Thinning down kitchen knifes with the Tormek.

[Merlin]

@Merlin

Sorry if I was not clear: I do not use the sides of the wheel but the usual circumference after having made sure it was perfectly true (using the Tormek Truing Tool TT-50)

Ah I see.
Thank you for the clarification.

M

[Thy Will Be Done]

Unless I'm missing something I don't think it's possible to thin knives on the top of a Tormek grinding wheel : you would hollow grind it and would not be able to grind at a low enough angle if the knife is in a jig. The jig would bite into the stone.
Theoretically you could use the side of a diamond or CBN wheel but I think it would be extremely difficult, either free hand or using the MB 100(?), this would require a knife jig to hold the knife and it would still catch on the stone.
Someone else may be more enlightened than me and suggest a way to do it.
I just can't see how a Tormek can be used to thin knives.
Once I tried to flat grind a scandi knife on the side of a diamond wheel free hand. It was a disaster!

Actually this is exactly how many Japanese forged kitchen knives are shaped after forging but they generally use a larger radius wheel than the Tormek which will further reduce the hollow grinding.  I have done it and it works but take care to avoid the apex of you will take out big pieces.  Also rocking the blade a bit will effectively grind flat although there will be some inevitable high and low spots.  This can be cleaned up on 220 grit waterstones if needed to give perfect flat or convex.

[LeU]

@Merlin

I continued my thinning experimentation and played with an Ikea 365+ knife, the blade is 20cm long, and the entire knife is made of X50CrMoV15 which is a "German-style" steel with HRC~56. That worked well, but the steel is too soft, and having made the cutting edge very thin means that it gets bent/wobbly very fast

So I decided to move to a santoku knife kit with a 16cm blade nearly finished (and already hardened) and wood scales for the handle. I selected this particular model because it used Sandvik 14C28N and was supposed to be HRC~59.

Then I purchased a diamond grinding wheel: what a difference that makes!

Now I can do in 20-30mn what used to take several hours on a standard SG-250 wheel, without having to true it or to worry about where the blade touches, and the result is fantastic.

The "brushed" finish is very uniform and I am tempted to leave it instead of "finishing" the blade with finer sandpapers, but the most amazing is what difference this slightly harder steel made: I never had a kitchen knife so thin before, and this thing is insanely sharp, and it kept its edge so far, a real pleasure to use.

So I can confirm it is possible to make very thin knives with a Tormek, preferably a diamond wheel (which make a beter and faster job at it), and I recommend steel with a hardness approaching 60 HRC

[tgbto]

Out of curiosity, what is the coarseness of the diamond wheel you used ?

[Tony Montana]

@Merlin

I continued my thinning experimentation and played with an Ikea 365+ knife, the blade is 20cm long, and the entire knife is made of X50CrMoV15 which is a "German-style" steel with HRC~56. That worked well, but the steel is too soft, and having made the cutting edge very thin means that it gets bent/wobbly very fast

So I decided to move to a santoku knife kit with a 16cm blade nearly finished (and already hardened) and wood scales for the handle. I selected this particular model because it used Sandvik 14C28N and was supposed to be HRC~59.

Then I purchased a diamond grinding wheel: what a difference that makes!

Now I can do in 20-30mn what used to take several hours on a standard SG-250 wheel, without having to true it or to worry about where the blade touches, and the result is fantastic.

The "brushed" finish is very uniform and I am tempted to leave it instead of "finishing" the blade with finer sandpapers, but the most amazing is what difference this slightly harder steel made: I never had a kitchen knife so thin before, and this thing is insanely sharp, and it kept its edge so far, a real pleasure to use.

So I can confirm it is possible to make very thin knives with a Tormek, preferably a diamond wheel (which make a beter and faster job at it), and I recommend steel with a hardness approaching 60 HRC

I'm curious how you did it. Did you grind a sort of Primary/Secondary bevel?

[LeU]

Hi Antonio,

No, the idea is to get a "perfect V" profile without secondary bevel, so when there is one (that was the case for example of knives with scandy grind) I got ride of it, removing material that had been untouched.

For blades where the profile was more a "U" then a "V" I reshaped it entirely, basically as if it was a new blade that I had to grind from blank.

With he diamond wheel it is quite fast and since the wheel does not wear out as much as a natural or synthetic stone it is only a matter of doing the same on both sides (and this is why I count the number of passes).

So, again, when facing the machine, I place the blade pointing away from me on the circumference of the wheel (although there are diamonds on the sides of the grinding wheel I did not use them) and I go back and forth (i.e., not with the blade moving left-right parallel to the shaft, as Tormeks are normally used)

[aquataur]

The majority of cheap kitchen knives is made out of stainless steel with a composition that varies minimally from the above quoted.
An attempt to shape them like you did, LeU, is prone to fail from a start.
They are very forgiving to mistreatment however. You can make them usefully sharp and they are cheap. Perfect for the average housewife.

Hard steels inevitably are susceptible to rust and are non forgiving. So there is no clear vote for either of them.
Not everybody wants to drive and maintain a Ferrari.

[LeU]

@aquataur

Yes, it is clear that ordinary cutlery steel is not suited for thinning, it will not last long, but I did not want to ruin expensive Japanese knives straight away and needed some practice

That said 14C28N turned out to be much better than I expected and in the end I like it better than VG10 for instance because it does not chip easily and keeps an edge

[aquataur]

I have a hard steel core clad with stainless. Looks and works great and comes very thin to start with.
Best of all worlds for starters.

Unfortunately (for the part in me that is eager for the stone) it will take a looong time until this one needs some serious maintenance.🙄

[Tony Montana]

Hi Antonio,

No, the idea is to get a "perfect V" profile without secondary bevel, so when there is one (that was the case for example of knives with scandy grind) I got ride of it, removing material that had been untouched.

For blades where the profile was more a "U" then a "V" I reshaped it entirely, basically as if it was a new blade that I had to grind from blank.

With he diamond wheel it is quite fast and since the wheel does not wear out as much as a natural or synthetic stone it is only a matter of doing the same on both sides (and this is why I count the number of passes).

So, again, when facing the machine, I place the blade pointing away from me on the circumference of the wheel (although there are diamonds on the sides of the grinding wheel I did not use them) and I go back and forth (i.e., not with the blade moving left-right parallel to the shaft, as Tormeks are normally used)

That's interesting!
How is the result aesthetically? Did you consider the idea of finish everything with a fine bench stone?