lots of homemade examples, Dave Cofer @ the homeshop bbs has even built a cnc hydraulic press. I agree it takes a whopping big cylinder to go to 50 tons, when i looked at it there you could get a 6" cylinder for the HF price, then again I would expect a decent home made effort to easily surpass a grizzly/hf effort . my hyraulic press has been on hiatus pending a nice surplus hydraulic find. do some searching at the home shop machinist bbs, I have seen manual, power and cnc diy brakes there. Here's a finger brake made by another guy there. http://smg.photobucket.com/albums/09...oxBrake3xx.jpg
I'm also in market for some sheet metal equipment, I know they are not the same tool but I think i'm going to find a good used finger brake or make one instead of a hydraulic brake. I've a 4' 16 gauge brown boggs shear bought used, don't know that i'd want to make one, knives would be a challenge.