Make a Sheet Metal Bender
The machine successfully bent 19" wide 1.6mm sheet steel. Steel that large and thick was at the limit of what the machine could handle.
As usual, uses are limited more by imagination than anything else.
- Sheet metal furniture
- Car bodywork & some chassis parts
- Shelves with rolled front
- Small steel Shelving Units
- Custom toolboxes
- Square, octagonal, hexagonal etc tabletops with rolled edges
- Trailer panels & parts
The bed, which constitutes the left half of the machine in the diagram, is made from 2 layers of 3/4" wood (finished size), each layer at 90 degrees to the other. Thick sheet plywood could be used instead.
The hinged bending section, on the right, is more of the same with a strip of plank as a handle attached to its underside to make bending easier. This bending section is attached to the bed (on the left) by 4x heavy duty 4" hinges. Accurate alignment of these hinges is essential. An effective way to get them aligned is to hold the 2 pieces of wood at 90 degrees to each other when fitting the hinges. The hinges are all held using 3" wood screws in all holes. Don't use smaller screws, they're not suitable. The handle extends under the full length of the bending section, and is attached to it with 4 or 5 screws at the hinge end of the handle (the leftmost end of the handle in the diagram), and 2 more screws further out from the hinges.
The top bar, which runs across the top of the machine from front to back in the diagram, is 3" x 3" timber. Its held to the bed with threaded steel rod. At each end of the top bar is one wingnut & 2 penny washers, that screw down onto the M8 steel threaded rod that sticks up out of the base.
The 2 holes in the bed for the steel rods are made a tight fit, and the threaded steel rod screwed into place. A penny washer and nut on the underside completes the fixing of the threaded bar. Its possible to use bolts in place of the threaded rod if you can find some long enough.
Finally softwood strips are added to the base as feet, to prevent the threaded rod ends scratching things. The feet must be deep enough for the machine to sit happily with the bending section attached and lying down flat.
Loosen the wingnuts, and slide your sheet metal under the bar. Do the nuts up tight by hand to hold the sheet metal in place. Don't use a power tool.
Place a binbag on the hinged bending section, between it and the sheet metal, or you can use 2 layers of polythene. The plastic eliminates most of the friction, preventing the bending process pushing the workpiece away from the handle.
Stand on the crossbar and lift the bending handle up to bend the metal. If you don't stand on the crossbar, the workpiece will slip during bend.
When bending the maximum width and thickness of steel, it can prove necessary to use large clamps to assist the crossbar, or to have a 2nd person also stand on the bar.
This is a very basic metal bender, something any DIYer can make easily and at hardly any cost. Its not intended to be high performance equipment, but just to get the job done. It was constructed to fabricate structural car parts, for which it proved quite capable.
The main limitation is that the radius of bend is not sharp, due to the limited restraint on the metal. This is something that would take a full redesign to put right, but the bends made are quite sharp enough for most tasks.
Its necessary to stand on the cross bar to prevent the metal slipping during a bend.
If used regularly with maximum size metal, 2 issues can occur.
- the bending corner of the bar can become less sharp over time, and the bar need turning, and after a while planing, and eventually replacement.
- A lot of force is put on the hinge screws, and in time these loosen in the wood if bending the maximum metal size.
A much larger section crossbar could eliminate the need to stand on the bar. High forces act on the bar in both directions, so 4x4 or 5x5 is probably better than 2x6.
1 or 2 corners of the bar can be rounded to provide bends of large radius for decorative purposes.
A second top bar could be added behind the first to increase the grip on the sheet metal, helping to prevent slight movement during bending.
The best improvement is probably to replace the machine entirely with a design that produces a tight bend radius and handles larger steel. Nonetheless this basic design has many uses, and is within the price and time range of any regular DIYer.
To make U shape sections, maybe a U shaped bar radiused on 2 sides could be used. After the first bend, which creates the lower half of the U, moulding is bolted to the hinged bending section and the upper half of the U is bent. Maybe.
Somewhat similar designs are used to press a C shaped channel into aluminium strips. These are used as heat spreaders in UFH, and as heat collectors in solar panels, with pipe pressed into the channel along the centre. This use would require some modification of the design.