Forging by Kamis

M

munk

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Mar 22, 2002
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Spiraltwista recently posted that the temperature of the forging in Nepal was insufficient to fix a crack in leaf spring. Is this true? I thought watching color changes and pounding steel was a universal, and would/could restore metal.
I'm very naive and would appreciate some expert opinion.

thanks,
munk
 
For instance; If I took a leaf spring, and gradually by heating and pounding turned it into a rod, a crack would still be there?

munk
 
Hi Munk,
I'm far from expert, and you can take this with a grain of salt, as I've never forged a knife.
Forging heat for 5160 would be a red color.
Welding heat would be much hotter, a yellow color. You would also have to use a flux. Borax is the most common. The flux removes the scale that forms during heating, so you can forge weld the yellow-hot metal together.

So yes, I think what Spiral said is true.

Let's hear from some bladesmiths.

Steve
 
Interesting. What's a crack? Would fine filament, micro cracks be molded into the metal?

Later this month I'll get the forge going. So if I took a leaf spring on it's edge, crack or no, and pounded it into a round, any crack would still be there?

If this is true, perhaps HI should consider another metal source. On the other hand, despite recent examples of problems, I have to wonder if the still low failure rate is worth messing around with?

Would Rail be a good alternative?
If steel sheet were purchased- is there any thing that will not fail? Will the failure rate be the same?


munk
 
How do you get a half inch spine from leaf spring without pushing metal around? Cracks survive that?
Spiral suggested discarding material with visible cracks, which is right.
I'm calling my old man- he's a QA engineer.

Old Man say, product in should be consistant. He's not sure if one got sheet steel from India one month, if it would be the same the next. I think he was surprised the Kamis have been dealing with different sources of leaf spring with such a low failure rate.

munk
 
Munk, this is something I experimented with a while back to satisfy my own curiousity. I purposely introduced stress risers in a blade I was forging to produce a crack. I then proceeded to try and forge the crack out of it. No dice. Normal forging temps won't do it, that's why forge welding temps have to be much higher, in many cases approaching the metal's melting point.

Spiral's observation was spot on. If you forge a piece of steel with a crack in it into a blade, you're going to have a nicely forged blade with a crack in it. No matter how much you "move the metal around" the crack will still be in there somewhere.

If you are aware of the crack, have some flux, and are able to get the steel hot enough, I imagine the crack can be repaired, but bottom line, forging a hunk of carbon steel at normal forging temps ain't going to do anything about a pre-existing crack in the material.

Sarge
 
I see I dont have to add anything Munk.

Steve & Sarge have explained it well.

As Ive just got back from 2 hours yoga thats cool with me....

Spiral
 
You know, it's funny. I do my best thinking while asleep. I took an hour long nap just now, got up, and thought: if there's a crack there, and you move metal on both sides of the crack, you'll just have a covererd up crack.

This thread was not intended to be a referendum on Spiral's view, but a learning tool, at least for me.

I guess the next questions, already thought of during some of our 'failure' threads, would be:
Is the incidence of flaw increasing in HI or is this a normal statistical wave?
I think Bill used say he'd get one or two failures in 1000 blades, but I might me be misremembering. If we got 1 flaw in 200, is that acceptable?

Would there really be less flaws if the Kamis used sheet steel? Would the sheet steel be the same every time purchased? Would the hard use HI tools are put through put a additional strain on sheet steel? Who's sheet steel?

I don't know how the Kamis can take leaf spring, from all the different sources, in all kinds of conditions, and come up with a product as fine, long lasting and comparatively flaw free as they do.

Would rail steel be 'better' than leaf spring? I'm guessing no.

Thank you for weighing in, Silvrfalcon.


munk
 
Darn, Spiral. I wish I knew a little Yoga.

I need some relaxing hobbies.

Oh, here's a question: OK, you start to forge a blade. Is a hidden crack more likely to be revealed as you're heating and pounding, or is it more likely to become hidden?

I don't think we can chip in and buy the Kamis a magnuflux....



munk
 
I think the answear is in your last questians Munk.

That is There are so many varibles involved who can say, without comparing 1000 kukris made of old springs. {which were once bar stock.] & raw barstock or railtrack etc. of unkwown history..

But I would say the correct high quality barstock must be good. It what they make new lorry springs out of.

IncedentlyI am under the impresion {unresearched.} the Indian steel industry & just bought out & now owns the English steel industry as well, for about £9 billion or sumsuch.

Spiral
 
I would say forging will hide micro cracks.

Buffing definatly hides them.

As for tests tricky in a smoky dusty shadowy forge room in Nepal perhaps.

But I dont know.

Yogas good Munk, for body & mind, {& some say soul.}snt there a local teacher or class near you?

spiral
 
Reminds me the USA does not own Browning or Winchester anymore.

I did have a reason for writing this thread. If some data was useful, I wanted Yangdu to know it too.

munk
 
Yoga? One of my best friend's a three level Black belt who meditates and does Yogo. He's a hundred miles away and a little busy. He used to want to open a dojo. (I used to call it, "Dojo of the Lost Womb," which I thought was funny for some reason.)

There seem to be a lot of voices urging me to take up meditation.
There must be a reason.


>

Would you find cracks with a rock or file? Or just bend the spring?


munk
 
For what it's worth, I have an 18" AK by, I think, Shanker. I noticed a black inclusion or fold of some sort on the side of the blade. I asked Bill about it, and even posted on something about it in the HI forum at the time. The general agreement was that they were artifacts of the forging process, and were only cosmetic. I figured mine was mostly cosmetic as well, but, alas, it turned out to be structural as well. The chunk of missing blade is right where the inclusion was. I used to have the chunk of oak in which the blade chunk was lodged, but I think it might have gotten tossed in the woodstove by accident.

This discussion though suggests to me that the flaw existed in the original stock, and was just incorporated into the tragically beautiful blade.



akbladefailure01lo4.jpg



akbladefailure02vq0.jpg
 
Interesting question and I just sent a reply on the HI forum about blade failure. You might be able to forge weld a crack back together, but it takes extreme heat, and lots of flux, This is especially true of forge welding 2 pieces of high carbon steel together. High and low carbon can be forged welded together much easier, like in old time tomahawks where a high carbon bit is wleded into a mild steel hawk. Forge welding is the process by which damascus is made, and it makes a fine balde, but there is always the chance of occlusions when you are finished (I have had it happen to me before). I dont think welding a crack would work either as it would probably ruin the temper. In my limited baldesmithing experience if you see a crack in a blade you cant trust it not to break.
 
I can't add much to this conversation, but as far as rail steel goes, isn't it a lower carbon steel? I remember seeing some rail spike knives online and one of the smiths making them said that they didn't hold an edge as well bc they were only about .3% carbon (as opposed to 5160, which is .6%, right?). Does anyone know if the actual tracks are closer to a 1060/5160 type steel than the spikes?
 
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