Making roller dies

[Weldedwood]

I've read these forums for a long time and finally decided to sign up. I have the shop outfitters pedestal roller (338?)  I am having some dies made for rolling flat bar "the hard way". I'm building a rail for a curved staircase, and using 1/2" x 1 1/2" hammered flat bar as a cap rail. I know, it'll be slow rolling with my roller, but it's what I've got! My question is, after the bar is heated, hammered, and straightened back out, how wide should the grooves be in my dies? I know too big and it'll be sloppy and crooked, too tight and it will bind and get stuck. If it's 1/2" thick bar, 9/16? Anybody have any experience making dies? Thank you

[Judson Yaggy]

How close is the tolerance on your hammered bar?  That will drive the width of the groove.  I'd make it tighter rather than looser, if you hit a fat spot in the cap rail with the roller you can grind/sand/blend down the rail thickess.  

Be aware that if you are using the spiral stair formula in Parkinson's book, it's wrong.  Doesn't work.  

[Fatfudd]

I have some SWAG dies for rolling .5" steel the hard way with a harbor freight roller. The dies appear to be only a few thousands wider than .5" to bend the metal without too much flexing and distortion. You might contact SWAG for their exact measurements. 

[arftist]

The inside of the radious die needs to be significantly looser since the inside of the bend will thicken.

The outside will become thinner so just a little clearance is needed.

[Jim Coke]

Greetings Weldedwood,

      Hot hammering your stock will yield inconsistent thickness and will jam in your dies.  I would make a bending fixture than texture and hard way bend a little at a time. Your stock will pretzel and twist so slow is best.  Just this ol boys 2c

Forge on and make beautiful things 

Jim