abrogard

I don't understand. Thank you for the link, a good one. I'll download the table and keep the link. But I don't see what I care about the material stretching. I just want to know what force I must apply to bend and what force that will generate in the machine and therefore how strongly it must be constructed. I think we must be confusing different machines or something. Im of 1mm sheet metal is easily bent by a hand manually operated (no hydraulics) bender in my local hardware store. As a lad I used to bend such material with such a bender in sheet metal shops I worked in. Unless my memory is at fault in both instances. Possible, I admit. But I think unlikely. I can check the hardware store. This is a new one. I can see how significant this factor would be. All bets are off if the material effectively changes its nature during the process. But we can find calculations and even calculators, even tables, for press brake operations that are ultra simple, something like a constant x cross sectional area x Tensile Yield strength. I think that's about it. And I'd assume they cover the 'margin of error' implied by the 'hardening' factor somewhere within their constant. A similar formula with the same technique is all that I'd require here. Can that be found? If Relating to that: how about if I take a piece of 1mm steel 25mm wide x 150mm and fasten it in a hinge with 100mm protruding - like a miniature bender and bend it using a spring scale hooked on the top end 100mm away from the bending point and observe the maximum force reached? This result could be multiplied to reach a figure valid for a 1m wide bend? i.e. result x 40 ? Would give me a ballpark figure perhaps or a completely invalid figure for some reason?

In a Sheet Metal Bender or Folder (different times/places get called different names) what maximum force is experienced and where? Not a 'press brake' that uses a die punching into the metal. But an old fashioned manually operated bender that is like a hinge laying flat. The job gets laid on top. Job gets clamped just before the intended bend line and then the 'hinge' is closed and this forces the job to bend. We are talking bending to 90 degrees. And generally making as tight a bend as possible, smallest internal radius. The purpose of the query is to enable choosing of materials to construct a viable machine. Proposed material: mild steel, 1mm thick, 1metre wide. If it makes any difference we could say to make a bend 100mm (4") from the end. The internal radius of the bend could be, for the sake of the exercise, say, 2mm. I have a couple of rough drawings on the web attempting to show clearly what I mean. There's a point 'C' marked which indicates where I expect the greatest force to have to be applied for it is the area of the actual small radius bend. But I don't know. I'd love to know. Here's the drawings: https://imgur.com/a/XljBilZ