I've been wanting a bigger and better brake for years so I finally did it this weekend. I used 3.5 inch angle with .25 inch thick walls. I clamped the two pieces back to back with "C" clamps for the entire build and belt sanded the tops, very smooth and perfectly aligned. I cut the hollows out for the hinge pins with a 4 inch grinder and cutting wheel. The pivot points are 3.5 inch long .75 inch round bar 1 inch out past table. I drew cross hairs on each round bar then lined them up with the table and joint and from end to end with levels and straight edges, tack welded them then tapped into perfect alignment before fully welding. I'd like to find a thicker plate for the pivot point and add bearings in the future. They came out perfect and will last me a while I think. I used 1 inch heavy wall square tubing for the handles. Just using angle and "C" clamps right now as a hold down but plan to improve on that in the near future. Bending .125 inch aluminum fairly sharply and can bend well over 90 degrees, about 135 actually. It operates so smooth you cannot even tell thin sheet metal is in it being bent. Worst problem of having a 28 inch brake and trying to bend heavy metal which takes a lot of upward force, is finding something heavy enough to bolt/clamp it down to so it won't pick up! This thing really works smooth and is very heavy and heavy duty too.
Pivot point, .75 inch rod.
Temporary clamp, 2 inch angle, bending .125 inch aluminum.
Sheet metal box folded five times, 4 corners plus a 1 inch lip to fasten with rivets.
This brake is going to be a joy to use I think.