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I Forge Iron

leaf spring straightening


iron766

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Hi guys i am endeavouring to make my version of the rusty/dusty/krusty power hammer and i am asking you how do i straighten the leaf spring? the sprig is in 5 separate sections at the moment due to cleaning off all the scale rust. their clean and ready to be straightened. any suggestions would be greatly appreciated. thanks.

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Getting the spring isn't all that hard . The tough part is getting it re hardened and re tempered. That is best left to a spring shop. When i was checking into it I found that buying a new spring would be cheaper than having an old one reworked. If I buils a spring helve hammer I'll just leave the curve in the spring.
Finnr

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If I was the one building the hammer, I would not mess with any heat treating solution due to bending the spring.
That is because I am not qualified to apply or discuss heat treatment of any sort with leaf springs for purposes of restoring the original spring properties that it was designed for.
So, if it was me making the decision to heat, bend, and heat treat, I would avoid the heat treating issue completely just by leaving the spring in its natural shape.
Then I would adjust the springs installation orientation (angle of incidence) in such a manner that would maximize its use as it is presently shaped.
It may even give the hammer a more streamlined appearance!
Be safe!
Old Rusty Ted

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Good Idea Blackbeard
You might want to check out this set of photos (up close) in the mean time. It has a close-up of the spring and the hammer.
Just use this URL like Blackbeard gave us. Then slip down to the photos. The spring looks like there is some bend in it to me. But not much.
FERRUM D. Gentile: Krusty The 100 pound mechanical powerhammer
Be safe!
Old Rusty Ted

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You might also consider the safety implications of using a junk yard spring for your hammer. You don't know (without some hi-tech testing) what the stress history of the spring is and therefore how close this thing is to breaking under the kind of load that you are putting on the spring. This may be the one single part that you would want to spend a few bucks on to get a new, still flat spring from a spring shop. Consider that this spring is at the level that can cause a lot of damage to critical body parts (head, eyes, etc) if it breaks and goes to flopping around at/near the speed of light.

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I used truck springs that had a slight bend left in , the curve caused no problem, but it was always at the back of my mind that they could break being used, it wouldnt be to difficult to enclose the whole spring in a cover, it would be worth doing this even if you use new springs.

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I see no real reason why the leaf spring helv must be straight. It may take some tweaking of the design to use an arched spring. Using a forge to straighten a spring would be relatively easy but getting a quaility heat treat over such a long item is beyond the capability of many blacksmiths. A spring shop with heatreating facilities would appear to be a desirable option

I would be scared to take a leaf spring and cold straighten it and use it in this type of application where a spring failure could be fatal without a subtantial guard.

I would plan on using used springs, if I were building one, but we must keep in mind spring failures on trucks are very commom and a used spring may fail due to fatigue at any point. (speaking as a former tractor trailer driver and a road side scrounger who picks up broken springs for forging stock)

Use a multileaf spring pack should be used to reduce the negative results of a spring failure as a single leaf failure will not be catistrophic. Also add enough clips on the spring pack so the a broken spring leaf will remain in place if it breaks.

The good news is that leaf springs usually fail a leaf at time so inspect the spring pack daily for cracks near the center of the spring. If broken leaves are ignored then the pack can fail catastrophically and wack our vulnerable heads or other anatomy.

This is a cool design and as an mechanical engineer it appears to be one of the best options for a shop built mechanical hammer.

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Springs used to be recurved and a lot of old blacksmith shops had a form to see when the spring was back to its original bend. When you hammer a piece of metal on 1 side all the time it will curve in that direction. They used to take the springs off a car, take them apart and hammer them on one side until the proper curve was attained according to the form. That is why when you are forging a knife you hammer the same amount on both sides of the blade so when you harden it, it won't get a curve to it. If you take any piece of flat bar you can curve or straighten it this way. Make sure where you are hitting with the hammer is on the anvil so it is a nice solid hit and it will curve into your hammer.

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  • 2 weeks later...

I have straighten a lot of leaf springs some 60mm wide by 6 or 8 mm by useing a BIG hammer 13 pound and a real large Block of hard wool 700mm high 600mm wide--- have some cord to stop the spring from going onto orbit. if you hit it worng or it brakes in 2 -----i then sharpen about 6 inches of the side of the spring steel tool that is 600mm long to make a hammer slasher for cutting cars up ---I hit them with a 4 pound hammer to cut panal steel and the like ---I tip water from a plastic coke Bottle onto the hot part to stop up setting the temper..as i sharpen them with a 7 inch grinder.. I have the gringer in one hand and the water Bottle in the other.... I have a Roveing Vice on one 44 gallon drum and another 44 gall drum to put the grinder on.. I have Holes slashed in the top of the drums , some were for the water to go stops me getting wet----to add ,,Make shore evey one has a hard hat on ---

----

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