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Sorry if I'm sure this has been discussed here a myriad of times but with all my research I still can't find any answers to my questions. I've seen and read about Smith's in third world contries repurpose steel to make knives, tools etc. But you never hear about their products that they have made failing. On this and every other forum you are told to steer clear of repurposeing steel such as leaf and coil springs because of spring fatigue introducing micro fractures resulting in future failures of your products. What I'd like to know is if anybody has repurposed steel and actually had a failure? Was the failure pre existing or because of something the Smith caused? And if this is just an old wives tale we tell because this is what we where taught?

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I've heard about them failing, though generally the remains are still used for different purposes. Also such blades tend to be on the soft side compared to the ones the Hunters I know prefer---they use a diamond hone to touch up the edges!

I have had a number of blades made from worn springs fail---generally the crack(s) show up at heat treat though sometimes it's in final polish---ouch!

It can be very hard to differentiate who caused the issue, sometimes you can see oxidation in the broken section that indicates it was a pre-existing crack. Sometimes evidence of overheating---like large grains and burnt looking steel indicates that the smith goofed.

I steer people towards lightly used springs---ones changed out at Lift and Lower shops on new cars for instance or drops from spring repair places that make their own.  I warn students about possible issues and have seen them crop up with their work, (though students trying to exceed their skill level can often put cracks in brand new material through overheating and contact quenching!)

^^^^^^^^^^^^^^^^^^^^^^^^^^^My Experience over the last 37 years smithing.^^^^^^^^^^^^^^^^^^^^^^

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For practice anything will work. You guess at the steel, you guess at the heat treating, you guess at most everything. Failures are expected.

For producing a working product you must ask yourself, what is my time worth? What is the cost of new known steel with a known heat treating method? Which is more valuable?

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The issue isn't as simple as repurposing old material, it's the risk/cost ratio.  When labor is only valued in pennies and good material is relatively costly (compared to income and potential sale price of the product) the risks of problems or deficient final product are nil. However, for most of the "western world" (used loosely), time is valuable and proper material is relatively cheap.  Why risk an inferior product to save 5 bucks in material when you are putting hours of labor and $$$ of fuel in?

That's not saying to simply never used "found" material, it's just the risk/reward ratio should be weighed based on YOUR situation and expected final results.  Doing things on the cheap is sometimes more costly in real terms than doing them right to begin with.  Plus if the product itself is meant to be sold, good business practice is the ability to stand behind your work--can you do that with mystery metal on something like a quality knife?  

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From my experience you can certainly use re purposed steel and have some decent results. The knife I've carried with me for years is one that I made from an old circular saw blade and I've never had any problems with it (medium usage). That being said I would have to agree with what has been said already: such metals are significantly harder to work with for a myriad of reasons. Steel, especially high carbon steel placed under repeated shock, has a tendency to develop micro-fractures which are invisible to the eye but will show up more as the steel is worked. This type of metal is also often corroded, bringing with it more difficulty in working, not to mention that there is no guarantee of the makeup of the metal, making precise heat treating very difficult. Feel free to make knives from that kind of metal if you want, but I will almost always choose new metal over that.

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My thinking is to use the scrap stuff when first starting out.  Make some knives and things to use around the house.  Test them all out and write down what you figure out.  A coil spring is a lot of steel so heating a test piece and quenching it will tell you a lot about it - write it down and label that coil spring.  I have huge, long and old truck leaf springs that were given to me.  There's a ton of steel there.  If I do a test piece and record what works and what doesn't I'll have that info.  

If you have money falling out of your pockets, don't mess with the scrap.  You might as well buy steel from a local supplier.  If you plan on making knives to sell to others as a business, you also want new steel.  It saves a lot of time to pull new 5160 out of your stock shelves than to mess around testing a piece you got out of a scrap yard.  For those like me that don't have the money to invest in new steel, I use the scrap but I'm also not running a business selling knives or edged anything to customers.  

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On 11/30/2018 at 5:17 PM, MC Hammer said:

My thinking is to use the scrap stuff when first starting out.  Make some knives and things to use around the house.  Test them all out and write down what you figure out.

This is a good point. If you haven't made a knife before, there's not much sense paying for steel for a knife that may very well not turn out.

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I used to go to a spring shop and buy their brand new drops for US$1 a pound.  New steel, known alloy. Almost as cheap as buying scrap.

However; not being near a spring shop anymore, I now generally suggest a newish coil spring and cutting it along a diameter making around 20 "(" pieces that a starting bladesmith can experiment with, all the same steel; so they can learn the forging ranges and what the best heat treat is for that steel.

(For my own knives it's generally pattern welding, often scrapmascus or some weird historical steel experiments).

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Blister steel, crucible steel, real wrought iron, blooms,  a mix of all of the above?  Also steel 100 to 200 years old; jolly good fun!

Memo I'm overdo to forge a knife for my SiL out of a piece of 1828 anvil face  (William Foster date stamped, missing 80-90% of the face.  Bought the anvil to remove the last little bit of the face and try an oldschool refacing.)  Fur trade knife out of correct steel.

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On 11/30/2018 at 4:58 PM, FlatLiner said:

I've seen and read about Smith's in third world contries repurpose steel to make knives, tools etc. But you never hear about their products that they have made failing.

That's not because they don't fail; it's because we don't hear about it.

On 11/30/2018 at 4:58 PM, FlatLiner said:

What I'd like to know is if anybody has repurposed steel and actually had a failure? Was the failure pre existing or because of something the Smith caused?

One of my first knives was made from an old hayrake tine; it snapped in the heat treatment.

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On 11/30/2018 at 2:58 PM, FlatLiner said:

Was the failure pre existing or because of something the Smith caused?

I believe it's always best to assume "operator error" than to blame it on preexisting conditions. Especially when just starting out. 

More often than not forging coil/leaf spring when it's a bit too cold, or heating it too much is the problem.  

 

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(or letting it contact quench)  Last Saturday I had to go into the classroom and ask who had left their High C workpieces sitting on a cold surface after coming out of the forge at the end of the class.

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I made a knife from a short leaf spring I had found on the roadside.  I cheated and cut the shape out with a torch much to astonishment of blacksmith friend of mine who said I had just ruined the steel.  I did grind it back a bit from the rough shape cut out and then forged both a distal taper, full tang taper and the proper wedge shape to the edge.  I don't recall any particulars in my heat treating of it but I guess I nailed it.  I use the knife daily in my kitchen and am amazed at how well it holds an edge.  Every month or so I give it a few swipes on the steel and it just keeps on slicing and dicing.  Sure there is a risk of using mystery metal but sometimes it works out just fine.

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Cutting with  torch just messes up the HAZ, grinding back to "good" steel negates that issue. I guess some folks only hold onto the basic warning.  When I tell students to cut a coil spring along a diameter I tell them they can cut with a torch with an angle grinder cutting disk or hot cut it in the forge, (easier with a solid fuel forge for heat and with a long chisel...)

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Doesn't hot cutting in the forge scatter the fuel everywhere?

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I'd give $100 to anyone that could hot cut in a forge haha. In seriousness though, this works very well and saves a lot of time compared to simple shaping the metal by hammer. Once my coal forge gets up to a full heat its pretty much just as fast as cutting with a grinder. You can pick up a sufficiently wide chisel at harbor freight for just a few bucks that should work just fine, its what i used for years before finally making a cutoff hardy tool.

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PatrickN; your employer has forges that other forges would fit inside; any of them going cold for Christmas?  $100....

(Tongs there have 4 wheel drive and engines!)

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It seems that I don't think outside of the box enough, that certainly would be a viable option. As I am a man of my word and don't think that anything should ever be said idly, there's $100 up for grabs to anyone that wants to send me a video of this happening, and it would be $100 well spent in my opinion. Blacksmith inception.

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Nelson R,

I've cut several pieces right in the forge though my cohorts claim I just burned the pieces in half by getting distracted.  But the shower of sparks when I pulled the pieces out were an announcement of "another unintended successful cut". And no, no YouTube film clips exist, (thankfully). 

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In my experience this is more an academic question than practical. Not that that's a bad thing and if you're really interested in developing some kind of statistical study I think I'd start on the blade fora. The problem is most of the data is anectodal so results would be gray zone results. 

If a person is using salvaged spring and is worried about fractures fold and weld it a couple times. Micro fractures gone, old memory, bye bye.

I recommend coil spring for blades as it's much easier for beginners to forge AND control the shape. Leaf is problematical controlling, especially for new folk.

The TAZ, Torch affect zone is mostly at the seriously chemically affected zone of the oxy jet's path. It gets pretty strange, the oxy want's to make relatively pure iron while the C2H2 acetylene wants to make high carbon WITH hydrogen embrittlement issues, steel.  In my fab school days we were told to grind it back past the torch marks by 1/2" to be sure. We were assured this was over kill but the common consensus of what was right.

You don't need anything fancy to cut a spring, it's heat treated to be springy, NOT hard. A hack saw works just fine and fits almost anywhere. A saber saw with as coarse a blade as you can find works fine on leaf but wire brush the sand, dirt, etc. off it the grit dulls saw blades quickly. Don't hog the feed and you'll be surprised how easily it cuts. BEFORE  you take a torch to it of course!

New steel is so much cheaper than salvaging it and you KNOW what you have, you can even ask the supplier for the batch number. (mill run)

I'm of mixed minds where new comers are concerned, inexpensive or predictably consistent material. On one hand it's cheap and you don't have to sweat destroying products. Or spend money and work with steel that will be the same every time so you don't have to evaluate and adjust technique every single time. 

A criterium I consider is how demanding the product is. If we're talking wall hooks or weeding forks then how predictable and consistent the steel isn't so important. However were we talking using blades or say a steel prod for a cross bow then being able to predict exactly (for values of exact) it will perform and how to achieve that IS important.

That's my take.

Frosty The Lucky.

 

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I've used exclusively scrap materials to forge things out of and it can be a little frustrating when you have something that's higher carbon than you realized, but I've had nothing but success with the scrap stuff.  I've used purchased mild steel and love it, but you can't beat scrap prices.  I just made my first knife from a coil spring and I was happy with how it turned out.  The quench went well and the tempering was easy enough in the kitchen oven.  I made a couple of punches from the coil spring as well that turned out great.  I tempered them with the residual heat left in the punch.  I do normalize the coil springs cuts 3 times before starting to work on it though.  That was recommended to me to relieve any built up stresses that may be in there due to being a spring on a car or truck or whatever.  I also always cut sections out of them and never try to straighten out a large coil spring.  I think you can put micro stresses and cracks in it trying to unroll it.  I think this happens when the spring starts to cool off and you are ranking on it not realizing it's probably too cool to take that stress.  Taking an angle grinder and cutting out a small piece is way easier. 

I think if you are a knifemaker you almost have to buy your steel or if you are a full time blacksmith you'll want to buy most of your steel as well.  Neither of those types have the time to wander a scrap yard when they have orders waiting to be filled.  If you are a hobby smith, I say go for the scrap and have fun with minimal amount invested.   

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I won't go that far; but if you are a bladesmith you have to tell the customer that the alloy is unknown.  You can tell them it's OCS (old Chevy spring) or a leafspring off a truck but you CAN'T say it's 5160 without formal testing of it.   Scrapmascus a term I first heard used by Billy Merritt, can be used for patternwelding. of scrap metal.

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