I have built a number of back saws from parts over the years, and as I've mentioned in previous posts, I always find it a challenge to end up with 100% straight saw plate/tooth line. I believe David Weaver shared his similar experience in his post "I hate saw kits".
I tend to favor thinner and longer saw plates than are typically found in vintage back saws, which certainly doesn't help with this challenge. I guess the reason I like thinner plates (.015, .018, .020" for dovetail/smaller tenon saws), if they cut quickly and I think they are a little bit easier to get right on the layout line as you have less width of the curve to consider.C
Candidly, I'm not 100% sure of the "greater accuracy" with thinner plates deal; with a wider plate (that is easier to get straight that helps with accuracy) and you really just have to align the cutting edge of the tooth line with the layout Mark.
Below are some pictures of my third-generation dovetail saw with parts from Ron Bontz: .025" x 12" long, 16 PPI filed rip with a Maple tote and TFWW split nuts. I was able to get the saw plate/tooth line straight and I like the profiles on the tote a little better.
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The lessons I learned are:
* It is easier for me to do all the shaping of the tote before cutting the mortice for the saw back and a slot for the plate. except for the cheeks adjacent to the saw back mortice, I do these last.
* I wait until the tote is complete with mortice for saw back cut, holes for saw nuts and slot for the plate cut and then dry fit the saw back and saw plate to mark the holes on the saw plate, before permanently attaching the plate to back with Loctite. I struggle with visualizing where the holes need to go in the plate and how much the plate needs to project out of the back so that everything lines up with the tote. The only way I've been able to do this is to actually assemble it, Mark plate and then punch/drill the holes in the saw plate.
Lately I've been making the holes in the plate slightly oversize in an effort to avoid any potential tension that might cause a bend in the plate when assembled. I'm not sure if this makes a difference, because not really sure what I'm doing wrong that causes the bend in the plate.
* For me, a drill press is essential to get all the holes in the tote lined up correctly, even then I usually end up having to adjust them a little bit with a small round file. I usually drill to preliminary depth on the drill press, and then finish with a forstner bit in a brace to get the right final depth for a flush fit with the saw nuts. In this saw, I still ended up with the bolts slightly below the surface of the tote.
Here are pictures of generations one and two. The earlier version (on top) has a 0.018" thick plate, but as you can see has a big bend in the tooth line – ughhh I hate that!
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