Leif Hansson of Norsewoodsmith has wrote an excellent series of posts regarding how to make a backsaw.
I have used some of that information for inspiration, and I hope I will be able to make a usable saw shaped tool.
We have on board a large plate of 3 mm copper (1/8"). While I know that copper isn't a super traditional material for backs, the esteemed Badaxe toolworks actually make a saw with the back made out of copper. I would have preferred brass, as I like the shiny gold look of it, but copper should be able to do the trick too.
For once there is a slight advantage to working out here compared to at home in my own workshop. Because we happen to have a small hydraulic press, that can be used for bending saw backs.
In order to make my backs, I first sawed out a strip of copper from the plate. I chose to make the strip 4 cm wide (1" 9/16) Because that would give a back of around 3/4" height when folded.
After the sawing, I lightly chamfered the edges to remove any burr. I also scratched a line down the middle to help me determine where to start the folding.
For the first part of the bending, I placed the strip inside the V of a piece of anglebar that I had placed on the supporting blocks for the press. I then pressed a smaller piece of angle bar onto it, and thus formed a V shape from the strip. The small angle bar bent a bit, so for the next back I used a piece of 2" flat bar instead. That actually worked better.
The V shape was further bent by gradually pressing the sides closer to one another.
Once I was past a 90 degree angle, I placed the entire back between the support blocks, and stepped on the hydraulic press with all my weight. That was resulted in the pressure delivering its full potential - 15 ton.
I flipped the back over and gave it the same treatment from the other side, and finally I placed the upper support block something like 1/4" from the rounded side of the back, and pressed again. This resulted in the two sides touching each other nicely.
There are definitely some tool marks left on the copper from the folding, but since the material is so thick, I can easily remove them using a file, and still not compromise the stiffness of the back.
Also the sides didn't end up being exactly the same on each side, so the backs will require a bit of filing to look really nice.
Each of the backs I made are 10.5" long, not because of any calculations, but due to the fact that the copper plate had a section that would allow that specific length. I think they might be long enough for a 12" blade, since the handle also offers some support for the rearmost end of the blade.
My plan is to make a set of 10" saws with small handles that my boys can use in the workshop. One filed with rip teeth, and the other with crosscut teeth.
Ripping out a copper strip for a back.
Scratching a line in the middle.
Initial bending using angle iron.
Still a bit of way to go.
The final and nicest looking back is for Brian Eve.