Stone has become non-circular

[dozzy]

I have had my tormek grinder for 8 years and have used about 5-6 stones in that time. My latest stone which is about 4 months old (now about 220mm in diameter) is starting to become non circular. This has never happened to me before on previous stones. The stone is about 5mm out of circular. It appears to have a bulge on one side so as its rotating, the stone appears to rise and fall as if it is not mounted through the centre of the stone. (Im trying to be as descriptive as possible so you can understand what I'm talking about)

I suspect it's got something to do with the rubber drive wheel although as its running I can't see any movement in the drive wheel.

Has anyone else experienced this?

Thanks. Paul

[jeffs55]

I had the exact same thing happen, maybe not in the same time frame but the same result. It became egg shaped. The only cure is to use the diamond dressing tool to restore the round shape. Start with the lightest cut needed to attack the "bulge". From there you just keep the diamond cutter going into the stone until you ultimately make a cut that goes all the way around the stone. You are of course going to remove an amount equivalent to the the height of the "bulge". No alternative so just do it.

[Ken S]

Welcome to the active forum, Dozzy.

My first thought is that expressed by Jeff. You are an experienced Tormeker. Have you been using the truing tool regularly? If so, it seems odd that the stone would be so far out of true. I second Jeff's wise comment about using light cuts with the truing tool.

Is there any side to side wobble?

Do you travel a lot with you Tormek? If you have gone through several grinding wheels, you either do a lot of work in one location or move around! If you transport your Tormek, do you remove the grinding wheel before transporting? (Jeff Farris, who probably transported a Tormek more than anyone, always removed the wheel.)

If you happen to live near a dealer, I would take your Tormek into the store. Make sure the demo unit is working properly. Then try putting your grinding wheel in the demo unit. it should either run properly or not. This will determine if the problem is in the stone or  your Tormek itself.

While there, if you suspect your drive wheel, swap the demo part with your unit, and see if the trouble follows.

If you have not upgraded to the EZYlock shaft, this might be a good time to do so. It really is more convenient, especially if you take the stone on and off frequently.

Keep us posted.

Ken

[Elden]

   Welcome to the forum, Paul. I am curious to know what your primary usage of the Tormek is. 30mm of wear in 4 months (as well as 5- 6 grinding wheels in 8 years) points to some serious usage!
   Jeff hit the nail on the head, probably in your area the terminology is "is spot on". The Tormek TT-50 or the older ADV-50d needs to be used to bring the grinding wheel back to being "in round". As a grinding wheel starts to become out of round, that is further amplified by further sharpening and use of the stone grader
   When purchasing a Tormek truing tool, make sure to purchase one with the diamond cutting tip included. The price of the truing tool without the tip looks attractive, however, it will not function unless a tip is added.

   Addendum:
   Ken has posted as I was typing. He brings up a good point. The shaft can be bent if the Tormek is mishandled. My used Super Grind arrived with a bent shaft due to being mishandled.

[Ken S]

Eldon makes an excellent point about purchasing a truing tool. If the designation ends with"U", it is an upgrade unit for those who want to upgrade their older units and who already have the diamond cluster. I Mistakenly ordered one. The dealer gave me  refund, however the upgrade part I also ordered ended up with a lot of shipping cost. The product listing is plain enough IF one reads carefully.

Ken

[dozzy]

Hi everyone, thx for all the replies. I have a mobile knife sharpening business hence the high usage and so yes I do transport the unit around in my vehicle. I always keep it tied down but I don't remove the wheel during transportation. I do have a truing tool and will use that to bring it back to circular (at a big loss of about 5mm of stone though 😢) and then keep an eye on it.

As I watch the stone rotate I don't see any obvious wobble to the drive shaft but I guess a small wobble in the drive shaft could be exaggerated at the extremities of the stone. There is no vertical movement in the stone though so hopefully that also indicates that the drive shaft is straight.

Great forum. Stay well. Dozzy

[Tournevis]

Hi dozzy,
May I suggest you to check the roundness of the Centre hole of the wheel also ?
As the wheel is directly in contact with the shaft a small "nick" at the centre could interfere seriously the roundness at the circumference of the wheel.(the play will be going worst and worst due to vibration during transportation)
But perhaps it's not the point.

[OnealWoodworking]

I had the exact same thing happen, maybe not in the same time frame but the same result. It became egg shaped. The only cure is to use the diamond dressing tool to restore the round shape. Start with the lightest cut needed to attack the "bulge". From there you just keep the diamond cutter going into the stone until you ultimately make a cut that goes all the way around the stone. You are of course going to remove an amount equivalent to the the height of the "bulge". No alternative so just do it.

How does a stone become 'egg shaped' like that? What caused your issue?

[Herman Trivilino]

I'm shocked that the OP went through so many grindstones without ever needing to true one.

For me, the question is not what makes one go out of round, it's what doesn't?

The trick, though, is to catch it at the first sign of trouble. An out-of-round grindstone quickly gets much worse.

[jeffs55]

Oneal, I am sure that we all press our cutting tools into the stone to begin grinding. At some point there must have been a more pronounced "press" that became cumulative at that point. Then it just became worse, after all, a  pothole in the road does not fill itself in. If not that, then maybe a weak spot in the stone was more susceptible to being gouged out. Since the stone turns, the gouge would have been spread over the entire stone or at least the part nearest the gouge. If the stone were stationary, I would simply have dug a hole instead of shaping an egg. I am saying that the high point is the part that was not affected by grinding. Everything else was affected by becoming the low spot on the wheel. Even though the "low spot" is the entire wheel except for the bulge. Here is where I posed the question on 10-31-11 to Jeff Farris and his answer:

http://forum.tormek.com/index.php?topic=1348.msg4104#msg4104

[Ken S]

Very good question, OW. It is a bit of a mystery, but is a real life situation. I am a believer in what Herman posted; early and light retiring cuts before the situation deteriorates.

Jeff, nice search find.

I was surprised with how much retiring was necessary with both my SG-200 (T4 wheel) and SB-250 after very little use. Good grinding practice calls for an initial truing of all new wheels. I think that is a good practice for Tormek users.

Ken

[SharpenADullWitt]

I think I remember a post by the old forum moderator, Jeff Farris, about the wheel becoming out of round by sitting in water on a regular basis. (water evaporating at the top of the wheel, but  not the bottom)
I also seem to remember a post where someone had their shaft become rusty, and I seem to remember something about just a tiny bit bent (where the wheel would exaggerate that).
The first is an easy fix (remove the water tray for full/even drying), the second is easily checked.  (remove the shaft and roll on the table.)

[Ken S]

Good points, SADW. Switching to a stainless steel EZYlock shaft is a very good investment in the longevity of your Tormek.

Also, for those of us interested in a more in depth understanding of the Tormek, I know of no better source than studying the posts of the former moderator and forum founder, Jeff Farris. I do this when time permits, and have always learned something. This is easily done after logging in. Just ckick on his name and click on read posts. As a no longer posting member, the post numbers remain static, with number one being the most recent. Keeping track is easy. Your study time will be well rewarded.

Ken

[GrodanB]

I have had a strange experiance with the stonewasher. Do not know if  this was the correct fault but my stone got out of round more than once (fast). I saw that my washer was not equal on both sides. Turned it around and my problem was much smaller. Today is the first time i a year that I need to remove a small bump in the wheel. First five millimeters of my wheel was almost all used up by the truing tool...

But rememeber that this was happening during the steep lerning curve first months after I got the T7...