Thread: CBN - too much runout on my bench grinder? Better grinders?

The nut/shaft relationship is highlighted in the video.

Originally Posted by Oddy

Yes that would be part of the issue. I imagine the thread on the shaft would also contribute



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Given that the spherical washers are explicitly sold to compensate for nuts that are not properly perpendicular to the shaft (according to both the video clips I just watched), my preference would be to replace the nut with a decent quality one and see if that doesn't sort it out. It should be easier to either buy a nut or have one made locally than to import the washers from the US. You might be able to get a machine shop to align your existing nut for even less outlay.

Having said that, I really like the simplicity of the design of the spherical washers, and they certainly seem to do the job. It's just that they're addressing the symptom and you can fix the cause directly.

I think the shaft may be the problem as well but I could be wrong, on my grinder the nut/shaft relationship could only be termed a rattling good fit and as it is left had thread the nut would have to be machined. I got inquisitive tonight, put a dial indicator on it and got 2 thou run out at the outer rim. A few weeks ago Joe Hovell one of our fellow forumites was at my place and we had a fiddle to try and minimise the run out which is where all this got started. We flattened the nut on one side then played with moving the wheel around the shaft, moving different spacers and washers etc and got it a whole lot better than it was but nowhere near as good as it is now.

Thank you to all that have contributed to this thread. I bought a 240 grit CBN wheel from Timberbits a few weeks ago, delighted with the grind on turning tools, but a bit disappointed that there was a bit of run-out which I hadn't addressed until this morning after reading all of the above tips and experiences.
My grinder is an old GMF 3 phase industrial unit, a very solid piece of gear. Armed with a piece of chalk and a crude way of identifying the high point, I rotated the wheel 180 degrees on the shaft and filed the retaining nut and washers to remove any slight burrs. I am delighted how perfectly true it ran. I also touched up the shoulder on the shaft where the washer mates up, there seemed to be a bit of crud or a nick on it which was easily removed. More good luck than good management, but end result was spot on.
Then I noticed that there was a bit of sideways wobble. The wheel has a variety of chalk marks on it now, but after a few tries I reckon it runs as true as it was designed to.
A great result after a half an hours fettling.
Everyone's 'two Bobs worth' contribution is very much appreciated.
Have a great day,

Alan...

The spherical washers are available here in Australia.
And here are the specs for them if you miss the link on the site.

Malwarebytes Anti-Malware REALLY doesn't like either of those links - not sure what the issue is?

Good to know that these items are available locally though.

Working for me

Dave TTC
Turning Wood Into Art

Hi all I am thinking of going down this track ,using a CBN wheel on a bench grinder ,one about 1450RPM with Tormek jigs. Which is the next question is the wet Tormec grinder rev's fast to use the CBN wheel given that the Tormek is about 100 rpm.
The stone wobble problem can be over come by making a new inside flange out of aluminum that incorporate the insert that is a very neat fit on the shaft, this should if the inside of the stone is true hold the stone straight .
regards Rod

The CBN wheel comes with very well made flanges, not your usual pieces of pressed tin that we are used to seeing. On another grinder I custom made a set of flanges and took a lot of care doing it and the problem was still there, this was with a normal grinding wheel.