bead rollers

[50bmgshooter]

I need some info on bead rollers

im helping a friend out with some tin work, he bought .040 black alu, and borrowed a bead roller from someone else (harbor freight model)
OK here's whats happening
when we make a run on a test piece the edges of the black in the alu show crack lines.
this has happened no matter what we do- change dies, put tape on the alu over the plastic, try running the bead in steps.
the first shot through you see a crack.
I think its the roller or dies them selves.
told him we should just buy a good electric one.
so I was thinking getting this one http://mittlerbros.com/bead_rollers.htm 24" and use their Nylatron dies

thanks
mike

[wrenchnride247]

Try backing off the pressure some. Those HF dies are kinda sharp on the edges. Black aluminum? Is it anodized already? What spec is the aluminum 3000, 5000, 6000? Your leaving alot out of your question.

[jkeyser14]

It sounds like you have anodized aluminum. Anodizing is an oxide (ceramic) coating. It is brittle and will crack when bent. There's nothing you can do to avoid it, but you can try to lessen it by stressing the material less (less pressure or a more gradual or shallower bead). Also, the thinner the aluminum the more flexible the coating will be since stress increases exponentially with thickness.

If you are just getting started trying to fab sheet parts I'd recommend you buy yourself some un-anodized 5052 aluminum since it will be the easiest to work with.