I'm still working on this guy.
My understanding of the saw straightening process is growing by leaps and bounds, though it is woefully far from complete. What value is there in showing you all of these seemingly endless pictures of a beat up old saw? Well, if nothing else, I want to show that this is something that can at least be attempted.
The knowledge gained here is already having an effect on my skill at actually sawing stuff. I am seeing the saw itself differently now. Before, a saw was a tool that was used to cut something. Now I see a saw as a series of tiny knives, held in accord through their connection to an armature body of hidden strengths, tensions and harmonics. A saw is like the UN.
It also could be thought of as a device for honing ones ability to endure frustration, a hateful thing to be fought perhaps? (?)
Nah.....I love this!
Using a straightedge, I map out the areas that are still the most in need of attention.
In reading a thread on sawsmithing hammers, someone posted this excellent reference.
From 1903...."The Handyman's Guide" by Paul N Hasluck.
It frustrates me to no end, that this common knowledge has been all but lost. In my grandfather's depression era world, you fixed things. You took care with what you had, saved up to buy what you needed, but never bought what you couldn't afford. He said that having too much can be worse than not having enough.
I like to think that my grandfather would approve of me working this way. I think of this a lot.
The idea is that each strike of the hammer has an impact on the steel, literally. You can't actually make more steel, you can't really alter it that way. The steel is what it is. What you do have, you can make thinner. Thinner metal would seem larger, would occupy a greater surface area.
A round face affects the steel in a radiating fashion, like ripples in a pond.
You see the little dimples to either side of the hammer strike?
A wrinkled piece of paper is smaller than a perfectly flat sheet. When you impact the blade, you are creating contour that effectively "shortens" the blade.
A cross-pein hammer has less surface area at the point of impact. It's influence is greater, but over a smaller area.
I try to use this to my advantage.
You will notice that I am striking the steel obliquely. In lieu of having a cross-pein hammer, I am trying to angle the hammer blows to most effectively work the steel.
With the largest of the lumps worked down, it's time to think about removing the bow. First, I check against the straightedge.
A good 1/8" out.
Here is where the directional application of force really becomes apparent. Striking along these perpendicular lines causes the blade to bow upward.
This technique was always referred to as "hammer shrinking" the metal, but that isn't what is really happening. You don't "shrink" anything. you are increasing the surface area, at the expense of material thickness. Always remember, you are making the steel thinner every time that you strike it.
In any event, striking along these lines causes the blade to bow upward, away from the anvil. Keep referencing against the straightedge until things are looking very freaking straight. That's what I'm doing, at least.
Checking across the width, you can see that there are still plenty of high spots that need addressing. I don't know if a perfectly flat surface is something that I CAN achieve, it might be nearly impossible, given the prior welded repair, but I want to give it my best shot.
It turns out that these longitudinal undulations (and removing them) are somewhat crucial to the operation of the saw.
So, I got this thing to a state as near to perfection as I felt was possible....I mean flat! No tensioning yet, because I am still trying to figure out the whole tension thing and, while single edged saw seems fairly straightforward, a ryoba is another beast entirely. Anyways, I thought that I was getting close. I felt that it was time to start refining the process a bit.
I took the saw out for a test drive, and low and behold....the bugger bound up. Not horribly, but still.....I thought that I was getting so close! Granted, by this time I have removed nearly all of the set that was in the blade, but I figured that would better allow me to determine where the remaining trouble areas were.
The binding was one thing, but the most alarming aspect of the saws performance was the way that it rocked back and forth throught the stroke of the cut. Obviously there are still some big deviations in the blade that need work. The rocking motion is due to the sides of the blade interfering with the already cut surfaces. That there is no set to this saw magnifies the action, but it still shouldn't happen.
Altering the set of a saw would be an easy fix, would make it work, but it wouldn't work as well as it could. I think that I can do better.