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Thread: 4130 tears when I try to bend it

  1. #1
    Gunco Member ErikJL's Avatar
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    Default 4130 tears when I try to bend it

    After assembling a jig to make the lower bends for a homeade receiver, I tried it out on a piece of .05" 4130. It seemed to work OK except for three tears, each about an inch long, located right on the bends.

    The jig is very similar to the one described on this site:

    http://www.geocities.com/homebrewkit...IE_SET_UP.html

    My digital camera has horrible picture quality otherwise I'd post photos. What can I do to keep the metal from tearing? I was thinking about trying some grease, but I want more opinions before I go ruining another piece of my 4130.
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    Gunco Member romack991's Avatar
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    Also what state is the 4130 in? If its been pre-heat treated then its gonna tear. A possible solution is to hot work the metal. Cold working produces a lot more stress in the part.
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    RIP Sangrun Hunter's Avatar
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    What is it they call the pre-heating? Aneeling the metal?

    Take a sooty flame from a torch and soften the metal by running the flame over the peice. That releases the grain and relaxes the steel for easy bending and shaping. I actully learned that on West Coast Choppers show when Jesse James was building a custom gas tank.

    Sorry for my non-technical description.

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    Gunco Member romack991's Avatar
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    sorry for my technical babble, im just used to talking in those terms.

    heating the part up is what you do for hot working. completely different than annealing. heating should help a lot. It will lower the force required to bend the metal and also lower the stress.

    You'll have to heat the metal a little over 1000deg F. This allows the metal's grains to change. (just to clairify, you bend the metal at this temperature, dont allow it to cool)


    But I think you might have pre-heat-treated metal. Because I have bent a .04 4130 sheet with no problems. That or your bend radii are much smaller than mine were or what said about not having material clearance.
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  5. #5
    Gunco Member ErikJL's Avatar
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    I actually have too much clearance in the channel, something I'll need to address before I weld it together (I just have it screwed for now). It's supposed to be 1.35" but it stretched out to 1.40" after I bent that first piece.

    Also, the 4130 isn't heat-treated that I know of, unless it comes that way when you buy it raw. I could try and hot-work it, but frankly I'll probably end up burning myself or ruining the metal.

    romak what you said about the radii being too small might be my problem, as I'm just using a piece of .25" thick 1 1/4" wide steel bar to press the 4130 sheet through the die. I could try rounding off the corners where the bending occurs on both the metal bar and the corners of the die with my grinder.
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    Gunco Member romack991's Avatar
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    dont round too much or you'll have other problems, thats what happened to my first bend.
    The goal of engineering is failure.
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  7. #7
    Gunco Member ErikJL's Avatar
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    I'm thinking about using a thicker piece of 1 1/4" bar for the male die as well. romak is your jig like the one on the link I posted?
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  8. #8
    Gunco Member romack991's Avatar
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    Its pretty similiar, Female Jig is a different.

    Here a rough side view of the components.
    Attached Images Attached Images
    The goal of engineering is failure.
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  9. #9
    Gunco Member ErikJL's Avatar
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    Did you make your male die out of a single block of steel? I was thinking of having a machine shop do this so the slope of the die is perfect.
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  10. #10
    Gunco Member romack991's Avatar
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    It's an I- Beam shape piece of steel. Roughly 5/8 thick middle section that has the proper taper. And two 1/4x1.25 pieces (top and bottom) that are screw to it. Screw heads counter-sunk. Works pretty good.
    The goal of engineering is failure.
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