A customer from Italy recently asked me about an apparent bow along the toothline of his new backsaw. He wondered what would cause this and is it a concern? Should he have it fixed and what would it cost?
Lots of things can cause a backsaw blade to warp…being dropped to the floor, bent in over-zealous thrusting, improper storage…these are nightmares to the SawWright. And that’s just the tip of the causal ice berg. Believe it or not though many backsaws are warped from the moment they’re made, and are delivered that way to the customer….like my Italian friend above. Machine tooth punching (or even manual tooth punching of old) almost always warps the saw blade due to the tension created by the process. So it’s very common to buy a saw and find it warped when new.
Ya…I know, it sucks. You just plunked down $150 to $300 on a brand new, high-end saw only to open it up and find its warped!!! But honestly, I don’t think it matters. I’ve tuned up and used hundreds of new and old backsaws and found the tolerances required for true cutting to be amazingly broad. In fact, many of my favorite user saws in my own till are far from arrow straight at the toothline.
Take my dovetail saw for example…
It’s a Groves & Sons from the golden age of Sheffield…probably circa 1870 and I love it. But the toothline is anything but straight. I laid a machinists straight-edge across the side of the saw blade at the teeth and found that it bowed over 1/32nd of an inch along its length. Now that might not sound like a lot, but over a short 9 inch toothline, its akin to a woodworking potato chip. When sighting from the heel to the toe, it is quite a striking wave. When I first rehabbed the saw a few years ago, I did my best to true the back and blade, but small dovetail saws are the most fussy in this aspect. I’ve found that the thinner the saw blade, the more difficult to manipulate the tension and effect a truing. So I let it be.
But the saw cuts as true as any…and to the full depth of the blade…
How’s that? Should a warped backsaw cut a warped line?
Maybe not. I’ve seen many, many warped backsaws cut perfectly straight, just like mine. I’m sure all the engineers and techy types could explain why. But I’m not really interested in the why…I am simply thankful that the reality exists.
So should you automatically fix a warped backsaw? That depends…make a cut with it, and I say if it cuts true, it is true.