Why is the forger so important?

Hi all,

New to the site here. I recently have been getting into Japanese knives (started with a Tojiro santoku, then got a Takamura R2 and a Kurosaki AS gyuto) and I've been wondering, why is the forger of the knife so important? From a layman's perspective, it would seem like the grind and geometry of a knife have less to do with how it was forged and heat treated than how it was ground. That being the case, why are people who only do blade forging, like Keijiro Doi, Hiroshi Kato, etc so highly respected and command a premium for their knives? I would love to understand why the forging process is so important.

Thanks!

Because if the knife is forged poorly all the grinding and geometry in the world won't make it worthwhile to use. Correct me if I'm wrong but my view is that the forging is what dictates the grain structure, hardness and durability of the knife, all this save durability is then set in stone once the knife is heat treated, you cannot make the knife harder change the grain structure. You can grind the knife out, causing it to thicken behind the edge and this may produce a gain in edge stability (possibly one qualification of durability), bit it will cost steel from the knife and time.

spoiledbroth said:

Because if the knife is forged poorly all the grinding and geometry in the world won't make it worthwhile to use. Correct me if I'm wrong but my view is that the forging is what dictates the grain structure, hardness and durability of the knife, all this save durability is then set in stone once the knife is heat treated, you cannot make the knife harder change the grain structure. You can grind the knife out, causing it to thicken behind the edge and this may produce a gain in edge stability (possibly one qualification of durability), bit it will cost steel from the knife and time.

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So if that's the case, what's the difference between the forge on a $100 knife and a $600 knife? Is the variability in the forge so significant that it commands that difference in price?

Hi I am also new here, please correct me if I am wrong. :newhere: I believe even with the same steel, with different heat treatment the steel can perform differently, heat treatment can affect the strength of the blade, the sharpness, edge retention etc. For exmaple a random $100 AEB-L knife cant possibly compare with the one made by DT.

Fit and finish can also add a lot to the price and production time of a knife

spoiledbroth said:

Because if the knife is forged poorly all the grinding and geometry in the world won't make it worthwhile to use. Correct me if I'm wrong but my view is that the forging is what dictates the grain structure, hardness and durability of the knife, all this save durability is then set in stone once the knife is heat treated, you cannot make the knife harder change the grain structure. You can grind the knife out, causing it to thicken behind the edge and this may produce a gain in edge stability (possibly one qualification of durability), bit it will cost steel from the knife and time.

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As far as I am aware there is no evidence that forging actually affects grain structure etc and all of that can be controlled by HT.

It may of been different in the days of less pure steal when you wefe trying to "even" the steel out, but even then.... i don't think so.

But feel free to correct me if I am wrong, I'm only going from my memory.

Well you cant grind or finish a knife as long as it is not forged
if the result after HT is wrecked then its like giving a wrecked car a paintjob and engine tuning.. well makes no sense if the car is a wreck .. sounds not stupid or am i wrong

In japanese knife manufacturing you mostly have an expert for the forging, the grinding , the handles. and so on.. expert craftsmen.

Most japanese knife we buy have kind of the name of the smith .. "its a kejiro Doi Yanagiba..." or its a ikeda, takeda, ....
without the foundation the rest is useless. so the smith gives birth to a knife and then the other craftsmen can polish it to a diamond.

The difference in price is also in the work hours you have to invest to make it that unique.
well if your knife is super hyped then youll of course also increase your prices to rip-off level.

a 600 Dollar knife has to have more than something special to justify the high prize.. but sometimes the difference is just a number
i got me a Kejiro doi yanagiba and his aogami2 steel is something completely different than any aogami2 steel that is laminated in a factory..
he used a special forging technique and this knife has the best grip in my hand (its also my most expensive knife and i would only regret NOT buying it) .. this kind of craftsmanship convinces you into a serious sick knife addiction and spending trillions of dollars on knifes that you dondt need

malexthekid said:

As far as I am aware there is no evidence that forging actually affects grain structure etc and all of that can be controlled by HT.

It may of been different in the days of less pure steal when you wefe trying to "even" the steel out, but even then.... i don't think so.

But feel free to correct me if I am wrong, I'm only going from my memory.

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you would be wrong in this case... forging does directly effect the HT. Some people try to recreate the effects of forging through heat cycling, but its not exactly the same.

I think it needs mentioning that some great japanese knives (especially those using very modern steels - can PM steel even be forged without degrading it? - or very thin geometries) are made by stock removal not classic forging; in a way the steel manufacturer that supplies the blank is the one who forges. Heat treat becomes no less important

PS I thought a "forger" was not a forge smith doing forging, but someone that did forgery (making counterfeits)?

JBroida said:

you would be wrong in this case... forging does directly effect the HT. Some people try to recreate the effects of forging through heat cycling, but its not exactly the same.

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Interesting, care to explain?

In the western garagetweaker world of knifemakers bliss the word of advice is usually forge - anneal - normalize (heat cycle, to deal with grain growth from forging) - quench - temper.

Don't mean to come off rude, I'm sincerely just interested. My guess would be that some japanese smiths like to forge at reducing heats to normalize, and go straight to quench. Given the soft steel laminates, they can deal with pretty bad warpage (from tensions left not annealing) post quench?

JBroida said:

you would be wrong in this case... forging does directly effect the HT. Some people try to recreate the effects of forging through heat cycling, but its not exactly the same.

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Thanks for the info. Intriguing and I should read up more on it. But I really hated material science at uni and was just going by my memory.

Cheers for correcting my wrong.

I think among other things Jon has also in mind cold forging (for what it's worth, Carter talks about it too in one of his recent vieos). HT is indeed the very central part of the knife making that influences nearly all relevant propertis of the blade, but it is not the only one. Forging does influences the grain structure and the HT does not 'erase' it all.

Matus said:

I think among other things Jon has also in mind cold forging (for what it's worth, Carter talks about it too in one of his recent vieos). HT is indeed the very central part of the knife making that influences nearly all relevant propertis of the blade, but it is not the only one. Forging does influences the grain structure and the HT does not 'erase' it all.

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Please explain.
If it is forge-anneal-normalize-quench-temper then I'm under the impression that the grain structure is indeed reset.

Again, I'm just interested. A good knife is a good knife, and forging is cool 👍

Robin, I 'know' only as much as I read in Verhoeven + a few more papers (and it is all a bit mixed in my head, need to re-read it anyhow). But you do not 'erase' or 'overwrite' the grain structure, nor you want to do that, as that would mean to over-heat the steel in the HT which you of course do not do. The way the steel is treated mechanically is important - the most well know process of cold rolling of steels like 52100 (1.3505) which refines the grain structure.

Matus said:

Robin, I 'know' only as much as I read in Verhoeven + a few more papers (and it is all a bit mixed in my head, need to re-read it anyhow). But you do not 'erase' or 'overwrite' the grain structure, nor you want to do that, as that would mean to over-heat the steel in the HT which you of course do not do. The way the steel is treated mechanically is important - the most well know process of cold rolling of steels like 52100 (1.3505) which refines the grain structure.

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I better get to reading that voerhoven then
Thanks. In my experience the cold rolled steels I've used and use, need an annealing cycle as they tend to have some tensions, even though they should come properly annealed. After annealing they behave as they should. The smelt and ground tool steels/pm behave better through HT as delivered.

I agree on that. Even with my limited experiece I can confirm that steels like O1 or D2 that come ground to exact shape do behave better (and do not need to be flattened to begin with - part wihich I still can not do well enough). You should definitely read the Verhoeven. I actually had it printed in A4 with soft cover - makes the reading MUCH easier as you will be jumping between text and figures often. It is very well written and super easy to understand even for someone without the proper background (like me).

Back on topic... I wonder consider ht part of overall process of forging as I believe the blacksmith would do this for hizukiri (free forged) knives. I intentionally simplified the topic because, the op isn't really asking for this level of detail :lol:

The forger is important because forging is a skill!
Especially in Japanese laminated knives, there is much skill involved in the fire-welding of the composites, and even though it appears that nowadays most laminated steel used in Japan is rolled industrially anyway, even then forging laminate, or even mono steel, is still a process requiring skill.

Which may also answer the question about the difference between a $100 knife and a $600 knife; perhaps in the latter would be laminated in-house, by the smith, rather than brought in pre-rolled?

Lastly, the metallurgy question is a truly venerable chestnut that seems like it would survive nuclear holocaust.
In fact, it could be the title of a non-fiction best-seller;
"After the Bomb; Cockroaches, Twinkies and Forged vs. Stock Removal"

Well put Dan 👍👍👍

Thanks Robin.

RDalman said:

Please explain.
If it is forge-anneal-normalize-quench-temper then I'm under the impression that the grain structure is indeed reset.

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This is my understanding too.
There are a number of reasons to forge a knife rather than purely grind it. For me, metallurgy/grain structure is not one of them.

I would only echo what Dan said. There are actually many things that can go wrong during forging (cracks, over-heat, decarburization, etc.) and since most smith do not have a complete metallurgical lab at the back of their workshop, they can not simply measure all relevant parameters, so often with trial and error they need to develop a process that yield high quality product, so we are not talking just about skill, we are talking about SKILL

For me as a hobby knife maker the stock removal has the advantage of not being exposed to so many variables. I can (and for technical and practical reasons do) outsource the HT and so unless I overheat the blade after HT I have a good chance to produce a blade that, a least from the metallurgy point of view, sound is. Still - forging is for me the holly grail. Who knows, maybe one day I will have that possibility.

Thanks all for the interesting discussion, and yes "Smith" is probably the word I was looking for, not "forger". Sounds like making a knife is very complicated (as I can imagine from the variability in prices and how long some of the smiths have been in business). I guess the only way to find out how much the forge really affects the knife is to buy more knives ;P (my girlfriend will kill me)

I just quick read the Verhoeven chapter 8 on control of grain size by heat treat and forging. At forging temperatures you would normally have grain growth which is detrimental, but the plastic deformation of forging keeps this from happening. However, from this chapter, if you read the part about normalizing cycles (this is heating and cooling after forging), if done correctly, the pearlite grains are all transformed to new austenite grains and back, and also get refined by the cycling. What you get in the end is influenced by what you had at the start, but it seems if you repeat the normalization cycles enough, it's not quite as important? Most western knifemakers use a triple normalization.

It could be that traditional Japanese bladesmiths heating by eyeing the color of the steel and cooling slowly by covering the blades in rice husks and straw (or whatever it is they use), there's more "effect" leftover from forging, but I haven't read anything about that...

On the thing about forging, I think there is a certain romance about using old traditional ways to handcraft an item. Even though a modern stamped or water jet cut blade that is then ground may be great, it doesn't have that air or cache of artisan handmade to me. And I bet that 90-95% of the shape of the blade is determined by forging. Takeda blade geometry has got to be forged. I think there is a picture from Will Catchside in his sub-forum about his forged blades being forged extremely close to final geometry too. The possible geometries you can grind on can also be limited by the forging: you can't put material back in places by grinding.

Also, I guess you can reuse found steel and/or use steel that is not available as suitable bar stock...

milkbaby said:

At forging temperatures you would normally have grain growth which is detrimental,

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I'm not disagreeing with you, just wanted to point out that forging temperatures vary, as do the temperature/time schema for grain growth of different alloys. In addition these variables also differ according to to section; a 500x500mm ingot will require different treatment to a 50x2mm (or whatever) blade.
As the Buddha once said "….too many variables to say for sure..."

milkbaby said:

On the thing about forging, I think there is a certain romance about using old traditional ways to handcraft an item. Even though a modern stamped or water jet cut blade that is then ground may be great, it doesn't have that air or cache of artisan handmade to me. And I bet that 90-95% of the shape of the blade is determined by forging. Takeda blade geometry has got to be forged. I think there is a picture from Will Catchside in his sub-forum about his forged blades being forged extremely close to final geometry too. The possible geometries you can grind on can also be limited by the forging: you can't put material back in places by grinding.

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OK, now it's starting to make sense. just looking at a Takeda, it looks like the iron cladding goes almost all the way to the edge, which must be forged. that's pretty crazy and now i can kinda see why his knives are priced the way they are. is it the same with other kurouchi knives?

AzHP said:

OK, now it's starting to make sense. just looking at a Takeda, it looks like the iron cladding goes almost all the way to the edge, which must be forged. that's pretty crazy and now i can kinda see why his knives are priced the way they are. is it the same with other kurouchi knives?

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that likely just means it will need some thinning behind the edge...

AzHP said:

it looks like the iron cladding goes almost all the way to the edge, which must be forged.

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And please believe me that that low, even line of exposed steel is not easy, either.
Kurouchi is different. You could make a kurouchi-like effect without forging.

Dan P. said:

And please believe me that that low, even line of exposed steel is not easy, either.
Kurouchi is different. You could make a kurouchi-like effect without forging.

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Oh really? I thought a true kurouchi was what happens when a smith leaves the black steel from forging without polishing it? Are the kurouchi-like effects made differently? Are they more likely to be rubbed off?