I'm using my HF 20 ton.
Had a recent project that needed some bends in 1/8" strap and in 16ga sheet up to 20" wide. None of the cheaper commercial brakes can handle 16ga well, and a typical lever operated brake is too much work for my needs. So I built a primitive and simple press brake for my HF 20 ton press.
Top bending die:
Started with a piece of 1/2 HRS I had lying around. 3" wide and 20 something long, cut it to 21". Set it on the mill and cut a 80* included "edge" on one side to form the bending die. It has to be less than 90* due to spring back. Welded a piece of 2" x 0.250 strap across the back to keep it from bending the "easy way", and welded a piece of 1.75 x 0.120 scrap roll bar tube vertical in the center of the 2" back rib. Drilled and tapped that for a 5/16 bolt that I will weld a piece of bar stock onto for a "wing bolt". Cleaned up the inside of the tube with a "tootsie roll" on a die grinder and that tube slides over the ~1.470" (metric I guess) press pin that came on my press. This holds the bending die correctly oriented and it rides up and down on the press carriage so I don't need separate springs to raise it. I also added 2 pieces of angle on each side to form "ways" to guide it during it's travels using the vertical side beams of my press. One of these side guide ways has a corner cut off so that it will fit through the frame at a 30* angle allowing it to be inserted without dropping the table completely out the bottom.
Bottom receiving die:
Just a piece of 1/4” x 6” strap stock cut full width of my press table. Then 2 pieces of 1.5 x 0.25 angle turned inverted and welded on top. The angle is separated by 1/8” gap in the center (used some 1/8” scrap as spacers for uniform spacing) and shimmed up 3/8” on the outside edge to give me the < 90* inside angle, again, for spring back. The gap is necessary to complete the sharp bend on sheet by going past the bottom die, and it makes completing the last bit of a heavier sheet/bar easier since more spacing equals less pressure to bend. For really heavier stuff, I’ll need a wider and heavier bottom die, plus it will likely need a hardened top die.
Took about 4 hours I guess, scattered over a couple of days so it’s hard to estimate, but not bad at all and I probably spent more time figuring out how to make it out of what I had on hand than actually making it. But it bends 10” wide 16 ga (all I tested so far) effortlessly and I can get about 85*+ bend even on light sheet. I also tried a piece of 1/8 x 2 strap and again it was effortless and no damage to the die. I’m sure it could bend 1/4 or heavier with a hardened top die. I also plan to build dies for bending round bar, and may get some 4140 pre hardened to make a top die that should be sufficient to bend up to 1/2 plate 4-6” wide, but that’s going to be about all my 20 ton will handle, if it can handle that. I know I’ll have to set the bottom die pretty wide and live with bends that are not sharp, but that really does not matter. I might even use 4140 3/8 or 1/2” round rod to form the top die and avoid the gouges sometimes seen when using press dies on heavier plate. You can even use round rod for the bottom dies as long as you space them so you can get the bent material to a point where it forms a tangent line to the bottom die rods that describes and angle less than 90*. Lots of ways to do it...
