How tight to turn that bowsaw toggle . . .

[Jessica Pierce-LaRose]

So I basically wrapped up my bowsaw build from Gramercy parts. I made a poor choice of wood (more than anything else, I should have used quartersawn something or other rather than just grabbing whatever scraps were handy, flatsawn yellow birch in this case)

Still getting the hang of it a bit, I think one of my holes is a hair oversized, but it seems to work quite well as long as I put the far handle on that side. The frame makes the saw want to twist a bit when it gets too close to horizontal, which is annoying, but a good reminder to re-orient the blade or the work, and certainly better than not being able to turn the blade in the frame when I want to. Adding some neoprene washers helped a bit in this concern, and at least made it manageable.

Anyway- my question is how tight to tension the thing. In a moment of overzealousness, I may have tightened it a hair too much and snapped one of the arms. I glued it and it's holding up now, although I'm sure sooner or later it'll be something I need to replace. Okay, user error (and poor wood selection there)

I've adjusted the cord a bit so I get the tension I *think* I want at an even number of full turns (maybe I should make a toggle that would work with half turns) still need to work a bit to prevent bowing of the blade in use but it's not really a problem if I let the saw do the work and don't force things.

I guess I was curious though if anyone's got some pointers - ideal would be a video showing deflection and maybe the pitch of a rung blade.

All in all, I'm overthinking it and just need to put it to work. It's certainly a nice tool to have, I've enjoyed making curvy scrap, that's for sure.

[Mark Dorman]

a picture here showing tension, http://www.popularwoodworking.com/techniques/bowsaw_basics/2
I've seen this once before a pic with the toggle horizontal and the arms about 45 degrees.
So I think he is showing when the string is tight enough. All guessing on my part because I don't have a bow saw yet. It is on the to build list.

[Jim Matthews]

I'm looking for my bowsaws to cut straight, setting the tension to that point is where I stop.

I find thinner blades difficult to tension properly. When they "twang" like a guitar string, I make a test cut.
I second the notion of replacing threaded rod with thread. If you break another arm, you're looking at a retrofit - did the kit come with a template?

jim
wpt, ma

[Jessica Pierce-LaRose]

Sorry - by "toggle", I meant the little wooden flap thing that twists the thread to apply tension. No rod on this one. Maybe I also should have said "turning saw" rather than "bow saw" for clarity, as that's what this really is, the giant-coping-saw version of the tool.

I simply ordered the kit from Tools For Working Wood / Gramercy - the knobs, the blades, and the brass pins to hold the blades. The saw I made is sort of in between the Gramercy design and the design Bill Anderson presented in Popular Woodworking and the Woodwright's Shop.

But your comment, Jim, makes me think I'm pretty much on the right track - I get it tight enough to cut straight as I start the cut. I still deal a bit with the blade flexing as I make turns, but I think it's similar to make a cut with a bandsaw - as long as I let the saw do the work, and don't force things I can basically avoid that belly-ing in the cut.

Cut some curves in a small square block of 8/4 stock to really give it a workout. Certainly a fun tool. I'm tempted to try using it to cut out an electric guitar body next time I do that, rather hauling my dad's junky bandsaw out of the garage and setting it up.

Certainly easier than the time I broke the only bandsaw blade we had and cut out a guitar blank from mahogany with a coping saw because I wanted to do it that day . . .

[Brian Kerley]

Pluck the blade and it should be about one octave above middle A.

j/k :)

I hold the toggle and let the saw hang. If the saw hangs at less than 45 from horizontal...it's pretty good. Also, if during the cut it seems the blade is bending too much, then apply an extra turn.

[Steve Branam]

It's not at all obvious how much is enough. It's obvious when it's too much! The snap-crackle-pop is a good clue.

I listen to the musical note it all makes, the blade itself as well as the toggle contacting the crosspiece. I suspect every saw will sound a little different, depending on the characteristics of the wood. I made mine out of Honduran rosewood (thinking I had pulled a piece of hickory off my stack :rolleyes:).

When it sounds like things are pretty taut, I look at how much blade deflection I get as I cut, but I don't have enough experience to saw how much is the right amount, and again it may vary from one to another. A given blade probably has a critical range where it performs well, any looser and it does poorly. In general I try not to apply too much pressure on it, instead letting a light touch and constant motion do the cutting. The blades are fairly delicate, so I'm always afraid I'll snap one forcing it too much.

Here's the one I built: http://www.closegrain.com/2010/06/building-gramercy-bow-saw.html.

[Tony Shea]

Hey Joshua, how about a pic of your bowsaw??! I would love to see your take on this kit. I also just recently completed one in pear wood. Also probably not the best choice in wood but I wanted to try. I also am not used to the handle rotating while the saw is in use. I just have to get used to holding the frame with my index finger and thumb while sawing. I do wish I had bought the cross pins that have a taper that helps keep them in place while sawing. I may try another version with this setup when time allows.

[Jessica Pierce-LaRose]

Hey Joshua, how about a pic of your bowsaw??!

Oops! Of course, without pics, it didn't happen . . . .

233067

Still a bit of fairing, sanding, and cleaning up the shoulders of the tenons so they look a little nicer, and a bit of finish, I suppose. But it works like it should now. Probably should replace the cord - I used masonry twine because that was what I had at hand. I've been playing with it a bit, and it works very well so far.

Seems like some of the lines and angles look a little funnier in the photo than in real life.

One thing that occurs to me is I need to lower the curve bit on the arms closer to the handle - it's a little high to rest your finger into comfortably.

After stock preparation, pretty much all the work was done with a single gouge, a carcase saw, and a 40mm narex chisel. I think I only busted out the spokeshave for the stretcher.