Wednesday, June 24, 2015

Simple saw tuneup

So, while in the midst of my masters level coursework on Japanese saw rehabilitation, I needed to cut some wood. Specifically, I needed two short lengths of 2x12 that I am turning into a reasonable facsimile of a Japanese style saw vise, so what do I grab?

I swear that I'm not doing this just for the pleasure of tormenting Sebastian (he hates this poor little saw, haha), but it is a handy tool to have, it gets used on a daily basis...... and this one in particular can be improved.

Mark's rule:

  • 8) start on modern western softer thicker blades

This is your garden variety handsaw, something that you can buy in most any home store. The last time that I went to Home Depot, while they didn't have this exact saw, they had another brand that was more or less identical. It's backwards ( ie: cuts on the push stroke), but uses a Japanese style tooth pattern, similar to ChoMasaru, actually. The teeth are impulse hardened.

From day one, this saw exhibited a slight tendency to drift to the left, just a bit more than you can overcome easily, so you had to start the cut slightly off to compensate. Stuff like this didn't used to bother me. I always figured that I just kinda sucked at sawing, you know? Well I've gotten slightly better with the saws, so when this guy started to drift (as it always has), I thought "Screw this! Your time has come, Sucka!"

Unfortunately, this was a spur of the moment decision, so my pictures are a bit worse than usual.

The last time that I was at Home Depot, I took a good look at the handsaws they carried, four different types, if memory serves.

  • $9.....Bottom rung super cheap/crap Western style tooth. Painful to use, dull, bowed and ugly. This would be the only saw that you would ever need, because after one use, you would likely never cut anything else by hand, ever again. Made in China.
  • $12.... Basically the same as the saw above, but with a Japanese style tooth. Bowed along its length, and the tooth cutting operation had left a significant bur edge along one side of the entire blade. This would cause the teeth to snag and load up with wood fibres during the cut, and would also cause the teeth to cut unevenly. This saw would drift like a SOB ! 4 out of 5 were significantly flawed, but a few weren't so bad. Made in China.
  • $18....short toolbox type panel saw, Japanese tooth pattern, bowed along its length but the tooth finish was a bit better. Impulse hardened. This saw would at least be functional. Made in China.
  • $32.....Stanley "fat max" short toolbox saw. Japanese tooth, impulse hardened. The tooth finish looked decent on these saws. Some were bowed slightly, but they weren't bad. Obviously this line of tools is targeted at the working professional who understands the value of quality tools ( and big pickup trucks!). Made in China.

Yep. All crap. They sell about 350 kinds of power saw, though. Also, that these crap saws are all made in China? They just build what we want to buy. This is our own fault.

Notable was the erratic quality control. If you need to buy something and know what to look for, you could get a usable saw there, but if you just grabbed the first one off the rack? Good luck with that.

Time for a tuneup!

The shiny, brighter patches are where the saw rubs during use. Some of these areas are from the saw binding, getting kinked, smacked into something, having a tree fall on it.....whatever.

Used, and used hard. The saw plate is very stiff, so there haven't been any severe bends, but there are a couple of mild kinks.

This horizontal line shows one slight kink.

And here is a second one.

Neither of these kinks amount to much by themselves, and are barely visible when you sight the length. The saw still cuts pretty good, but it could be better. What the heck, right? I might learn something.

Theoretically, a decent handsaw has the blade under a certain amount of tension. The tension helps to keep the saw teeth in line. A saw that is poorly tensioned feels floppy and dead, whereas a nicely tensioned saw feels alive. The tensioning process is now done by machines, but back in the day, it was performed by the sawsmith, sharpener, or metate.

Bob Smalser goes into this "Straightening of a western saw" thing in some detail, and his work could be considered the Bible on this subject.

It seems highly unlikely that this saw was ever tensioned. The saw plate itself is so thick and stiff, it probably wouldn't have been necessary. But......what the heck, right? Bob says that the first thing to do here would be to remove the tension at the tooth line. Theoretically you want the blade to be in as neutral a state as possible before you attempt the straightening process.

Tension in a saw blade, an interesting thought. In the illustration below, fig.13 is a good analogy of how I imagine a handsaw blade to be under tension.

This from Drabble and Sanderson saw doctors guide 1925

This wouldn't be correct in a literal sense, but I like the analogy. This work specifically is in dealing with large sawmill blades, blades where rim speeds are in 100's of mph and the blade itself operates at heat. I could go on here, thinking out loud, but......back to the project at hand.

Bob says remove the tension at the edge. The small hash marks running perpendicular to the teeth represent where I aim to strike, running the full length of the blade.

Strike on the oblique, to direct the force along the length.

Run down one side, the saw reacts by bending into a gentle curve.......flip the saw over and repeat the operation on the opposite side. The curve disappears.

Back to " The Handyman's Guide".

Here are those two gentle kinks, all marked out where I want to strike.

This saw blade is thick and stiff. I need to strike nearly 2x as hard as I have been with the Japanese saws. How hard?

Mark's rule :

  • 4) don't hit harder than it takes to have an inspect-able result

I hit along one series of those lines that represent a kink, maybe 10 strikes. Sight the length, and if the kink is gone.......that was hard enough, haha. Far better to hit lightly than to strike too heavy. I run the line on one kink.....sight the length....some effect, but not gone the line of the second kink.....sight the get the idea. I maybe did each of these lines 3x's.

Mark's rule:

  • 2) work by halves - sneak up on straight little by little
  • 3) don't focus on a couple square centimetres

Sight down the back of the saw, too. Maybe the kink is harder/more pronounced towards the back of the saw? The only really important thing here, is that I am training my eye, learning to see how the blade responds to the hammer's blow, the kinks and bends. As I look at the saw, I am learning to see, but it is now becoming so subtle that it can barely be described as "seeing". It is becoming something between sight and imagination.

As you check your work, it is likely that some new kinks or bends might manifest themselves, bending the saw to the other side. At the very least, I have been very lightly (1/2 as hard) hammering the side opposite the kinks, kind of generally working lightly over the entire general area.

Mark's rules again.

  • 3) don't focus on a couple square centimetres
  • 1) work from both sides

I do all of this work on the anvil, though not shown on this picture. And you don't need an anvil per se, just a heavy smooth chunk of steel. In fact, a regular mild steel block might be preferable, at least for the straightening process. Mild/low carbon steel would have a touch more "give" to it, if that makes sense.

So after striking the lines, working out those kinks, the saw is actually quite straight, better than new! As I look at the saw more thoroughly, I see many small rub marks, all over and on both sides of the blade.

I map them....

.....then strike, except this time I am using a small ball-pein hammer, because the marks themselves are more round in nature. I figure that the hammer should match the work.

Those little they get hammered out, the shape of the saw changes. Fix one thing, two others might show up. If you only concentrate on a single area, nothing works. Work the entire blade and the deviations have a tendency to cancel each other out.

Many of these distortions are artifacts left from the factory. When they punched out the blank for this saw, those goofy little holes....each hole represents energy input, and distorts the blade slightly. Most of the energy leaves the saw immediately, as the metal slug is punched free, but a little bit remains. That is the distortion you see around each of those penetrations.

Hammering down the high spots is, in my imagination, allowing the remaining energy to be spread more evenly throughout the body of the saw. Even and relaxed, good things.

It is straight, although the set of the teeth now need to be adjusted, haha.

Something for another day.

The tension was a removed, now I want it back. Going back to the previous illustration Fig. 13, you want the toothed edge to be straight and "tight". The body of the saw should be "loose". Hammering the length, about 1" up from the edge, gives tension to the toothed edge.

I try to do both sides evenly, but I need to sight the length to be sure. Adjust the plan accordingly.

I bend and flex the blade, sight down the front, the back, hold it up to the light......just kind of "look" at it for a while. It feels like this saw needs something more.

Both sides, of course.

Double/triple check that things look good, then I take her for a spin. Miracle of miracles, the saw works like a charm. Success!

This saw now cuts straight and true, effortlessly cutting the line, and requires much less attention to use. Instead of working to stay the line, now I can concentrate on power, keeping my stroke clean.

In general, as my sawing has improved, I have begun to slow my stroke fairly dramatically. I concentrate on the saw, the blade, and try to "feel" the teeth as they cut. My arm speed has slowed, but my cuts are actually quicker to execute, and clean. Less to clean up afterwards. Slow is fast, right Gabe?

Ultimately, this is a trial and error process. It's no big deal.

  • 16) It's only a saw. You are only You.

This whole process start to finish, took maybe 15 minutes. A lifetime of crappy sawing, fixed in 15 is short, and there is much to learn.

1 comment:

  1. This removing the tension from the edge with the hammer, did it make a noticeable change in how the saw cut before you re-tensioned? It seems quite counter intuitive that striking along the tooth line with a cross peen would remove tension. My grandfather has an Irwin hard pointed saw, but as a full length panel saw. It cuts very well, but the saw flops around in use like a beached fish. It seems obvious to me now that it needs tensioning. Any reason you used a round faced hammer to tension? How did you know when the saw felt like it had enough tension?
    Lol, I'm full of questions today. As far as the smaller distortions, how does it go for you to sight them visually? I mean to say, are you having much luck holding the saw up in front of you and viewing the plate at a low angle? Most of the time when I am looking at a saw the distortion I can see in the plate does not readily suggest how to be corrected with the hammer. You're doing great work! Though a humble little saw, that tool now has a lot more value.


Like all of us, I am figuring this out as I go, so when you see something that is incorrect or flat out wrong (and you will!), let me know. This is a learning process. Real people and names, please. Constructive comments and questions are very welcome, but hate speak/politics are not! Life (get one!) is too short.

Thanks, Jason