CBN Wheels....wobble???

[Dennis Peacock]

What if you get a CBN wheel for your SSG and it has a wobble to it? I'm trying to setup my SSG to run CBN wheels and there is no noticable runout on either end of the shaft. Please advise.

[Kevin Jenness]

Assuming the wheel is not at fault then the seat at the inner end of the arbor may be the problem. You can compensate by using two piece spherical washers. Woodworkers' Wonders carries them as do machinist supply houses like MSC.

I just put a cbn wheel from Hurricane Tools on my bench grinder. It came with several machined spacers for the inside of the wheel and instructions to not use the stock stamped inner flange. Spins like a top!

[Bill Boehme]

It usually means that the hole in th wheel is slightly larger than the shaft diameter. One way to correct the problem is to use spherical washers to make the wheel run perpendicular to the shaft.

[Dennis Peacock]

Thank you! Looks like spherical washers are in my future! Y'all are awesome! :D

[Mike Turner]

I just recently got some CBN wheels from Woodworkers' Wonders. I got a spherical washer kit from there too. They run really true.Ken at Woodworkers' Wonders is great to work with too!!!

[JohnC Lucas]

What is an SSG. Could not answer this question because I don't know what your talking about.

[scott ward]

Slow speed grinder is my guess

[JohnC Lucas]

Ahh. Brain wasn't working this morning. Did you have to use an adaptor for the spindle size or does the wheel fit directly on. If you used an adaptor that could be the problem. Other than that try loosening the nut, rotate the wheel a little and tighten. Quite often one or two tries of that will solve the problem.

[Dennis Peacock]

Ahh. Brain wasn't working this morning. Did you have to use an adaptor for the spindle size or does the wheel fit directly on. If you used an adaptor that could be the problem. Other than that try loosening the nut, rotate the wheel a little and tighten. Quite often one or two tries of that will solve the problem.

Good Morning John,
SSG is Slow Speed Grinder.... :)
No adapter required for the CBN wheels but there is enough "play" between the hole in the wheels and the shaft on my grinder that yields a fairly significant wobble.
I did go ahead and order the wobble washer set from Ken.

[David Delo]

Dennis,

Not sure what brand SSG or CBN wheels you have but here's my experience marrying the two with Ken Rizza's wheels and several different brands of SSG's. Had the CBN wheels on a Delta variable speed grinder and when the grinder went kaput, tried them on the famous Woodcraft no-name and Rikon 1/2HP grinders that I had at the time. Issue for me was I needed to use the spherical washers but that didn't leave much room for the nut to screw onto the shaft. It worked fine but I always felt a little uneasy when starting the grinder waiting for a wheel to fly off. Bought a 1HP Rikon that was designed to use CBN with a longer shaft and a much more substantial shaft shoulder for the wheel hub to rest against. Here's a couple pics to show the difference.
383450383451383452383453383454

[Don Jarvie]

I have the PC SSG and the Hurricane CBN wheels fit perfectly on the shaft with no play. I would think that since the wheels are machined true the grinder shaft may be an issue.

[John K Jordan]

What if you get a CBN wheel for your SSG and it has a wobble to it? I'm trying to setup my SSG to run CBN wheels and there is no noticable runout on either end of the shaft. Please advise.

As others mentioned, the spherical washers worked perfectly for the three CBN wheels I use.

Side-to-side wobble? I think that problem is sometimes due to irregularities in the standard washers that come with the grinders. For the CBN wheels on the Tormek I didn't use the spherical washers since the shaft was too short but I did flatten one washer with sand paper on a surface plate. The other washer I used was precision machined. No detectable wobble.

If the wobble is radial runout due to sloppy fit between the shaft and the hole in the wheel I'd probably try to center it with a bit of shim. I have extremely thin plastic and brass shim stock.

JKJ

[Chris Parks]

One spherical washer to a wheel and never two, there is a recent thread where someone tried two and it does not work. There is probably nothing wrong with the shaft, the usual problem is the very poor tolerances of the threads on both the nut and the shaft and the nut can flop all over the place.

[Randall Mack]

I have an older Woodcraft grinder. On one side even with the spherical washers the wheel would wobble. I tried washers one side then the other side of the wheel including just one washer without success. After close inspection I could see that the ledge on the shaft where the wheel or washer rests against had 2 small dings that deformed the edge slightly making it impossible for the wheel to seat properly. I carefully filed just the spots where metal protruded and that took care of the issue. If you have to do this be careful since you could make it worse.

[Dennis Peacock]

I got the spherical washers in on Thursday. I've spent an hour this morning just trying to get both sides to run true. One side was easy enough to get to run true. The other side continues to fight me all the way. The wheel wobbles enough to vibrate the entire grinder and bench I have it mounted to. My hope was that with these new wheels and washers that it would vibrate as badly as the old AO wheels I had on there. I finally got frustrated enough to come back in here in the house and post here on SMC.
I can't find any shaft runout, perfectly smooth, even when running full speed with no wheels on it. I guess I'll have to go and look even closer at it.

Another question....both side tighten in the same direction. How to you get the wheels tight without spinning the other side loose?

[Dennis Peacock]

Ok, I went back out to the shop and removed both wheels. No burrs or bumps on either shoulder for either side of the motor. I put my dial indicator on both sides to check shaft runout. Left side, dial never budged from 0.000" and the other side moved to what I'd call 0.0002". I put the flat washers back on first (cleaning everything from shaft to both sides of each washer piece) that came with the spherical washers I ordered from Ken. Then I put on the 80 grit wheel, then both halves of one spherical washer and then the nut to hold it on the shaft. I left it a touch loose, turned on the grinder and it spun up and the wheel lined up pretty good. I did the same for the other side. Wobble with the 220 grit wheel. I put my dial indicator on each wheel (in the flat hub space near the grinding surface, but far enough back to not be effected by those surfaces) and measured each wheel. The dial indicator measured eactly the same for both wheels.....0.015"
The wheels I ordered came from Buffalo Woodturning Products. They look like really good wheels, but I'm lost at this point on how to get these mounted without the side to side wobble.

[Chris Parks]

Swap the wheels and make sure the washers are lubricated on the sliding faces, also do not over tighten the nuts.

[Glenn C Roberts]

Had the same issue with the Rikon 1 Hp. I used ball bearings, with the same shaft diameter, between the cbn and the stop on the shaft on the motor side of the wheel. Smooth as silk. I don't think the stock hubs are cast to any exactness, and those wheels did have a terrible wobble. I did use their hub against the nut and wheel though, or maybe I used another bearing - don't rememder. The bearings were a little wide, so I had to move out the guard plate a tad, because it biased the wheel alittle outboard - away from the motor. Smoooooth!

[Ken Fitzgerald]

Dennis,

This may sound crazy but it's coming from me. What did you expect?

Are the nuts making contact a full 360º against the washers or wheels? When I first got my Woodcraft slow grinder I had a similar problem with one wheel. It turned out that the threaded hole in one of the nuts wasn't perpendicular to the face of the nut. Thus the face of that nut was only touching in a small area. The grinder was new but it's 220 miles round trip to the Woodcraft where I bought it. But my Ace hardware store had a RH nut of the right thread and size. I replaced the nut. The new one made contact as you would expect (360º) and there was no more wobble.

[Dennis Peacock]

Dennis,

This may sound crazy but it's coming from me. What did you expect?

Are the nuts making contact a full 360º against the washers or wheels? When I first got my Woodcraft slow grinder I had a similar problem with one wheel. It turned out that the threaded hole in one of the nuts wasn't perpendicular to the face of the nut. Thus the face of that nut was only touching in a small area. The grinder was new but it's 220 miles round trip to the Woodcraft where I bought it. But my Ace hardware store had a RH nut of the right thread and size. I replaced the nut. The new one made contact as you would expect (360º) and there was no more wobble.

Hummmmmm......that's something I haven't thought to check. I'll look at that tonight after work.

[Chris Parks]

Hummmmmm......that's something I haven't thought to check. I'll look at that tonight after work.

My post explains why this is the likely cause due to poor tolerances.