File Sharpening Saws
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- This topic has 42 replies, 11 voices, and was last updated 5 years, 7 months ago by Mark68.
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4 September 2018 at 12:29 pm #550894
You can fix that saw Mark, but it will take some effort. I think if it were me, I would take a flat file and completely remove those teeth and start over because the gullets are uneven. That may sound a bit radical, but it really isn’t hard to do. Paul did a video some time ago about recutting and resizing saw teeth that shows how to do it. He did it on a smaller backsaw, but the procedure will work on any saw. He uses a template that he makes to accurately establish tooth position which can be a hard part of the process to get right and I think he used a hacksaw blade with the number of teeth per inch he wanted to make that template. But since you’re going for 10 tpi, you should have, or easily be able to find, a scale marked in 10ths on an inch to use to mark the template. Maybe you can use your other saw for that?
The Nicholson flat files you sent the link for will work fine. Get a fine cut and/or medium cut version(s). Bastard (coarse) cuts are too aggressive for a saw plate. You don’t need a handle on it either. A handle won’t work when you’re flattening the plate – it gets in the way. Look in the video section under tools and techniques and you’ll find that video I mentioned. It’s going to take a couple of hours to do this but the experience is well worth it. Never give up – woodworkers are not allowed to let the saw win!
- This reply was modified 5 years, 7 months ago by harry wheeler.
- This reply was modified 5 years, 7 months ago by harry wheeler.
If tooth shape were the only issue, I would not file off these teeth. I’ve worked with worse. The bigger issue is that you filed them backwards, that’s what clinches the “file them off” deal.
Consider this, though. Besides being backwards, the teeth aren’t uniform in shape. Before you file the teeth off, consider jointing, shaping, setting, and sharpening the saw a few times. Get your filing skills tuned up a bit more. Get it to be a sharp saw, albeit one that cuts backwards. At that point, file them off and do the saw for real.
Make sure you are using the proper size saw file and make sure it is a saw file, not a triangular engineer’s file.
4 September 2018 at 2:53 pm #550905So you would continue to grind away on teeth that are cut backwards just to hone your filing skills before finally removing them and starting over? I must admit, I would never have thought of that!
- This reply was modified 5 years, 7 months ago by harry wheeler.
Mark, one of the confusing things about filing teeth is how things depend on each other. If you file gullets deeper, it moves the teeth apart, for example. When you look at a saw that has teeth that aren’t spaced uniformly and that aren’t the same height, it is confusing what to do. I still struggle with this. Luckily, rip saws don’t need to be perfect to cut. So, don’t get too hung up. I’m writing this because, if you practice on this saw more, you might or you might not get the teeth evenly spaced with even gullets. Once things are out of whack, it can be hard to get back to uniform while you’re learning. So, don’t get hung up. What I suggest you focus on for now is learning that, when you see a bright spot at the tip of a tooth, looking from above, it means there is a flat spot and the tooth is dull: The front and back of the tooth don’t meet to make a chisel edge. When you joint the teeth, you are going to make a bright spot at the top of every tooth. Stop and look at them. The bright spots won’t all be the same width when the teeth aren’t all the same size and height. You want to take extra file strokes where the bright spots are wider. You can focus on downward pressure or a little sideways pressure, either forward or backward. I can’t guide you there, but be aware they have different effects. If you see different width bright spots when you joint, consider making a pass along the saw where you don’t try to get rid of the bright spots. Just bring them to a narrow line. You goal is to make all the lines about the same thickness. Since you can make a line narrower by filing on either side of it (one tooth or its brother), it’s not clear which tooth to file sometimes, so don’t go for the final line thickness all at once. Take a stroke or two, move to the next tooth, maybe even do a run of a few teeth, then review. This will guide you where you need extra file strokes to get to uniform bright lines. Now, you can make a single run down the saw taking the same number of strokes and eliminating the bright lines/spots. No bright dot means you’ have a chisel edge, i.e., have a sharp tooth.
Ideally, when the saw teeth are uniform, you can make a light pass to joint the teeth and then a quick, uniform pass with each tooth getting the same number of strokes, and the teeth will be sharp. But, for dealing with non-uniform teeth, I find I must do the things I just described, but maybe that’s because saw filing is still a weak skill for me (or because I keep trying to rescue abused saws).
You don’t need perfect. If a tooth here or there is low, don’t worry about it. The more you read, the more confusing it will seem. So, go file that saw and see what happens. Watch the shiny spots. Having the teeth backwards so that you really don’t care gives you great freedom to explore. Filing a junk drywall taping knife is another way to explore. (It actually produces a useful tool. I use my toothed narrow knife quite a bit).
EDIT: Thank you for the reply Ed.
Oh well, let’s just say my attempt to ‘reshape’ the teeth back to a forward cut, wasn’t successful. I was actually doing quite well until I messed up.
Anyway, I had another Spear and Jackson saw (10 tpi) that I’d not used, and I have successfully changed that into a rip cut. I now have a cross cut S&J and a rip cut S&J and both are working quite well.
When it came to modifying the S&J saw (I’d never used), I found the process relatively straightforward; probably due to all the practice I put in on the now messed up saw!
Thanks all for the advice
I forgot to say: Your goal is to remove the bright spots. Stop filing the instant the bright dot is gone! It is tempting to file a little more just to be sure, but you shorten the tooth when you do that. When you joint, you make the teeth the same height. If you give a bit more when filing a tooth, just to be sure, you lower the tooth below that jointing level. If every tooth gets exactly the same extra, you’ll be okay. But, if they get random extra, you’ll have wonky teeth. As long as you can see the bright spot, you have feedback. That’s why I said to get the lines to uniform thickness, nearly gone, previously, then make a pass of uniform # of strokes. Or, stop the moment the bright spot is gone.
[quote quote=550909]I forgot to say: Your goal is to remove the bright spots. Stop filing the instant the bright dot is gone! It is tempting to file a little more just to be sure, but you shorten the tooth when you do that. When you joint, you make the teeth the same height. If you give a bit more when filing a tooth, just to be sure, you lower the tooth below that jointing level. If every tooth gets exactly the same extra, you’ll be okay. But, if they get random extra, you’ll have wonky teeth. As long as you can see the bright spot, you have feedback. That’s why I said to get the lines to uniform thickness, nearly gone, previously, then make a pass of uniform # of strokes. Or, stop the moment the bright spot is gone.[/quote]
I really need to get a file but I’m not sure which. A Nicholson smooth and/or medium coarse is what I’m going to search for.
Why do they call it ‘jointing’?
4 September 2018 at 7:35 pm #550911A fine cut (~63 tooth) or medium cut (~36 tooth) Nicholson will work. Obviously, the fine cut will take a little longer. And as to why they call it “jointing”, I suppose it resembles what we do to wood when we’re preparing it for an edge joint. In reality, all you’re doing is flattening the tooth line to get them all to the same height. As I suggested earlier, filing those teeth down and starting over is your best bet and suggestions to the contrary are just bad advice. A guy with a lot of experience might be able to fix them without filing the plate down, but that’s the deep end of the pool and you don’t want to be in there just yet. Rather than listening to the pontification coming from any of us, you’re much better off watching Paul and doing it the way he does it. You can also find other some guys on YouTube that show the same thing but with subtle differences and different commentary. Don’t give up – you’ll get there.
4 September 2018 at 7:46 pm #550913That’s a plan Mark and since you already have 10 tpi saws, you might want to think about recutting the other S&J at something else like 6 tpi. Those heavy cut saws are handy when it comes to donkey work and the larger teeth are actually a little easier to do. A saw file needs to be large enough that only about 1/3 of it’s thickness is down in the cut at max depth so keep that in mind if you go to larger teeth. Good luck with it.
Just watched the video with Paul creating teeth on a Disston. It’s fascinating.
Found this Nicholson second cut file:
http://www.mytoolshed.co.uk/nicholson-flat-second-cut-file-10in.html
That will do the job?
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