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Thread: CBN 8" wheel with runout?

  1. #1
    Join Date
    Jan 2018
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    CBN 8" wheel with runout?

    I finally got the wheel delivered a few moments ago, and rushed to put it on the new Rikon grinder.
    Did a little twirl by hand (not under power) and noticed a far amount of run-out as the wheel spun.
    I was under the impression the thing was machined flat over the surfaces, front and sides, so I wondered if that was normal. Of course I could be wrong, and only the face is machined flat but, I'm not sure.
    The original wheel did not seem to "wobble" that way, so I don't think it's the shaft.
    Young enough to remember doing it;
    Old enough to wish I could do it again.

  2. #2
    Join Date
    Sep 2012
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    Tampa Bay area
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    You can rotate it on the shaft a few degrees each time until you reach the least amount of wobble. Or you can get a set of the self aligning spherical washers from here: https://woodturnerswonders.com/colle...er-3-piece-set

  3. #3
    Join Date
    Feb 2014
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    Lake Gaston, Henrico, NC
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    5,503
    Does the shaft have runout without the wheel on it? If not, I'd send the wheel back. I think this picture is from 2014, and it still runs that true.
    Attached Images Attached Images

  4. #4
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    Tom, although I have a dial indicator, I'm wofully inept at using it. That being said, I have what I think is an .001 deg runout at the motor end of the shaft and about the same at the thread end. From along the length of the shaft there is obviously a crown.
    With the wheel in place and tightened to about 5 ft. lb. measuring at the rim it appears I have a high spot ~.021 deg from low to high.
    It's taken me 2 weeks to get it here UPS standard, so if they have it in stock (finally) at the local Lee Valley, I'll see if they can exchange it. Otherwise I'll try the specialty washers.
    Young enough to remember doing it;
    Old enough to wish I could do it again.

  5. #5
    Join Date
    Nov 2009
    Location
    Peoria, IL
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    2,259
    Quote Originally Posted by Aaron Rosenthal View Post
    Tom, although I have a dial indicator, I'm wofully inept at using it. That being said, I have what I think is an .001 deg runout at the motor end of the shaft and about the same at the thread end. From along the length of the shaft there is obviously a crown.
    With the wheel in place and tightened to about 5 ft. lb. measuring at the rim it appears I have a high spot ~.021 deg from low to high.
    It's taken me 2 weeks to get it here UPS standard, so if they have it in stock (finally) at the local Lee Valley, I'll see if they can exchange it. Otherwise I'll try the specialty washers.
    Dial indicators do not measure in degrees, they measure in thousandths or an inch. Where did you buy the wheel? Talk to them about a return.

  6. #6
    Join Date
    Feb 2004
    Location
    Perth, Australia
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    7,917
    Aaron, go to Wood Turners Wonders (Ken Rizza) for self-aligning spherical washers ... this is self-explanatory

    https://woodturnerswonders.com/colle...two-cbn-wheels

    Regards from Perth

    Derek

  7. #7
    they measure way finer than thousands of an inch, at least when I have glasses on

  8. #8
    Join Date
    Nov 2009
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    Quote Originally Posted by Warren Lake View Post
    they measure way finer than thousands of an inch, at least when I have glasses on
    Of course they do, especially last word dial indicators. But the point is they don't read degrees.

  9. #9
    Join Date
    Mar 2010
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    Somewhere in the Land of Lincoln
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    1,550
    Is there much slop in the fit on the motor shaft? Hopefully not. It sounds like a quality issue with the wheel though. If there is some slop you could loosen the arbor nut and try to "true" it up. The high spot will be opposite the low spot. If you had .021 thousandths run out the wheel would need to shift .0105 to be perfect. That's a lot of slop if it will move that far. Ideally a wheel like that should just slip on since you have no trueing options. I'm sure I'm not telling you anything you don't know. Good luck.

  10. #10
    Just be aware that you can get an arc distance error with an dial test indicator like a Last Word ( Starrett) indicator. And that a dial test indicator is for comparison only and not direct reading even if the lines lead you to believe so.
    Tom

  11. #11
    Join Date
    Mar 2003
    Location
    SE PA - Central Bucks County
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    56,616
    Runout on the shaft is going to multiply when you extend it out 8" to the edge of a rotating wheel...
    --

    The most expensive tool is the one you buy "cheaply" and often...

  12. #12
    Aluminum wheels with CBN abrasive have to be created on lathes, so it's extremely unlikely that your wheel is significantly out of round or that the center hole isn't true and concentric. You'll probably have your wheel running true in no time.
    Cry "Havoc," and let slip the dogs of bench.

    I was socially distant before it was cool.

  13. #13
    Join Date
    May 2016
    Location
    Northeast PA
    Posts
    522
    As others have said, get the spherical washers. They are cheap & worked wonders even on my cheapo Delta variable speed grinder. My CBN's wobbled terribly without them, once I put the spherical washers on it was smooth sailing.
    ---Trudging the Road of Happy Destiny---

  14. #14
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
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    10,619
    Quote Originally Posted by Aaron Rosenthal View Post
    I finally got the wheel delivered a few moments ago, and rushed to put it on the new Rikon grinder.
    Did a little twirl by hand (not under power) and noticed a far amount of run-out as the wheel spun.
    I was under the impression the thing was machined flat over the surfaces, front and sides, so I wondered if that was normal. Of course I could be wrong, and only the face is machined flat but, I'm not sure.
    The original wheel did not seem to "wobble" that way, so I don't think it's the shaft.
    As Derek mentioned, get a spherical washer set from Ken Rizza at Woodturners Wonders. They are cheap. I won't install a CBN wheel without the washers.

    I've seen this runout several times with CBN wheels without the spherical washers. The problem was not the wheels but imperfectly made washers and nuts that came with the grinder. I like to put a machined (not stamped) washer on the motor side but the machined washer is probably not needed. The spherical washers are self aligning.

    JKJ

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