Dan, there is .001" clearance when the blank is in position between the die and the stripper. The brass has to flow and if the stripper deflects and rises the blank will wrinkle. The support bars were found to be needed after my first unsuccessful attempt.
Zee, The material I used was from a roll of .02" brass used for forming, I haven't tried brass shim stock yet but I suspect it would form allright. It may need to be annealled which is easy with brass or copper. When we formed steel we used stock that was made for forming. I remember a job I had where the steel was delaminating after forming and after investigation it was found that one of our purchasing agents got a deal on some steel strip stock for us. It was the last time he found us a deal anywhere. Good forming steel can be found in coils in the scrap or can be sourced from a local tool & die shop. If you would like to harden the part after forming you can use 1070 steel. Steel requires much more pressure to form. All of the forming I have done has been at room temperature.
Dave
