Unknown saw tooth pattern and sharpening

[RussellT]

I have an old saw that belonged (I think) to my grandfather which was recently retrieved from a shed with a leaky roof.

I have cleaned it up and am thinking about sharpening it, but I can't find any information on the saw tooth pattern. It is a crosscut saw and the teeth are similar, but not the same, as M tooth patterns I have found on the web.

Each "M" is the same with one point set left and the other right. The outer edges of the legs of the M are sharpened with a fleam angle and the inner V at the top of the V is sharpened square across the blade like a rip saw.

So far, so good. I decided to try and follow the existing teeth and file them to the same shape as they were. When I put my file in the first V at the top of the M it rocks around and the angle is closer to (but less than) 90 degrees than 60. That seemed odd to me so I'm thinking again.

Can anyone advise me on angles etc please.

Russell

 

[dannyr]

I'm not the expert, but do fettle my own saws.

there are M pattern tooth cuts but never seen one like this

is an alternative explanation that your granpa got halfway through sharpening (with a pretty deep file cut) then left the saw without doing the other side?

looks like a nice saw and worth doing

 

[Jacob]

I'm not the expert, but do fettle my own saws.

there are M pattern tooth cuts but never seen one like this

is an alternative explanation that your granpa got halfway through sharpening (with a pretty deep file cut) then left the saw without doing the other side?

looks like a nice saw and worth doing

Or started out to halve the t.p.i. but gave up! He should have file away every other tooth but instead has removed every third one and just got it all wrong?

 

[AESamuel]

Seems like an attempt at a combination rip/cross pattern but with large gullets to deal with sawdust.

 

[IWW]

I think grandpa probably had a fair idea of what he was doing, he wanted a saw that would handle green or less seasoned wood so he converted his saw to something that In principle is the same as an "M-tooth". But if he was getting on a bit, his eyesight may not have been the best, hence the teeth are not as neat as they might be?

From eyeballing the pic of the teeth, what I think is that the last person to sharpen it (possibly someone other than grandpa?) used the same (large) file on both the large and small gullets. Triangular files with an angle >60, are rare & not carried by your local ironmonger, as a rule! I think it's far more likely he just used an over-sized file with normal 60 deg corners.

The larger the file, the larger the radius of the corners so the wider & shallower the arc they leave at the bottoms of the gullets. If you used a file that is more like the size one would normally select for that size of tooth, the 'sharper' corner bottoms out in the wider arc before the sides touch the edges & the file will wobble from sisde to side giving you the perception the abgle is >60. I suspect if you put a protractor against the upper parts of the teeth you would find the angle is indeed 60 or pretty close to it. As someone who sharpens a few saws, I encounter this situation often.

One solution would be to use a file of the same size & corner radii as the previous sharpener. But it would be better to use a file of a more appropriate size for the small gullets, and if you are not a highly experienced filer, use a guide stick so you can maintain or restore the correct rake angle on the trailing tooth.


Work out the "tpi" of your saw by measuring across the bases of two adjacent teeth & select a file appropriate to that size of tooth from one of the many tables available on the web such as here.

Drill a hole in a stick & scribe a mark that gives you your desired rake angle when the file is pushed in with one side aligned to the mark. Now all you need to do is hold the file perpendicular to the saw plate & the stick level, & file away. You can do all the tooth-forming from the one side (in fact it's better to do it from one side as you'll get more consistent angles), then re-set it & sharpen from alternate sides as normal...

You will probably need to do the large gullets as well - just use a larger file that will comfortably fill the gullets and a larger stick....

And it will almost certainly benefit from a good "topping" before you try re-forming the teeth. Here is another easily-made tool to assist in that operation:


Cheers,
Ian

 

[RussellT]

Thanks for all the comments. I'm wondering more about grandpa now - I never met him so this saw is a rare tangible connection. No-one ever mentioned he had any particular interest in woodwork so I'm dubious about any special sharpening - however I'm going to try and keep the tooth pattern as it is. It's part of the history of the saw and it'll be interesting to see how it cuts.

Thanks Ian for the advice on sharpening, I'll have another look with a protractor and let you know how I get on. I'm not sure I'll be brave enough to post pictures of my sharpening attempts.

Russell