The hardware for this saw has three functions. It must hold the blade in tension, accommodate blade rotation (when desired), and hold a turned handle. Of these, the first and last are nearly trivial. The second, to allow rotation, yet lock securely when tensioned, is a little more troublesome.
My first design placed an O-ring between the handle and the arm of the frame, hoping that it might provide enough friction to lock the blade in place when it was tensioned. I had some reservations concerning the viability and durability of this design, but went so far as to make the tooling for cutting the O-ring seat.
I had read in the past that some (or maybe most) old frame saws used tapered pins to prevent rotation, but could not think of a good way to make them. When Tony (of Raven’s Edge Toolworks) brought up tapered pins on the WoodNet Hand Tool forum, I started considering them a little more seriously.
The traditional pin is tapered over most of its length. Presumably, the hole it fits into is also reamed out with a matching taper. Now, I have a few tapered reamers, but the idea of using wood as the bearing surface for the pin does not appeal to me. I know that this design has worked well for hundreds of years and millions of people, but still…
Last night, I finally realized that a flanged sleeve with an internal taper (to match that on the pin) might be an even better solution. The flange of the sleeve bears on the outside of the arm, preventing it from being pulled through, while the sleeve eliminates metal on wood wear.
I spent several hours this afternoon at my lathe, and came up with the prototype below. For two reasons, the taper is shorter and steeper than is usually seen. It is easier and faster than turning a long taper, but I also hope that it will be less prone to sticking when the blade is loosened.
The pins are made from two pieces of brass. The blade end is bored out to receive the smaller (handle) end, then the two are soldered together. This is faster and easier than machining the entire part from a solid bar.
The flanged sleeve is made from steel that was heated to 550 degrees in an oven, then wiped down with mineral oil. This heat “bluing” provides some measure of protection against rust.
Frame saw pins and sleeves, picture 1.
Frame saw pins and sleeves, picture 2.
Frame saw pin and sleeve, picture 3.
Interesting take on the tapered pin. I like the idea of the flange eliminating metal to wood contact. Question – Do you have a saw blade for this already? Or are you making your own here too?
I will be making my own blade when I have the frame completed. It never seems to end well if I try to plan too far ahead, so I want to take the dimensions directly from the finished frame.
I like very much that you’re innovating and trying new things. A frame saw is important to hand toolers who don’t have a bandsaw to resaw boards. So any advancement in the hardware to make them perform better, and allow for easier adjustment is a good thing.
Tapered pins split the cheeks.
The reason you occasionally find tapered pins in old bowsaws is that the pins were cast and engine turning wasn’t common before 1850ish. Higher end saws had parallel pins.
You don’t want the pins to lock in the cheek. You want them to rotate with a little effort. When you saw the handle is buried in the palm of your hand and your fingers imobilize the cheeks. This way you can trivially rotate the cheekout of the way when you turn the blade without stopping the flow of sawing.
Thanks for stopping by, Joel. Your input is always welcome.
It is interesting to hear that the higher end bowsaw pins were parallel. That does raise a few questions if you have time.
Do you draw a distinction between bowsaws and frame saws? I think of a bowsaw as smaller (around a 12″ blade) than a frame saw (about 20″ – 30″ long). Perhaps more importantly, I see the bowsaw being used mainly for curved work, while a frame saw is used more often for straight cuts in joinery or sizing stock.
Presuming a difference between bowsaws and frame saw, do you know if the pins used in large frame saws were also parallel, or were they tapered?
For a bow saw, I see your point about wanting the handle to rotate, since you may need to reposition it often during a cut. A frame saw, being used mostly for straight cuts, would appear to benefit from having the blade being fixed more securely.
As you may have gathered, these are totally new tools for me, and I have a lot to learn about them.
when i talk bow saws I am talking turning saws.
In the English tradition turning saws did get bigger – for chairmakers and such but they ware always for curved work.
It’s the continental Europeans who used frame saws to cut stock instead of hand saws. The designs I have seen are all over the map. I’m at work and I don’t have any european catalogs here but the 1869 Franz Wertheim is on line http://www.toolsforworkingwood.com/store/blog/375/title/1869%20Franz%20Freiherr%20von%20Wertheim%20Catalog%20-%20Now%20Online. the frame saws in that catalog look like they have wooden pins. If you have wooden pins, especially larger ones as drawn because it is a larger saw you will get more friction (you can also use rosin) so the pin will naturally hold better than a smaller brass pin. I doubt the pin was tapered – as you have the same breakage problem – repairs are pretty common BTW – but I don’t know for sure.
joel
Great design! I assume the bushing will be fixed to the arms with epoxy or such. Also I’m sure you are aware but your pic shows the pin taper flush with the end of the bushing. Make sure the pin is always slightly bigger or you’ll lose the benefit of the taper.
Jeremy, Yes I will probably fix the bushing. I may try it loose and see if that works, but am prepared to epoxy it.
The pin is actually about 1/32″ proud of the bushing. It took a few tries to get the proper length, but I finally figured out that I needed to turn the pin first, then sneak up on the correct diameter of the bushing, and test as I went along.