Nakiri wip

[83kamaleon]

Hello everyone, I'm building a nakiri, I set the bevels and I went up to the 400 grit before heat treating, leaving a half millimeter on the edge, now I'm thinking that it coulb be thinned behind the edge to have better cutting performances, I ask advice from you experts, does it seems thick? can i thin it after the hardening?with Wich grit is better to proceed? or should I go back to the grider now, I'd like not to scratch it again

https://imgur.com/a/EFC9usc

 

[milkbaby]

It's probably too thin behind the edge right now if you haven't heat treated it yet. That's because during heat treatment, a very thin edge will likely deform, often making "bacon" edge. How are you planning to heat treat?

 

[83kamaleon]

It's probably too thin behind the edge right now if you haven't heat treated it yet. That's because during heat treatment, a very thin edge will likely deform, often making "bacon" edge. How are you planning to heat treat?

i'm sending it out for heat treatment it's a suminagashi with a vg10 core,i hope it doesn't warp then,there's not much i can do now

 

[Tim Rowland]

83kamaleon:
Sorry for the bad news but I agree with milkbaby on how thin it currently is pre-heat treat.
The thinnest I ever go with edges pre-heat treatment is .040" and that would be typically on thicker blades.
Thinner blades I grind after heat treatment to minimize any chance of warping.
Yes you will use a lot more abrasives on the grinder and a hand rubbed finish takes much longer but its better than doing hours a work and having nothing to show for it in the end because the blade is trash.
On your next blade try to just profile your blade, and round over any edges you want and send it off to heat treatment. When you get it back grind it nice and slow with a bucket of water next to you to cool the blade after each pass, I also suggest doing this with no gloves so you can feel if the steel is to hot before you heat it up past the temper point and ruin the heat treatment.
It takes a lot of patience and practice.
Your only real solution that I can see it to grind away some of your blade making it shorter but getting it to around that .040" at the edge and finishing you bevels after heat treat.
FWIW, I think what you have accomplished looks good and has a nice shape to it.

 

[83kamaleon]

quenching it between two plates maybe?

 

[Tim Rowland]

Unless they are free floating/hinged aluminum plates I don't think that will work since the sides of the blade and your edge are different thicknesses your edge would be unsupported and still viable to "bacon".

this was ground to thin before I heat treated it and you can see the resulting bacon edge. It happens to everyone, just a frustrating learning curve.

 

[milkbaby]

Agreed with Tim... Since you're sending out to heat treat, I would discuss with them what the minimum edge thickness they recommend. Then you can grind back the edge to that thickness.

I don't work with stainless steel, so I don't know what the common recommendation for edge thickness would be. For the simple carbon steels that I've used, around 0.020-0.010" have been okay for avoiding bacon edge in my heat treatment procedure (forge HT with oil quench). As with anything, test with your steels under your shop conditions and go with what works...

Like Tim, here's a pic of my bacon. I adjusted the knife afterwards but obviously no longer the originally planned edge profile.

 

[merlijny2k]

I ground mine too thin too and got them back bent but not baconed. Wonder why.

In any case you sort of loose your polish during HT as it comes back al black and scaled anyway.

 

[83kamaleon]

I was a little bummed out,so I went to check the specs of the dealer,it doesn't say anything about quenching, how's it possible? It makes me hope a little bit it won't warp,what

do you think?

 

[83kamaleon]

i wrote them an email,they confirmed no quench,and that 0.5 mm should be enough,i'm crossing my fingers

 

[Tim Rowland]

Any update on how your heat treatment went?

 

[83kamaleon]

Any update on how your heat treatment went?

apparently it went well,but i've only seen pictures cause the knife has been sent back but hasn't arrived yet,i'll keep you guys updated

 

[Tim Rowland]

Were did you send it of for treatment if you don't mind sharing?

 

[83kamaleon]

Were did you send it of for treatment if you don't mind sharing?

Well I don't mind sharing but since I live in Italy I don't know if it would be useful.I sent it to a knifemaker that I've met on an Italian knifemaking forum,he was kind enough to give me this favour

 

[Tim Rowland]

Ahh ok,
I was just wondering if it was a large facility to see if it was going to be done in a vacuum chamber oven, or in a regular HT oven wrapped in foil like most air hardening steels.

 

[83kamaleon]

The blade is back, it didn't warp at all while another blade that I had left considerably thicker has a little warp on the edge.I'm thinning it and it's not easy now that it's hard,I reached 0,3mm on the edge, it's a full flat grind,should I move to the water stones or should I go ahead on the grinder?is it fine a full flat or should I try some convex and how?

 

[merlijny2k]

I'd switch to the stones. At such low thickness you can literally burn the steel in under a second if you apply too much pressure at some point in the process. If you see a burnmark it means you have crossed 650 C. Far above the tempering temp for most knifesteels.

 

[83kamaleon]

I'd switch to the stones. At such low thickness you can literally burn the steel in under a second if you apply too much pressure at some point in the process. If you see a burnmark it means you have crossed 650 C. Far above the tempering temp for most knifesteels.

that's what i had tought,on the stones should i keep the angle i have set on the belt grinder and go to a zero grind or should i raise the blade so that i establish a secondary bevel?

 

[milkbaby]

For finish grinding the bevel on a belt grinder, if there is a lot of metal still to remove, I like to use a relatively coarse belt like 40 to 60 grit that is also fresh. And I always grind wet to help manage the heat. An old belt won't cut as well and more likely to overheat. The downside is you have to spend more time to get the low grit scratches out so you risk burning up the heat treat as mentioned. If it's already very close to final geometry, then I might risk starting around 90 or 120 grit belt or even just going to diamond plate. Note that I use a 1x30" belt grinder with tiny platen which makes it very difficult to manage the heat. If you have a much larger grinder that doesn't heat up as much, you do it more easily.

The type of bevel you grind depends on what you're trying to achieve and partially how much meat you have available to work with. If the steel is left pretty hard, you can grind to zero and then sharpen a small edge bevel at whatever angle you prefer to add back a teeny bit of steel with a little more strength behind the edge. For example below, I put a flat wide bevel grind to zero on the knife then sharpened an edge bevel at the usual angles I might do (10-15 degrees per side, I don't measure just go by eye and test edge in real life). You can see the shiny edge bevel is tiny, around 0.5 mm or less, and there is not too much thickness added back behind the cutting edge to make it feel hard to initiate the cut.

 

[83kamaleon]

Thanks for the reply

 

[83kamaleon]

here's a little video of the knife almost finished,still has to be polished and sharpened better,i'm not very sure if the microbevel is very orthodox but i guess it will make sharpening easier.i'm not even sure if i have to etch it or not since it's suminagashi vg10,what do you guys think? the handle is not glued yet

 

[milkbaby]

Very nice, it looks excellent!

Whether to etch or not is a matter of taste. It looks pretty nice right now tho.

 

[83kamaleon]

Very nice, it looks excellent!

Whether to etch or not is a matter of taste. It looks pretty nice right now tho.

Thanks a lot,I like it like this but maybe I'll give it a quick etch just to see how it looks and then decide,still not fully satisfied of the grind, I'm looking for info about the proper traditional grind for the nakiri,but with no luck so far,if anyone has info it would be appreciated

 

[milkbaby]

From what I can find, double bevel kitchen knives weren't a Japanese thing until probably the time of the Meiji Restoration ~1870. Not sure if you could say there is a "traditional" grind for Japanese double bevels?

I think it's common for double bevel jknives to be asymmetrical and convex, usually right hand biased. Check out this good thread started by kippington for info:
https://www.kitchenknifeforums.com/threads/a-basic-explanation-of-asymmetry.33951/

In my opinion, experiment for yourself to get at what you feel works the way you like. Handmade knives are often vary from piece to piece, it's testing and optimizing that can make yours stand out from factory production focused ones.

 

[Nikabrik]

From what I can find, double bevel kitchen knives weren't a Japanese thing until probably the time of the Meiji Restoration ~1870. Not sure if you could say there is a "traditional" grind for Japanese double bevels?

Interesting. Do you know the history of double bevels in Tosa? They seem like a special case, because they're putting double bevels on Japanese blade shapes. That could easily be something that began during the Meiji Restoration, as a different mode of adopting double bevel knives - or it could be that they got there their own way.

 

[merlijny2k]

Wow, nice knife. Looks pretty thin already from the video. Doesn't appear you have that much meat left to traditionalise the grind with. Then again it should cut pretty good as it is from what I can see. Cutting vid?

By the way what does Suminagashi mean and how does it differ from your run off the mill VG10&damascus cladding san mai stock?

 

[milkbaby]

Interesting. Do you know the history of double bevels in Tosa? They seem like a special case, because they're putting double bevels on Japanese blade shapes. That could easily be something that began during the Meiji Restoration, as a different mode of adopting double bevel knives - or it could be that they got there their own way.

I never took that course during my education at the University of Google, so I really have no idea... But hang on, I went back to school and found these two things:
http://tosawave.blogspot.com/2017/12/off-to-tosa-yamada-to-find-out-more.html
https://www.japaneseknifeimports.com/blogs/news/63928965-regional-knife-makers

From the write ups, it looks like Tosa region was mostly specialized in agricultural tools like sickles, axes, hoes, and the like? So maybe they didn't have a long history of making the traditional single bevel kitchen knives? Double bevel would be easier to make than single bevel in my opinion, and maybe that's why.

By the way what does Suminagashi mean and how does it differ from your run off the mill VG10&damascus cladding san mai stock?

It's the same as the prelaminated "damascus" clad san mai, basically multiple layers of alternating contrasting cladding around the core steel. Like here:
https://www.dictum.com/en/steel-cca/japanese-multi-layered-steel-suminagashi-719610

Edited to add: the pics below are for prelaminated multilayer/suminigashi san mai. If you forge your own layered cladding, its looks can depend on how you squeezed it down in thickness.

If you just grind the steel into a knife by stock removal, you get straight lines that follow the topography of the grind:

If you forge it, then you'll get distortion of the layers which gives it the look of suminigashi (Japanese floating ink art):

 

[83kamaleon]

still working on the knife really slowly,i think i'll redo the handle cause the balance point was about at the pinch grip but the chef likes it at the bolster so i'm gonna make an heavier handle.I'm looking for some ebony that i guess is one of the heaviest woods,anyway here are a few pics of the knife polished and also etched,which version do you like the most?

 

[Tim Rowland]

83kamaleon, where do you live?
If in the USA I can send you some ebony, but take caution as some ebonies are known to crack very easily. I would suggest african blackwood as it has similar color and density.

 

[83kamaleon]

83kamaleon, where do you live?
If in the USA I can send you some ebony, but take caution as some ebonies are known to crack very easily. I would suggest african blackwood as it has similar color and density.

Living in Italy,I guess shipping would be too expensive,im I going to look for some african blackwood then