This is a picture of the pressure die assist die we had to make (the big one on the left). The smaller one is the clamp die. The dies for the big CNC tube bender machine we have are really big and so these dies are really heavy if made from steel--not to mention all of that die material is very expensive and hard to machine. Because there is so little pressure when bending a 3/4 tube, we don't need all of that expensive steel in there. The weight makes everything harder to work with as well.
