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  1. #1
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    May 2019
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    Default Bench grinder CBN wheel runout

    I am getting 0.5mm lateral runout on my CBN wheel, measured with my dial indicator. When I remove the flanges, it goes down to 0.1mm. I am suspecting that the flanges aren't centered because the CBN wheel has a raised area around the arbor and it contacts the flanges not at the rim. The flanges arbour is also wider than the grinder. Is there a solution to this? Pic related20220726_180929.jpg

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  3. #2
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    Jun 2005
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    Get some flanges made to suit the wheel would be my suggestion. A problem with these import grinders is the loose thread tolerances between the nut and the spindle allowing the nut to move where it wants and the stock flanges don't help much in that regard.
    CHRIS

  4. #3
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    It looks like the grinder shaft is too short for the wheel's hub thickness.
    My recommendation is to buy a grinder that has a long enough shaft so that the flange sits fully on a non threaded part of the shaft. If teh sat is too long a few washers may be needed.

    If you get a custom flange made, to be sure that things are centred and supported the flange should have a cross section like this.

    Screen Shot 2022-07-27 at 6.40.31 am.png

    I personally don't like the flange idea because the flange is going to have to provide the necessary support on a threaded section of the shaft. Long terms the thread could be worn and even damaged. This is not ideal and is why I recommend getting another grinder.

    If you have to pay for a flange to be made and you cant get it done at mates rates you might as well buy the grinder.

  5. #4
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    Quote Originally Posted by BobL View Post
    It looks like the grinder shaft is too short for the wheel's hub thickness.
    You're right. Keep in mind, though, that I also have a matching inside flange. I have the options of removing the inside flange, which is probably not recommended, or replacing the inside and outside with something thinner like a washer, or replace only the outside with a washer that fits the thread - that way they won't match, but at least they'll be centered. The advantage of the latter is that the thread is 12mm, and it's easy to find washers in that size. The shaft is 1/2", and it's considerably harder to find anything in that size.

    I'm not considering another grinder for now - I can live with the runout.

  6. #5
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    The flange can be the nut if the shaft is too short.
    CHRIS

  7. #6
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    Quote Originally Posted by yoboseyo View Post
    You're right. Keep in mind, though, that I also have a matching inside flange. I have the options of removing the inside flange, which is probably not recommended, or replacing the inside and outside with something thinner like a washer, or replace only the outside with a washer that fits the thread - that way they won't match, but at least they'll be centered. The advantage of the latter is that the thread is 12mm, and it's easy to find washers in that size. The shaft is 1/2", and it's considerably harder to find anything in that size.

    I'm not considering another grinder for now - I can live with the runout.
    Provided the wheel does not touch anything and the inner part of the hub sits up against a shaft shoulder, removing the inner flange is not going to be a problem.

  8. #7
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    Quote Originally Posted by Chris Parks View Post
    The flange can be the nut if the shaft is too short.
    That's a good idea. The nut itself is too small, as I'm using an adapter for the wheel. If I find a nut with an outer diameter a tad bigger that might just do it. The difficulty is that the thread runs in the opposite direction to normal. Might be hard to find such a nut

  9. #8
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    Quote Originally Posted by BobL View Post
    Provided the wheel does not touch anything and the inner part of the hub sits up against a shaft shoulder, removing the inner flange is not going to be a problem.
    Thanks, I'll give that a go. If ok, then I just need to find a 1/2" flat washer

  10. #9
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    Find someone with a lathe and make a nut with the flange and the extension bush to go into the CBN wheel all in one piece. That way the inner flange should not need removing though it is only meant for conventional wheels and removing it won't be an issue.
    CHRIS

  11. #10
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    CBN wheels dont need the flanges to work properly.
    Just push the wheel right up to the shoulder on the shaft and tighten up there.
    If there is runout there may be a problem with the shoulder or shaft.
    Jim Carroll
    One Good Turn Deserves Another. CWS, Vicmarc, Robert Sorby, Woodcut, Tormek, Woodfast
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  12. #11
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    I agree with Jim. It is likely the grinder.

    However, you can purchase self-aligning spherical washers: Self-Aligning Spherical Washer Sets - for two CBN Wheels – Wood Turners Wonders

    "Some problem grinders will create a little side to side vibration in the wheel due to seating problems against the the shaft shoulder near the motor housing, or unequal pressure from the shaft nut. This vibration will interfere with the accuracy of sharpening. We have found If you experience this problem these self-aligning Spherical Washers will do the trick of eliminating any vibration at all. Washers are NOT needed for 6" or 10" wheels.

    The Spherical Washers act as a ball and socket to compensate for slight misalignment andwill eliminate undue stress from the shaft nut. The hole size on this ball and socket set is slightly larger for efficient equalizing action"

    Regards from Perth

    Derek
    Visit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.

  13. #12
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    Quote Originally Posted by Jim Carroll View Post
    Just push the wheel right up to the shoulder on the shaft and tighten up there.
    How do I stop it from spinning inwards?

    Quote Originally Posted by Jim Carroll View Post
    If there is runout there may be a problem with the shoulder or shaft.
    I measured runout on the shaft itself and it was negligible, although that effect would multiply

  14. #13
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    The spherical washers overcome the poor nut/thread problem all these grinders have. They work but if the shaft and nut had tighter tolerances the washers would not be necessary and are in essence a band aid solution.
    CHRIS

  15. #14
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    Quote Originally Posted by yoboseyo View Post
    How do I stop it from spinning inwards?


    I measured runout on the shaft itself and it was negligible, although that effect would multiply
    I doubt the arbor runout will ever be much of a problem on a grinder.

    I've got three, two big imports and a small baldor, a cheap buffer and had another import grinder. the flanges are terrible on all of them, including the baldor.

    The CBN wheel that I have on the baldor grinder now is just retained with a large washer - that's all I'd use is washers or stacks of washers that fit - nothing special, and if a nut has a burr or something on to contact them, just hand lap the nut a little.

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