Grindstone radial excentricity, despite TT-50 and new bushings and shaft

[jetchick]

Sorry if this has been mentioned elsewhere on this forum. I searched and could not find a similar post.

I had trouble tracing down a source of grindstone "hop" (radial excentricity) despite truing with TT-50, and also installing new nylon bushings and shaft.

Finally tracked it down to enlarged arbor hole in grindstone. Solution is to just line up the stone and the shaft in the same direction, every time you swap stones.

Quickie YouTube attempt to explain problem and solution. The improvement is noticeable (hard to get on video, but it is a real improvement).

https://youtu.be/PW49DKdOb_Y

Has this problem been noticed before? I did not find any mention of it in the User's Manual.

Thanks,

Stefan Jetchick

[Rem]

Welcome on, JC.  I'm a newbie myself.

That is damn interesting.  I have a new shaft dogsledding its way to me and I will adopt your procedure.  Makes sense to me.   thanks for putting that video together.  R   

[Ken S]

Welcome to the forum, Stefan.

My compliments on your well done video.

I use a procedure which might be helpful. The other end of the shaft is generally less variable. Once the nut holding the rubber drive wheel is secured, the shaft and drive wheel remain in the same orientation (exception noted andcorrected below).

The leather honing wheel is held in position by three plastic pins. If we label the drive wheel and designate a selected hole and pin, the leather honing wheel will remain in the same orientation with the drive wheel and shaft, even if it is removed and replaced.

With these three aligned, we can mark an up orientation on the outside of the honing wheel. If we always keep this arrow facing up when we attach the grinding wheel, we will have a consistent shaft orientation.

If we move the grindstone around until we find the optimum orientation, we can draw an up pointing arrow on the grinding wheel. The next time we install the grinding wheel, aligning the two arrows upward will reestablish the optimum orientation.

Switching grinding wheels, if we retain the up arrow orientation of the shaft, we only have to locate the optimum orientation of the second wheel. The third wheel is done the same way.

I have not personally encountered the problem, although it has been discussed on the forum. Jeff Farris, the previous moderator, suggested slightly loosening the grinding nut (this was pre EZYlock) and rotating the wheel ninety degrees until the "sweet spot" is found.

Thanks for asking this auestion. I look forward to reading more replies.

Ken

ps The exception: If the drive wheel is removed, draw an up arrow on the shaft itself to return everything in proper orientation.

[SharpenADullWitt]

http://forum.tormek.com/index.php?topic=852.0

I think Jeff may have discussed it even before this forum, as I saw a post which looks like it linked to a forum, originally on his site.   But the above is the only time I have found it that I remember.
Ken could probably tell if it was in the old faq or in one of the older manuals (not sure about the newer ones).  I just remember this when there was some discussion about someone taking their Tormek somewhere, and was told to try it in several positions, before truing.

[Ken S]

SADW,

That seems like the topic that I remember. My idea with the orientation arrows could easily be expanded to include placing different color arrows for each grinding wheel on the washer. For the really obsessive, use separate washers for each grinding wheel. You still have to find the sweet spot, but once found, it should stay found.

Is the washer stamped or machined? I don't know if that would make any difference or not.

Ken

[Jan]

Welcome to the forum, Stephan.   

I think your explanation is correct.

By swapping the grindstones we are always losing some small part of the exactly round shape achieved by truing because we cannot guarantee exactly the same montage of the grindstone. The described stone/shaft orientation procedure surely minimizes the eccentricity but cannot fully restore the state after truing.

Jan

[wootz]

Stefan's video is also interesting in showing how to check if the grindwheel is out of round - with the Universal Support in the horizontal position; while checking if the stone is out of square is easier with the US in the vertical sleeves.
This check could be a nice addition to the preflight checklist  http://forum.tormek.com/index.php?topic=2717.msg14499#msg14499
As is the stone-washer-shaft alignment when mounting the stone.

The washer position is as important as that of the shaft and stone.
I mark the shaft, the washer, and grindwheels, and always mount the stones aligning all these marks to compensate for manufacturing or wear imprecision...
Doing so we don't end having to true the stones needlessly as we mount or change them.


Cheers to Ken and SharpenADullWitt for reviving the thread on minimising the stone lateral wobbling. It does affect knife sharpeners when working at the bolster end.

[Ken S]

Wootz,

Good thoughts! I believe we are using markers where center punched alignment holes would be used in industry. The theory is very sound.

The more I use a Tormek, the more convonced I am of the value of things like pre-flight check lists to simplify and solidify our technique. Surely having a grninding wheel wnich does not wobblw and is true puts us two giant ateps ahead.

Ken

[Rem]

Surely having a grninding wheel wnich does not wobble and is true puts us two giant ateps ahead.

Ken

And one that comes off is icing on the cake ......   R   

[Ken S]

Rem,

Just because we are next door neighbors doesn't mean we have to spell everything identically.

Besides, I'm the moderator, not the editor-in-chief, and my fingers get clumsy sometimes.

Ken

[Rem]

I figured it was a test to see if I was watching ..............   R   

[Ken S]

I think you passed the test. We are mailing you the result. You should know by the end of the year, weather permitting.

Ken

[Rem]

Yeah, no kidding .... and I still don't have a shaft.  I think I'm getting the shaft   R

[Ken S]

Did Big Bear send you a tracking number so that you can check the progress of Rex and the team?

Ken

[Rem]

I don't want to talk about it  !!!!!!!


Oh, ok .... yes, but I have inadvertently nuked it I guess.  I emailed BBT today to re-send.   I also recommended they consider using another courier in the future.  Perhaps a porcupine team.  Hard cheese.    R