SJ Wheel wheels rant

[sharpening_weasel]

I'd like to preface this by saying I love and have used the SJ-250 stone for the past three years, not without issue, but at least with an acceptable level of annoyance. When I first recieved my T8 after upgrading from the t4 to support a growing sharpening business, I had to send one t8 and a different SJ-250 stone back to tormek due to absolutely atrocious wobbling of both the drive shaft and a warped stone. Customer service was stellar- Stig was almost instantaneous with replies and very helpful throughout the whole return process. My current stone still wobbles, but far less then the previous one. I've made use of Tormek's (and I believe I've seen it mentioned somewhere on the forum, not sure who to credit with that one) process of marking a line on the shaft, lock nut, and marking the stone into four quadrants to help align everything and remove as many variables as possible. I have to fiddle around with it for 3-5 or so minutes each time I set it up to get it running as smoothly as I can.

Now, onto my gripe.
The damn thing still wobbles. I've been assured by Stig that "The SG stones should run nicely and within the tolerances, see handbook page 162. The Japanese stone has almost twice as much [wobble] since they are made in a different way and the hole is slightly larger." I feel like this should not be the case for an almost FIVE HUNDRED dollar piece of equipment. If I'm paying this much for something, I think it should have at least the same tolerances as the relatively cheaper SG-250. Again, I'm not complaining about the level of the finish it leaves- that part is superb, no problems there. In addition, for no good reason, the SJ-250 stone will seemingly randomly (to me at least) go back out of true at random intervals, no matter if I've lined everything up identically to my previous settings. As a result, I have to go back and painstakingly true it up with the stone truer- at first a pucker inducing maneuver but as time went on it's gotten less stressful. Yay I guess. Each pass of the truer is money lost down the drain, in far greater quantities than just normal wear and tear would ever do, no matter how light the passes are.

In summary: the more expensive stone has almost 2x the wobble and 2x sloppier tolerances, resulting in increased sharpening time, increased stone wear (due to occasional truings), and general annoyance each time I switch stones. I feel like this shouldn't be a problem for an almost 500 dollar piece of equipment.

I'd be curious to hear other ideas/input.

[Stickan]

Hi,
I understand your frustration and I hope to be able to help.
There are a couple of things we need to cover.

A tip is when you mount the SJ wheel, always mount it so the label of the stone always shows "SJ-250" in level. The first time you might need to true it, but after that, it should be ok. Tighten the Ezy-lock harder by holding the honing wheel with your left hand and pull the stone towards you before you start the machine, tighten the Ezy-lock first,  this also straightens the stone a little. This is not needed on the SG stone, I usually just start the machine and it tightens.

The SJ material is more sensitive and more expensive than the SG stones, so we cannot have the same solution with a "bushing" as in the SG stones, because it would crack the stone.
This is why it has almost double the tolerances than the SG stones. With that said, when we used natural stones back in the days, the runout was even more than the SJ stones and the result was still very good at that time.

It pleases me that you have good results, the edges become extremely sharp. Try the tip with the label being in level and let us know the outcome.

Sincerely,
Stig

[tgbto]

I don't know if you have the same experience, but I feel like the SJ stone somehow amplifies the imperfections : once there is the slightest low spot, it looks like the pressure of the knife will kind of dig just behind it, and the stone will indeed get quickly out of true.

I use some kind of a trick to both clean and kind of keep the stone true without the heavy-duty makeover that comes with using the truing tool :
I attached a very fine diamond plate onto a thick and flat piece of aluminium.
Then I rest it on both a USB in the vertical position and one in the horizontal position, then I lower the USB just so the plate barely contacts the SJ wheel. It keeps it clean, and removes very little material at a time, while making sure that low spots don't have the time to develop.

That being said, I think the SJ stone will clearly wear out much faster than the others. And repeated BESS measurements have shown that - at least on my standard knives - I need to hone afterwards. Which eventually will result in more or less the same surface aspect than standard SG+honing. Honing with the standard Tormek compound then with a 1 micron compound onto a leather honing wheel is both faster than changing wheels and gives only marginally less polished edges than the SJ wheel with no honing, *and* it takes care of the burr. Which makes the SJ wheel a pricey and time consuming luxury, all things considered.

[Stickan]

The Japanese stone was intended for cabinet makers and hand-tools, like chisels and carving gouges, that needs to have an extreme edge on some detailed work. We also have many Luthiers that swear to it, because it doesn't round the edge. This is not as critical on a knife.

Its become popular for knife sharpeners in recent years. I used it a lot in my early years at Tormek but when I became good at using the honing wheel, I used that more. The difference is that the PA-70 compound and leather honing wheel can not fully remove small scratches like the SJ stone can do. However, it polishes very well at the tip of an edge, which you can see using a magnifier.

When it comes to wear, I have not met many that have worn out an SJ stone during my years at Tormek, if any...

Why you need to hone after you have used the SJ stone seems strange, since the honing compound has less grid than the SJ, I think there is something else that might need to be adjusted. I had a user that said the same thing some years ago and I tried adding 1 degree when using the SJ stone, which removes burr faster, I got an answer back from him with a positive answer when he tried the same thing.
Might be worth trying.

[tgbto]

Stig, thank you for the answer, I will try that.

I had posted my findings in this thread, I will try to follow the same process with the +1 dps variation. Will it however not polish just the edge, then ? Or should I first use the wheel with the same angle THEN add 1 dps ?

[3D Anvil]

I can't claim to know the science behind it, but I think you're almost always going to get a keener edge stropping lightly on softer media after sharpening on a stone.  This is even true with straight razor honing, where the finishing stone can be 30k or even finer, but the best edge is only obtained after stropping on leather (with or without compound/emulsion).  The guy from the Science of Sharp website found that the best results are obtained by using a multimedia approach, i.e., going from the stone to a linen or denim strop, and then to a leather strop.

Here's the result of a test I just ran:

Henckels 8" chef knife
1.  Killed the edge on Tormek stone grader;
2.  Sharpened on CBN 400, CBN 1000;
3.  Sharpened on SJ-250, finishing with several alternating passes, as light and quick as I could manage while maintaining good form;

* BESS score: 165g.  Not bad!  Sharper than most factory edges.
* BESS score: 125g after a few passes on denim strop loaded with Flitz.
* BESS score: 105g after a few more passes on denim.
* BESS score: 75g after stropping on leather belt with Tormek paste at +1.8 deg. (one pass) and at the exact edge angle (two passes). 

Hair whittling.

[3D Anvil]

Regarding the wobble issue, I guess maybe I got lucky?  I've been following the advice to always mount the wheel label-side up -- especially before resurfacing the stone with the TT-50 -- and my SJ-250 has very little wobble.

I don't know if this contributes to smooth running, but I generally clean the wheel with a Japanese rust eraser, or if that doesn't get the majority of the swarf off, I use a King Nagura stone.  I don't trust my stone grader to do the job because it has some ruts and gouges in it from rounding corners.  I suspect it's not really flat anymore.   

[RichColvin]

Regarding the alignment of the grindstone that Stig references, I have this page with diagrams:  https://sharpeninghandbook.info/Grindstones-Affixing.html.  It may help explain the why also.