Intro: Easy to Make Bending Press Brake With Flexible Hinge
I have seen some great home-made bending presses. But I wanted to fold up a box from a single sheet of aluminium with the edges turned right over on all sides. This can usually only be done on a press with removable and cutaway noses (the bit over which the bend is formed is called the nose). This is what I had in mind. The box is for the heater on my vacuum forming machine.
The aluminium I bent was 0.038in or about 1mm thick and the longest bend was 310mm, just over 12 inches.
Clamping handyman bench
Wood saw and plane
Hot-melt glue gun
Two shelf boards (mine were melamine-faced chipboard)
An old car seat-belt
The Homemade Mini Bend Brake https://www.instructables.com/id/Homemade-Mini-Press-Brake/#intro looks great for narrow strips, but couldn’t bend up four sides of a rectangle.
In bending, there are two big problems – holding the metal against the bending nose, and stopping the metal from sliding out of the press. Also the hinges have to be very strong.
As I haven’t any welding gear I wanted a hinge I could use with wooden boards. They are old melamine faced shelf panels. I connected them with strips of seatbelt webbing fixed with hot-melt glue. The belting is in tension when it holds the top board against the workpiece. These pictures show how it works.
Each strip of seat belt is about 150mm long. It can be cut easily with strong scissors. When all the strips were attached to one board I turned the board over and pressed the edge of the second board as tight up as possible, with the strips coming through between. Each strip goes from the front of one board to the back of the other.
A safety thought. If the strips beak away from the glue it would collapse and that would be when I am leaning on it pretty hard, which could be nasty. So I nailed down each strip of belt with a carpet tack. If the glue comes unstuck the belts should rip gradually and lessen the danger. I put the tacks away from the ends to allow a long tear before there is nothing.
To use the bender I put it in a handyman vice workbench. One board and the flat workpiece go upright in the vice. The top board will bend the workpiece and can hinge over from left to right. As shown in this picture the belts are arranged so that they are in tension when the top board is pushed to the right.
I found it was tricky to hold the board and the workpiece, and it sat too far down in the vice. So I nailed a couple of bits of thin ply to the top edge of the bottom board to stop it falling down. And I used an offcut of wood to hold it a couple of inches above the work surface.
I needed a nose to bend the plate over. I use a couple of bits of wood I had saved up. At first I could use a nose wider than the workpiece, but as soon as the sides were bent up I needed it to fit between them.
I found I needed to over-bend the aluminium by about 30 degrees since it springs back. So the nose needs to be made pointed about 30 degrees. You can why the whole thing needed to be raised up in the vice, to allow for it to bend beyond 90 degrees.
This shows the wooden nose piece.
I sometimes found the nose tended to slide down. So I clamped some non-slip table mat between the workpiece and the bottom board. Here you can see one of the last bends being made. You can also see extra wood was needed to clamp the workpiece without squashing the sides I had already formed.
For the last bend I needed a nose piece long enough to support the bend but able to be removed from the box afterwards. It was shaped like this, cut away at the back so that it could be turned around and got out of the finished box. Glad I thought of that before the last bend!