SJ-250 and deburring

[tgbto]

Hello all,

I already mentioned having a different experience than what's advertised by Tormek when it comes to the SJ-250. Namely, here's what they write on their website :

Since the surface left by the Japanese Waterstone is so fine, we do not recommend honing afterwards on the leather honing wheel.

I had a bit of time this afternoon so I decided to explore this a bit more. I had to touch up a Wusthof classic chef knife and a Chroma Haiku Santoku (both given for ca. 58 HRC CrMoV steels, with the Chroma having 0.8% carbon vs 0.5% for the Wüsthof). They were initially 180 and 195 BESS.


I used jvh's TormekCalc spreadsheet which is so convenient as I have everything I need to know on the screen at once.

I first ground them edge leading on the "in between" SG, ie not graded coarse nor fine with a substantial pressure (see SG std.jpg). Then a few passes with light pressure (see SG light pressure.jpg)

I then graded the SG stone fine with a diamond plate, then gave them a second pass (see SG fine.jpg). It may not show on the pictures as the ocular quality is poor and lighting is not much better, but the burr is clearly visible, both by its ragedness and the fact that it doesn't reflect light like the bevel does.

I then moved to the SJ stone, still edge leading. It starts being interesting as one can no longer feel a burr, nor is any visible under the microscope (see SJ-r.jpg). So, what would the BESS score be ?

Well... 320 and 295.

I had marked the place where I performed the BESS test with a sharpie, and the dent left by the test media is clearly visible on the pic (SG dent.jpg)

So I honed both on the leather wheel with the standard issue Tormek compound and they ended up at 105 and 125 BESS. And the edge was no longer damaged by the wire (final.jpg).

This looks to me like a confirmation that the SJ does indeed require honing afterwards, at least on these standard knives. I'm no metallurgy specialist, but it looks like while it polishes the bevel, it also somehow creates a tiny wedge of nicely polished yet very soft metal. Maybe that's not the case with much harder steels... I'll try and see if the results change much. Until then, the SJ really is just for looks.

Sorry for the picture quality, that's the best I can do with my setup.

Cheers,

Nick.

[cbwx34]

Hello all,

I already mentioned having a different experience than what's advertised by Tormek when it comes to the SJ-250. Namely, here's what they write on their website :

Since the surface left by the Japanese Waterstone is so fine, we do not recommend honing afterwards on the leather honing wheel.

I had a bit of time this afternoon so I decided to explore this a bit more. I had to touch up a Wusthof classic chef knife and a Chroma Haiku Santoku (both given for ca. 58 HRC CrMoV steels, with the Chroma having 0.8% carbon vs 0.5% for the Wüsthof). They were initially 180 and 195 BESS.


I used jvh's TormekCalc spreadsheet which is so convenient as I have everything I need to know on the screen at once.

I first ground them edge leading on the "in between" SG, ie not graded coarse nor fine with a substantial pressure (see SG std.jpg). Then a few passes with light pressure (see SG light pressure.jpg)

I then graded the SG stone fine with a diamond plate, then gave them a second pass (see SG fine.jpg). It may not show on the pictures as the ocular quality is poor and lighting is not much better, but the burr is clearly visible, both by its ragedness and the fact that it doesn't reflect light like the bevel does.

I then moved to the SJ stone, still edge leading. It starts being interesting as one can no longer feel a burr, nor is any visible under the microscope (see SJ-r.jpg). So, what would the BESS score be ?

Well... 320 and 295.

I had marked the place where I performed the BESS test with a sharpie, and the dent left by the test media is clearly visible on the pic (SG dent.jpg)

So I honed both on the leather wheel with the standard issue Tormek compound and they ended up at 105 and 125 BESS. And the edge was no longer damaged by the wire (final.jpg).

This looks to me like a confirmation that the SJ does indeed require honing afterwards, at least on these standard knives. I'm no metallurgy specialist, but it looks like while it polishes the bevel, it also somehow creates a tiny wedge of nicely polished yet very soft metal. Maybe that's not the case with much harder steels... I'll try and see if the results change much. Until then, the SJ really is just for looks.

Sorry for the picture quality, that's the best I can do with my setup.

Cheers,

Nick.

Pretty sure in one or two of the Tormek videos, they mention that the edge should be honed on the leather wheel, after the SJ wheel? 

If so, not sure why their website would differ.

I don't think you can say the SJ wheel is "just for looks though"... it does work to refine the edge, even if you have to hone it afterwards.  Since you're experimenting, you might also try some edge trailing passes on the SJ wheel, and see what happens.

[tgbto]

Cb,

I will try to experiment edge trailing. However they also say in one of their advanced classes that edge trailing creates more of a burr, although it prevents from digging into the soft stone.

And when I say it's just for looks, I mean that I haven't noticed any difference in sharpness (BESS or cutting test) nor edge retention (even though I have no CATRA tester to back this up) for any standard knife, whether I polish it on the SJ or not.

I do not have any very high-quality hard-steel western style knives so I don't know it that would make a difference in sharpness or honing time with those. For my standard HRC58-61 CrMoV knives, I even feel it requires MORE honing after a SJ polishing step compared to just the SG graded fine.

[Arthur]

I completely agree that the SJ stone not only polishes, but also sharpens, and also creates a burr on the edge of the blade. Always after SJ I use a leather circle with chromium oxide.

[RickKrung]

Following Knife Grinder's deburring book protocol, sort of, as modified by an email exchange with Vadim quite a while back, I routinely finish the grinding phase at the grinding angle, edge leading, with the SJ wheel.  Followed by increasing the angle, based on the type of steel - none of mine are very hard - so it is 1.0º-2.0º on a rock hard felt wheel with 1µ diamond paste (edge trailing) and then dry stropping on a hanging leather strop (KG's kangaroo tail).  There is always an improvement in sharpness following both the rock hard deburring and stropping.  I am confident stopping at the SJ leaves a burr. 

Rick

[tgbto]

In the Tormek presentation video for the SJ, they repeat the claim that there's no need to hone (around 1:00).

There's some kind of a debate in the Advanced Sharpening Class at around 1:11:30. Wolfgang says normally you don't have to hone after the SJ but with some steel varieties you do need to hone very slightly.

So maybe it's a question of steel, but those I experimented with seem fairly standard to me, and I have to hone - not that lightly - to get rid of the burr...

[cbwx34]

Maybe it's a matter of perspective? 

I see it as... the SJ wheel improves the edge off the SG wheel, vs. the SJ wheel = honing/finishing on the leather wheel?  Doesn't mean that it doesn't leave a burr... just an improved edge.  And just like coming off any wheel, there are steps you can take to reduce the burr even further... light alternating passes, adjusting the angle, etc.  (One step I haven't tested yet, is the information from Tormek... that finishing the edge by starting on the side opposite a burr may reduce it further).

Also the more steps you add (felt, strops, etc.), the better your edge should get.

...There is always an improvement in sharpness following both the rock hard deburring and stropping.
...
Rick

Tested how?

[tgbto]

Maybe it's a matter of perspective? 

Maybe, and maybe a question of what it means to "improve" the edge. I have not seen an improvement in BESS scores between SG > SJ > honing or SG > honing. Nor have I seen any reduction in honing time. As a rule, I always start grinding/honing with the handle in my right hand, and finish with the handle in my left hand. So the burr is always on the "good" side for the next step.

The edge is shinier with the SJ though, and I have no means to quantify edge retention between SG > SJ > honing and SG > honing. My guess would be that edge retention is improved with SJ as the edge has less microteeth that will be easily blunted, but I have guessed wrong so many times that I wouldn't bet on it.

[cbwx34]

Maybe, and maybe a question of what it means to "improve" the edge. I have not seen an improvement in BESS scores between SG > SJ > honing or SG > honing. Nor have I seen any reduction in honing time. As a rule, I always start grinding/honing with the handle in my right hand, and finish with the handle in my left hand. So the burr is always on the "good" side for the next step.

The edge is shinier with the SJ though, and I have no means to quantify edge retention between SG > SJ > honing and SG > honing. My guess would be that edge retention is improved with SJ as the edge has less microteeth that will be easily blunted, but I have guessed wrong so many times that I wouldn't bet on it.

Tormek did a video, and KG did a followup ( https://www.youtube.com/watch?v=6LtJCaFCRgc ) that starting on the side opposite the burr produced a better result, so if I interpret your post correctly, instead of starting on the with the opposite hand, you'd start with the same side you finished the previous step... so if you finish with the left hand off the SG, you'd start with the left hand on the SJ... (if I got it right).  Whether it matters in this thread... 

What I'm saying (just to clarify), is what if any improvement does the SJ make after the SG, with no further honing, and what (if anything) can be done to improve this. 

[nevertakeadayoff]

I didn't read all the posts.

I was getting bad results with the Jap stone until I switched to trailing edge... after all, it is a polishing stone ; )