Warped Back Saw Plate

[Jimmy Harris]

So I've finally given up on it. No big deal, since it was an unbranded Tenon saw from probably the 1970's or 1980's. I think I paid about $10 for it. And when I bought it, I saw that the saw plate was warped, but I figured I could fix it. I've done that before. Here's what I didn't know when I bought it... It wasn't warped front to back, like I assumed. It was warped top to bottom. And the handle holding one end flat was causing it to appear to be warped front to back. But take off the handle, and you can clearly see that the saw plate is straight, front to back, but has a big and steady curve in it across the short side, from top to bottom.

On several occasions, I have spent a good amount of time trying to work the bend out of it, but it eventually works its way back. The metal's memory just wants to pull it back. And then it binds in the cut and won't track straight very easily. Maybe I could tension the plate with a ball peen hammer to get it to work, but I'm tired of messing with it. It was a cheap saw anyway. Besides, I'm not one to pass up on an excuse to buy a new tool.

Still, I've never seen a saw do that before. Has anyone else?

[Jim Koepke]

Some of my saws have arrived in pretty poor shape, but never as bad as you describe.

Is there enough straight back to shorten the saw?

Tracking The Line.jpg

This one was made from a backsaw blade that came in a box of used parts. It was in pretty bad condition and required a lot of sanding over time whenever there were a few spare minutes in the shop.

jtk

[Jimmy Harris]

The warp kind of runs evenly though the entire plate. But I just think it's better used as a cabinet scraper or scratch stock. IMG_1869.jpg
Not the best photo, but you can see a bit of the warp. And that's right after straightening it, so experience tells me it'll get worse over time.

Here's the side of the saw:IMG_1871.jpgas you can see, it's not a high end saw. I replaced the nuts because they were rusted on. Those replacements were the cheapest I could find.

And here's probably my favorite saw. It started life as a $10 plastic miter box/saw combo. But I got bored one day and filed off the teeth, cut new ones, and sawed off the handle and made a new one out of a cutoff of yellowheart. That's just to prove I'm not afraid to spend time reworking on a cheap saw! IMG_1868.jpg

[Tony Zaffuto]

I have a very old British open handled backsaw, and the spine is "sway-back" in that it dips in the mid-section, better than 1/8". There is a bit of wave of the plate at the spine, but nothing at the toothline. I tried to straighten it out, but no luck. I had a well regarded sawsmith try to straighten it, with no better luck.

I suspect the saw has had this condition longer than I've been alive (71 years), and I suspect it will have this condition through the next half dozen yard sales of widows selling off okd tools!

[Derek Cohen]

Jimmy, I suspect that the problem is caused by a compound curve, that is, the combination of a dip (sway back) and curve in the back support (steel back). If you remove one and not both, the problem remains. Then there is a third factor to check on, which is the accuracy of the blade slot in the handle. If this is curved, ir has an internal high spot, it will force the blade into a curve when the nuts are tightened up.

This saw plate/back was like that, plus the plate had dropped ...



I was attracted to the handle when I saw it lying on a table with many others for sale ...



This is what it looked like back in the shop alongside a LN ...



Once the brass back was straight in three dimensions, and the plate re-sited, redrilled and new nuts, this is what it became. I sharpened the teeth and love it



Regards from Perth

Derek

[Jimmy Harris]

Thanks Derek. But it's the saw plate itself, and it's just a steady curve throughout. I've completely disassembled it many times trying to fix it, and when I do, it's pretty clear that's the issue. The handle will actually put a compound curve in the plate because it flattens the heel, and the toe remains unsupported. And I've found that if I carefully adjust the back support, I can reduce that curve by creating uneven tension on the plate that kind of creates a new curve to counter the old curve. So I can get the saw to work, but without a lot of set, it just wants to bind once the cut gets past about halfway down, as the saw gets a lot of weird waves in it.

And the back support on that thing was pretty wonky. It wasn't bend though. But it also wasn't folded over in the middle. So one side came down about 1/8th of an inch below the other. I had thought that maybe that was contributing to the issue, so I filed it flat with the other side. But that didn't help.

It's just a weird thing I thought I'd share because I haven't seen or heard of anything like it before. No worries though. I already bought an antique English backsaw to replace it.

And that's a beautiful dovetail saw you've got there! You're right about that handle! I bought a LN dovetail saw a while back, a newer one in cherry, and while it's a fine saw, I've found I just really like these antique saws better. The handles just feel more refined and the saw doesn't feel as clunky. It's subtle. It could also be the saw tooth pattern, as the LN is a hair more aggressive than I'd prefer. Either way, to me, when you find a good antique saw, there's just nothing better! Maybe it's psychological or maybe it's the 100 years of break in. Or maybe they just spent more time and effort making those things. Who knows.

[Mike Brady]

I noticed that the vertical dimension of the saw plate has decreased considerably in your finished version. It appears that you decreased the taper of the tooth line gradually from toe to heel. I'm curious as to why you did that.

[Derek Cohen]

I noticed that the vertical dimension of the saw plate has decreased considerably in your finished version. It appears that you decreased the taper of the tooth line gradually from toe to heel. I'm curious as to why you did that.

Mike, the decrease in the taper was solely due to straightening the plate in the back. This indicates the amount the plate had dropped!

There are, no doubt, many saws with tapers that are not true tapers.

Regards from Perth

Derek