Frame Saw: Important tweaks

After a bunch of sessions with the new frame saw, I determined that it wasn’t working the way it was supposed to. It didn’t cut quickly, the kerf was too wide, and the blade wandered all over the place. I suspected that more than one thing was wrong, and I had a few ideas.

First, I caught on to the fact that the blade wasn’t really sharp, although it had the appearance of being sharp. I really need to learn that if the guy who made your saw doesn’t have a name like Wenzloff, it probably isn’t sharp, so you should save yourself a lot of trouble and sharpen it before using it. Groan.

I reshaped the teeth to have a fairly aggressive zero-degree rake angle, and took a considerable amount of care when sharpening to make sure that the tips were all very close to the same height. The result looks like this:

When doing this, I realized two additional things about this blade. First, it had way too much set, and second, the saw plate is a little thicker than I thought it was. This latter point was a big deal, because it seemed like the tips of the points originally were chamfered or slightly rounded. I couldn’t see this originally, even with reading glasses. And obviously, it makes a big difference in use, because, as I find over and over again, sofa-shaped blades don’t cut wood very well. (I wonder why.)

The difference in sharpening alone was really remarkable. Because the process removed most of the set, it made for a wonderfully thin kerf, and therefore, it tracked a line much better, even though the blade wasn’t terribly taut. And the more aggressive and sharp teeth cut much faster and smoother.

Now, the second problem I was having was that I couldn’t increase the blade tension too much, because the little screws that I was using to hold the blade in place were snapping due to the tension:

Yikes. So I cut and filed a few brads for this purpose:

Now that there’s enough tension, I don’t have a problem with the blade twisting around (thanks for the pointer, Dan). The only issue I have now is that it’s difficult to keep the blade straight when tightening it up. Christopher Swingley uses a wrench on the flats, which seems like an idea that might work.

After making these two changes, this saw really seems to be on the right track, and I think I’ll be able to do decent work with it. I already sawed out some 3/16″ slices from a couple of smaller boards (without even marking!), and they came out great.

There always seems to be a lot of discussion about frame saws, and what kind of blade is appropriate. Tom Holloway’s saws use thin blades, and I can attest to how effective they are, having played with them. Bob Easton uses thicker blades from old Disston saws and that seems to work too. It seems to me that there’s more than one way to skin a cat.

A case in point here is what I edited in as a note in my last post, that there’s a version of a Japanese saw, the “oga kobiki” or something, that has a gigantic blade, but seems remarkably easy to use. Check out the pictures in this link if you haven’t yet. You see how that tiny woman is using that huge saw? Look at how beautifully the cut turns out. Oh, how I would love to examine that saw that they’re using.

So it seems that if the kerf is even enough–not too wide, not too narrow, of constant width, and straight–it doesn’t matter how big your blade is, as long as it’s slippery and sharp.

I don’t think this is going to be the last blade for this frame saw. I’ve got some ideas that might make it faster. Let’s just say that the gigantic teeth on the Japanese saw got me thinking.

I also got to thinking that I might need to do something about my saw vise. It works pretty well for small saws, but when you start to file the big teeth, it shakes too much. What to do here? Finally make my own? Cave in and get one of those new Gramercy saw vises? Find someone who has a good one and mug them?

Published by bricsuc

I have no idea what I'm doing.

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2 Comments

  1. Very nice saw! Another way to keep the web from twisting as you tension it is to bury the ends of the web in a kerf cut in the ends of the frame (or glue on wooden stabilizers on each side of the web.

    I think you hit the nail on the head regarding the performance of these saws when you mentioned the giant teeth in the Japanese saw you linked to. The saw in that sequence has a couple of features that make it more suited to resawing than the blades commonly commercially available to us for making these saws today.

    First, as you noticed, the teeth are huge. The Putsch blade is about 5 TPI. This is fine for ripping 1″ or 2″ thick stock, but when you resaw, the thickness suddenly jumps to 6, 8, 10 even 12″ or more. For sawing something this thick, the teeth on a typical rip saw are way too small, even at 4 or 5 TPI. This causes the gullets to clog up with swarf long before they can clear the kerf and leads to slow cutting and a saw that tends to drift in the cut. The only solution to this is fewer, larger teeth per inch, as seen in the Japanese saw. There are no saw webs commercially available that I’m aware of that come with teeth that big so we are basically left to make our own.

    I retired (and repurposed) my frame saw several years ago because I just couldn’t get it to perform well, push or pull. I’m convinced it was the blade, not the design (I used a 1-1/2″ wide bandsaw resaw blade; another huge mistake). I could never tune that saw just right but I can resaw just fine with my 5 point hand saw, though it is slow going for the reasons I mentioned above. The benefit of the hand saw is the wide saw plate, which helps to minimize drifting induced by clogged gullets. I think this is the problem with most saw webs on the market when we try to use them to resaw with. Too many TPI and too narrow of a web to stabilize the saw. They just weren’t designed for resawing. I think the web in the frame saw in Roubo was like 3 or 4″ wide. I would suggest making a web of 2-3 TPI tops, maybe even more like 1-2 TPI. I think this would be much more appropriate for resawing than the 5 point webs we typically see used. The Japanese saw you linked to seems to agree with that.

    The other unique thing about the Japanese saw is that they file those teeth with positive rake (tooth leans into the cut). This makes them very aggressive but also fragile. I don’t think you could file a push saw with positive rake like that. The saw would likely just buckle in the cut or the teeth would break. The pull stroke is what makes a saw with such an aggressive rake possible to use.

    If you do decide to make your own web, please let us know how it turns out and compares to your current setup. I would be very interested in the results.

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  2. Hi Bob, yeah, I have given the stabilizer idea some thought. I also just realized that, since the tension now seems high enough to keep the blade from twisting during use, I could just make a stabilizer that I can slide or clamp on when I’m tensioning and skip the glue.

    I think you pretty much summed up what I am going to try next. I really like the idea of at least a little positive rake angle and I think it might be feasible, but I need to draw up some ideas. I also need to learn a different filing technique, because the usual triangular tapered files are probably not going to be ideal for this sort of thing. Unfortunately, I don’t have the time right now to do anything, so I’ll have to revisit it in a couple of weeks.

    Resawing is tough enough work, and these frame saws turn out to be kind of tricky, so I can see why people generally wouldn’t care to go to so much trouble to perfect one when you could just get a silly bandsaw. However, this is not really an option for me at the moment, and I don’t like giving up anyway, so I’ll keep fooling around with this thing.

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