Thread: Two compass/table saws

2??

Paul

That is an interesting configuration reminiscent of Disston's D17, which was similar except it had a deep gullet before and after the group of two and those teeth were filed rip.

I understand why a saw might be configured with two larger teeth filed rip, but not why they would be crosscut. In cutting a circular table a saw would encounter cross grain, oblique grain and straight grain.

I don't believe those teeth are the same pitch with only the rake differing. I think the large teeth are a larger size too and possibly they should be rip and have been altered to be crosscut.

Unfortunately there are a few possibilities here and the task of deciding original from modification is not made easier without the saw in front of us.

The only compass saw I have sharpened is not a good performer, but admittedly I did not persist with it as I had no immediate application. The thick blade on a compass saw, which I think immediately distinguishes them from the keyhole saws, are not conducive to smooth easy cutting.

Regards
Paul

It looks like the 'big' teeth have a shallower slope to their back side, and extend gullets. Can't see how you can change the slope on the back of the tooth & keep the rake constant (which it appears to be), yet still maintain a 60 deg. gullet. But it looks like the gullet angle is the same for both large & small teeth, so that means the back slope has to be the same angle for all teeth & what looks like a shallower angle is an illusion.

I stared at it for a while trying to decide if the two larger teeth have any fleam on the saw pictured. There seems to be a teeny bit, but not totally confident I'm seeing what I think I'm seeing. It would make more sense to my simple mind if they were filed with little or no fleam, to act as rakers. If it's a general or pruning saw as the Disston catalogue says, the implication is it will be used for cutting green or wet wood, in which case the bigger gullets might be of some help. However, like others, I'm a little skeptical of this tooth pattern's value. My usual assumption is that good ideas take hold, while natural selection does its work on not-so-good ones, and they soon acquire the obscurity they probably deserve....

Cheers,

I don't believe the teeth are the same ppi. I can't say what either of the two sizes are because the pic is enlarged. It seems that compass saw teeth are normally 8ppi to 9ppi: I have one of each. I also have one at 13ppi, but it has a removable handle and says on the plate "......ed to cut nails" ( I think the first word is either "tapered" or "shaped") and I suspect it is out of a plumber's nest of interchangeable saws and is the hacksaw blade, although at first glance it looks exactly like a compass saw.

So I printed out a pic of Paul's saw. I measured 22mm to 23mm between any two of the various small points, but 30mm between the larger points.

I think that the larger teeth are about 6ppi and indeed should be rip. In fact the larger teeth look to have less rake than the smaller crosscut teeth, but this could also be photgraphic distortion. I would also suggest this saw came from the factory this way.

Regards
Paul

Originally Posted by Bushmiller

I don't believe the teeth are the same ppi.....

Agreed, Paul, I wasn't saying the teeth are the same, I was just figuring out where the extra width comes from. Is it because the gullets are cut deeper, or the slope of the back of the larger teeth is shallower? Either would produce a wider tooth. After squinting at them for some time, I decided the extra width is added by making deeper gullets and the other parameters are the same. If they are not, it means the gullet angles are different for small & large teeth, which they don't appear to be. If they weren't, it would greatly complicate sharpening, you'd need two different files, a 60 deg. for the 'standard' gullets, and one for whatever the other angle would end up.

All just conjecture on my part, if I had it in my hands I'd be able to take a few measurements & knnow for sure. I suppose I could print the pic & use that, but photos have a habit of distorting perspective, so it may not be reliable, as you've already pointed out.....

Cheers,

It's worth noting that if you look up the patent for this saw quoted on the etch, the saw pictured also has the same tooth pattern. The patent is actually for the handle and the teeth don't rate a mention.
The teeth pattern might be superior for a table saw expected to cut a circle experiencing both with and across grain in the same cut. However, I bet the benefits didn't outweigh the financial benefits of automated punching and filing of teeth that would have been introduced around this period.
I suspect a bunch of subtle filing techniques fell by the way side around this time.
http://patentimages.storage.googleap...s/US151363.pdf
image.jpg

Originally Posted by Bushmiller

I also have one at 13ppi, but it has a removable handle and says on the plate "......ed to cut nails" ( I think the first word is either "tapered" or "shaped") and I suspect it is out of a plumber's nest of interchangeable saws and is the hacksaw blade, although at first glance it looks exactly like a compass saw.

Funny you mention that.
I couldn't get my newish phone to spot focus as well as my last one, so I don't have the clear 'from above' pic I was trying to get ... but this 'table/compass saw' was filed by an 'online saw guy'. It has no set - which you'd believe looking at the teeth.

15ppi. Sloped gullets. EC Atkins "Nail Saw" - although I don't believe it is filed for that purpose now.

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Paul

That is a similar style of saw to mine, although mine is a Disston. One of the saw bolts has a wing nut type on the back similar to that seen on a bevel gauge. The teeth on the metal cutting saws were filed rip straight across similar to modern hacksaw blades but without any "wave."

Yours is definitely now intended for timber.

Regards
Paul