too crude for such a precision task and a lathe
bit blank used as a scraper will remove a tiny chip from the corner at the
bottom but not from the face, although it drags as if it's trying to cut.
I'm trying to fit them to require moderate hand pressure to install or
remove, like the ones on my Bison 3-jaw. AFAICT the interference is just a
few ten thousandths though only 0.001" calipers fit into the area. I could
have bought a disk micrometer at the ham radio flea market but I didn't have
a use for it then.
Does anyone have a way to do this? There isn't enough clearance to surface
grind them.
This is the style, and the crosswise tongue underneath is the problem. The
lengthwise tongue fits well.
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tia, jsw
Reply to
Jim Wilkins
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You can get other wheels or dress down to fit. Also, if you have one that was dressed at an angle for grinding a special application the flat face might reach deep enough.
Carbide won't cut it? Must be pretty doggone hard.
Reply to
Bob La Londe
<snip>
Just something you might not have considered... Valve grinding/lapping compound.
Reply to
Leon Fisk
^ |
It will work. You absolutely MUST get it thoroughly cleaned out when you are done, but I expect you know that.
Reply to
Bob La Londe
It will work. You absolutely MUST get it thoroughly cleaned out when you are done, but I expect you know that.
Bob La Londe CNC Molds N Stuff
-----------------
Thanks. The manufacturer didn't know or care about debris between the top and main jaws.
The parts move very little relative to each other, and I think the compound would just scrape off as I hammer or screw the top jaw down. After posting I reconsidered how I was doing it, and clamped the lathe bit in a drill chuck as a handle which let me apply considerably more pressure, enough to raise tiny chips. That let the first set go together with less hammering together and prying apart so I tried sooting the surfaces to show actual contact and then scraping those spots, until my hands cramped. These small, recessed surfaces were clearly not ground as well as the exteriors of the jaws.
Hey, I have an EZE-LAP that fits those narrow recesses...
Reply to
Jim Wilkins
This is best done manually, by a form of scraping.
Obtain a small tube of Hi-Spot Blue paste:
.
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And some very fine (800 or 2000 grit) wet/dry sandpaper, and a small machined aluminum rectangular block around which to wrap a piece of that sandpaper.
Very thinly coat the chuck side of the mating interface with Hi-Spot Blue. Install and remove the jaw. Under a bright light, inspect the mating surfaces of the removable jaw. The high spots will have some blue, perhaps in a bulls eye pattern (the center being where metal squeezed the paste completely out). Use the sandpaper to very slightly reduce the high spot. Don't be impatient, or overshooting is certain. Repeat until the plastic hammer is no longer needed. Clean very well, oil, and install. Do for all jaws.
The above assumes that the chuck is correct and the jaws need adjustment. If the jaws are perfect and the chuck needs scraping, smear the jaws with blue and reduce high spots on the chuck side. Be even more slow and careful, and practice on a beater, because an overshoot will destroy the chuck for anything precise. Scraping a beater into precision would be a good exercise.
Joe Gwinn
Reply to
Joe Gwinn
This is best done manually, by a form of scraping.
Obtain a small tube of Hi-Spot Blue paste:
.
formatting link
And some very fine (800 or 2000 grit) wet/dry sandpaper, and a small machined aluminum rectangular block around which to wrap a piece of that sandpaper.
Very thinly coat the chuck side of the mating interface with Hi-Spot Blue. Install and remove the jaw. Under a bright light, inspect the mating surfaces of the removable jaw. The high spots will have some blue, perhaps in a bulls eye pattern (the center being where metal squeezed the paste completely out). Use the sandpaper to very slightly reduce the high spot. Don't be impatient, or overshooting is certain. Repeat until the plastic hammer is no longer needed. Clean very well, oil, and install. Do for all jaws.
The above assumes that the chuck is correct and the jaws need adjustment. If the jaws are perfect and the chuck needs scraping, smear the jaws with blue and reduce high spots on the chuck side. Be even more slow and careful, and practice on a beater, because an overshoot will destroy the chuck for anything precise. Scraping a beater into precision would be a good exercise.
Joe Gwinn
------------------------
That is pretty much what I have been doing. Fine SiC paper had no noticeable effect, so I stepped down to 180, then Al2O3 paper which seems better, and for the next pass I dug out my diamond hones. That steel is Hard, I can barely scratch or scrape it with a lathe bit. Instead of bluing I smoked the surfaces over a candle which is faster and less messy, no applicator needed. The contacting surfaces show up very clearly as shiny against the grey or black background.
I didn't expect much from a 6" 6-jaw for $231. The reviews suggested it might become a project but should be worth the trouble / practice when done. Better too tight than too loose. My 4" 6-jaw has proven very useful on plastic and tubing but its capacity is too limited. Any work that requires roundness and concentricity is done on a live pipe center at the tailstock end.
Another question. I think a backplate's location on a threaded spindle is a compromise between centering on the angled thread flanks and how squarely the back end seats on the spindle flange. In order to square the back end to the threads and spindle axis as much as possible I'm considering placing a compressible material like thin cardboard or an O ring between the spindle flange and the backplate while I take a truing cut on the opposite end, then reversing it. Hopefully this would give the seating face less and the threads more centering authority if the contact isn't square. If the cutting drag screws the backplate on tighter I should notice the change when backing the bit out again. Has anyone tried this, or have a better method?
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Threaded spindles may be considered obsolete, but the trade school lathe I learned on had a D1 mount that was badly burred by chips that hadn't been cleaned out of the chuck before installing it.
Reply to
Jim Wilkins

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