I recently bought a 12-ton press to use with a steel rule die I had made by some local folks. It's an 11.5" circle with a center hole punch. Anyway, I set up the press and put down a 1.25" thick piece of HDPE (13"x13") on top of which I put my leather (2-3oz), then the die, which has the rubber pieces around the cutting edges. The die has a wooden backing, as well. On top of the die I put a 1/4", 12.5"x12.5" steel plate. I brought the ram down and began pressing. I didn't know how hard I would need to press to cut the leather, so I used some scrap pieces. I quickly discovered that there is an issue. The way a shop press is designed, there is the "bed" onto which you place items you want to press. This bed is only 6" or 7" wide. So when I put the cutting surface down, it hang over on each side of this bed. I thought using a steel plate would distribute the force evenly over the die, but that wasn't the case. The die cut the leather only where it was supported beneath by the bed. So, at 3 o'clock and 9 o'clock (as you look at the die) it was cutting, but at 12 and 6 o'clock it wasn't.
The only explanation I can think of is that the hdpe is somehow flexing under the force, and only cutting the areas supported by the shop press bed. My idea now is to get another steel plate and place this between the shop press bed and the HDPE. Do you think this will work? I tried to make do by rotating the whole cutting "sandwich," but somehow things got out of alignment and I ruined a piece of leather. I am also surprised by the amount of force to get through 1.5 mm leather. The die is brand new, so it is quite sharp. So...I'm still in trouble-shooting mode. Any suggestions and wisdom would be appreciated. Thanks.