Old Disston backsaw mystery
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Tagged: Disston sharpening taper
- This topic has 7 replies, 4 voices, and was last updated 7 months, 1 week ago by Craig Alderson.
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22 September 2023 at 5:29 pm #814080
I’ve been restoring a Disston backsaw that I recently found in an old rat-infested toolbox in an old rat-infested garage at my family’s old house. Everything in the toolbox was in pretty sorry shape, including a trio of Bedrock planes, alas. I’m doing my best to bring them back to life. I originally thought that saw was from the 1880s or 1890s, but I was astonished to discover that apparently it dates to prior to 1865. I think it may have been passed down from a distant great-grandfather, who we know was a woodworker.
The saw is coming along pretty well and my next step is to joint and sharpen it. It has a 12-inch saw plate and is filed 22 tpi, so my guess is that it was used for dovetail and other detail work. I noticed that the teeth line angles upward (I.e., toward the saw back) beginning about 3/4” from the end, for a total deflection of about 1/8”. It could be sloppy sharpening from years past, but it sure looks deliberate. I know with old dovetail saws it was common to taper the width of the plate, and I’m wondering whether that’s the case here. I’m trying to figure out whether in sharpening it I should try to preserve this angle or try to straighten out the teeth line.
Is anyone familiar with this practice of angling the end of the saw? Would it have been to make starting cuts easier, or was it for the same reason as the taper of saws, or was this just perhaps an individual customization?
That’s very interesting! My pure speculation would be that it’s similar to how Paul sharpens the first inch or so of the teeth at a less aggressive angle for starting the cut. By angling that portion of the saw, your ancestor would know which teeth were sharpened in this manner, and would be able to keep them out of the way once the cut was started. If that was the purpose it’s brilliant! I’ve not seen or heard of such a thing so I’m curious to hear other responses, but your theory of it being used to start the cut makes sense.
23 September 2023 at 4:23 pm #814170That was my first thought, too. My second thought was, “Hey, wait a minute.” If I’m starting a cut and I’m holding my saw parallel with the surface being cut, the angled teeth mean the saw is going to contact the corner nearest me first. If I push forward now, the saw is going to dig into the wood. That angled end is going to create a slight pressure akin to pushing the saw down into the wood. That doesn’t seem like it will particularly help get the cut started, and it seems more likely to cause a ragged beginning of cut.
I could lift the heel of the saw to bring the teeth parallel to the surface, or to contact the far corner first, but at that point, what’s to be gained by the angled tooth line? You could do exactly the same thing with a straight saw edge, and it would be more predictable in use and easier to sharpen. I don’t get it. I haven’t actually tested any of this on real wood, yet; I’m just musing.
23 September 2023 at 5:27 pm #814175I should add that if the teeth at the toe are filed with a shallower rake, a la Paul’s method, there’s no reason to get them out of the way of the cut once started. Those teeth are still just as capable of cutting as the main line of teeth, so why disengage them from the cut? Why not just have a straight tooth line?
24 September 2023 at 1:37 pm #814268Can you Take a picture so all are on the same page with an answer for you?
24 September 2023 at 9:54 pm #814308Could it be a tapered saw blade, as the upper one in the attached photo? I think that one of the tenon saws that Mr. P Sellers uses is an antique one with a tapered blade, so probably not a modern concept.
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You must be logged in to view attached files.25 September 2023 at 5:34 pm #814373Yes, I initially thought it might have been some kind of taper, but it’s not a blade-long taper as in the photo. The tooth line in the photo is straight; it’s just that the plate there is narrower at the toe than it is at the heel. In my case, the width is the same until the last 3/4” to 1” of the toe, when the tooth line angles upward. It’s not a sharp angle, as the intersection of the lines is a little rounded for smoother cutting, and there is not a continuous curve at the toe of the saw. It’s more like two pencils being crossed at about 177*. (I’m sorry, but I’m not able to take a photo for this, so the verbal description will have to do.) it’s very curious.
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