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Thread: Bench grinder CBN wheel runout
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26th July 2022, 11:31 PM #1Senior Member
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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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27th July 2022, 12:28 AM #2GOLD MEMBER
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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
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27th July 2022, 09:48 AM #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.
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27th July 2022, 10:18 AM #4Senior Member
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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.
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27th July 2022, 10:26 AM #5GOLD MEMBER
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The flange can be the nut if the shaft is too short.
CHRIS
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27th July 2022, 10:30 AM #6.
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27th July 2022, 10:44 AM #7Senior Member
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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
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27th July 2022, 10:46 AM #8Senior Member
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27th July 2022, 01:54 PM #9GOLD MEMBER
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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
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27th July 2022, 02:07 PM #10
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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27th July 2022, 03:01 PM #11
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
DerekVisit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.
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27th July 2022, 06:13 PM #12Senior Member
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27th July 2022, 06:36 PM #13GOLD MEMBER
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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
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28th July 2022, 07:03 AM #14GOLD MEMBER
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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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