440 stainless for press brake die?
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  1. #1
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    Default 440 stainless for press brake die?

    I need to make a press brake die set, top and bottom. It is a custom radius set that is 16" long, there is a 25mm radius that needs bent over the entire length. I have some 440 stainless sitting here that is perfectly sized, would that work or are there mechanical issues with trying to use material of the sort? I only need to press a few sheet metal parts, no production runs or crazy numbers. I don't have much experience with press brake dies, normally I would look for some 86/87xx series but I do not have anything sized correctly right now.

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    First off - what material are you bending?
    Last edited by Limy Sami; 05-15-2021 at 05:36 PM. Reason: pyto

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    18-16 gauge CRS sheet that already has one draw/formed operation completed.

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    Real bad idea, ss to soft...Phil

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    Phil can you elaborate a little. I have never heard of 440c stainless being too soft. I was worried about issues with cracking along the center line of the radius from grain alignment, cracking from hardening and ductile fractures, but never would I have expected to hear 440c stainless being to soft.

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    We formed and welded 1/4" A36 to bend 1/4" 5052 to a 70 degree overbend. It works without issue.

    If you are concerned about galling, use die film. I don't have personal experience with stainless dies, but 304 stainless bends against HRC 60 (I think?) dies with only surface marking. No galling or gouging.

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    img_20210515_133823.jpg
    img_20210515_133834.jpg

    This handles 12 tons per foot without issue (calculated).

    For the punch I wouldn't be concerned about material. Even aluminum is fine.

    You didn't mention what angle you are bending to. I'm assuming you want to air bend a 90. If so, are you sure you don't already have V dies that can work?

    If you need a deep overbend, that's the only time I would be concerned about the forces trying to split the die apart.

    If you want to bottom bend it's a whole different deal.

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    Its soft compared to steel and will gall quite bad, anytime you bent metal it will slide in the dies and gall, if this is a one time jig go for it but if it is a use every day dont...Phil

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    Quote Originally Posted by Phil in Montana View Post
    Its soft compared to steel and will gall quite bad, anytime you bent metal it will slide in the dies and gall, if this is a one time jig go for it but if it is a use every day dont...Phil
    440C is softer than steel? 440C, the same material knife blades are made out of is softer than steel? Am I missing something? I know 303, 304, 316, are very malleable due to the near lack of carbon, but 440C has more carbon than 4140 (for just one example) a full percentage point in some cases.

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    A huge factor in galling is shoulder radius. If you make a large enough radius you can use material barely harder than what you are bending. If you have sharp corner radii even very hard steel will suffer.

    In your case I'd use what you have but make the shoulder radius as large as possible (which is pleasant for all dies anyway. It's only an issue if you have holes near the bend zone.)

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    You've said it's just a few parts. Make the dies out if any old scrap you've got around the place.

    I agree that 300 series stainless would be a bad idea, but the unknown 400 series stuff hanging around my shop is plenty hard enough.

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    will it work, yes
    will it gall and marr, yes both the material and the die which will leave marks on everything after.

    one time use, sure, go for it. ive seen dies with plastic inserts for 1 or 2 parts that work until they deform too much

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    440c is plenty hard, but like others have said, it is likely to gall. Doing something twice is always way more expensive than doing it right once.........jus sayin

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    There seems to be a good amount of for and against. Roll the dice and see what happens I guess. Nothing ventured, nothing gained at this point.


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