Tojiro F-312

[calostro5]

Yesterday, I bought this knife.
I think this ist a good entry level japanese knife, except for what I think is a big inconvenience: I find the knife too sticky. When I start cutting an onion, it's easy at the beginning of the cutting, but deeper, harder. I feel that the resistance to penetrate the knife goes up. You can think "that's normal", but I haven't more knives (even thicker behind the edge) and I don't feel this resistance.
I think this is due to the finishing of the blade, the coarse grinding and the matt area. If I try to slide a finger when the blade is wet, I find it harder than on other more polished blades.





Am I right about my assumption?
Could I solve it using sand paper and polishing the blade? I don't mind loosing the factory fnishing.

 

[Tsundoku]

Yesterday, I bought this knife.
I think this ist a good entry level japanese knife, except for what I think is a big inconvenience: I find the knife too sticky. When I start cutting an onion, it's easy at the beginning of the cutting, but deeper, harder. I feel that the resistance to penetrate the knife goes up. You can think "that's normal", but I haven't more knives (even thicker behind the edge) and I don't feel this resistance.
I think this is due to the finishing of the blade, the coarse grinding and the matt area. If I try to slide a finger when the blade is wet, I find it harder than on other more polished blades.





Am I right about my assumption?
Could I solve it using sand paper and polishing the blade? I don't mind loosing the factory fnishing.

I would like to see the back side of the knife, is it single beveled?

 

[calostro5]

I would like to see the back side of the knife, is it single beveled?

The back side is equal.


Double side grinded and 50/50.
The grinding is flat in spite of it looks like the matt zone is concave in photos.

 

[Tsundoku]

The back side is equal.


Double side grinded and 50/50.
The grinding is flat in spite of it looks like the matt zone is concave in photos.

The double bevel and flat grind might be the big contributors to the stickiness of the knife. Usually it's the shinogi part of the knife helps to separate between cuts. I would recommend to create a shinogi yourself, create a compound double bevel or asymmetrical "V" bevel.

 

[calostro5]

The double bevel and flat grind might be the big contributors to the stickiness of the knife. Usually it's the shinogi part of the knife helps to separate between cuts. I would recommend to create a shinogi yourself, create a compound double bevel or asymmetrical "V" bevel.

I think the knife has already a second bevel.


My sharpening skills are no good enough to create a double bevel.
Anyway, I think that the finishing of the blade makes it more sticky.

 

[Tsundoku]

I think the knife has already a second bevel.


My sharpening skills are no good enough to create a double bevel.
Anyway, I think that the finishing of the blade makes it more sticky.

It's mainly the geometry of the knife is causing stickiness, the flat grind introduces a tighter gap when you cut, especially for vegetables/fruits with high water content. If you can somehow alter the geometry of the knife from being one flat surface, it will help to resolve the knife sticks to food.

 

[calostro5]

It's mainly the geometry of the knife is causing stickiness, the flat grind introduces a tighter gap when you cut, especially for vegetables/fruits with high water content. If you can somehow alter the geometry of the knife from being one flat surface, it will help to resolve the knife sticks to food.

In this case, the solution is more difficult that I thought.
As I said, my sharpening skills are not good enough to modify the geometry of the knife, and I don't know anybody near of me who is able to do it.

 

[Tsundoku]

In this case, the solution is more difficult I thought.
As I said, my sharpening skills are not good enough to modify the geometry of the knife, and I don't know anybody near of me who is able to do it.

Which is the reason why a skilled sharpener/factory grind is essential to define a good knife. The blacksmith can deliver a perfectly shaped knife, but it's the grind that defines the knife. If the knife does not come with a proper grind, the knife becomes difficult to use.

 

[calostro5]

Which is the reason why a skilled sharpener/factory grind is essential to define a good knife. The blacksmith can deliver a perfectly shaped knife, but it's the grind that defines the knife. If the knife does not come with a proper grind, the knife becomes difficult to use.

It's clear that I have still much to learn.
I didn't know the importance of the grind. I thought a fine grind was the only thing to consider.
How should be a good grind?

 

[Tsundoku]

It's clear that I have still much to learn.
I didn't know the importance of the grinding. I thought a fine grinding was the only thing to consider.

We all learn together!

 

[calostro5]

We all learn together!

How should be a good grind?
What is the effect of a convex/concave grind?

 

[Benuser]

Don't insist on equal bevels on both sides. The knife isn't strictly symmetric. You may work on both bevels one by one. I want at least the right bevel to be in line with the face, forming a continuous arc. You may start at the lowest angle, moving the edge and slightly increasing the angle and feel on the stone where the any friction remains. Give it one or two passes at that angle on a medium-fine stone. Go on looking for the next place, until the very edge got reached. Before deburring the other side, start there as well at the lowest angle. That's how I make smooth convex bevels and eliminate the last vestiges of facetting.

 

[calostro5]

Don't insist on equal bevels on both sides. The knife isn't strictly symmetric. You may work on both bevels one by one. I want at least the right bevel to be in line with the face, forming a continuous arc. You may start at the lowest angle, moving the edge and slightly increasing the angle and feel on the stone where the any friction remains. Give it one or two passes at that angle on a medium-fine stone. Go on looking for the next place, until the very edge got reached. Before deburring the other side, start there as well at the lowest angle. That's how I make smooth convex bevels and eliminate the last vestiges of facetting.

That is too difficult for me.
Moreover, my stones are a shapton kuromaku 1000, a Makita 1200 (probably is a king) and another 3000 stone rebranded whose manufacturer I don't know (I find this stone too soft, so I would like to get another fine stone maybe a shapton kuromaku 5000 would be a good choice?).
I am left-handed.

 

[Benuser]

That is too difficult for me.
Moreover, my stones are a shapton kuromaku 1000, a Makita 1200 (probably is a king) and another 3000 stone rebranded whose manufacturer I don't know (I find this stone too soft, so I would like to get another fine stone maybe a shapton kuromaku 5000 would be a good choice?).
I am left-handed.

Being left-handed may explain the problems you're encountering. Japanese knives are optimised for right-handers. Right side convex, left face flatter, edge off-centered to the left. The idea of different geometries on both sides isn't exclusively Japanese: but the Japanese went a bit further in it by off-centering the edge which improves food release even more. They could do so as left-handers tend to be ignored in their culture. Retailers advertise often describing their knives as ambidextrous, or 50/50. Even if a symmetric edge has been put on a standard knife, that doesn't make it truly ambidextrous as the fundamentals are not. Expect all kinds of wedging and steering issues as the grinding hasn't been addressed.
The only more or less symmetric Japanese blades I know about are lasers, where the anorexic geometry favours cutting performance over food release, equally dramatically poor for both left- and right-handers.
The flat left face is the reason recentering the edge as some retailers offer isn't a real solution. The cutting will certainly improve for a while, but produce still sticking on the flat side.
Expect wedging and steering still to occur after a few sharpenings, when the area behind the edge hasn't been thinned.
A few makers do deliver versions with an inverted geometry for left-handers: left side convexed, right one flat, edge off-centered to the right. I know about Masahiro and Misono having them always in stock.

 

[Tsundoku]

Being left-handed may explain the problems you're encountering. Japanese knives are optimised for right-handers. Right side convex, left face flatter, edge off-centered to the left. The idea of different geometries on both sides isn't exclusively Japanese: but the Japanese went a bit further in it by off-centering the edge which improves food release even more. They could do so as left-handers tend to be ignored in their culture. Retailers advertise often describing their knives as ambidextrous, or 50/50. Even if a symmetric edge has been put on a standard knife, that doesn't make it truly ambidextrous as the fundamentals are not. Expect all kinds of wedging and steering issues as the grinding hasn't been addressed.
The only more or less symmetric Japanese blades I know about are lasers, where the anorexic geometry favours cutting performance over food release, equally dramatically poor for both left- and right-handers.
The flat left face is the reason recentering the edge as some retailers offer isn't a real solution. The cutting will certainly improve for a while, but produce still sticking on the flat side.
Expect wedging and steering still to occur after a few sharpenings, when the area behind the edge hasn't been thinned.
A few makers do deliver versions with an inverted geometry for left-handers: left side convexed, right one flat, edge off-centered to the right. I know about Masahiro and Misono having them always in stock.

That is too difficult for me.
Moreover, my stones are a shapton kuromaku 1000, a Makita 1200 (probably is a king) and another 3000 stone rebranded whose manufacturer I don't know (I find this stone too soft, so I would like to get another fine stone maybe a shapton kuromaku 5000 would be a good choice?).
I am left-handed.

Indeed. Many left-handed chefs have adapted into using right-handed knives in Japan. You could find some left-handed knives, but they are a rarity compare to the dominating right-handed knives.

 

[M1k3]

Sounds like the face of the bevels are pretty flat, increasing friction a bunch.

Convexing the blade faces, especially THE USERS non-dominant side, will help tremendously.

 

[Benuser]

Sounds like the face of the bevels are pretty flat, increasing friction a bunch.

Convexing the blade faces, especially the non-dominant side, will help tremendously.

The blade's non-dominant side, or the user's, who happens to be left-handed?

 

[M1k3]

The blade's non-dominant side, or the user's, who happens to be left-handed?

The users.

 

[Benuser]

I would try to recenter the edge, and indeed convex the bevels, especially the left one, to have it in line with the face.

 

[Benuser]

But before entering into geometry discussions: make sure there's no tenacious burr. A burr that is being overlooked may make a knife to behave very strangely. A hard lesson I've learnt when I started sharpening, when @Pensacola Tiger pointed this out, some 25 years ago.

 

[Tsundoku]

But before entering into geometry discussions: make sure there's no tenacious burr. A burr that is being overlooked may make a knife to behave very strangely. A hard lesson I've learnt when I started sharpening, when @Pensacola Tiger pointed this out, some 25 years ago.

How did the knife behave strangely?

 

[Benuser]

The burr caused huge friction, with wedging and steering to the opposite side as a result. Burr on the right side, clockwise steering or vice versa.

 

[Tsundoku]

Found some diagrams online which explains the wedging effect from the knife. To have a sharp (narrow) compound double bevel will definitely help.

 

[blokey]

If anyone interested I have the Santoku version of this knife, similar issue, despite really thin it is not as a good cut as the thinness would suggest. (Still very good for the price tho) here’s a choil of mine, was working on some thining.

 

[M1k3]

If anyone interested I have the Santoku version of this knife, similar issue, despite really thin it is not as a good cut as the thinness would suggest. (Still very good for the price tho) here’s a choil of mine, was working on some thining.View attachment 184328

That looks super flat. Lots of friction...

 

[blokey]

That looks super flat. Lots of friction...

The whole line is basically piece of stamped steel pressed against wheel until there’s a edge, then again it is only $35.

 

[calostro5]

The double bevel and flat grind might be the big contributors to the stickiness of the knife. Usually it's the shinogi part of the knife helps to separate between cuts. I would recommend to create a shinogi yourself, create a compound double bevel or asymmetrical "V" bevel.

Don't insist on equal bevels on both sides. The knife isn't strictly symmetric. You may work on both bevels one by one. I want at least the right bevel to be in line with the face, forming a continuous arc. You may start at the lowest angle, moving the edge and slightly increasing the angle and feel on the stone where the any friction remains. Give it one or two passes at that angle on a medium-fine stone. Go on looking for the next place, until the very edge got reached. Before deburring the other side, start there as well at the lowest angle. That's how I make smooth convex bevels and eliminate the last vestiges of facetting.

Sounds like the face of the bevels are pretty flat, increasing friction a bunch.

Convexing the blade faces, especially THE USERS non-dominant side, will help tremendously.

I have just sanded the knife. This is the result:




The surface is not so sticky and the food is released easier. The behaviour of the knife has been improved.
Maybe I have ruined the finish, but easily I have corrected the problem (partially at least).
Grinding the blade as you suggested is far from my skill.