This is a simple sheet metal brake that I designed. It's relatively inexpensive at a total cost of $49, it's easy to build, and it works really well. After looking at the other designs on instructables and youtube, they seemed to be either too complex or too weak. I think that this design is a happy medium in ease to build, quality, and cost since you can make it out of scrap material.

This was my second attempt, so I was able to improve the design and eliminate all of the weak spots from my first design. I found that the metal brakes tend to flex when using normal door hinges and at the bottom bar. To prevent this, I used a much more robust style of hinge, thicker metal, and I also boxed in the bottom bar to give it more strength.

The tools that I used are a bandsaw, drill press, angle grinder, and TIG welder. The metal was different sizes/thicknesses of 90 degree bar and a small piece of flat plate.

*** I updated the design after testing, so some of the photos from the first few steps will be different from the final design at the end. Mainly I improved the hardware used and the clamping bar. ***

Supplies

Hinges (2): $16

Metal: $25 of scrap at local metal supplier ($.90/pound)

Stainless Steel Hardware: $8

Step 1: Notch Bars for Hinges

The hinge needs to be positioned right in the center of the two bars. It's really important that it's positioned as accurately as possible, so take your time. Use a caliper to measure the outside diameter of your hinge. Divide that diameter in half, then mark it on your bar material. After marking with a sharpie, I used blue painter's tape to give me a more accurate line for cutting. I placed the bar flat against the bandsaw table, then made the cuts. I used a Dremel to notch the back of the bar, then use a hammer and punch to break it off.

Step 2: Weld Hinges

If your measurements and cuts were accurate, then the hinge should be centered. I just eyeballed it and it looked pretty good, so I went with it. The good thing about the hinges is that there's almost no play with them, so you can get it lined up as best you can without worrying about the hinge moving around.

I took an old package (similar thickness to a heavy business card) and placed it between the two bars before clamping them into place. I just wanted to give a little space to ensure that the hinge wouldn't bind if they weren't lined up exact. I'm not sure if this is necessary, but it worked out for me.

Step 3: Fabricate Clamping Bar

I measured in 1" from the end of the clamping bar and drilled a 1/2" hole. I started with a small drill bit to start, then finished it off with the larger bit. Once you have both ends drilled, then debur them and make sure that the bolts fit through easily without catching, but also snug enough so that there's no play.

I positioned the clamping bar against edge/groove of the metal brake. then swung the metal brake upwards to the farthest that I thought I would bend metal. This pushes back the clamping bar into position so that it's parallel to the bending bar and also spaces it back so that it doesn't bind in use. After that, be careful not to bump anything and tack weld the bolt into place.

Step 4: Box in Bending Bar

Next I cut a piece of scrap sheet metal that I had and used it to box in the bending bar. Make sure that your hinges are fully welded in because these will block access to the hinges once they're tacked in. Also, make sure that you leave spaces so that you can mount your handles. Lastly, just do small cold tack welds because you don't want to warp the bending bar.

Step 5: End & Notes

That's pretty much it! You can view the video to see how it works.

I did have some issues when building this.

The bolts stripped. I purchased stainless steel bolts from West Marine and they both stripped. I did some research and found a better solution. See the update in the next step.
The clamping bar had issues. I originally tack welded a single plate/strip down the center of the clamping bar to reinforce it, however it warped the bar pretty badly, so I had to remake another. For the second try I just used a clamping bar without any reinforcement, but I noticed that it would flex a lot when trying to bend thicker material. So I reinforced it a different way and you can see the update in the last step.

More notes:

I use C clamps to mount the sheet metal brake onto my welding table. It works out well for me since I won't be using this very often. So I can mount it when I have a project, then easily put it away and it doesn't take up much space at all.
I use adjustable wrenches as the handles. They work well and it makes things simple so that I don't need to store anymore parts and keeps the sheet metal brake small and easy to store.

Step 6: Update: Clamping Bolts

I did a little research and apparently stainless steel was a poor choice for the hardware. Stainless has the tendency to gall, where the two surfaces can seize together. So I switched to normal zinc plated hardware and revised the design.

Instead of welding a bolt, I decided it would be best to weld a nut. This way if the threads on on the bolt stripped, I could simply unscrew the bolt and replace it with a new one. I also included a locking collar, which is just used as a thick washer, which won't deform like a thinner washer (the set screw is not used at all).

Here's a breakdown of the hardware and cost.

Zinc Plated Full Thread Bolt (1/2-13 x 2-1/12" Long): $1.40/pc
Nuts (1/2-13): $0.45/pc
Shaft Collar (1/2" ID x 1" OD x 7/16" Thick): $2.99/pc

Step 7: Update Clamping Bar

I ended up needing to reinforce the clamping bar so that it wouldn't flex when trying to bend thicker materials. I wanted to make sure that it was as rigid as possible without warping the material at all. So I started with the piece of 90 bar, then welded the flat piece at the top to help prevent it from warping inwards once I welded in the plates on the underside. Next I tack welded the plates in and it was still flat once I finished. Tested it and it works really well.

Step 8: Update Measurements

These are the measurements/material that I used. Keep in mind that I was limited to using scrap material, so I just went with the widest/thickest material that was available at the time. Obviously the wider/thicker the material, the more rigid the brake will be. The only exception is that you'll want a sharp edge for the clamping bar so that you can get tight bends. If you're using thicker material, then the edge will be more blunt/rounded, than thinner material. Also, the wider that you decide to make your sheet metal brake, then the more it will tend to bend. So I'd suggest estimating the largest sheet metal that you anticipate bending, then just go a few inches wider.

I've only used the brake for one project and bent 11 gauge (.09074") without any issues. I'm not sure how well it does with thicker material or steel, but hopefully that helps you guestimate abilities of this brake.