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Jack Wheet

Hardest Steel I've Ever Worked

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On 1/14/2019 at 1:45 AM, Gerhard said:

After Saturday's fun I might have to retract what I said.....

I have several orders for cleavers but no suitable material to make them from, best option 8mm thick leaf spring from a Toyota Land Cruiser.

I started on a piece at the end of a previous forging session, struggled a bit and just assumed I was tired.....

Saturday a friend dropped by and we took turns holding and striking, and it was not easy.....

I've forged some of that very same leaf spring before without much hassle, but I realised it was always narrower pieces I'd cut out, never the full width spring........?

So, what would you suggest for my situation, cutting the piece narrower and/or grinding it thinner?

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On 1/14/2019 at 12:26 PM, Joshua States said:

I have had metal cutting abrasive wheels not cut through HC steel before and it was usually caused by the edge of the wheel glazing over during long cut times. The edge can be cleaned with a grinding stone conditioner or by running the saw full-out and bouncing it on the work piece lightly (the second option is kind of dangerous). It will resume cutting again.

When forging HC steels and you anticipate not completing the forging in a single session, you should normalize before you store it. Bring the steel up to past critical temp and let air cool until all color disappears when held in shadow or the dark (typically this is about 800* F) and then you can quench to remove the residual heat. Water quench is fine for this regardless of what was said above. It will cause no effective hardening. 

In your post, you said this was the hardest steel you have ever forged, but I see from your previous posts that you have only been forging for a short time, so the comparison is vague at best. Without knowing a lot of the details about what the steel really is, what heat you are forging at, what equipment you are using, and what the quechant and quench temps were, it's very difficult to pin down what is happening. Leaf springs are notoriously varied unless they are more than say 20 years old. In which case they are not ideal because they probably are so damaged that they will form more cracks than you could work around.

Yes, it's true I have nowhere near the forging experience of most other members here, and mainly have just worked with mild steel. However, I have a feeling that the pitiful experience and lack of progress I made with this steel means that the statement " hardest steel I've ever forged" will remain true for quite some time. If it would help, I can give as much information as I am able to provide those needed details. 

Also (and this will truly showcase my naivety), isn't any steel from leaf springs HC, meaning that it would make at least an acceptable blade, regardless of the specific grade? I would much rather buy and use a better, non-mystery material, but don't really have the means to do so atm, and the spring steel was me trying to make-do.

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In general, yes, leaf springs make decent blade steel.  It helps if you mnow exactly what alloy it is, but the basic 5160 treatment works for 99% of them, maybe not optimally, but functionally.  I find the difference in hardness at heat between 5160 and A36 mild to be about 4:1.  That is, the 5160 takes me four times as long to get the desired shape compared to mild.  And I have been doing this for 20 years.  

See if you can organize a couple of strikers with sledge hammers.  Assign everyone a number.  You are the lead smith, or #1.  Arrange the signal to stop before you get going, because once you get into the rythm it's easy to keep going.  The usual signal is you taking the last blow by just dragging your hammer off the steel.  Yell "STOP!" at the same time, of course.  Be warned if your strikers get out of synch it can get dangerous fast.  There have been broken noses, lost teeth, and concussions from hammerhead ricochets.

And whatever you do, don't say "when I nod my head you hit it." (Old blacksmith joke, sorry)

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If leaf springs are what you can work with right now, then that's what you use. I am not against using mystery steels at all. Your experience forging mild steel is going to give you a lot of good practical knowledge on the basic techniques, so that's a good thing. The things that you probably are up against with the leaf that differ from the mild are both the thickness and the heat required to forge efficiently. Your spring steel is going to require a higher heat than the mild just in general. The thickness of the material will raise the required temperature significantly. Something to look for and learn to recognize, is when the bar is heated all the way through before you start forging. If you have a thick piece of steel and do not heat it all the way, it will fight you tooth and nail at the anvil. The piece should be uniform in color (you aren't color blind by any chance are you?) with no shadowy section in the center. If the center of the face is darker, do not start forging. Wait until the shadows disappear.

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21 hours ago, Alan Longmire said:

I suspect it's just a thick piece and more than you can currently deal with.  That is not a put-down, it happens to us all when we start out.  You should have seen the first time I tried to hand forge a 1.5" sway bar, about two months after I began forging.  Barely dented it.  A few years later I stuck it under a power hammer and it squooshed just fine.  Once I had it down to around 3/8" thick it worked just like any leaf spring I've used, i.e. tougher than snot, but manageable.  

This.  

17 hours ago, Alan Longmire said:

I find the difference in hardness at heat between 5160 and A36 mild to be about 4:1.  That is, the 5160 takes me four times as long to get the desired shape compared to mild.  

And this.  

My first time forging 1" diameter W1 was a surprisingly humbling experience.  

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22 hours ago, Jack Wheet said:

So, what would you suggest for my situation, cutting the piece narrower and/or grinding it thinner?

I would suggest getting somebody to hold it for you the beat the snot out of it with a cross peen hammer and flatten/fix up.

I made Kukris from the very same Land Cruiser leaf spring, a 40cm length gave me two blades in yin-yang fashion. That half-width leaf spring was easy to work, the belly was mostly grinding.
 

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This is a phone pic of leaf spring at my working temp. The next one is where I stop pounding on it. I’ll do some tapping at this temp but not pounding. I am no expert by anymeans. This is knowledge given me and a little of my own learning experiences. The steel looks hotter in the second pic but with the naked eye it isn’t glowing. 2lb hammer by the way.

Jon

edit: pics are reversed

F1717163-FB17-447D-9B57-269D1D1999FB.jpeg

4A1E6AF1-B22D-44C1-8EA5-19456792001E.jpeg

Edited by Jon Bishop
Pics

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