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Hi Steve, There are two types of common brakes for cold metal forming, hydraulic press brakes and a hand brakes. Hand brakes are limited too 16ga x 10ft wide. You can however bend shorter thicker metal provinding you take the time to adjust the brake for the correct clearence of the bend equirement. I don't know if there is a upper limit for press brakes. Very common is a hydraulic 90-ton press brake rated for 1/4" x 8ft and a 120-ton rated for 1/4" at 10ft. Once again you can also bend shorter thicker metal with the proper dies and adjustment. What is the correct clearence for bottom dies or a nose bar? 8 times the metal thickness. That applys too hand brakes or press brakes. That also apply's to bend radius of pipe. Trying to bend sharper radius will cause metal fatique or crack along the bend radius. This fatique fracture will occur being visable or not. That means the bottom die on a press brake needs to be 2" wide opening to bend 1/4" material or the nose bar needs to be set back 2" from the leaf. The top die needs to be a radius equal to the plate thickness. It's both the width and the thickness of the metal that sets forming limitations. Now if your wanting to hot bend thick metal then there's no limtations. You do however have to beware of total heat required along with bend radius requirements. As stated by Carl and MattK in previous posts:
A simple method to bending 1/4" plate is too use a thick steel welding bench. Set the 1/4" plate to extend past the bench edge by 1/2", then clamp (several clamps) a angle iron on the scribed bend line, then heat to a bright red thru in thru then apply bending pressure with a pipe wrench with a cheater bar. The clamping angle needs to have a radius ground to keep with-in the bend radius requirement. If you have a hand bearing press you can also make dies to make a bend with or without preheating. T_Bone
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