Thinning / Bevel reworking of a Denka 210: Guide me please

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Hi guys,

as mentioned in the new-knife thread, I got this second hand Denka, which is even more ready for some polishing up than a new one ;). I'd like to bring this up to speed and do some refinishing. I have thinned one gyuto before, but that was more an experimentation knife. This time, I'd like to get it done somewhat better. Thus I'd be grateful for some advice on how to go about it. Here's the knife as it is now:

4H2A7810.jpg



4H2A7814.jpg



I've watched a lot of videos about thinning and have the basic understanding, I'd say. What I don't have is the understanding of how much I should aspire to do in order to bring out the best of the knife both visually and performancewise.

Performance isn't bad now, but as you can see, the bevel is even lower than on a new knife I assume that the denka has about 3-4mm less cutting edge. So I'd like to raise that, it would probably be good to bring up the bevel at the nose to thin that out a bit more.

This is what I would have aimed for: basically mildly lifting the shinogi line for most of the knife, with a more pronounced upward curve towards the front.


4H2A7810b.jpg


Question 1: Do you agree? :)


What I'd really like to achieve is a crisp border between the bevel and the side with the rest of the KU finish. I don't like it when the KU is also taken off beyond the limit of the bevel / when this border is "smeared" like here:

4H2A7822.jpg



I admire the work of @Hz_zzzzzz in the Show your work! Uchigumori and co... -thread. This is where I got the ideas from:

183218-F6E95749-48FB-4025-A6FA-BC572D695FF4.jpeg


Something like this is what I'd love to achieve... it will be less perfect, of course.

Question 2: Any tricks on how do to this? Are power tools required? Or is it enough to be super steady on the stone, strictly remaining on the bevel? I read about taping the side of the knife, but I don't see how this would resist a whetstone, especially with the tsuchime holes this knife has.

Question 3: Assuming I get all this done and want to do some kind of poor man's kasumi without finger stones, could I improvise something with my stones?

I'd have tried to do the thinning and refinishing with my existing stones unless you say I need something else for it.

What I have:
Nanina 220 Pink Brick (Should do most of the reprofiling)
Suehiro Cerax 1000
Suehiro Rika 5000
A Belgian Blue
+ I can get all the wet sandpaper that I might need.


Any comment or advice is highly welcome :) Thanks for reading.
 
I think it would be good to get a reasonable scope around this project. Do you want to keep the existing geometry and just follow that to remove some material, or are you looking to alter the grind a decent amount? You say the performance isn't currently good, but what negative aspects are made obvious to you in use? For me, I'd work on getting the performance to where you want it to be, and then concern myself with how nice I want to keep it looking with use. It will take a decent amount of practice and more abrasives (stones, papers, powders, etc.) to get the finish as good looking as the one @Hz_zzzzzz posted, fwiw.
 
If I remember correctly you're a left-hander. Which makes my wonder if you want to improve its performance and looks for yourself or for reselling. Could we get a choil shot? And tell us what you didn't like so far in using it.
 
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I wrote down my process in the original post

Quick dirty kasumi on a TF Denka. Flattened and thinned on SG 220, 320 and 500. Spent 3-4 hours on stones and had 5 gram steel removed. Followed by 5 minutes on 400 grit and 800 grit sandpapers. Then quick kasumi by a 15-minute uchi fingerstone session.


Given what you have, the jump between Naniwa 220 and Cerax 1000 might be too big but it’s possible (just time consuming). You might want to consider laying down the knife, holding the 1000 grit stone in hand, and applying stone’s edge on the knife to get rid of the scratch from 220 grit. This would be faster than normal way. The cost is your stone’s edge will be rounded. Use the back of your stone if you want to try it. Or you might what to consider getting Shapton Glass 500 grit double thick stone, which is one of my favorites and should serve well in your set up.

Sandpapers are a lot easier to make a smooth look than stones so I’d definitely get some.

If you don’t have fingerstones, I think some stone mud (your 1000 grit stone should be good enough), applied by 3M fine sanding sponge or 3M Trizact 3000/5000 grit sandpaper (soft texture one) can also get the job done.
 
Yea the majority of my time was spent on sg220 and 320 to get the bevel flat and edge thin. A good foundation from the coarse stone is most important for polishing and something you can benefit from for any future projects.

Just be careful and don’t make the edge too thin. If any part of edge become foil you might need to reprofile. What I usually do is 1. I reprofile the knife first by super high angle sharpening or even 90 degree sharpening on the side of coarse stone; 2. I sharpen at something like 30 degree per side to make an edge bevel; 3. When I thin the knife, I will make the edge from step 2 smaller and smaller but I will not remove it completely with coarse stones. I will try to make it almost invisible with my last stone.
 
First, thanks a lot for all your replies already.

I think it would be good to get a reasonable scope around this project. Do you want to keep the existing geometry and just follow that to remove some material, or are you looking to alter the grind a decent amount?
Hmm, difficult to say. I don't know if altering the geometry would significantly improve the performance. If yes, I'm all for it :D I wouldn't know what to do exactly, so the question also is what I can achieve myself. This is why I thought raising the bevel and thinning the tip should be a good way to go to improve the knife like I outlined. But if you have a suggestion what (else) i could / should do, please, let's have it :)

You say the performance isn't currently good, but what negative aspects are made obvious to you in use?

And tell us what you didn't like so far in using it.
I actually said the performance isn't bad :) But not great, either. Knife mainly wedges in hard ingredients, like sweet potatoes. I assume that wedging is due to the bevel being so low. Also, the tip is somewhat sluggish in onions etc. Not terrible, but not nearly as good as other knives. And if you look, you see that the bevel is actually even lower in the front part of the blade. In most other blades I have, it actually is higher there.


Could we get a choil shot?
I could have thought about that one :D Yes, I'll see I get a decent one uploaded soon.

If I remember correctly you're a left-hander. Which makes my wonder if you want to improve its performance and looks for yourself or for reselling.
Until our recent exchange, I was a left-hander. Now I'm ambidextrous. :cool: Sounds a bit mad, but I actually resolved to learn using knives with my right hand :D I can write decently with the right hand, so cutting should be learnable, too. Seems easier than ditching all my beloved biased knives and hunt for lefties.
So yes, I want to keep this knife and improve it for using it, but I want to keep it's bias and not work it towards a leftie or something like that.


I wrote down my process in the original post
Thanks, yes. I wondered how you got the transition so crisp, without any smearing. EDIT: I just saw you answered this in the next post, thanks a lot! And yes, I'll look into a 500 grit stone :)

That tip needs some work.
Thanks, yes. I guess in two ways. 1. it obviously has been broken in the front, that should be easy to fix by filing down from above. 2. It is a bit too thick and the bevel is too low, which should take more effort to get really nice.
 
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I did raise the shinogi by a bit and I didn’t tape the kurochi. It’s because this Denka is thick so the angle between the bevel and kurochi is big enough to make me confident about not scratching the kurochi by much. If your Denka is the thinner ones (like 3mm spine), I think taping the kurochi would be helpful. The tape doesn’t need to cover the kurochi entirely as you need a little space to grind the entire bevel. Whenever you feel your stone start to scratch the tape you can raise the spine a little bit to stabilize the holding.
 
If your Denka is the thinner ones (like 3mm spine), I think taping the kurochi would be helpful.
Great advice! Yeah, it's pretty thin, so I'll definitely be doing this.

I'd start by knocking down the shoulders at the top of the grind and seeing how that improves wedging.
Great, that was the plan :)
 
Oh yeah, that would explain the flatter than usual belly.

EDIT: Asked the seller about it, he says the tip was never broken. Take that as you will ;)
 
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When I thinned my KU Tsuchime Wakui, I taped the KU with electrical tape and found it very helpful. Depending on the angle of the bevel the tape will be higher than the shinogi line. On my Wakui it was 5-8mm above the shinogi. The very bottom of the tape touched the the stone and made it easier to be confident about not scratching the KU since the shinogi is less defined with the Tsuchime that was in it.
 
I actually said the performance isn't bad :) But not great, either. Knife mainly wedges in hard ingredients, like sweet potatoes. I assume that wedging is due to the bevel being so low. Also, the tip is somewhat sluggish in onions etc. Not terrible, but not nearly as good as other knives. And if you look, you see that the bevel is actually even lower in the front part of the blade. In most other blades I have, it actually is higher.


Thanks, yes. I guess in two ways. 1. it obviously has been broken in the front, that should be easy to fix by filing down from above. 2. It is a bit too thick and the bevel is too low, which should take more effort to get really nice.
I hope you don't mind my question, but I'm not sure to understand what you mean by a bevel being high or low?
 
I’ve tried this before.. on the same knife :).

1. Yes. It really depends on what you want to improve when deciding on geometry changes. I opted to thin behind the edge and mostly leave the shinogi. Should have thinned upwards a few mm, although I’m appreciating the somewhat beefy cutting feel where it is now.

2. Tape? I’m useless here.

3. Mud up your cerax and see what happens.. you can hide all sorts of scratchy madness with a low grit kasumi. I know Naniwa pro 1k can cheat out a fantastic texture on the stainless.

1BD3A981-C212-4D47-AF8A-58847EC0BA5B.jpeg

8C614519-3880-4051-8E9C-D3D9A71F4155.jpeg


This is where I got to with mine. The left face is much cleaner as I went flatter (righty bias) and the right came “messy” with the KU ground off above the shinogi. It’s far from done, shoulders are up next but add that to the infinite project lineup.

Keep in mind this is an unintentional kasumi. I went too far thinning and had to quit polishing at 400 grit. The rest was done in a panic on a softer aggressive shobu suita. Powders/sandpaper/micro mesh would likely, with time, leave a better finish.

Do it my friend! To see the vertical marks come out is highly satisfying
 
The measurement you're probably after is thickness behind the edge. Height of shinogi is related to the thickness behind the edge. The higher it is, the thinner your knife will be overall. However, the actual thickness (say at 5mm/10mm/20mm behind the edge) also depends on the overall thickness of your blade steel. What I mean is, a 20mm high shinogi on a 3mm thick blade, vs a 20mm high shinogi on a 1.5mm thick blade is completely different.

If you want to get rid of wedging, the approx thickness I use as a rule of thumb something like 0.2mm/0.6mm/1.1mm/1.6mm @ 1mm/5mm/10mm/20mm behind the edge. I'd say the first 10mm behind the edge has the greatest impact on your cutting performance. You will find a big difference between 1.1mm vs 1.3mm @10mm behind the edge.
 
Do it my friend! To see the vertical marks come out is highly satisfying
Great pictures and information, thanks! That looks encouraging and is the direction in which I'll go with this :)
I hope you don't mind my question, but I'm not sure to understand what you mean by a bevel being high or low?
I never mind :) Terminology again. I meant a higher shinogi line / raising the shoulders.

The measurement you're probably after is thickness behind the edge.
Thank you for the guidance. I'll be looking into this.
 
Great question.

Following, listening, and learning.

My initial thought was “send it out,” but I know you want to do it yourself.l: I respect that.
 
Thanks @Jeff. Yes, I considered finding someone experienced who would certainly do a better job than me. But the reports of people here doing these kinds of refurbishes encouraged me that with good info and careful work, I should be able to do a decent to maybe somewhat good job at this.

If you're interested, here is some of the better videos on the subject:

Jon of course is always giving great information:


Haven't seen this one yet, but it is very long and the sharpener seems to know his stuff:
 
Thanks! Take my remark with a grain of salt, but I'm wondering whether it makes sense to restore a flat wide bevel. I would start by thinning the first centimetre and make it flush with the right face. Strangely from the second photo the very edge seems off-centered to the right. It got far too much sharpened on the left side. I would aim for the opposite.
 
Thank you for looking and helping :D

I'm wondering whether it makes sense to restore a flat wide bevel.
I'm not sure I get exactly what you mean.
My makeover's goal is two-fold:

a) Raising the shoulders a bit so it wedges less in dense ingredients
b) Optically getting a crisp shinogi line that isn't "washed out".

Strangely from the second photo the very edge seems off-centered to the right. It got far too much sharpened on the left side. I would aim for the opposite.

I can take another photo, but I believe the macro perspective blows a small difference out of proportion. The previous owner had the knife professionally sharpened. It came with a beautiful, but not super useful polished edge that effortlessly push-cuts paper but struggles on tomato skin ;)

But why not borrow a USB microscope and have a look?

Cutting edge is in good shape along the blade. Left and right side seem pretty equal to me:
edge 1.jpg


edge 2.jpg


At the heel though, the edge has suffered. That's what's sharp in the macro shot, and should explain why the edge looks bad:

edge 3.jpg
 
Thank you for looking and helping :D


I'm not sure I get exactly what you mean.
My makeover's goal is two-fold:

a) Raising the shoulders a bit so it wedges less in dense ingredients
b) Optically getting a crisp shinogi line that isn't "washed out".



I can take another photo, but I believe the macro perspective blows a small difference out of proportion. The previous owner had the knife professionally sharpened. It came with a beautiful, but not super useful polished edge that effortlessly push-cuts paper but struggles on tomato skin ;)

But why not borrow a USB microscope and have a look?

Cutting edge is in good shape along the blade. Left and right side seem pretty equal to me:
View attachment 198284

View attachment 198285

At the heel though, the edge has suffered. That's what's sharp in the macro shot, and should explain why the edge looks bad:

View attachment 198286
Have you considered to convexing instead of creating a more appealing sharp shinogi? My guess were performance could benefit.
 
Hey @Benuser, no, I haven't, because I haven't come across a how-to in the stuff I watched. I mean, this is how the TF house-grind seems to be made, so it probably wouldn't be bad. But all the knife thinning stuff I could find always shows straight bevels.
So if you have a nice source, I'll gladly look into it :)
 
I think that is why you would want to send it out for a heavy thinning like this. A professional belt sander would leave slightly convexed bevels. Stones leave them flat (at least thats the easiest outcome). A wheel would leave it concave.
 
Murray Carter on convexing on stones.

As for further convexing behind the edge, you may use sandpaper as well. Traditionally done one a somewhat giving backing, but I have better results with sandpaper on a stone. You avoid inadvertent rounding of the edge. With a light touch there's no facetting to be feared.
The advantage of convexing were a far better food release than with a flat wide bevel. You may further increase food release by off-centering the edge to the left. The bevels aren't supposed to be equal. With a convexed right bevel you still may choose to have your left one straight or convex, depending on the blade's steering. But that is of later concern.

Whatever you do, make sure not to create both faces equal as far as being each other's mirror image, or expect severe wedging, even when thin.
Perhaps it is a choice between authenticity and performance. Not sure if that knife hasn't undergone too much to still be concerned about the maker's assumed approach.
 
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