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View Full Version : Why are so many knives 'clad' (san-mai or others)



Matus
07-31-2013, 01:56 AM
I have a relatively simple question - what are the main drivers (from point of knife makers) to produce clad knives? I can indeed understand that lower-end market may prefer damascus-clad blades because they look nice (I am thinking of Shun knives here, for example), or - at the other end of the spectrum - stainless clad carbon core (easier care).

My understanding (in particular with stainless-clad knives) is that the cladding can not really be hardened and so at the end the knife may be easy to flex or even not too springy (= after even light flexing it stays flexed) - that is the case with the Shun knife I have (150mm Petty).

I also understand that - in particular with hand forged blades - it is far from easy to forge the clad blades.

However I do not quite understand stainless clad knives where the core is stainless as well (though I am about to get one :O ) - Why just not use the 'core' steel for the whole knife? Or are these steel so expensive?

I am just curios.

maxim
07-31-2013, 02:11 AM
To sharpen it easier and as you mentioned to be able to bend it back. Instead of braking it. If you harden whole knife with that steel it will be way to brittle. That is main reasons.

bkdc
07-31-2013, 09:11 AM
It's the cheap modern implementation of real damascus. In the old days, soft steel and hard steel were folded over many times to produce a blade with thousands of layers of hard layered with soft steel, and this resulted in a hard sharp knife which was also tough. As Maxim said, it prevents the blade from fracturing.

Chefdog
07-31-2013, 09:42 AM
Efficiency and economy, without sacrificing performance.

maxim
07-31-2013, 09:53 AM
hmm I will not say it like that, Japanese have never liked make mono steel knives or mono steel damascus. Even Tamahagene sword is laminated, Just other way around (soft steel inside and Hard outside)
As i been told it needed to be done to get that crisp edge without braking the blade. In many cases Swords was bend and they had to bend them back to repair them. It is much better that sword got bend then it was broken in the battle
Then they took that idea and transferred it to kitchen knife.

tk59
07-31-2013, 11:49 AM
The cladding is often chosen to make it easier to machine to a nice finish or for contrast since some hardened "stainless" steels will discolor somewhat.

mhlee
07-31-2013, 11:50 AM
It's the cheap modern implementation of real damascus. In the old days, soft steel and hard steel were folded over many times to produce a blade with thousands of layers of hard layered with soft steel, and this resulted in a hard sharp knife which was also tough. As Maxim said, it prevents the blade from fracturing.

Cheap implementation and prevents the blade from fracturing? These are two extremely incongruous statements.

Even if it's a cheap implementation, which these cheaper damascus clad knives can be, not everyone can afford real damascus. And isn't any process that's used to prevent a blade from fracturing worthwhile?

Whether it's done for aesthetic or practical purposes, if it's done for the benefit to the knife in terms of quality or price, and to the knifemaker (less loss), it's going to be worthwhile to someone. How about less opinion and more facts?

I'm not a knife maker so I'll write what I recall reading here. I may certainly be incorrect in my recollection.

But, from what I recall from what makers have written, "san mai" construction is done for a number of reasons, including these reasons. IIRC correctly, the use of softer steel for cladding also helps the harder core steel absorb shock when used and it's also done because some core steels are extremely difficult to put a good finish on. And, yes, from what I also recall reading here, some core steels are just really expensive.

maxim
07-31-2013, 12:14 PM
It is really not that expensive (the core steel)
Most expensive is labor and it take a lot of time to hand-forge steels together.
Pre-laminated steels is another story

Marko Tsourkan
07-31-2013, 12:30 PM
Efficiency and economy, without sacrificing performance.

+1

In the old days, good steel was expensive, so it had to be rationed and used only on the edge.

Nowadays, steel is relatively inexpensive, but san mai construction reduces cost of producing a knife by making polishing easier (soft cladding is easier to polish than hardened monosteel), and making it easier to straighten the blade. Factory made prelaminated blanks that many companies and makers use offer even more efficiency in production.

The drawback of a san mai is that it can be bent and cladding could be easily scratched if laminated with soft steel. Also, lamination often doesn't bode well with cryogenic treatment - an important step in heat treating process.

M

bkdc
07-31-2013, 02:36 PM
Cheap implementation and prevents the blade from fracturing?

The old samurai implementation would be to take two steels (one hard and one soft) and fold it over and over and over again until you're left with 2 to the nth power of layers of alternating hard and soft steel. This would result in a brittle steel and a soft steel in many microscopically thin layers. The soft steel would make the blade tougher. I don't think this is economic or in line with modern manufacturing. But it sure would be expensive. I stated that it is a cheap implementation of damascus. Damascus meaning to fold steel over and over.

James
07-31-2013, 02:47 PM
The old samurai implementation would be to take two steels (one hard and one soft) and fold it over and over and over again until you're left with 2 to the nth power of folds in steel. This would result in a brittle steel and a soft steel in many microscopically thin layers. I don't think this is economic or in line with modern manufacturing. But it sure would be expensive.

I think you're confusing this with damascus steel. AFAIK the soft and hard steels were not folded together, rather the soft steel would be encased in hard steel where it would serve as a flexible backbone the sword. According to wiki (yes yes, I know), blacksmiths would fold the soft steel to purify it. They would also separately fold two harder steels, tamahagane and nabe-gan, to make make the hagane (cutting edge) and kawagane (sides and and back).

Here's a nice diagram from wiki:

http://upload.wikimedia.org/wikipedia/commons/c/c4/Katana_brique.png

maxim
07-31-2013, 03:09 PM
Yeah +1
Tamahagene is folded only to remove impurities.

PS for the steel cost, i ordered ones in same steel hand-forged Laminated blade and mono steel knife from same make and forged Laminated was more expensive.
So steel price is definitely not the factor !


I think you're confusing this with damascus steel. AFAIK the soft and hard steels were not folded together, rather the soft steel would be encased in hard steel where it would serve as a flexible backbone the sword. According to wiki (yes yes, I know), blacksmiths would fold the soft steel to purify it. They would also separately fold two harder steels, tamahagane and nabe-gan, to make make the hagane (cutting edge) and kawagane (sides and and back).

Here's a nice diagram from wiki:

http://upload.wikimedia.org/wikipedia/commons/c/c4/Katana_brique.png

maxim
07-31-2013, 03:26 PM
You can also take as example Mizuno Wa Gyutos Blue 2 steel laminated is $340
And they Solid Pure Sweden Stainless is $280
In same sizes. In fact in Japan Sweden Stainless is more expensive steel then Blue 2. And much more steel was used there

WillC
07-31-2013, 04:37 PM
I do find it interesting that people consider that san mai must be some cost saving measure. San mai adds many more processes and complications to producing a blade in mono steel. These processes add cost which far exceeds to extra cost in materials to produce a blade in mono steel. Thats just the way it is today. San mai is a value added process. It adds interest and uniqueness to the piece. It has some benefits and downsides compared to mono. We have covered all that before.
When done well with correct balance on core and cladding, correct forge tapering of the blade and geometry, san mai is wonderful and artful done right. Each maker has there own way of doing things.
I have always loved making san mai. I made san mai before i made any mono blades. But im a forge freak like that:laugh:
Just from my point of view as I often make san mai and mono blades which are ground and finished back to back.
It is not quicker to grind or hand finish soft clad knives. It moves quicker but much higher care must be taken because of this. I have noticed no difference in speed to hand finishing clad or hard steel. Modern abrasives cut both. Today hand finishing hard 14c28n vs soft 304L stainless. The 14c28n took a polish easier. More care was needed with the soft material with pressure to avoid gauging.
On straightening. Ha ha this is a two headed monster. Yes it can be a little less stressful gheat treating san mai, as it can be straightened easily. Towards the tip though it will want to sit where the core wants to point. A warp towards the tip in san mai can be more of a pig to sort out than mono as you have more forces at work. Sometimes I feel I have to give san mai blades time to settle, as in a difficult warp clad and core can want to point in opposing forces. So its not as straight forward as all that. I suspect someone doing something one way, will always think someone doing it another has it easier, until they try for themselves.:D
Finally. If you have a floppy, warp prone blade in san mai. It is because the geometry of the blade and possibly the core balance is overly thin, ( Or designed that way for a reason) Soft steel gives as much stiffness as hard steel, up to the point it bends. It comes back to geometry designed for purpose. If you want a stiffer knife, you use a thicker stronger geometry. This can still of course be as thin as can be at tip and edge.

Those are my thoughts anyway, from direct practical experience.


Love the diagrams of different constructions btw, very interesting. I have seen some wonderful construction diagrams also for Saxon Swords and sea axe.
These constructions were never about saving money, they were about saving precious core material when it was more valuable than gold or anything else. Besides any structural advantages.

mhlee
07-31-2013, 04:47 PM
Thanks, Maxim. I stand corrected regarding cost.

bikehunter
07-31-2013, 04:52 PM
Thx, WillC. Doesn't seem as simple as some folks make it sound.

maxim
07-31-2013, 05:02 PM
Spot on Will :D :surrendar:

Bit of topic but in old days as cladding for knives and tools they used Watetsu and Rentetsu from UK, they are the softest cladding out there softer then normal iron. But it was super difficult to polish more then any hard steels. Because of scratching and digging you could not use any power tools on it. But it was super popular because for carpenters it was sooo fast to sharpen and swarf helped the process. Now good old quality Watetsu cost more then new Tamahagene

Matus
08-01-2013, 02:34 AM
Thank you all very much for your answers. Very interesting and informative. I have definitely learned something here :)

ChiliPepper
08-01-2013, 06:44 AM
Yeah, understood prob just half of it but enlightening and interesting nonetheless. As usual, when you scrape the surface a whole new dimension appears...

panda
08-01-2013, 01:00 PM
what knives use watetsu and rentetsu cladding?

maxim
08-01-2013, 01:12 PM
Mostly tools, Kiridashi knives etc. Now there is nothing, its to expensive. And will be most likely used on swords