Hard japanese knives on Tormek

[troflog]

Hello
Just got my T4. I have some japanese knives with hardness between 60-65 hrc. Are those impossible to sharpen on my regular Tormek stone?

[kwakster]

From what types of steel are your knives made ?

[troflog]

Hello
One is hrc 62 aeb-l richmond artifex and one rsuper agomi steel at 63
https://www.chefknivestogo.com/rilaaosu24gy.html

[Ken S]

Troflog,

I think we have two questions: Is it possible to,sharpen your hard Japanese knife with the SG-200?
And, since you just got your Tormek, is this a good first knofe to sharpen?

I have no experience sharpening Japanese knives; my knives are all western style. However, my standard method of testing grinding wheels is to grind for five minutes on a metal lathe tool bit. These are a hard alloy. The SG-200 does cut these tool bits. It is not optimized for these steels, however, it will cut them at a slower pace.

There are more experienced knife sharpeners than me on the forum.

As to the second question, I would be reluctant to touch a $280 US knife until I had learned and practiced on less expensive knives. The common advice is to use thrift store knives. Personally, I think you would be better served by practicing on less expensive knives with good quality steel. Here is an example:

https://www.amazon.com/Victorinox-Fibrox-Chefs-Knife-8-Inch/dp/B000638D32/ref=sr_1_3?ie=UTF8&qid=1533020284&sr=8-3&keywords=swiss%2Barmy%2Bchef%2Bknife&th=1

This knife was a favorite demonstration knife of Jeff Farris, the forum founder. The flat blade construction was easier to sharpen, and the good steel took and held a good edge.

Keep us posted.

Ken

[troflog]

Troflog,

I think we have two questions: Is it possible to,sharpen your hard Japanese knife with the SG-200?
And, since you just got your Tormek, is this a good first knofe to sharpen?

I have no experience sharpening Japanese knives; my knives are all western style. However, my standard method of testing grinding wheels is to grind for five minutes on a metal lathe tool bit. These are a hard alloy. The SG-200 does cut these tool bits. It is not optimized for these steels, however, it will cut them at a slower pace.

There are more experienced knife sharpeners than me on the forum.

As to the second question, I would be reluctant to touch a $280 US knife until I had learned and practiced on less expensive knives. The common advice is to use thrift store knives. Personally, I think you would be better served by practicing on less expensive knives with good quality steel. Here is an example:

https://www.amazon.com/Victorinox-Fibrox-Chefs-Knife-8-Inch/dp/B000638D32/ref=sr_1_3?ie=UTF8&qid=1533020284&sr=8-3&keywords=swiss%2Barmy%2Bchef%2Bknife&th=1

This knife was a favorite demonstration knife of Jeff Farris, the forum founder. The flat blade construction was easier to sharpen, and the good steel took and held a good edge.

Keep us posted.

Ken

I have one of these. This knife is quit common in Norway. For most people that not into knives this is the most expensive knife they have.

[kwakster]

Technically you should be fine, because the aluminium oxide in the regular Tormek stone is harder than both the steel matrix (duh) as well as it's content (carbide type & volume)
The hardest carbide type in AEB-L is chromium carbide @ 1735 Knoop
The hardest carbide type in Aeogami Super is tungsten carbide @ 1880 Knoop
Aluminium oxide measures 2100 Knoop and will easily abrade steel + carbides.

Personally i always use an abrasive that is harder than both the steel matrix as well as it's contents for the best possible edges that also last the longest.
This is of less importance with edges of a coarser type, but gets increasingly more important with edges of a more polished type.

However, due to the design & shape of the blades the round Tormek stone might or might not be the best choice for sharpening.
In other words: the Tormek stone can do great on secondary bevels if your knives have these, but is totally unsuitable for sharpening those wide single bevel knives.
For those you will need completely flat stones.

[Fernando]

Technically you should be fine, because the aluminium oxide in the regular Tormek stone is harder than both the steel matrix (duh) as well as it's content (carbide type & volume)
The hardest carbide type in AEB-L is chromium carbide @ 1735 Knoop
The hardest carbide type in Aeogami Super is tungsten carbide @ 1880 Knoop
Aluminium oxide measures 2100 Knoop and will easily abrade steel + carbides.

Personally i always use an abrasive that is harder than both the steel matrix as well as it's contents for the best possible edges that also last the longest.
This is of less importance with edges of a coarser type, but gets increasingly more important with edges of a more polished type.

However, due to the design & shape of the blades the round Tormek stone might or might not be the best choice for sharpening.
In other words: the Tormek stone can do great on secondary bevels if your knives have these, but is totally unsuitable for sharpening those wide single bevel knives.
For those you will need completely flat stones.

a very well-founded explanation, I was only guided by the Mohs Scale, thanks for the data of the knoop scale, I did not know it, but wikipedia explained it to me

[Fernando]

I have one of these. This knife is quit common in Norway. For most people that not into knives this is the most expensive knife they have.

Not only in Norway, here in Colombia, victorinox is considered a high-range knife including fibrox, which for me is mid-range, so that we can make an idea 1 out of every 50 people gives me a victorinox to sharpen, here the knife kitchen, as we say in Spanish "has the 3 B: Bueno, Bonito y Barato" in English "good, nice and cheap" is the Tramontina brand knife and has a range between 15 and 25 dollars. against the more than 50 dollars that a fibrox of 8 inches costs here.

[kwakster]

These Kohetsu Santoku's in HAP40 steel @ 65HRC also came from Chefknivestogo US, as they weren't available in my country.
Very nice knives i might add, and the steel takes & holds an excellent edge.

https://www.bladeforums.com/threads/kohetsu-hap40-santoku.1509214/

[troflog]

These Kohetsu Santoku's in HAP40 steel @ 65HRC also came from Chefknivestogo US, as they weren't available in my country.
Very nice knives i might add, and the steel takes & holds an excellent edge.

https://www.bladeforums.com/threads/kohetsu-hap40-santoku.1509214/

Have you sharpened one of these on a Tormek?

[kwakster]

On the one that had it's apex damaged from cutting hard crusted bread i used my Tormek T7 to grind the old edge flat and put on a new initial edge.
The polishing was then done on Paper Wheels with diamond compounds.

[troflog]

On the one that had it's apex damaged from cutting hard crusted bread i used my Tormek T7 to grind the old edge flat and put on a new initial edge.
The polishing was then done on Paper Wheels with diamond compounds.

So the standard stone i capetable of sharpening this hard steel? I get a little confused since many threads indicate that the standard stone cannot sharpend above 60 hrc

[Jan]

In the attached table you can find the hardness of selected carbides in tool steels. You can see that the hardest carbides may be as hard as or even harder than silicon carbide (the black stone SB-250).

Jan

P.S.: [1] W. THEISEN: Hartphasen, in Hartlegierungen und Hartverbundstoffe: Hrsg. Hans Berns. Springer-Verlag Berlin. 1998, S. 28

[kwakster]

Imo it's not so much about the hardness of the steel matrix, as a Tormek aluminium oxide stone is harder than any steel that i know of.
Sharpening the knives you mentioned on the regular stone would be no problem, even if they had a higher hardness.

What is however important for your end results is what type of carbides are in the steel, as well as how many of them.
HAP40 is a Japanese matrix high speed steel with lots of carbide formers in it, among which vanadium which can produce vanadium carbide @ 2660 Knoop (some even claim 2800 Knoop)
There may be not many of these very hard vanadium carbides, but there are also the tungsten carbides, the molybdenum carbides, and the chromium carbides.
Next to these there is also quite a bit of cobalt in the alloy, officially to give it it's red hot hardness necessary for machining other steel, but it might also enhance the properties of certain other alloying ingredients.
Now so far i've never used a Tormek aluminium oxide stone on HAP40, but in the past i did use one for grinding a completely new edge on several home made knives from full hard M2 high speed steel (old machine hacksaw blades @ 65-66 HRC), and the results were far from optimal.
The SG-250 aluminium oxide stone would definitely grind the M2 steel (at the expense of quite a lot of aluminium oxide abrasive, the stone got visually smaller), but the final edge apex was far removed from being truly sharp and the edge that i did get was inferior.
Only when i later resharpened the edges with diamond did i get the sharpness i was looking for (hair whittling) as well as a noticeable better edge quality & longevity.

My current Tormek T7 is fitted with an SB250 Blackstone, which consists of black silicon carbide @ 2480 Knoop (another manufacturer even claims 2550 Knoop)
Hard enough for almost every type of carbide found in modern steels (except vanadium carbide), and also capable of creating an initial coarse edge on even high vanadium carbide steels like S110V steel by cutting the steel matrix and "scooping" away all those very hard (but also very tiny) vanadium & niobium carbides.
And it also does it without visible premature wear on the stone.
For burr removal or further refinement i then use diamonds, which will of course cut any type of carbide cleanly, no matter how hard they think they are.

[Jan]

Thanks for very nice recollection, Kwakster, appreciated. 

Jan