Machining dies for 3-roll bender

[Whipsmart]

I thought I'd pass along a technique that I use for quickly machining dies for a 3 roll bender.
http://s1208.photobucket.com/albums/...lbenderdie.mp4

[Eric Estlund]

Looks good, Peter.

[EnginCycles]

Nice approach. I am more curious how you added the keyway to the two rollers that are being driven with the drive mechanism. You appear to have a nicely tooled up shop so I am wondering if you broach it with a press or have another way of doing it. Also did you make them out of 1018 or something stronger like 4140? The ones I have are hardened, ground and polished and I think it has a good effect in keeping from adding small dings in the tube from a random chip.

Cheers,
Drew

[Whipsmart]

Thanks!

I might have a useful tool here and there ;), yes...

As for the keyway, I just side cut with an end mill starting from the center hole, and moved out. I cut in 1/2 * end mill diameter + protrusion of the key, so that the arc that is formed by doing this doesn't interfere with the key. It was the simplest way to do it at the time, and I'd do it again. It might not cut the mustard for some applications, but for this it worked just fine. Also, the keyway isn't full depth through the wheel - IIRC it's ~.75".

I haven't invested in keyway broaches yet, as I've always had a workaround that was sufficient. I do have a rotary broaching tool, which is really the bee's knees. It's great to be able to make your own internal hex bolts for things!

And as for the material, it's 1018. I have yet to encounter a problem with the roll bender due to embedded chips, however I have used a rotary draw bender that got a piece of material stuck to the die, and that sucker could not be picked off!