Bending Brass for the Backs
Now I have the steel and brass cut to to rough size:
OK - not quite yet. There's one more step I must complete before I can actually start making saws. I need a way to make the initial bend of the back.
One of the most obvious requirements of making a back saw is having a way to bend the back over. With patience, and more than a little skill, it could be done with a simple hammer - I've not found this skill, myself. Every time I've tried something similar, the results have been poor - besides, I wanted to make more than a couple saws. The solution - a metal brake, made specifically for bending the backs.
- I should point out that a brake is not the only solution to bending the brass. You can bend brass simply by mounting it in a vise, and bending it over with a hammer - a piece of angle iron mounted beside it in the vise would be helpful. However - for doing multiple backs (why not?) this brake is very handy, and I believe it also aids in producing a better quality back - less hammer marks, a more consistent bend, and less chance of producing stress cracks in the brass as it's bent over.
The challenge for me was to build one using only materials I had on hand... I did not want to spend any money (mostly because I didn't have any) - especially for building a such a specialized item. I looked at what I had on hand, and lo, it was was the iron I had purchased to make a mobile stand for my band saw - a project I hadn't gotten around to yet. Here's a schematic of what I came up with:
The entire affair is bolted together using #10 flat head machine screws, where the head of the bolt was made flush through using a countersinking bit. You'll notice the screws I used are much longer than necessary - that's because that's the size I had on hand. The two sets of two washers you see are to make a space for the brass to fit, with the flat bar above the washers being the piece of steel that the brass is actually bent over. It probably helps to actually see what I'm talking about, so here's a photo of the brake with one of the brass blanks inserted into it, ready to bend (sans the 2 handles, added later):
It might seem to you to be a rather complicated affair just to bend brass - but trust me, there is a method to the madness. You see, the trick to successfully bending is to make sure the bending point of the brass will be centered on the turning axis of the hinge, such as shown in this diagram:
This configuration allows one to bend the brass easier, with more consistency, with less damage to the brass itself, and allow me to bend the brass a full 180 degrees, leaving only the thickness of the steel it is bent over. I can later use a hammer to close the brass completely over the saw blade. Many bending brakes cannot achieve this - getting you only about 120 degrees of bend, leaving too much hammer work, which means more potential for damaging the brass (at least for me).
OK - this next part is tough - I don't know if I can explain the building process for the brake adequately, but want to explain some of the reasoning behind it at the same time, so I hope it doesn't come off sounding like gibberish.... Please refer to the schematics and photos above (and also some of the photos that follow where I'm explaining the bending process) for help in clarifying some of the rambling that's about to happen.
The finished length of the brake is about 18", and it has the capacity to bend a back of about 11 inches in length. I can't recommend making one with a longer capacity without beefing up the steel quite a bit. This one, working at it's own full capacity, is probably at more than it can handle without damaging itself.
The angle iron is 1/8" x 1-1/2" x 1-1/2", the flat iron is all 1/8" x 1-1/2". I started by installing a pair of standard 3-1/2" door hinges onto two lengths of angle iron, letting the hinged portion protrude past the iron the same as it would on a door. I added 3 screws through the hinge and iron to help stiffen the hinge a bit, you'll notice it in subsequent photos.
A second 11" angle iron is added on the right angle iron, between the two hinges to raise the "bed" of the brake so the brass can be positioned where it is bending on the axis of the hinges. This has the added benefit of stiffening this portion of the brake - and thusly will make a good place to install the handles. Without stiffening this angle, the brake will not be strong enough for it's own good. The handles are just 2 lengths of the same angle iron, and are attached with a minimum of 3 machine screws, through both angles and the "handles".
An 1-1/2" piece of flat iron is installed on the top of the left angle iron to raise the "bed' on that side of the brake, then another 1-1/2" piece of steel on the top of that again. This last one separated from the previous with a stack of washers that add up to the thickness of the brass I am using, and this is where the brass is inserted for bending as you can see in the photo above. This top bar is centered vertically on the hinges axis, but held back from the center horizontally about 1/2 the thickness of the brass, so the brass that is being bent is actually centered on the axis see the last diagram, and the photo below:
Here you can see the handles are installed with two screws. Wait - didn't I say to use a minimum of three screws to attach the handles? Yup. I did. I know why I said that, too.
I also cut a couple notches in this last flat bar, so I could center the bending edge on the axis of the hinge - you can see those notches in the photo above by the hinges, and you can also see how it is centered on the hinge fairly well.
Just for clarity - here's a shot of the brake opened up from the other side:
Notice the added screws in the hinge to stiffen them. On to bending some brass!