Compound (double) bevel?

[aquataur]

Greetings,

this is my second post...
I just recently stumbled over Vadim´s Work and bought the deburring booklet.
I wrote to him, not knowing that he has left this planet... (the web site says nothing about that...)

So you guys may know the answer.

Hereabouts (Austria/Germany) there is a guy well known, Friedrich Kollenrott, who is kind of gold standard on sharpening. He and some other guys recommend "thinning" the blade region close to the edge, up to about 1/3 of the blade height or thereabouts, particularly after it has been re-sharpened times and times, which lets the secondary facet become larger and larger due to the edge gradially approaching the back of the knife.

He wrote a document which has become a kind of "sharpeners bible":
https://www.feinewerkzeuge.de/pdf/Schaerfen_von_Messern_211207.pdf
Pictures #4 and #5 show what I mean.
The supporters of that method say the knife cuts easier this way. (This is all about kitchen knives). But this might be another myth.

I read nothing about this here, at least I did not recognize it.
in this thread https://forum.tormek.com/index.php/topic,3419.0.html a "microbevel" is mentioned and the pictures here https://forum.tormek.com/index.php/topic,3437.0.html suggest that it would be a compound bevel. I am not quite sure, if this is the same thing.

I have tried grinding that flat with the jigs, but had the stone collide with the jig.
I was uncertain as what angle we are speaking about.
Apart from that, this would produce a hollow secondary bevel (is this the right term for it?), which may be counterproductive.

I have tried several ways of doing this free style on the tormek, but the result left a lot to be desired...

The only way I can imagine is doing it on the side of the stone, much like Vadim tried it on a single bevel knife. I have bought the MB-100 to give that a shot.

I have a T-3 and use stones only. I thought up a method for trueing the side.

So I would appreciate to hear your thoughts on this subject, folks. I may toss the subject in one second if you say this does not pay. It certainly causes head ache.

Thanks,
-Helmut

[cbwx34]

...
So you guys may know the answer.

Hereabouts (Austria/Germany) there is a guy well known, Friedrich Kollenrott, who is kind of gold standard on sharpening. He and some other guys recommend "thinning" the blade region close to the edge, up to about 1/3 of the blade height or thereabouts, particularly after it has been re-sharpened times and times, which lets the secondary facet become larger and larger due to the edge gradially approaching the back of the knife.

He wrote a document which has become a kind of "sharpeners bible":
https://www.feinewerkzeuge.de/pdf/Schaerfen_von_Messern_211207.pdf
Pictures #4 and #5 show what I mean.
The supporters of that method say the knife cuts easier this way. (This is all about kitchen knives). But this might be another myth.

I read nothing about this here, at least I did not recognize it.
in this thread https://forum.tormek.com/index.php/topic,3419.0.html a "microbevel" is mentioned and the pictures here https://forum.tormek.com/index.php/topic,3437.0.html suggest that it would be a compound bevel. I am not quite sure, if this is the same thing.

I have tried grinding that flat with the jigs, but had the stone collide with the jig.
I was uncertain as what angle we are speaking about.
Apart from that, this would produce a hollow secondary bevel (is this the right term for it?), which may be counterproductive.

I have tried several ways of doing this free style on the tormek, but the result left a lot to be desired...

The only way I can imagine is doing it on the side of the stone, much like Vadim tried it on a single bevel knife. I have bought the MB-100 to give that a shot.

I have a T-3 and use stones only. I thought up a method for trueing the side.

So I would appreciate to hear your thoughts on this subject, folks. I may toss the subject in one second if you say this does not pay. It certainly causes head ache.

Thanks,
-Helmut

Thinning the blade is not the same as adding a microbevel to a blade.  Probably the biggest advocate of thinning in the U.S. that I can think of is Murray Carter.  He does it by laying the blade flat on a stone and thinning the entire blade each time he sharpens, for example:  https://youtu.be/5stV_1kID-U?t=57  The method in the document you referenced seems similar, although not quite flat (if I read it right.)

I don't think you'll have any better luck using the MB-100 and the side of the stone... you will still have the issue of the clamp/jig getting in the way.  You could (depending on the knife) use the SVM-00 (small knife holder)... this holds the knife by the handle allowing you to achieve a lower angle.  Or set as low an angle as you can for a few passes, then raise it to sharpen, which will "thin behind the edge" a bit.  Or pick another method, you could for example just use a stone or even sandpaper on a flat surface for thinning, then sharpen on the Tormek.

Whether it matters or not depends on the original shape of the knife and what you're cutting.

[aquataur]

Thanks.

I suspected that thinning and microbevel are not the same. The second bevel is not micro I agree. Sometimes those drawings are exaggerated to better show the effect, and the terms are somewhat misleading.

Also, the guy you mention seems to do something different.

What really gets me is that nobody else seems to talk about the claimed necessity of thinning. I did a lot of research on the web, but if you don´t know the right buzz words to begin with, you are lost. I initially assigned the failure to find support for my theory to this circumstance.

However, I found Vadim´s site with all this research, and I received the impression that he would surely use this method if it had any worth. He said that customers felt his knives were the most long lasting and sharp knives, without thinning.

So maybe I should drop this notion, because it creates a lot of hassle without evidence of a noteworthy merit (at least I cannot find it). What is your personal opinion, from your past experience?

I appreciate any other view because I am guaranteed biased, having used this German guy´s guidelines as my sole reference.

[HaioPaio]

For easy cutting in a kitchen environment, a thin knive is much better than a wider knife. The width above the bevel is the key metric.
Speak to professional chefs or experienced hobby cooks.
They will confirm that the sharpness of the very apex of the edge will allow shaving hair from your arm, but not effortless cutting of raw carrots. It needs a thin geometry and a keen apex to achieve that.

The Tormek is a great tool for sharpening a variety of tools including knives. However, changing a knives geometry towards a thin knife with only 0,2 mm width above the bevel is not the area where a Tormek is best.

[cbwx34]

Thanks.

I suspected that thinning and microbevel are not the same. The second bevel is not micro I agree. Sometimes those drawings are exaggerated to better show the effect, and the terms are somewhat misleading.

Also, the guy you mention seems to do something different.

What really gets me is that nobody else seems to talk about the claimed necessity of thinning. I did a lot of research on the web, but if you don´t know the right buzz words to begin with, you are lost. I initially assigned the failure to find support for my theory to this circumstance.

However, I found Vadim´s site with all this research, and I received the impression that he would surely use this method if it had any worth. He said that customers felt his knives were the most long lasting and sharp knives, without thinning.

So maybe I should drop this notion, because it creates a lot of hassle without evidence of a noteworthy merit (at least I cannot find it). What is your personal opinion, from your past experience?

I appreciate any other view because I am guaranteed biased, having used this German guy´s guidelines as my sole reference.

I don't think you can say that because Vadim's research didn't include this it doesn't have worth... the simplest answer being it may have been something he hadn't studied yet.  He was already breaking the "norm" simply by sharpening at a lower angle (12° if I remember right) than most were used to.  (Other factors may also come into play.)

I think your reference and what Murray Carter did are similar... it's just that your reference uses a "2-3°" angle, vs. laying it flat on the stone?

Others have talked about it.  For example in the "Razor Edge Book of Sharpening" (which you can now get for free HERE,) they talk about the "relief" of the blade...

You cannot view this attachment.

... which is essentially the same as thinning.

On my personal knives I use the "pinch test", where I pinch the blade lightly above the bevel, and drag it down over the bevel, if I feel a "bump", I know it's getting too thick, and will at least thin above the bevel by grinding a bit at a lower angle.  (This is probably the alternative to thinning the whole blade.)  It may not be necessary to thin to the extent that your reference does... again it depends on use, and the knife itself.

I also think knives are made a bit thinner now than in the past, and sharpened at a lower angle, which may be one reason it's not talked about as much?  (Just a theory.)

The easiest answer is: it's your knife, try it and see if you notice a difference based on how and what you use it for.  That will tell you if it's worth it.  You could take a "practice" knife, and just manually thin it on the side of the wheel by hand if that's the only abrasive you have, and see if you notice a difference. 

[aquataur]

don't think you can say that because Vadim's research didn't include this it doesn't have worth... the simplest answer being it may have been something he hadn't studied yet. 

I do not think that he is (was) the end of all wisdom. I thought that if all those customers never missed anything, it might not be worth exploring the alley.

That said, maybe he just did not find a practical "machine" method for it.
Although I think he may have been close... I mean that video where he sharpens a knife on the side of the wheel. You are right that you will run into the jig with that shallow an angle, but not if you have the jig above the stone. I will try this and see.

I think your reference and what Murray Carter did are similar... it's just that your reference uses a "2-3°" angle, vs. laying it flat on the stone?

Exact. Thinning the whole knife appears tedious and counterproductive for me. But a portion...
I think with that shallow an angle we cannot set anything by measuring degrees. We would have to work with marker pen and see what portion is affected and choose a sensible setting. My reference speaks of 1/3 to 1/2 of the knife heigth IIRC.

Others have talked about it.  For example in the "Razor Edge Book of Sharpening" (which you can now get for free HERE,) they talk about the "relief" of the blade...

Thats a great resource, I will look into that. As I said, it´s all about knowing the right key words...
Edit: Hah! What a great book. Yes this guy´s really into "relief". What a relief for me ;-) He does it basically on everything, knives, axes...  I think this demands more investigation.

[cbwx34]

Just had a thought... an alternative to the knife jig that might help is the "Platform Jig"... which would allow you to sharpen at a lower angle.

[aquataur]

Yes...

I stumbled over this jig already. It appears quite logical to me.
I have plans to make a version of it using the DBS-22 platform. (more to come)

One has to see how hollow it gets.

re: grinding on the side:
I have tried grinding on the upper part of the stone (towards the highest point of the stone, but on its circumerence, to a depth of approx. 1cm). I used the newly acquired MB-100, folded outwards and the USB. This way you have the USB´s long arm resting right over your working area.
Edit: removed ambiguousity.

The MB-100 has to stick out fairly far, but it still holds securely. I had to dial the knob on the SVM-140 in as much was possible (I don´t have the small jig). Since the angle is so shallow, the distance to the stone does not need to be big. In fact I would have appreciated to shorten it even more with some spacer (or collar). But it worked.

I had the knife only so much down that the jig was not in the way, which was much more than I planned for the relief anyway (5-6mm). This setup clearly exposes the imbalance of the SVM-140. (I must read again how this is fixed. I saw it somewhere.)

This worked well. The secondary facet grew pretty rough. I used the dressing stone to make the grit finest. Much better. I then swapped supports and ground the edge the traditional way on the circumference.
It turned out that this would probably benefit from a higher than normal edge angle. I could not easily get rid of the burr.

The real snag about this method is that it is hard on the stone. I think if I did another knife like this, I would need to true the side. I devised a method to do this (more to come).

That said, I did a total overhaul of the secondary bevel. An occational touch-up would be less hard on the stone. But since this is a consumable...so be it.

[aquataur]

This did not leave me alone.

Today I received two cheapish kitchen knifes. Both had a bold ricasso, which is a PITA. I routinely remove them on the bench grinder.

Those knifes tend to have a secondary bevel, and I just had to undo my previous attempts to touch this up. I did both of them on the side of my SG. This worked well, never had such a beautiful compound bevel before. Needless to say, it left a fair groove in the outer perimeter of the stone.
As I expected. I looked into my planned method again for truing the side with the diamond, but this failed. This does not work. There is always an obstacle.

I tried to fix the stone with a very coarse (F40?) SiC dressing whetstone (not unlike the rough side of the Tormek dressing stone), by holding its corner onto the side, but this did nothing in a reasonable time.

Then I remembered that I had spoiled a Corundum wheel on my bench grinder by grinding down some stainless steel stock. It was eating away material like hell. I had a nice stick there, 12mm, half a meter long, and lo and behold, holding this to the side by its corner and slowly proceeding inwards, you could see how the removed material would build up on the stick. At first I tried it with water, but then I did it without. The wheel was still moist of course. This works well. In 5 minutes, using a straight edge to check, my wheel was workable again. A touch-up with the corner of the dressing stone and bob...

I think the key is corner.

Back to the knives, the secondary bevel´s optics were less than perfect. I don´t know if this matters, but I polished them with whetstones. Took a J1000 whetstone that made it better fast, and then some polishing with a J3000 whetstone. NB: I polished the secondary bevel, not the edge.

I then made a proper 18 dps edge with the SG on 1000 and leather wheel.
The knives are, hum, very acceptable.

-Helmut

[3D Anvil]

I believe knife thinning has been standard practice among Japanese chefs for centuries.  Murray Carter studied knife making in Japan, which is probably where he picked it up. 

You can reduce the thickness behind the edge on the Tormek by sharpening at the lowest angle you can get without grinding the jig (probably around 10 dps) and then putting a standard cutting bevel on it, which is 15 dps in my case.  Or you can use the convexing feature of the KJ-45 to similar effect.  But to thin the lower third, or the whole primary grind, I think the old way is still the best way: a coarse whet stone and lots of elbow grease.

[tgbto]

I believe knife thinning has been standard practice among Japanese chefs for centuries. 

That is not how I was taught to sharpen traditional japanese knives (usuba-,deba and yanagiba-bocho). These knives are sharpened along the (very wide edge), which also serves as a guide. The knife is usually made with two materials bonded together during forging, a hard, brittle one on the back (which will make up the edge) and a softer one in front (see a more detailed explanation of the anatomy here).

You don't thin these knives as you want a straight edge for several of the traditional japanese cut. A hollow grind on these will lead the blade into the cut which would be a nightmare for, say, katsuramuki. A hollow grind has a significant impact as we're talking edges 3/4 to 1 inch wide.

You don't grind the flat face of the knife either because it is integral to the knife balance, resistance to shock, and stability during grinding.

So you just sharpen the edge (shinogi) on a flat stone, and when you get a good burr along the edge, you remove the burr by sharpening the ura (backside), which comes already thinned as it is hollowed on a wheel as part of initial manufacturing. This allows to just rest on the top and bottom flats and make quick work of backside sharpening. Chefs never touch the hollow of the ura. Then you progress to very fine grit stones and sharpening turns into honing.