forging leaf spring steel

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Bo T

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Feb 12, 2011
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There seems to be a lot of interest in making knives from reclaimed steel (repurposing). One reason that is given for NOT using steel from old springs is because over time they will begin to fatigue and develop minute stress fractures. If the steel is heated up to welding temperatures for the first couple of heats while drawing out the steel, will these stress fractures 'weld out'?
 
I brought this up once before and was told that once the cracks start, oxidization starts and will cause issues when forge welding, ie; you would get gaps due to rust left in the cracks.
 
That would be my guess, not to mention you'll loose some of the advantages of forging by overheating like that even though you can normalize and help the grain out. Best 5160 I've used is John Deere load shafts, though I don't know where you'd get them now, I got some a few years ago from a member who bought a bunch of drops from a place that made them.

I do use old coil and leaf springs for projects, but for knives I prefer a known alloy. It's cheaper in the long run.
 
Bo T said:
There seems to be a lot of interest in making knives from reclaimed steel (repurposing). One reason that is given for NOT using steel from old springs is because over time they will begin to fatigue and develop minute stress fractures. If the steel is heated up to welding temperatures for the first couple of heats while drawing out the steel, will these stress fractures 'weld out'?
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With proper care and experience it is possible to forge weld out any fractures and normalize the steel into very usable stock.
Don't ask me how I know this, as i'm far from experienced in forging, but the company I choose to involve myself with has made a decent living and reputation out of using reclaimed 5160 steel for almost 30 years now.
 
Karda said:
With proper care and experience it is possible to forge weld out any fractures and normalize the steel into very usable stock.
Don't ask me how I know this, as i'm far from experienced in forging, but the company I choose to involve myself with has made a decent living and reputation out of using reclaimed 5160 steel for almost 30 years now.
Click to expand...

But, usable for what?
 
A short and simple answer is that the micro-cracks are along grain boundaries. Once these separate, it takes an enormous amount of heat and energy to restore the separations. This requires nearly re-melting the steel. If the cracks are large enough, and oxidation has formed along them, there is very little chance of repair.

All this can be in the steel and not be visible to the eye.
 
LRB said:
But, usable for what?
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bladsmth said:
A short and simple answer is that the micro-cracks are along grain boundaries. Once these separate, it takes an enormous amount of heat and energy to restore the separations. This requires nearly re-melting the steel. If the cracks are large enough, and oxidation has formed along them, there is very little chance of repair.

All this can be in the steel and not be visible to the eye.
Click to expand...

Maybe so Stacy, All I know is that it makes a mighty fine khukuri. In 30 yrs of business, failures have been very negligible compared to volume sold and each and every failure was under warranty. Primary stock for these are reclaimed 5160 leaf springs. No new steel is used.
 
Don't get me wrong....I am sure that they can be forged into knives that won't fall apart, especially in kukri thicknesses.....and even more especially with some skill and practice ( 30 years in your case).

What I was explaining is the metallurgical reasoning behind the caveat about making knives from them.
 
I understand what you wuz sayin'
And I know it's straight shooting.
Are there better steels with less work and worry? Sure.

I just hate hearing that you can't and you shouldn't.... Because if you have the skill and knowledge, you can and you should.
Part of the blessing of blades made from reclaimed steel is that it used to be someones junk and is now in my hands as a heirloom quality handmade chopper or slicer. To me that make them all the sweeter.
 
If people want a knife without a story, they can go to WalMart.
The folks I talk to when I put my knives out in public want a knife with a story- either "How I made it out of the best ingredients, with the best modern techniques, to be the very best knife anywhere" or "This used to be a (leaf spring, file, saw blade) and now it's a knife."
I'm here to learn all I can about the RIGHT way to do things, and at the same time there's something about being able to make a tool out of steel that used to be something else that's really compelling, to me and lots of other folks.

Edit: I'm looking at the first slipjoint I ever made, sitting here on my computer desk...carried it every day and used it hard, then a couple days ago I was slicing some cooked ribs, of all things, and the backspring broke. Kind of heartbreaking in a way, but there you go: it was made from old lumbermill bandsaw blade and chances are, had a stress crack hidden in there like a time bomb. Sigh...
 
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I take pride in my high performance knives so I want to get my steel from a source that also takes pride in the quality of their product. There is no doubt that reclaimed steel can make a great blade. I make myself knives and tools from scrap metal, often. I have experienced stress crack issues in old leaf springs and it was very disheartening. That is just my opinion.
 
I suppose I really should qualify my statements made here.

Using reclaimed steel is an art unto itself.
Using reclaimed steel requires knowledge in virtually all aspects of knifemaking. Sometimes in minute detail. From metallurgical knowledge, so that you know what youre working with, to metalworking knowledge, so that you can make something of the steel.
You really need to know what you are doing and looking at. Especially in the forging and heat treating processes.
In no real way is using reclaimed steel a good way to start out as a novice knifemaker. It can cause more bad habits and confusion than it saves you money in the end. Better to work with known material and processes until you know what you are doing.
 
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I agree with everything that has been said here so far. From my own experience, having the scrap steel just sitting there allowed me to pick it up on a whim and start playing with it. I don't use that steel anymore. I went to sharpen my mother in law's knife for her, and it didn't harden properly. I have to make her a new one. One of the kitchen knives I made seems to be Rc 55 or 54 based on other known knife hardnesses. It was useful to get me going, but guessing if the metal is 1050, 1060, or 1070 isn't worth the hassle anymore. I would need a Rockwell tester to verify hardness before tempering, and that is the price of a lot of known steel. I just bought 36" of 1/4"x3" 1095, 36" of 1/4"x3" 5260, and some smaller 1095 for $120.00 shipped to my door.
 
Oops- small correction.
Looking at that folder with the broken spring, turns out it was new 440c, but back then I didn't have a tempering oven that could go to 1150 (spring temper for 440c). It was way too hard.
The 3 folders made with sawmill blade are going strong, no issues. Lucky, I guess.
What I've learned is that making folders takes enough time and energy that it's worth it to do it "right." Heck, the same could be said for making any really finished knife, but folders in particular I don't want any kind of failures.
 
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