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    Saw blade topography: taper grinding

    I've been researching hand saw making and wanted to understand the implications of blade taper grinding. This is a feature where the thickness of the blade is ground thinner in some areas more than others for various (supposed) reasons: lighter weight, better balance, better flexibility, less binding, thinner kerf, etc.

    Few new saws sold today offer this feature, typically only higher end brands like Lie Nielson, Bad Axe, and Pax. There are others, but apparently many more vintage saws had tapering. Disston was an early and vocal proponent. I've been curious how significantly this affects the performance and wanted to see the data for myself.

    Well, there's no substitute for researching an original, so I purchased a Disston D-23 from Chris Black who makes and sells tools in Rolesville (who I highly recommend) and began measuring. I have no idea why this kind of information isn't all over the web but it's not. There are plenty of sources for handle shapes, but nothing on blades that I've found. So here's my offering.

    (click to open full size)


    This uses an earth grading convention to draw the "topography" of the saw thickness. Each line represents a thousandth of an inch and I show the locations for the spot measurements as well.

    I was surprised at how comprehensively they ground it. I was expecting only the edges to be more heavily profiled, but it's obvious they ground across the entire face except where the handle attaches to what probably started as a 0.038" thickness plate.

    So if I get some sheet stock to make my own, I want to understand how important taper grinding might be and how it could be done for just a few saws at a time. Eventually I found some YouTube videos of the grinding process, done on large 24"+ diameter wet wheel grinding stones. It might originally have taken just a few minutes per saw with a stone large enough.

    Unless someone here has one (!), it can also be done with a belt sander with careful attention not overheat the steel. The Disstonian Institute reports that the original Disstons had just 0.75% carbon, so 1075 is all that is needed to match them, which should also avoid issues with the grinding process accidentally making them overly hard. I plan to start with annealed sheet and temper it after filing all the teeth. (I used to temper various tools in a blacksmith shop. It's pretty straight forward if you start with annealed.)

    But is taper grinding even important? Most of this saw's blade is between 0.031"—0.037". That's a hair's breadth and I find it hard to believe that it really makes a difference. Only a small portion of the tip is <0.030".) My saw cuts well, but the tooth set is a lot more responsible for the kerf thickness clearances than the taper. And teeth are much more challenging to set to such a close tolerance. So I doubt I'd want tapering unless I was a pro working the saw all day, but I'd still try one saw just as a control case.

    I'd love to measure other vintage taper-ground saws to compare if anyone in the Cary-Apex area is willing to share. The handle has to be removed, but I use a carbide-tipped 1970's Brown & Sharpe calipers and a white charcoal pencil to spot all the dimensions for photography so that it easily wipes off. Then a quick trace is enough to measure and scan for drafting in CAD.

    I know there are probably dozens of NCWWers with more saw, tool, and tooling experience than me—any insights?
    Last edited by SteveHall; 04-23-2018 at 10:04 AM.

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    Re: Saw blade topography: taper grinding

    Steve, thanks for sharing your findings. I seem to remember reading a blog along the way by a saw maker whom is grinding his own saw plates. He was using an angle grinder and a disc. His results I'm uncertain of. If I have the time I'll dig around for it and share the link. Saw making has been an interest of mine and I have fiddled around with backsaws and a few others along the way. That said, good luck with your venture and please share more.
    Last edited by Graywolf; 04-14-2018 at 06:46 PM.
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    Re: Saw blade topography: taper grinding

    Too bad I'm not closer....

    20180415_194429.jpg

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    Re: Saw blade topography: taper grinding

    Wow, great collection of Disstons.

    Quote Originally Posted by Chris C View Post
    Too bad I'm not closer....
    You actually are close—I have several projects going in Greenville and drive down frequently. Exactly what percentage of Ayden is woodworkers? You make the fifth I know/know of there. Any chance I could buy you lunch at Bums or Skylight some time in return for measuring one or two of your saws?

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    Re: Saw blade topography: taper grinding

    Quote Originally Posted by SteveHall View Post
    Wow, great collection of Disstons.



    You actually are close—I have several projects going in Greenville and drive down frequently. Exactly what percentage of Ayden is woodworkers? You make the fifth I know/know of there. Any chance I could buy you lunch at Bums or Skylight some time in return for measuring one or two of your saws?
    There's not many of us way out here on the flat lands.

    You can absolutely measure one or all of my saws. I have several that are 1870's vintage.

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    Re: Saw blade topography: taper grinding

    Had no idea such things were done to saws - you ask is it important, well as you said most modern saws don't do this -- suggesting it's acceptable to not do this.
    However, I did find reference on google to old Popular Mechanics from Feb 86 that said "A Taper-ground blade also prevents binding and helps to ensure smooth sawing."
    The other thing that came to mind -- I've seen folks 'play the saw' - it's arched with some reverse pressure on the tip and you can get different notes from it by changing the arc.
    I'd expect that a ground blade's reduced thickness would make it easier to bend to play.

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    Re: Saw blade topography: taper grinding

    Thanks, Chris, I'll send you a PM to connect...

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    Re: Saw blade topography: taper grinding

    Quote Originally Posted by JGregJ View Post
    However, I did find reference on google to old Popular Mechanics from Feb 86 that said "A Taper-ground blade also prevents binding and helps to ensure smooth sawing."
    That's the part I'm a little skeptical about. I measured only 0.005" difference across the majority of the blade's cutting width. The set on my saw's teeth measure about 0.065" which is 0.028" larger than the thickest part of the blade cutting area. I don't see how the extra 0.005" in the blade could make a difference. It seems the only way to test is to make two identical with one ground, but the grinding is the hard part without a huge water stone!

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    Re: Saw blade topography: taper grinding

    Anyone who has used a tapered handsaw and a non-tapered hand saw will understand why you want a tapered handsaw.

    A tapered handsaw can bind in the saw kerf, but a non-tapered handsaw WILL almost always bind in the kerf...

    (the result being the saw operator utters a few choice words and re-positions him or herself and starts again...)
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    Re: Saw blade topography: taper grinding

    A very interesting discussion! I sharpened saws and tools commercially for many, many years. As I bought out a shop with a Foley Saw Filer when I was starting out, I sharpened a large number of hand saws. I noticed the older, better quality saws had a taper, and I believe they weren't all Disston. The other feature that has generated much discussion is the saw tooth on the top of, and near the front end of the blade. There have been several suggested reasons for it being there, but I am of the, "Well heck, I don't know,' faction. I'd be interested in opinions as to why the tooth was prominent on the older, higher quality saws.
    Experience is a hard teacher; she gives the test first, and the lesson later.

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    Re: Saw blade topography: taper grinding

    Quote Originally Posted by sawman101 View Post
    A very interesting discussion! I sharpened saws and tools commercially for many, many years. As I bought out a shop with a Foley Saw Filer when I was starting out, I sharpened a large number of hand saws. I noticed the older, better quality saws had a taper, and I believe they weren't all Disston. The other feature that has generated much discussion is the saw tooth on the top of, and near the front end of the blade. There have been several suggested reasons for it being there, but I am of the, "Well heck, I don't know,' faction. I'd be interested in opinions as to why the tooth was prominent on the older, higher quality saws.
    That is simply a decoration and that is all.
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    Re: Saw blade topography: taper grinding

    Steve, I was wondering if you needed any more saws to measure, I've a few projects going on around the Raleigh area next week, I have a few really nice specimens
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    Re: Saw blade topography: taper grinding

    Quote Originally Posted by Graywolf View Post
    Steve, I was wondering if you needed any more saws to measure, I've a few projects going on around the Raleigh area next week, I have a few really nice specimens
    I sure would, even of duplicate models/years since I'd like to explore variations in the manufacturing method. Do you have split nut models? I've set up a system to quickly measure but am still finishing the special driver(s) (this week/weekend after the picnic?)

    PM me and we can try to coordinate our schedules.

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    Re: Saw blade topography: taper grinding

    I have a couple split nut saws and several of later vintage, most of them are 19th century vintage and several early to mid 20th century. Sizes ranging from 28" to 24" and a few others. Ill pm you to coordinate.
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    Re: Saw blade topography: taper grinding

    Steve came by yesterday and measured several of my saws. This is a very interesting project. He is extremely detail-oriented in his approach. I'm so glad I got to be a part of this research. I would suggest that anyone here who has old vintage saws participate if they can.

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