How to "Detension" a Saw Plate?

[Stew Denton]

I have been reading with great interest on removing bends and kinks from saw plates, as I am hard at it on one. The plate has a kink, not super bad, but enough to make me want to repair it.

Some of the information talks about taking the tension out of the plate before flattening it, and then re-tensioning the plate afterwards. There is plenty on putting the tension back, but I have found nothing on how to remove the tension.

Any advise would be appreciated.

Thanks and regards,

Stew

[David Weaver]

Stew - you don't need to worry about taking the tension out of the plate. You can just make your repairs and then once everything is as you like making your tensioning strikes on both sides of the saw when you're done.

Hammering on a saw is an experience-based thing. Some of it is easier to learn by trial and stopping and examining what's going on than it is to read or to write about. Kinks are tough to remove, though. I've always considered a saw that had any considerable kink to be a lost cause, and saved hammering for straightening the ever common bowed auction or flea market saw.

Just do what you think is reasonable after you get your kink out, though, and try the saw out. If a saw is completely out of tension, it'll flop around with no conviction - it's a very easy thing to diagnose. If you don't notice anything, then there's no problem.

[Winton Applegate]

One thing to know about steel is it has "a memory" meaning it doesn't take much to bend a kink OUT as opposed to the amount of energy that went into putting it in to start with. The steel "wants" to get back to it's original formed state and has stresses in it that will help get back to straight. The trick is figuring out how to support it and where to put the force to help it get back.

This has sort of something to do with your tensioning comment.
I am no saw expert at all.
I have straightened some BRAND NEW back saws specifically two of the same brand and size that came to me with exactly the same bow in the brass back. Took an astonishing amount of bending WAAAYYYY past straight to get it to remain straight. I got them both straightened out though.

That was different because it was a mechanical joint and two different metals.

I would think that with some practice and a wooden post or similar set up it wouldn't take too much to take the kinks out of a panel saw. An "S bend" could get tricky though.

[Kim Malmberg]

I'm far from an expert myself but having had various success with various kinds of issues I do have some experience.
If a saw has a definitive curve I normally start by holding the saw in the handle with one hand and with the other hand I bend the saw plate without brute force but still forcefully fought to create tension in the steel. I also twist the saw plate a bit as I bend.
The idea behind this is that many a time if you have a smaller issue with the plate the tension has moved marginally thus causing the bend. You can fix this simply by 'massaging' the plate as described above. You might even hear small cracks or from the saw plate when the twisting and bending finds the spots where the tensioning is uneven. So there are times when this technique will bring the saw plate back to straight without the use of a hammer.
My attempts at hammering out kinks have been mixed. Sometimes I have made things worse and sometimes I have made dents in the plates because I was using the wrong kind of hammers. I seriously recommend auto body hammers. There is a reason they were made for this purpose.

Most people suggest hammering against a metal surface. I don't have a piece of solid steel as long, thick and straight so I have been using a wide oak plank. This might not be ideal but that is what I have.

David's tip on retensioning a saw plate is very good. I have a couple of sloppy saws that have been calling for my attention so maybe I should stop ignoring them and see what more damage I can do to them.

One more thing. Before you do a lot of work, do check if the set is even on both sides. A saw with different amounts of set to either side will cause a bend.