while looking for something else I found this old drawing I did long ago to build a small metal bending brake. I think the only variation was I only used 2 hinges at the bottom. works well and stores easily. hopes it helps..
It would help if the top angle had slotted holes for the bolts so that it could be adjusted to whatever gauge of metal that you’re working with. So that you don’t have rounded corners per se and always a sharp break
I built a floor model a bit more robust, it has been in service nearly 30 years. Mine has a bending range up to 48" wide (max width) 18 gauge, and 6" wide 11 gauge, I have to get a helper bar to bend the wide, thicker stuff (no mechanical leverage, pure lift ability), the limitations on the thicker stuff is me and the clamping method. The bends are not sharp. The clamping method has proven itself to be the weak link, the last 10 or so years I've had to enlist a couple of wide mouth welding vice grips and a rather large C clamp to ***ist the original clamping method. I'll have to go measure everything if someone wants those measurements. These pictures were taken a few years ago. The frame work is 4" channel (the legs and the floor level feet). The bending platform is about waist high. Opps, pushed the wrong ****on... the description will continue.
pic 1) This is the work surface. The legs going to the floor are 4" channel. At the floor (under the boxes, I'll get a picture of those later if anyone is interested) are 2 more pieces of 4" channel, about 18" long. Those two channels are welded onto the ends of the side pieces, centered, facing forward and backwards, channel standing on its side in the vertical position. There is a piece of thick wall 1.5" square tube that is placed across the top of the front ends of the floor channel. This tubing is to stand on to keep the free moving bender in position and to keep it from flopping over when bending the metal. It is removable to gain storage under the bender when its not in use. The top surface you can see a piece of 4" channel laying flat surface up, welded on top of the channel legs. (it is reinforced under, I'll show a pic of that bracing later). The picture shows two pieces of 4" channel on the back side, edges up. Those are also welded to the surface channel, those two pieces are for material support behind the bender. The angle iron at the right side is the bending bar, the hand grasp round stock is barely visible at the center section of the angle. The material to be bent lays across the flat surfaces. The clamping bar to hold the material in position is leaning against the two wheel cart on the right side of the picture. to bend the metal, that is clamped in place, I grab the hand grasp, and pull it up while standing on the square tubing that is across the feet channel. Until the sheet metal gets thicker then 18 gauge, or wider then about 36", it really bends stuff pretty easy. The rectangular end plate is the offset pivot point. The left side is welded to the channel, and the right side bolts to the bending arm. This is the bending bar held in the 90 degree bend position (the angle will bend a few degrees past 90 so I can get an actual 90 degree bend). to show its reinforcement bracing. The angle is 1/4" x 2" x 2". My finger is resting on a 1/2" thick, 2" wide flat bar. That bar full length and is s***ch welded on both sides to provide reinforcement for the angle. the curved hand grip is 1/2" round bar stock, as are the bracing bars that are welded to the bottom surface of the angle. When dealing with thicker or wider material, I often will put a 3' long bar between the round hand bar and the 1/2" support brace.the material hold down is in the clamping position, you can see the "T" handle for the clamping screw on the right side of the bender. This is one end of the clamping bar, and the offset bending bar pivot plate. At the front of the pic we see the bending bar and its center 1/2 brace in the flat (0 degree bend) position. There is a tube welded to the bending bar angle with a space cut out for a nut. The plate on the left side is the off set pivot plate, it is fully welded to the bottom of the 4" channel, and both top edges are s***ch welded to the top of the 4" channel. The bolt p***ing through both the plate, and the bushing is a 3/8 grade 8 bolt, and has been there from the first bend. The other end of the break is a mirror image of this side. The piece at the top of the picture is the end of the clamping bar (the next picture shows the end view of the clamping bar). The design was for the captured nut on the "T" handle to hold the bottom of the clamping bar against the 4" channel iron base. The piece above the nut is to lift the clamping bar off the material after its been bent. The problem is the 3/8" bolt allows the clamp bar to flex too much on wide, or thick material bends. There is 49" of material width that can fit under the angle iron part of the material clamp, and that same 49" material width that can fit between the complete bolt ***embly for the pivot plate. I can bend a full width 48" piece of sheet metal. This is the end view of the clamping bar. The angle at the top is 1/4" x 2" x 2" x 49" long. The bottom piece is 1/4" x 3" x 56" wide flat bar that is s***ch welded across the full contact length of the angle iron, with a notch cut out to clear the pivot point bolt. The top lift plate is a 1/4" x 2" x2" plate welded to the end of the angle iron. The other end of the clamp bar is a mirror image of this end. This is what the end of the break looks like when its ready to do business. The rectangle is the pivot plate (this material was recruited from something else, the two small holes were from its previous life). On the right side is the bend bar in the 0 bend position. On the top is the material clamp bar. This is the bottom reinforcing for the material holding channel. The angle on the left side is the bending bar held in the 90 degree position, my thumb is holding the curved hand grip grasp up. To the right of it is the front edge of the 4" holding channel. Welded on both sides of each piece to the bottom surface of the holding channel are 2 pieces of 1/4" 2" x 2" angle that tightly fits between the flanges on the 4' channel. The 1/2" round bar is welded to both of those two pieces of angle that are welded across the channel. Then the round bar is bent and welded flat against the bottom surface of the 4" channel at both ends where the material holding channel meets with each 4" channel leg. The 1/2 round bar is welded into a position that is called a Bridge beam brace. It effectively makes it very hard for the 4" channel to flex in any direction. These days when I need to bend sheet metal, I use the "T" handles, but I also clamp a vice grip on top of the "lift up" plate on both sides, it holds the material better. Also when ever possible, I add a "C" clamp from under the material holder channel to the top of the material clamp towards the center. I could probably replace the hold down clamps with bigger bolts, and add a bridge beam brace to the top of the material hold down and eliminate most of the flex, but I just don't use it enough to warrant that much effort. As is this thing still does really well on 24" wide pieces of 18 gauge as long as there is a clamp at the center and at the nearest end. Often times that crisp sharp bend many guys want in sheet metal is what starts those sheet metal tears on the bends. most of the time, a small radius is what should be there instead of the sharp crisp bend. Anyway, that my sheet metal bender. No patented on it, so feel free to copy it in any size you choose. If you need actual measurements, or pictures of the bottom, I'll get them for you.
Check into Dave Gingery's "Shop From S****" series; one of his books is about how to build a sheet metal brake.
I hope all you realize that my "patent#" is just make believe. for those who think it's real, send me a dollar and you can build it.
Me and another coworker built a heavy duty break at work for bending 14 gauge for steps in school buses. Everything is heavy, 36" long by 3/8" thick angle iron and 1" pivot pins. The hardest part is getting the moveable angle iron and stationary piece corners to pivot parallel and right on point. We missed the first time and all our bends were angled. After a little rework, we got it work pretty good. It takes two guys to bend a 32" long 14 gauge sheet 90* !
I built one along similar dimensions, except 49" long but with the same 1" pivot pins. Yeah, I'm an old guy and struggle to bend 18-gauge at full width - hell, even at half of that width. But it works! damned heavy, though, and I struggle to mount it in my Workmate.
Similar to mine, built close to 30 years ago. Not a tight bend but in some situations that is better.
Building your own metal brake can work well if you keep the design simple and focus on rigidity. Many people start with heavy angle iron and a solid hinge setup to get clean bends on thinner sheet metal. Taking time to align everything square makes a big difference in results. It’s also smart to be realistic about material thickness so you don’t overbuild or underbuild the brake.
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