"Joe Gwinn" wrote in message news:
4fn4nhlph7c326skd7anocgau43cq0m5a3@4ax.com...
On Sun, 13 Nov 2022 11:34:39 -0500, "Jim Wilkins"
<
muratlanne@gmail.com> wrote:
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. ...
This is best done manually, by a form of scraping.
Obtain a small tube of Hi-Spot Blue paste:
.<
https://www.mcmaster.com/high-spot-paste/>
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?
https://www.hobby-machinist.com/threads/thread-clearance-on-sb-heavy-10-spindle.64202/
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.
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