Thinning help

[loay625]

Hi i decided to thin my knife to improve how it move through large onions, and i have been practicing sharpening on it, and it sort of developed thick bevel.
Now after some thinning it seems the wide bevel didn't change and the knife still stuck middle way through the onion
What should i do now?
P.S(After thinning the knife seemed to be hollow ground) and the goal now is to remove the hollow grind )
Sorry for any mistakes English is not my first language.

 

[Benuser]

Just general observations. Don't know if it applies to your case. With a knife that has board contact, I aim for a thickness behind the edge of 0.2mm, 0.5mm at 5mm upward, and 1mm at 10mm. Just a rule of thumb.
Don't forget to at least touch up the edge after thinning. Depending of the steel, nasty burrs may have developed, even when the very edge didn't got touched.

 

[loay625]

Just general observations. Don't know if it applies to your case. With a knife that has board contact, I aim for a thickness behind the edge of 0.2mm, 0.5mm at 5mm upward, and 1mm at 10mm. Just a rule of thumb.
Don't forget to at least touch up the edge after thinning. Depending of the steel, nasty burrs may have developed, even when the very edge didn't got touched.

I don't have a way to measure the thickness behind the edge.
My knife when i got it i couldn't see the edge unless i tilt the knife at specific angle and it was kinda difficult to see, now the edge is wide as you can see in the photo, also after many bad sharpenings my knife now doesn't cut paper when it's vertical to the paper i need to tilt it a little bit like this /.
I didn't feel any burrs when i stopped thinning i put a quick edge to test the knife and then i felt a burr forming when sharpening

 

[HumbleHomeCook]

In that first picture of the right side, follow your edge bevel reflection from heel to tip. You'll see inconsistencies, especially up by the tip.

If you can't cut paper your apex isn't there yet.

 

[loay625]

In that first picture of the right side, follow your edge bevel reflection from heel to tip. You'll see inconsistencies, especially up by the tip.

If you can't cut paper your apex isn't there yet.

I can cut paper here's a video i meant a different thing but when i tried shooting a video it cut the paper no problem so nvm
Also here's closer images to the edge i can only notice the heel inconsistency,
Also sharpness of the edge was not quite my issue here, after some thinning the knife thinned a little bit behind the edge, you can see that from the choil shot but when cutting, the knife still stuck mid way through the onion.

 

[kpham12]

Looks like a Masutani? Good knife.

The choil looks a little bit thinner. Just thin a little more on both sides with your fingers applying pressure right behind the edge to make the edge bevel smaller. Then make sure you remove deep scratches with higher grit stones or sandpaper. Deep thinning scratches can cause drag when you cut through onions so it might not feel like it’s cutting smoothly.

 

[The_Real_Self]

I'd say you need to bring your bevel even wider if it's still binding on onions. There's a reason for laser grinds on knives and basically that is ideal for what you are after is somewhere along those lines. How far you take it will depend on how much cutting ability you're after.

 

[loay625]

Looks like a Masutani? Good knife.

The choil looks a little bit thinner. Just thin a little more on both sides with your fingers applying pressure right behind the edge to make the edge bevel smaller. Then make sure you remove deep scratches with higher grit stones or sandpaper. Deep thinning scratches can cause drag when you cut through onions so it might not feel like it’s cutting smoothly.

Yes it's the vg10, it moved through onions better than now but still not quite smooth with big onions, still great knife as my first but i'm trying to learn on it so it is at its worst days.
But how long it takes to notice the edge getting smaller? I've been thinning for like 2hrs and it seems like not going anywhere or i'm just blind , unfortunately i don't have before image to compare just a choil shot
I'll try polishing it after i remove the hollow grind then test again.

 

[loay625]

I'd say you need to bring your bevel even wider if it's still binding on onions. There's a reason for laser grinds on knives and basically that is ideal for what you are after is somewhere along those lines. How far you take it will depend on how much cutting ability you're after.

From what i read and watched everyone say that the bevel should get smaller when thinning. Or do you mean a different thing?

 

[Delat]

From what i read and watched everyone say that the bevel should get smaller when thinning. Or do you mean a different thing?

He’s talking about the blade road or wide bevel section. You’re talking about the edge bevel.

 

[Tethien]

I’ve had a similar situation with my shirasama, it took me like 6 hours to get to a spot where I wanted with a 140 grit diamond plate and even then I want to thin some areas

 

[Blank Blades.]

Yes it's the vg10, it moved through onions better than now but still not quite smooth with big onions, still great knife as my first but i'm trying to learn on it so it is at its worst days.
But how long it takes to notice the edge getting smaller? I've been thinning for like 2hrs and it seems like not going anywhere or i'm just blind , unfortunately i don't have before image to compare just a choil shot
I'll try polishing it after i remove the hollow grind then test again.

What stone are you using?

 

[ared715]

Just by the appearance in the first few photos it looks to me like you may need to apply a bit more pressure when thinning against the shinogi line. This will help improve how the knife moves through food as well. It will also help you maintain/get back to the original geometry so you can get closer to the way the knife cut initially when you got it.

I may be wrong regarding your situation but it just looked to me like raising the shinogi could help with the wedging issue. It can be a bit difficult with hollow ground wide bevels for someone starting out as it's difficult to tell how much metal is being removed when the entire bevel isn't making contact with the stone like a convex/flat grind.

If you can also let us know which stones you're using, it may help a bit as the finish left after thinning can effect how the knife moves through food too.

Hope this helps!

 

[Delat]

I don't have a way to measure the thickness behind the edge.
My knife when i got it i couldn't see the edge unless i tilt the knife at specific angle and it was kinda difficult to see, now the edge is wide as you can see in the photo, also after many bad sharpenings my knife now doesn't cut paper when it's vertical to the paper i need to tilt it a little bit like this /.
I didn't feel any burrs when i stopped thinning i put a quick edge to test the knife and then i felt a burr forming when sharpening

You can get something like this for not much money. it’s really helpful for setting benchmarks and measuring progress.
https://www.amazon.com/gp/product/B017KUC6XQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[loay625]

What stone are you using?

Norton crystolon 180#

 

[loay625]

Just by the appearance in the first few photos it looks to me like you may need to apply a bit more pressure when thinning against the shinogi line. This will help improve how the knife moves through food as well. It will also help you maintain/get back to the original geometry so you can get closer to the way the knife cut initially when you got it.

I may be wrong regarding your situation but it just looked to me like raising the shinogi could help with the wedging issue. It can be a bit difficult with hollow ground wide bevels for someone starting out as it's difficult to tell how much metal is being removed when the entire bevel isn't making contact with the stone like a convex/flat grind.

If you can also let us know which stones you're using, it may help a bit as the finish left after thinning can effect how the knife moves through food too.

Hope this helps!

When i tested the knife it was the crystolon 180# finish, also it seems that my stone is glazed now and my sandpaper doesn't do anything to it (still looking for sic powder in my country)
I somewhat thought it will take less time since the knife still quite new but either i'm wrong or the stone is slowing down.
I have the imanishi combo 1k/6k i will finish on it after done thinning

 

[Blank Blades.]

When i tested the knife it was the crystolon 180# finish, also it seems that my stone is glazed now and my sandpaper doesn't do anything to it (still looking for sic powder in my country)
I somewhat thought it will take less time since the knife still quite new but either i'm wrong or the stone is slowing down.
I have the imanishi combo 1k/6k i will finish on it after done thinning

Yeah crystolon isnt good for thinning because of just that. It glazes and you have to resurface it.

I recommend something a bit more muddy like the 220 pink or green brick, shapton 120, maybe the naniwa lobster course stone.

When u use these.(especially the shapton 120), make sure you leave a healthy enough amount of slurry on the stone. That basically reconditions the surface as you go and keeps the stone cutting

 

[loay625]

Yeah crystolon isnt good for thinning because of just that. It glazes and you have to resurface it.

I recommend something a bit more muddy like the 220 pink or green brick, shapton 120, maybe the naniwa lobster course stone.

When u use these.(especially the shapton 120), make sure you leave a healthy enough amount of slurry on the stone. That basically reconditions the surface as you go and keeps the stone cut

Yeah crystolon isnt good for thinning because of just that. It glazes and you have to resurface it.

I recommend something a bit more muddy like the 220 pink or green brick, shapton 120, maybe the naniwa lobster course stone.

When u use these.(especially the shapton 120), make sure you leave a healthy enough amount of slurry on the stone. That basically reconditions the surface as you go and keeps the stone cutting

Idk, i had tow options either shapton stones or crystolon since they are the lightest, cause shipping to my country is way to expensive.
From the quick search i did, the SPG burnishing fast, and the crystolon should be faster when conditioned.
It seems there's an issue with coarse stones either too soft, slow, glazing and all of them need conditioning the stone with the least issues was the debado ld 180# but the stone is like 100$. But i didn't test all of them so i may be wrong.

 

[The_Real_Self]

When i tested the knife it was the crystolon 180# finish, also it seems that my stone is glazed now and my sandpaper doesn't do anything to it (still looking for sic powder in my country)
I somewhat thought it will take less time since the knife still quite new but either i'm wrong or the stone is slowing down.
I have the imanishi combo 1k/6k i will finish on it after done thinning

If your Crystolon is glazed then there are a few things worth noting.

1, you can likely get it cutting again by using it on a very narrow bevel (ideally softer steels as well) at very high contact pressures to get the abrasive to fracture or release, exposing new particles.
2, if you grind very wide bevels on that stone I would expect glazing like that, it's really best suited to higher grinding pressure (force applied over a given surface area). Smaller bevels equal higher pressure for any given force.
3, rather than working on the whole face of the bevel, making contact with just the upper edge of the bevel will begin to convex the knife. This will continue whenever you are working on a hard corner where two bevels meet. This will allow you to grind at highest pressure possible for fast result.