Wandering saws

[Jelly]

I had about 9 metres of 25mm redwood to rip this evening, so set to with my big Disston Ripsaw as at 2 TPI as it goes through thin stock like a hot knife through butter. Unfortunately after about 500mm it was starting to uncontrollably yaw to the left.

I stopped and did some test cuts on scrap, and no matter what the grain was doing, or how I altered my technique still yawed to the left, so I jointed it and set it again... You've guessed it, still pulling left.

My solution was just to get my finer toothed, thicker plated S & J Ripsaw out and finish the work, sawed dead on line with sufficiently little deviation from the line over the 3.1m lengths that you couldn't tell it from the rough finish off the saw. I was then pretty sure that my technique wasn't at fault...

At this moment I twigged that about 2 years ago I was using it to break down big douglas fir boards and accidentally powered the toe of the blade into the saw-horse, bending it. I was able to straighten it and thought no more of it. But, on playing with a bit more scrap I realised if I used the bit of the saw from where it had been bent to the heel, it would cut straight, whilst the bit after the bend oscillated wildly.

My fear is that the saw is irretrievably damaged, and will now forever be an innacurate rough cut tool if it can be used at all. Is there anything I could try, other than taking the handle off and annealing then re-heat treating the plate which will undo my clumsy mistake.

 

[D_W]

Can you visibly see the bend? I'd hammer it straight if you can, and if you have a setup to hammer it.

 

[dzj]

Perhaps a tad more set on the opposite side might help.

 

[lurker]

Perhaps a tad more set on the opposite side might help.

This is the more likely reason, unless you can see the kink.

 

[Jelly]

I stoned the tooth line and re-set the saw, equally on both sides, no change, which is what had me puzzled.

The kink was hammered out 2 years ago, but can be seen from where the Hammer took tiny bits of the patina off, the plate flexes much much more in the area it was kinked than anywhere else.

 

[Jacob]

Sharpen and more set most likely solution on a normal saw; 2 tpi on 1" boards is a bit OTT and could be the issue?
4 or more tpi I would have thought better.
I've no idea if this is the problem as I've never seen a 2 tpi hand saw let alone used one.

 

[Phil Pascoe]

2tpi is massive - I've not seen one. Mine is 3 1/2tpi at the largest, and that's big.

 

[D_W]

I thought the 7 that I have that has 2 1/2 teeth per inch had big teeth.

George Wilson mentioned that someone at the museum (colonial williamsburg) had converted worn out saw to very large teeth (2 per inch) and was boastful about the saw's ability to cut fast and cut curves because of the shallow height of the plate.

It took me a long time to find a saw that was 2 1/2 teeth per inch without paying a mint for it. I never used it for 4/4 stock, but I'd imagine it would be rough and very hard on the back side of the cut, unless the rake was really relaxed (which would defeat the point a little bit).

 

[bridger]

Annealing and rehardening a saw plate is not something that can be accomplished in a typical woodshop. Thin flat plates are very hard to controllably heat and quench. Besides, the temper wasn't damaged by kinking. A skilled saw doctor should be able to get it back on track for you with a little hammer work

 

[Jelly]

I thought the 7 that I have that has 2 1/2 teeth per inch had big teeth.

George Wilson mentioned that someone at the museum (colonial williamsburg) had converted worn out saw to very large teeth (2 per inch) and was boastful about the saw's ability to cut fast and cut curves because of the shallow height of the plate.

It took me a long time to find a saw that was 2 1/2 teeth per inch without paying a mint for it. I never used it for 4/4 stock, but I'd imagine it would be rough and very hard on the back side of the cut, unless the rake was really relaxed (which would defeat the point a little bit).

That sounds quite possibly how mine came to be, it's got a very shallow plate for a Ripsaw and the teeth aren't original (too aggressive a rake and if you look closely with it up against a 1m steel rule, not perfectly even in spacing), whoever was boasting is very much on the money as to the fast cutting, mine will happily cut 4"-6" in one stroke (30" plate) in 1" stock, which is kinda the attraction for this job, Jacob is right that it's a bit overkill and a 4tpi works better, but who wouldn't like an onerous task like ripping to go a bit quicker?

The surface finish of sawn faces after cutting is dismal, kinda "hairy" with some definite splintering on the back of the cut, it's deal-with-able in denser hardwoods or decent Russian or Scandinavian redwood, in fast grown softwoods it makes a real mess, needing ¼" allowance to clean up the edge and take the splintered bits off with a plane after ripping.

I will have a play in thicker stock or re-sawing and see if it improves, failing that Jacob's suggestion of a full resharpen is next possible solution, still curious why it has a flexy bit though...

This is only one of two saws I've seen with such coarse teeth, the other came with the house my parents live in, hung up in the coal shed, pre-war beech handle looked more like a farmers saw in size, 36" plate running from 4" at the toe to 9" at the heel, toothing something like 1.5-2tpi, unfortunately my dad flogged it at a boot sale as it had dulled too much to be useful (and was blissfully unaware I could sharpen saws)... I'd love that one back!

 

[Jelly]

Annealing and rehardening a saw plate is not something that can be accomplished in a typical woodshop. Thin flat plates are very hard to controllably heat and quench. Besides, the temper wasn't damaged by kinking. A skilled saw doctor should be able to get it back on track for you with a little hammer work

I've got some dies to put into a commercial Heat Treatment shop when I get all the quotes back (gotta love Sheffield for the availability of uncommon engineering processes), so considered having it done at the same time.

My logic was that the annealing process should also stress relieve the plate, making it much easier to re-establish proper tension, that said Ernest Bennet still do old fashioned saw-doctoring and are round the corner so I could always see if they fancy a bash at sorting it before doing something radical.