Thinning Masakage Koishi gyuto bevel

[ModRQC]

What is your approach of grits vs work to do. In four months of practice, I can sharpen, but as to assess metal removal rate as I go seems to be beyond me for now. Say I have a knife where I need to remove .2 to .5 mm to get within thumb rule, what grit would you start? I’m thinking about using NP800 for that last part of the job, not going too agressive because it doesn’t seem like much steel to me, but perhaps it’s too high and will take too much time?

 

[McMan]

I think I'm in the minority here... I'm not seeing a ton to thin.
There's not too much meat behind the edge here:

Rather, I think this knife falls into the "doesn't mesh well with you" category. Wide bevels can wedge at times through tall hard stuff. It's the nature of the beast and a trade off for what they do well. You could knock the shoulders off (round them and blend that) but then you're more into changing the grind territory as opposed to just thinning. Plus, you're in trade-off territory--blending the shoulders on this particular knife would likely make food release worse (since you'd be lessening the division between the two concavities) but would improve against wedging.

From the choil shot, it looks like the knife has a neat grind that's somewhat uncommon--a sort of double-concave S-grind. Thinning or no, I have a feeling this knife will not perform in the way you want, and that this is mostly about the grind. So, either figure out what it excels at for you and use it there or sell it and grab something more akin to what you're looking for. Or, thin it and see what's up.

Edit: I guess I'm not in the minority... I just checked the poll

 

[Benuser]

What is your approach of grits vs work to do. In four months of practice, I can sharpen, but as to assess metal removal rate as I go seems to be beyond me for now. Say I have a knife where I need to remove .2 to .5 mm to get within thumb rule, what grit would you start? I’m thinking about using NP800 for that last part of the job, not going too agressive because it doesn’t seem like much steel to me, but perhaps it’s too high and will take too much time?

I'd say, that's a lot of steel to get removed. Don't be afraid of coarse stones. They allow you to remove steel without a lot of pressure. Better than a less coarse stone needing huge pressure. But make sure to stay away from the very edge.
Another option were automotive sandpaper. Works very fast. Again, stay away from the very edge. If it has been touched with a coarse grit a lot of work is to be done and inevitably some of the edge gets lost. You may end with a narrower blade with the same thickness behind the edge, and all work be done in vain.
P.S. If the steel you want to remove is at the level of the shoulder, where bevel and face meet, it can be wise to avoid coarse stones, as you want the edge to stay untouched. I remember removing shoulders of a Misono Swedish Carbon with a Chosera 2k. Your 800 can be very helpful and all you need. My remarks on coarser grits were about thinning further upward to the spine.

 

[mav.s]

Thanks for all the great feedback! Seems like consensus is to leave it as is. I may do just that and give it some time. Also hoping to hear from other Koishi owners If they have a similar grind or something different.

 

[ian]

I think I'm in the minority here... I'm not seeing a ton to thin.
There's not too much meat behind the edge here:
View attachment 92563
Rather, I think this knife falls into the "doesn't mesh well with you" category. Wide bevels can wedge at times through tall hard stuff. It's the nature of the beast and a trade off for what they do well. You could knock the shoulders off (round them and blend that) but then you're more into changing the grind territory as opposed to just thinning. Plus, you're in trade-off territory--blending the shoulders on this particular knife would likely make food release worse (since you'd be lessening the division between the two concavities) but would improve against wedging.

From the choil shot, it looks like the knife has a neat grind that's somewhat uncommon--a sort of double-concave S-grind. Thinning or no, I have a feeling this knife will not perform in the way you want, and that this is mostly about the grind. So, either figure out what it excels at for you and use it there or sell it and grab something more akin to what you're looking for. Or, thin it and see what's up.

Edit: I guess I'm not in the minority... I just checked the poll

Hmm, yea in that pic even the near-edge looks pretty thin.

 

[mav.s]

That shot is with the knife pointed slightly down. This ones more representative.

 

[ModRQC]

That shot is with the knife pointed slightly down. This ones more representative. View attachment 92565

I had a Kurosaki for a short while that was needle-like resembling this but even farther up the edge. Very laser in some cuts, seemingly wedging in taller or denser produce. I think @M1k3 explained it best when he said it can create suction. Just saying.

 

[JDC]

I think I'm in the minority here... I'm not seeing a ton to thin.
There's not too much meat behind the edge here:
View attachment 92563
Rather, I think this knife falls into the "doesn't mesh well with you" category. Wide bevels can wedge at times through tall hard stuff. It's the nature of the beast and a trade off for what they do well. You could knock the shoulders off (round them and blend that) but then you're more into changing the grind territory as opposed to just thinning. Plus, you're in trade-off territory--blending the shoulders on this particular knife would likely make food release worse (since you'd be lessening the division between the two concavities) but would improve against wedging.

From the choil shot, it looks like the knife has a neat grind that's somewhat uncommon--a sort of double-concave S-grind. Thinning or no, I have a feeling this knife will not perform in the way you want, and that this is mostly about the grind. So, either figure out what it excels at for you and use it there or sell it and grab something more akin to what you're looking for. Or, thin it and see what's up.

Edit: I guess I'm not in the minority... I just checked the poll

Well, if the op doesn’t want to wedge carrots, the edge is not thin enough, otherwise should be ok

 

[Kawa]

Just a brainfart,

If the knife is a fair bit smaller towards the tip, which seems to be the case in the last picture from the opening post, you might be able to simulate how thinning the knife will handle carrots. Cut a carrot that normally wedges with the part of the blade near the tip, even hold the knife halfway between heel and tip to make the cutting motion a bit more 'natural'.
You might feel difference in a positive way, or no difference at all.

In the last case that might also be because my brainfart doesnt make sence at all..

 

[McMan]

Well, if the op doesn’t want to wedge carrots, the edge is not thin enough, otherwise should be ok

If the OP doesn't want to wedge carrots, then a laser would be a good place to start
To my eye, the issue is not with this knife being thick behind the edge. The reason OP is having wedging seems to me to be an issue of grind/geometry. Wedging is a known side effect.

I'm not seeing much room to thin this knife.

Knocking the shoulders off then blending is a different ballgame than just thinning.

 

[JDC]

If the OP doesn't want to wedge carrots, then a laser would be a good place to start
To my eye, the issue is not with this knife being thick behind the edge. The reason OP is having wedging seems to me to be an issue of grind/geometry. Wedging is a known side effect.

I'm not seeing much room to thin this knife.
View attachment 92572
Knocking the shoulders off then blending is a different ballgame than just thinning.

Well, a laser can still wedge a carrot if not taking care of the thickness behind the edge. Such a concave grind makes the OP's knife thinner than most convex knives out there for at least 10mm starting from the edge. It will perform like a laser if the secondary bevel (edge bevel) is thinned.

 

[mav.s]

Well, a laser can still wedge a carrot if not taking care of the thickness behind the edge. Such a concave grind makes the OP's knife thinner than most convex knives out there for at least 10mm starting from the edge. It will perform like a laser if the secondary bevel (edge bevel) is thinned.

Great point JDC. This is kinda what I'm thinking as well. Might be a good project to smooth out this secondary bevel line. Thanks for all the great feedback! If I decide to move forward, will make sure to document the process.

 

[4wa1l]

I figured I'd add a post onto here rather than start a new thread, as I have a similar question.

I have two Masakage Koishi's, a 180mm gyuto and 165mm nakiri. I began to thin the gyuto and figured I would make it a routine part of my sharpening, similar to the Murray Carter style where you thin a little each time you sharpen. Unfortunately I noticed almost immediately that the wedging became awful. Cuts seemed fine until it hit the shoulder and it would become extremely hard to continue the cut. I ended up continuing the thinning process and tried to remove the hollow grind, mainly focusing on bringing the shinogi up toward the spine/rounding the shoulders (the line isn't that clear due to the hammered finish). I'm at the point where I have nearly flattened the hollow grind, but still have some wedging/sticking issues. Feeling the knife shows that there are some thicker spots remaining along the shoulder that I can probably keep working on. I have been doing most of this with a Morihei Hishiboshi 500 stone.

I also began to thin the nakiri. After one thinning/sharpening session I could feel the extra pressure that I had with my gyuto (not to the same extent, but the exact same feeling and sticking point). Will this become an issue with the nakiri too until I completely flatten the bevel and round the shoulders? Also it looks like by raising the shinogi or rounding the shoulders I am trying to change the grind of the knife? Have I completely messed up here or will I get to a point where I achieve the smooth cuts as good as, or hopefully better than I had with the ootb knives?

 

[M1k3]

Sounds like you're making the bevels flat. Add some convexity to them.

 

[4wa1l]

In the case of the nakiri is this still true? The hollow still remains and I have barely touched it compared to the gyuto. Is there something about the roughness of the sandblasted ootb finish (I think) that would reduce sticking at the shoulder, or is it simply a function of geometry?

 

[M1k3]

The sandblasted finish can drag. Geometry plays a big role in cutting feel though. But a rough finish that doesn't allow food to slide is just about as bad. I'd try smoothing it out with some sandpaper, about 2k grit. You don't need to go crazy with the sanding. Just enough to smooth everything out. Autosol or similar polishing compound would probably work also.

 

[McMan]

I figured I'd add a post onto here rather than start a new thread, as I have a similar question.

I have two Masakage Koishi's, a 180mm gyuto and 165mm nakiri. I began to thin the gyuto and figured I would make it a routine part of my sharpening, similar to the Murray Carter style where you thin a little each time you sharpen. Unfortunately I noticed almost immediately that the wedging became awful. Cuts seemed fine until it hit the shoulder and it would become extremely hard to continue the cut. I ended up continuing the thinning process and tried to remove the hollow grind, mainly focusing on bringing the shinogi up toward the spine/rounding the shoulders (the line isn't that clear due to the hammered finish). I'm at the point where I have nearly flattened the hollow grind, but still have some wedging/sticking issues. Feeling the knife shows that there are some thicker spots remaining along the shoulder that I can probably keep working on. I have been doing most of this with a Morihei Hishiboshi 500 stone.

I also began to thin the nakiri. After one thinning/sharpening session I could feel the extra pressure that I had with my gyuto (not to the same extent, but the exact same feeling and sticking point). Will this become an issue with the nakiri too until I completely flatten the bevel and round the shoulders? Also it looks like by raising the shinogi or rounding the shoulders I am trying to change the grind of the knife? Have I completely messed up here or will I get to a point where I achieve the smooth cuts as good as, or hopefully better than I had with the ootb knives?

Few pics might help.

 

[ModRQC]

Is the wedging occuring in all use of the length and with all produces? I would figure it rather present itself with taller and denser stuff, more towards the heel, in pure push cutting and/or with motion forward - meaning that the produce goes backward from say mid-blade to heel?

 

[4wa1l]

I'll get some photos tonight. Maybe someone can point out something obvious.

Halving an onion was terrible. On a push cut down and with some forward motion, the edge cut cleanly but would get stuck once the shinogi entered the onion. Probably starting with the front third of the blade and sticking a little back from that. Not at the heel.

I guess I was trying to save myself from a big thinning session by doing it regularly, but it seems that I still have a heap of work to do. I would like to avoid the same issue with the Nakiri if possible.

 

[Matus]

Whatever you do, do NOT remove the convex from the wide bevel if there is some. I used to have a Koishi nakiri, the grind was pretty much flat (plus some low spots, as expected). After working on it and adding some very gentle convex towards the edge, the knife became a much better cutter with less sticking-induced-friction. if your knife is just a little too thin behind the edge (I can't really imagine anything else), then just gently thin it there - no need to push up the shinogi - the knife is fairly thing already.

 

[ModRQC]

I'll get some photos tonight. Maybe someone can point out something obvious.

Halving an onion was terrible. On a push cut down and with some forward motion, the edge cut cleanly but would get stuck once the shinogi entered the onion. Probably starting with the front third of the blade and sticking a little back from that. Not at the heel.

I guess I was trying to save myself from a big thinning session by doing it regularly, but it seems that I still have a heap of work to do. I would like to avoid the same issue with the Nakiri if possible.

Try a pull push cut instead - have the knife work from mid blade to tip. Might take some adujstments to get it right but if your thinning is remotely sound it will be much better.

Your problem was best described by @M1k3 as suction instead of straight wedging. As you’ve flatten the secondary bevel in thinning you’ve made more of a V grind - hence suction and the shinogi will feel terrible in such cuts. Change your motion.

And seconding @Matus although he doesn’t need it, don’t do anything further before folks here sort you out.

 

[ModRQC]

Edit: as per @M1k3 you can still try to smooth the scratch pattern with blending or finishing automotive sandpaper. Could help, will not deteriorate things further.

 

[ma_sha1]

If the OP doesn't want to wedge carrots, then a laser would be a good place to start
To my eye, the issue is not with this knife being thick behind the edge. The reason OP is having wedging seems to me to be an issue of grind/geometry. Wedging is a known side effect.

I'm not seeing much room to thin this knife.
View attachment 92572
Knocking the shoulders off then blending is a different ballgame than just thinning.

Lots of contradicting opinions but I think the minority opinion from McMan is actually the correct one.

The edge & bevel portion is already very thin, wedging feel will only come if the carrot is taller than the shinogi. That’s because the shoulder, where bevel ends (shinogi) provide a sudden increase of thickness & resistance, it’ll basically split your carrot open by wedging/forcing it through using the shoulder from that point on.

No need to thin bevel or behind the edge, the area needs thinning is above the bevel, need to push up shinogi line by reduce the shoulder thickness. Measure the thickness of the shoulder at the shinogi line & compare to your Nakiri, I bet you’ll see that the shoulder is much thicker than the Nakiri’s.

 

[4wa1l]

Thanks for all the input so far!

It's hard to see in the photos but the right side hollow is almost fully removed so that the bevel is closer to flat. There is possibly an overgrind (I think that's what it's called) near the heel where the original finish is untouched.

The left side still has some hollow untouched sections remaining across more of the knife. I was thinking that I could work on this side more. I think it shows slightly in the choil shot too.

What surprised me was that the cutting seemed to be affected after the first time I tried to thin it. That was using only a Chosera 800, so I feel like there can't have been a huge amount of metal removed. There was definitely still significant hollow sections remaining in the middle of the bevel on both sides at that point.

Edit: I think I used the chosera 800 after the 500 stone last thinning to see if it made any difference.

 

[ModRQC]

There’s nothing wrong with this. I like that choil shot. Your bevels are indeed into a pretty straight V grind though and you perhaps lost some of the effects from the original grinding. You took good care of your work however and I hope someone here will help you get it as you want.

Suction will happen when halving an onion with such bevels especially since the knife is much fatter at the shinogi. My Mabs wedged OOTB when doing so push cutting. It « sucks » now that I’ve thinned it. I could feel it was much more keen to go through it - but the onion slowed it to a crawl anyway. Pull cutting to halve ended the problem - working with the tapering of the blade lenghtwise instead of hoping from a V geometry to a rather thick shinogi to have any kind of alleviating effects for suction just because it was much thinner. It just went further before wedging is all. Mind you, bulk of my push cutting was amazingly elevated by the thinning too. Just not a geometry to push cut shinogi high dense and moist produces that adhere like crazy to the flat bevels. Talk about pull cutting these though...

Wouldn't do wrong to smooth out the scratch pattern as @M1k3 suggested initially, from what the pics show it's coarse enough to drag a lot.

 

[M1k3]

Here's some things to watch while you smooth the bevels.

 

[JDC]

I feel that my recent observations on concave blades are worth reporting.

I was doing some caliper measurements on my knives' geometries:
My best performing gyuto has a thin convex grind and a nail flexing edge, all numbers fall inside what @ian suggested before.
All other knives measured a bit thicker than that, except one: my old, not in use Yu Kurosaki gyuto, which has a tall concave grind.
I haven't used it for a long time since the performance was below average (still a decent knife, just not as good as other knives that I reground).
It measured way thinner than any of my covex knives from say 3mm-10mm above the edge.
So I gave it a quick thinning behind the edge, and boom, a super performer is born, which cuts even better than my best performing convex knife in terms of falling through produces.
I only tested on carrots and celeries though. Food release was better than great, close to those S-grind knives. But I suspect it's gonna suck for produces that are a little softer, for example zucchinis and cucumbers. Will test and report back.

Anyway, a geometry with ~3mm thin convex and concave grind above that is definitely something worth a try. Give it a shot, Takefu knife users

 

[ModRQC]

In my experience the Kurosaki grind is hard to fault in technical use... but still wasn’t to my liking in terms of feel. It did suck a bit more with say potatoes, but really not something of a problem. Sold it because I found it very apt but rather boring in use. Also too light the one I had.

 

[JDC]

In my experience the Kurosaki grind is hard to fault in technical use... but still wasn’t to my liking in terms of feel. It did suck a bit more with say potatoes, but really not something of a problem. Sold it because I found it very apt but rather boring in use. Also too light the one I had.

Did you thin it? I found the original geometry boring too, quite normal and more suction on the bevels. It gets really fun after thinning.

 

[ModRQC]

Nope sold it before it even could have a scratch. Didn’t lose a penny on that one.

And while I’ll never know regarding that one, in my experience so far thinning doesn’t change a knife’s feeling as much as enhancing what’s already there as a potential, and of course making it easier to initiate the cut/fall through. Then again at around 130-140g iirc the Kurosaki would never be one to fall through.