Thursday, June 2, 2016

Handsaw bows and kinks

I have ended up with more than a dozen handsaws I don't use because I can't pass them up when a nice one is selling for $2-$3.  I usually don't buy them if they are bowed or kinked but I found a nice  Atkins  panel  saw that I bought even though it had both a slight kink and a small bow near the end.

If you do an internet search, you will find many methods for takings bows and kinks out of handsaws.  There isn't any question that the best way is to use a ball peen or similar hammer, an anvil and a lot of skill, but I lack all three.  A fallback method is to heat up the blade using boiling water, a heat gun or by putting the saw in the oven at 500 degrees and then bending it back into line by hand.  Bows are easier but I read suggestions that you could take out a kink with a crescent wrench or a piece of wood with a kerf in it.

I decided to try boiling water and a crescent wrench, not expecting success, but it worked fairly well.  I got most of both the bow and the kink out but the wrench left some nearly imperceptible "dents."  I also sanded and oiled the handle.

The tooth line is quite straight.  This was just an experiment with a $2 saw to see what would happen and I didn't put a lot of effort into it.  The bottom line is how it cuts and the answer is surprisingly well:

This basic method seems promising enough that next time I think I will put the saw in the oven and make a wooden "wrench" if there are kinks.  The oven will get the blade a lot hotter than boiling water.  It is very important not to heat the blade to the point that the temper is taken out, which is apparently around 700 degrees.  This can happen with a heat gun or a torch but the oven method seems safe.  I also read a suggestion that you could use C clamps and two straight pieces of steel on the blade to hold it straight when you put it in the oven .

How do bows and kinks in saws affect the cut?  I am not sure but it seems that they could offer resistance, widen the kerf and steer the saw.

All of this got me thinking about how delicate a handsaw is and how easy it is to put a bow or kink in one.  How was this handled in the old days?  Did the craftsman know how to straighten his saws?  Were saws sent out for sharpening and was this a skill that the sharpener had?  Were they just so careful that it never happened?  

1 comment:

  1. This is a great post, Andy. I've searched (fruitlessly) for a solution to a kink. I have a small one in my 26" PAX rip saw. I know the kink was my own fault, sawing too aggressively and not straight enough, needing to develop a better feel for it. I believe the woodworkers of old would have known exactly how to handle a kink or bow. Also that they would avoid getting them by using better technique. I know that most woodworkers sharpened their own saws, but some were sent out and I would wager that the sharpeners could remedy the bows and kinks. I think the question for us is, where has this information gone and how can we get it back?