# How straight is "straight" for a backsaw?



## railaw (Nov 15, 2011)

I've recently acquired a couple of backsaws on eBay; a smallish dovetail saw (with some serious rust issues, which were obvious on the listing) and a 14" Disston filed crosscut, in much better cosmetic shape. The chief requirement I had in choosing these saws to bid on was that they were advertised as "straight". I already have a 12" WS backsaw that I've struggled with for long enough trying to figure out how to straighten it that I felt that I needed to get a couple that didn't have this problem. That way, I could alternately ignore the 12" and take increasingly aggressive measures to straighten the plate (e.g. actually take off the spine; I've resisted doing this on the theory that I may never get it back on). 

Anyway, I received the new saws this week, from different sellers, sighted down the teeth and immediately saw that they are not straight. They aren't wildly out of whack, but they aren't perfectly in line either. The sellers had photos on eBay showing down the toothline, but such a photo really can't display the problems. The Disston 14" looks like it has a slight twist about 3/4 towards the toe. the dovetail saw has a slight wave in about the same spot, which seems to be causing it to bind in the kerf (though this could be due to a particularly bad rust spot in the same location; I haven't tried to clean it up more yet). 

My questions are twofold: 

1. how much twist, wave or non-straightness is allowable without a significant impact on performance? I need to sharpen the teeth and don't want to go down that road if at the end they won't perform right, or if I can't tell if i need to touch up the sharpening process, because of a pre-existing condition. 

2. Any anyone recommend/point to specific techniques that may serve to correct the problem? I've seen the wkfinetools article on straightening that's way over my ability hope to accomplish anytime in the next several years. I got these because I want to start using them with a minimum of tuning time. I know this has been at least partly covered on here in the past; partly addressed to me, but I didn't get anywhere at the time. 

I should note that I'm not certain whether the back of the Disston is totally straight either. Perhaps the outside is a little lumpy but straighter where its actually holding the blade?

If the answers I get are that the degree of wave/twist are significant enough to care about, and it's not easy to fix, I'll go back to the sellers. I feel I'd have a strong case as the descriptions were an unqualified "the plate/toothline is straight". But I'd rather try to get the tools working right than go through that trouble. 

I will post photos momentarily attempting to illustrate the magnitude of the problem. Thanks in advance.

Update: here are the photos.

















































Also: You can see on some shots a crack in the handle. I've heard epoxy recommend; why is this preferable to standard wood glue? and how do you get it in there?


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## Wema826 (Jul 22, 2012)

railaw said:


> 1. how much twist, wave or non-straightness is allowable without a significant impact on performance? I need to sharpen the teeth and don't want to go down that road if at the end they won't perform right, or if I can't tell if i need to touch up the sharpening process, because of a pre-existing condition.
> 
> 2. Any anyone recommend/point to specific techniques that may serve to correct the problem? I've seen the wkfinetools article on straightening that's way over my ability hope to accomplish anytime in the next several years. I got these because I want to start using them with a minimum of tuning time. I know this has been at least partly covered on here in the past; partly addressed to me, but I didn't get anywhere at the time.
> 
> ...





1. The straighter the blade the less binding, less wandering, faster cutting, smoother cuts. If the plate thickness is on average 0.020 inches and the teeth are set to a 0.002 set, which will give you a total kerf of 0.024, then you will be able to have a minimal bow and not notice the bind or performance issues. One trick I would attempt is the paper trick. simply take a sheet of paper folded over the teeth of the blade. and squeeze it in a vice along the tooth line. paper does not compress so this will apply pressure directly to the saw plate and if the bend is slight enough it may straighten it. also it will help align your tooth set to equal on both sides. 

2. Since you did buy these saws from ebay. I would use them as practice saws. attempt what they say on WKfine tools. Read from the saw blog gurro Matthew Cianci, you can also check out the LOgan Cabinet shop. They both offer saw rehab services and have online web blogs that tell you how to fix your own. The worst thing that will happen is you will totally destroy them.... then go buy some from veritas! or lie nielsen or some whenzholfs.

If the Back is bent. the saw will have to be straightened, simply said. with a bent back you will get a bent cut line. Practice practice, practice, practice. you will be able to get it back on. if all else fails. use epoxy. whats the worst that will happen?


Cracked handles. require you to spread the crack open. you can make a set of wedges that will slide against each other on the inside of the saw tote / handle and gently force the split open. then use a small brush or my epoxy applicator of choice, those plastic coated playing cards. I cut them in smallish strips and use them to apply epoxy in tight spaces. 

Best of luck in your saw repair endeavors! It is addicting. I attempted to repair a saw once and got hooked! ........


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## firemedic (Dec 26, 2010)

For the dovetail saw try this once its cleaned sharpened, set. 

With the handle remove hold the saw plate, teeth up and whack the back of the saw against a solid bench a few times at each end. If the back is pretty snug, what this does is stretch the plate a tiny bit and pulls it straighter - like stretching a sheet. You are trying to slightly bow the plate into the back.

Call me crazy, but I figured this out on accident a while back and have managed to greatly straighten several back saws this way since.


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## railaw (Nov 15, 2011)

So I have two votes for not attempting a return or either? If I did I think I'd spend a little more an get a rehabbed one eg from secondchancesawworks. I don't want to have them hanging around unused. Those tools will come much later, if I can help it. I can give the whack trick a try. I've heard it before, but not the detail about the ends and the intended effect.


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