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Bending 18mm diameter brass bar

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Joseph Noci 120/11/2018 20:34:25
396 forum posts
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I have some 18mm diameter drawn brass bar that I need to make some bends in. I am not sure of the class of brass - it 'may' be CZ121 but I am not sure. It does machine very nicely.

The bends are on a 50mm radius, although I can increase this to 70mm if need be.

I understand CZ121 can be readily hot worked at around 650deg to 700deg C. Has anyone done this with thick round or flat bar of this grade, and did it work ok?

I have tried annealing a section and the bend just cracked at less than 1/8 of the bend. so I suspect this is a material type that must be worked hot, not annealed.

Any advice would be appreciated.

Joe

Mick B120/11/2018 21:26:48
797 forum posts
47 photos

CZ121 is basically a 60/40 Cu/Zn brass. The high zinc content - as I understand it - gives it its free machining property, but also reduces ductility as evidenced by the discontinuous chip you get on turning or drilling.

I'd be rather surprised if you can do what you want to, though hot working might open up possibilities I've never explored myself.

I'd think it would be better to try to find some bar in a higher-copper brass like CZ108, which would behave much more like cartridge brass, respond to annealing and take cold forming successfully.

I suspect this'd be an expensive exercise, however - so if brass is absolutely necessary, maybe you'd test the possibilities with what you have first.

Joseph Noci 121/11/2018 06:11:54
396 forum posts
718 photos

Thanks Mick,

I have only the info on the various material web-sites to go on and there it is indicated that hot forming is possible. I was hoping someone had already dunnit..and could say no problem!

I will give it a try and post what happens!

Joe

JasonB21/11/2018 07:11:39
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The thickest I have bent is 5/16" square section into a 2.5" circle. I did it hot but did also have a couple of failures before I got a good one.

I would think that one of your problems will be the work loosing heat as it is put into whatever you are using to bend it with/around.

David George 121/11/2018 08:05:19
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528 forum posts
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Hi Joseph, You can get a brass which is more pliable ie less likely to fracture C464 ( naval brass) or have you thought of casting the component.

David

Neil Wyatt21/11/2018 08:31:16
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+1 for David's suggestion.

You will need to melt it under a flux to stop the zinc burning off.

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