Who knows what about 416 ss 1095 san-mai ala Bert Foster?

OK - then why do you prefer it over 420?
What have been your bad experiences with 420 that makes you prefer 416?

Leethal Cutlery said:
I've never had problems with 416 either. In fact I prefer it over 420. Not knocking anyone else, it's just personal preference. Also not saying I won't have any problems in the future :) but as of now its been good to me.
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This is why I use 420, in addition to 4-5 years of many failures and successes with all types of San Mai.

416:

Grade 416 has the highest machinability (we do not - in fact - want our steels to come apart easily!) of any stainless steel, at about 85% of that of a free-machining carbon steel. As for most other free-machining stainless steels the improvement in machinability is achieved by addition of sulphur which forms manganese sulphide inclusions (which causes hot-shorting, or where the grain boundaries easily tear apart); this sulphur addition also lowers the corrosion resistance, (which is one of the reasons we make San Mai blades!) weldability (welding - right? The ability to WELD to other materials!) and formability (forging) to below that of its non-free machining equivalent Grade 410.



420:

Grade 420 stainless steel is a higher carbon version of 410 (see above) ; like most non-stainless steels it can be hardened by heat treatment. It contains a minimum of 12 per cent chromium, just sufficient to give corrosion resistance properties. It has good ductility in the annealed condition but is capable of being hardened up to Rockwell Hardness 50HRC, the highest hardness of the 12 per cent chromium grades. Its best corrosion resistance is achieved when the metal is hardened and surface ground or polished.
 
One of the problems (well, the only problem, so far) I have with 416 is the softness. I just don't like the idea of two thirds of the blade being dead soft, which is why I don't use it for hard use knives like choppers. Just too "wet noodle-ish" for me. Since 420 hardens somewhat, I'll have to try it and see if I like it.
 
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We won't be able to harden 420 - or 416 for that matter - in our processes as you'd need to austenize it at around 1800 F*, which is too hot for our simple C. tool steels.
In truth, it will act more like clay does in creating hamons.
Which is another reason I use 1095, despite the fact that its manganese creates a darker etch than W1 or W2. I use 1095 because it's a deeper hardening steel than the W series steels, so I like to think that I am at least getting some hardness up above the bottom line of the jacket. But this doesn't always happen, because I frequently get some hamon right along the edge of the jacket, because, like I said, it acts like clay.
And, that hamon dancing along the edge of the jacket looks pretty cool!
But you won't get any of the SSs we use hard in our San Mai.
That actually sort of defeats the making of San Mai in the first place.
There are a lot of guys making San Mai with wrought iron, which is DEAD SOFT!!
But, that's the purpose of San Mai. ;)
 
Never said I had bad experiences with 420. 416 is just what I started with when I began forge welding stainless/carbon and have never had a problem with it so I stick with it. Like I said I'm not saying I never will, but I haven't yet and will continue to use it as long as it works.
 
Karl B. Andersen said:
We won't be able to harden 420 - or 416 for that matter - in our processes as you'd need to austenize it at around 1800 F*, which is too hot for our simple C. tool steels.
In truth, it will act more like clay does in creating hamons.
Which is another reason I use 1095, despite the fact that its manganese creates a darker etch than W1 or W2. I use 1095 because it's a deeper hardening steel than the W series steels, so I like to think that I am at least getting some hardness up above the bottom line of the jacket. But this doesn't always happen, because I frequently get some hamon right along the edge of the jacket, because, like I said, it acts like clay.
And, that hamon dancing along the edge of the jacket looks pretty cool!
But you won't get any of the SSs we use hard in our San Mai.
That actually sort of defeats the making of San Mai in the first place.
There are a lot of guys making San Mai with wrought iron, which is DEAD SOFT!!
But, that's the purpose of San Mai. ;)
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I agree. I've noticed on several of mine, even the one pictured earlier that they get the line of activity along the edge. Can't say it has any benefits or not but it sure looks cool. I get it really active when I add a layer of 15n20 in between the stainless/carbon

I also know that the Japanese use wrought iron cladding in their San Mai to toughen up the super hard steel core used in their San Mai. I've read Shosui Takeda say it helps his camp knives remain tough and durable even though they have a Rockwell of 63/64 core
 
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Not sure what you mean by "line of activity", but what I refer to is actual hamon in the exposed core steel.
That is no doubt influenced by the jacket of stainless, that would react not unlike clay. Or at least influence the natural hamon of a semi-shallow steel like 1095.
The distinct LINE of activity that follows the stainless jacket is where the carbon deficient stainless jacket has "sucked" a bunch of the carbon out of the carbon rich tool steel.

And I agree - 416 is what I used, too, when I started. Mostly because it was available.
Then I just ended up with a lot more experience, connected some dots, and refused to continue to roll the dice on each knife.
 
I thought about it a bit, Phillip, after I made that post, and you might be right.
420 MIGHT be a bit tougher on the skin of the blade than 416.
I do know, even in the annealed state, and probably because of the far reduced amount of sulphur, 420 is a bear to run through a band saw sometimes.
And that's another reason to not use 416.
Then again, I've seen guys use 303 and 304.
So whatever works.
I use the martensitic stainless because I surface grind the mating surfaces of the billet and 420 is magnetic for the chuck.
 
That's what I'm referring to as well. I say line of activity because most of mine look like the whispy ashi on really active hamons.
 
Like this
FB2B15D7-F17B-4B65-B7EA-1F7FE7BA61E4-6766-0000058921CD1652_zps0a22228e.jpg
 
WD-40 method? can you link me to where this method is discussed? Your nonchalant reference leads me to believe this is something that has been well covered and I am just oblivious to it...
 
Djinn said:
WD-40 method? can you link me to where this method is discussed? Your nonchalant reference leads me to believe this is something that has been well covered and I am just oblivious to it...
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I dont have any links but When welding stainless to carbon, oxygen is the enemy. There are several ways to prevent oxygen from getting to the surfaces to be welded. Some guys make a can around the billet to seal it when forge welding, others weld the seams of the billet up tight to prevent oxygen from getting to the surfaces to be welded.

The wd-40 method involves welding all the seams of the billet up except one. Then you spray wd/40 into the open seam filling the gaps of the billet up. Then you weld that last seam up. Then get your weld on. I've heard of guys using kerosene for this as well. Basically when you put the billet in the forge and bring it up to temp. the wd-40 ignites burning what oxygen might be trapped in the billet up so there is no chance of oxidation. I'm sure someone can and will explain it in better depth but that's the basis of it and its how I weld stainless to carbon in my shop. It's just one of many ways you can do it.
 
Wow, you guys have answered a ton of questions on this, been wanting to try it for awhile now. Great topic and thanks
 
I just want to clarify... I wasn't saying you needed PID control. I was just stating what I observed to be his setup in his shop.
And to mirror the above, thanks for the answers supplied in this thread.
 
I should add that you want to spray the wd40 in after you have let the billet cool from welding the other seams up.

Thanks Guys. Glad to answer any and all questions I'm capable of. :)
 
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