The old rules were "25 tons per inch per inch" for straight lines and
"80 tons per inch per inch" for holes. These are based on 50,000psi
shear strength for mild steel and mechanical presses that have a weird
tonage versus position curve. Example: for a 1" hole in 1/4" plate it
would be 80x1"x1/4" = 20 tons. These also assume reasonable die clearances.

You can get by with less tonage if you put some shear on the various
cutting edges. Works great on hydraulic presses, you can effectively
punch several dozen small holes in sequence, each one taking only a
small pessure. Same thing on a mechanical may stall it, NOT a good thing.

The forming part is trickier. For soft bends you can use the beam
calculator formulas. When you try to "iron" a edge, the tonage required
is very much a function of the clearance.

wrote:
Anyone have the formulas for tonage for a stamping die handy? I need to
start on the design of a two stage, progressive blanking and forming
die for a project, but don't have my handbook or die design book where
I can get to them right now. I know my material, the hole diameters and
the total length of the part perimeters. What I need to do now is
calculate the press tonage so that we can start the search for a press.

Craig C.