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From bad to worse, advice on cracks?


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I am trying to make my son a knife for his birthday. It was two day ago so I am already late but he is understanding. Anyways, I have tried to make two knifes from the leaf springs of my father's 1968 Ford pickup before I have it dragged out of the yard and send it to the crusher. My dad has been gone for some time so I thought it would be a nice thing to give all the blood relations a knife from Grandpa's truck. Well I don't know what I did to my dad but my plan seems to be cursed. The first knife was one wrong move after another, I won't detail them now but suffice it to say that no matter how many times I softened, flattened, heat treated and tried to straighten it I finally gave up after it seems to have taken an irrepairable twist.

So I forged out this one and I thought it was going fine until I was grinding the scale off it and lo and behold it is full of cracks. Is it something I did? Interestingly the warped knife and this one came from different leaf springs. Any advice would be appreciated, For the time being I have given up on the Grandpa Lou's memorial project and I just forged a blade for my son from some W1 I have- Thanks Todd

knife with cracks.jpg

Experience starts when you begin- Pete Culler

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toddmillerknives.com

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Unfortunately, that's not uncommon with old leaf springs, especially if the truck was used hard over its life. That's why you'll ofen read here about using new leaf spring drops from a spring shop, they haven't had the lifetime of fatigue cycles that a well-used set tends to pick up. :(

 

That said, forging too hot or too cold can also cause that sort of cracking.

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Unfortunately, that's not uncommon with old leaf springs, especially if the truck was used hard over its life. That's why you'll ofen read here about using new leaf spring drops from a spring shop, they haven't had the lifetime of fatigue cycles that a well-used set tends to pick up. :(

 

That said, forging too hot or too cold can also cause that sort of cracking.

 

 

g day Alan i agree but also he would have been better just doing stock removal and heat and quench in OIL he did not say what meadium he used but i bet it was water but over heating and cold hammering as you said above i try not to work the older stuff to mutch

tell

Terence.........(today started off perfect now --- watch sombody come and stuff it up ]

 

if it aint broke dont fix it

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Well that's good to know. I know the truck had it's share of abuse, in fact I am responsible for some of it. I am new enough to all this that I know I over work stuff because I can't get it right the first time. The blade that warped so much was oil quenched and the one with the cracks was just normalized and annealed. I guess I will rethink this project. Thanks Todd

Experience starts when you begin- Pete Culler

Please visit my website

toddmillerknives.com

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Those don't look like forging cracks to me. They look like the kind of cracks that you get from the fatigue in spring steel (in my experiance forging to hot or cold would have cracks perpendicular to those ones you showed, but i have been wrong before). if i am right, you didn't do anything wrong, other then using fatigued steel. That steel would be better suited for letter openers IMO. If you do use springs you have to be careful to forge HOT, at least an orange in the shade. Even if they don't have micro fractures 5160 seems to crack if you forge it at a red (it has happened to me a few dozen times :lol:). Good luck with the knife project

"I have surprised myself with what I can make with simple tools when a definite need arose. I don't think a man knows what he actually can do until he is challenged."- Dick Proennke

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  • 4 weeks later...

If you forge down the width of a rusty piece of steel, sometimes the rust "piles up" in the middle, causing linear cold shuts/cracks that look like this.

 

I use scrap a lot so I've seen it happen quite a few times. I have one blade where I tried to flatten out a piece of bed frame angle iron, and the "pile up" from the corner being compressed made a long cold shut all the way down one side of the blade :(. I had to keep that one...

 

If you grind the rust off of scrap before forging it should help avoid this...working at a higher temp can help, too.

My hand-forged knives and tools at Etsy.com: http://www.etsy.com/shop/oldschooltools

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The moment a leaf spring is mounted on a car it is under stress and stays that way until removed. As mentioned above if you have a piece of used leaf spring in your hand it's because it most likely has been replaced due to fatigue. Of all the scrap carbon steel around used leaf spring will have the highest probability of micro cracks.

 

But any automotive spring shop will be just as happy to sell you their new drop pieces as the used. I work about five minutes from RightWay Spring in Tacoma. The new drop pieces are usually 10-12 inches long which is perfect knife length for forging. The used springs will be whole and need to be cut up.

 

So NEW drop pieces don't cost any more then used. They have not been fatigued and stressed for many years. And they usually will already be cut to usable lengths.

 

It's not worth screwing around with the used. Sometimes the micro cracks won't even show up until you are well into the finish grind. That is frustrating to have wasted so much time for nothing.

Everything I need to know I learned from the people trapped in my basement.

 

 

I'm out of my mind but feel free to leave a message.

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