Here's another good site for those having issues with determining bend parameters for use in your own shop. The site can be a little overwhelming according to some reviews.

I find that the site has accurate information thoroughly explained. It's a work in progress so some other features are not complete.

http://www.sheetmetalworkbook.com/?goback=.nmp_*1_*1_*1_*1_*1_*1_*1_*1_*1.amf_4372114_117348834.gmp_2786625.gde_2786625_member_128568114