Is there a functional reason for the flexibility of a saw blade? I understand that thickening the blade at the top limits how deeply you can saw into wood. I’m asking, does the flexibility itself serve some purpose? Or is it just a consequence of the narrow gauge of the blade?
You want the blade to be thin, both to make the thinnest cut and to make cutting as easy as possible. (Every try cutting a steak with a butter knife? ) Most saws usually have a thick bracket on the top edge to make it a little more stiff. Blades under tension, like a hacksaw or bandsaw are also less flexible.
If you made a thicker saw, you would find it much more difficult to cut through the wood. Things like table saws can get away with thick blades because they have big motors that are much stronger than your humble arms.
If it wasn’t flexible, there would be a great chance of the saw fracturing if you jammed it.
The spring steel also helps absorb excess vibration from being transmitted to the user.
If the blade cuts on the forward stroke (in compression) then it has to be thick enough to resist local buckling (grab a sheet of paper at two points and push your hands towards each other to see what happens).
If the blade only cuts on the pull stroke (tension) then it doesn’t have to resist buckling and so it just has to be thick enough that the metal won’t tear apart as you pull it through the wood. Steel is extremely strong in tension so you can have a very thin blade (take the sheet of paper again and this time pull the two points apart instead of pushing them together. Paper goes taught and stays straight).
Pullsaws and most Japanese hand saws (dozuki, I think they’re called) cut on the pull and are very thin, making extremely precise cuts. I have a cheap pullsaw and it’s fantastic for flush-cutting dowels, trimming precise lines, etc.
The only blades I’ve seen that are sufficiently thick at the top to limit depth of cut are dovetail and miter saws. And it’s a stiffener, not a limiter. The intent is to keep the blade perfectly straight for the fine detail work of mitering and dovetailing.
Also, if a saw wasn’t flexible, it would be harder for folk musicians to stroke with a bow and make it “sing.” OK, not exactly functional, but some people seem to like the sound.
I learned from a “fine old German craftsman” to put hacksaw blades in so you cut on the pull. Works fine. However, whenever anyone else uses my saws, almost without exception, they are hard on the teeth by trying to make the saw cut on the push.
I guess I should add that I use “cut on the push” for thin material such as sheet metal like downspouts and such.
I’m trying to imagine the advantage in reversing the blade on your hacksaw frame. Could you elaborate?
The “miter saw” is called a backsaw. It is commonly used for cutting miters but that is not it’s only purpose (it can crosscut, also).
Well, for one thing, having the force ahead of the resistance (in the direction of motion) is a stable system. Having the force behind the resistance is unstable. In the latter case any slight misalignment of force and resistance gets worse as you push harder.
Don’t forget coping saws, whihc have a blade pulled taught like a hacksaw.
Some saws that will be passing through alot of material are usually better suited if they are flexible. Ridged blades for dovetailing, mitering and other jobs are good and can do different things, but for rough cutting where you pass through considerable material autonomously, the flexible saws usaully prove more valuable. Quantity versus quality.