Tag Archives: saw sharpening

Cutting New Saw Teeth

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When I remark that I’ve cut teeth entirely from scratch on many of my saws, some people think that it either involves stamping, a machine, or some sort of magic trick. It’s nothing of the sort. If a klutz like me can do it on the abomination of a saw vise that I have, anyone can.

It’s actually quite simple because it’s derived from normal saw-sharpening practice. You start with a file with a handle and flat block of wood as described in Lee’s book and any saw sharpening site out there. To get the tooth spacing, make yourself a little guide. I wrote my own PostScript program to do it (check the Plans and Guides page for PDF versions ugh, gotta restore that some time), but I imagine that there are plenty of ways you can do it with several packages.

Get some reading glasses; they help a lot.

Fold the guide over the front jaw of the vise, put the blade in, just peeking over the top, and make a first pass with the file, just filing in a little notch over the top of each line (sorry about the fuzziness, but I just don’t have a macro lens):

Notice that I’m not really getting the spacing spot-on; you can tell from the flats at the tips of the newly-formed teeth. Don’t worry about this on your first pass–you’re going to refine it later on. You don’t even have to worry much about the file itself on the first pass. The one I’m using here is way too big for the final tooth size (this will be a 16TPI saw that I will reveal later). I’m doing this because I don’t want to put unnecessary wear on a relatively expensive small saw file.

After you’re done with the first pass, do a second pass to go deeper. Make an attempt to correct for uneven spacing by putting a little pressure left or right as you’re filing, but use a very light touch; don’t make any extra strokes with the file just to even it out, and don’t press harder than you normally would. You still want to be fairly consistent in the newly-cut tooth valley size. The unevenness will disappear as you make more passes with the file.

In the saw above, the teeth are so small that I went most of the way with my second pass, this time using a file that’s appropriate for the pitch. You can see that the teeth are slightly uneven, but not by extreme amounts:

I then set the teeth, jointed them, and did a final filing. At that point, the teeth were quite even. It’s important to joint and file after you set the teeth because the act of setting the teeth dramatically alters the orientation and shape of the cutting edges. In addition, you’ll often accidentally set the teeth more than you need. A final pass at sharpening helps reduce the set. For the saw above, I used a fine-tooth saw set at its minimal setting, and it was still too much!

Rip Panel Saw: Choosing a Sawplate

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While the handle is in the varnishing stage, I’ve been worrying about how to approach the sawplate for the new saw. Being the cheapskate that I am, I have been considering using the plate from this thing that I picked up for a song and a dance some time ago:

The basic shape is right, but of course, I’d cut the tip off to make it look halfway normal, mill off the teeth, and cut new ones, and do whatever else is necessary to get it fit on the handle.

The trick to all of this is the thickness of the plate. It’s kind of a tricky business, because all of the old saws were taper-ground, and you won’t find a cheap saw these days that is. So I’d be giving that up, but I don’t have any old saws that I can cannibalize anyway.

Furthermore, until now, I really didn’t know the thicknesses of any of the plates that I was working with; I was only able to sort of guess by looking at them. Well, that all changed when I finally got off my butt and bought a micrometer. Why I didn’t get one before, I’ll never know. It’s really taken a lot of the guesswork out of a lot of stuff.

I’d been wondering about this because I’ve got saws that turned out in certain unexpected ways due to this, and I really didn’t know about it before. For example, my crosscut carcase saw works wonderfully, but a rip version of it didn’t turn out the way I wanted it to. The plate on those two saws is .0263″, but you’d really want something more like the 0.020″ thickness found on most dovetail saws.

What’s .0063″ of difference? Well, one way to think about it is that it’s 31.5% thicker, which is pretty significant. In theory, you’re cutting 31.5% more wood, and so it’s 31.5% more work to do it. (This does not hold for a crosscut saw, where you are slicing fibers out instead of scooping shavings.) You can also look at it visually; take a look at the following image that I just cobbled together as a PostScript program:

The difference between .020 and .0263 looks pretty striking here. These thicknesses are at the cutting edge. I have the measurements for the tops of the saws that are taper ground, but I’m going to set that aside for the moment.

As you might have noticed, I put labels on this image. Of course, after I got my micrometer, I obsessively measured all of my saws. I don’t have a Kenyon saw, but it’s listed here as a representative for a big tenon saw (the Wenzloff versions have .025″ plates).

There are some surprises, such as that Stanley dovetail saw with the gents handle. This is a relatively new one that I picked out of a basement. I never bothered with it because I already had the Crown equivalent (.0205″), but you can see that it’s quite thin! This is the saw featured in Korn’s book, and it should be pretty obvious that if you’re willing to learn how to sharpen it, it will give you experience with a thinner plate and should work just fine. It’s no wonder he has no trouble recommending it.

So getting back to the question at hand, is the lovely “Kobalt” plate going to work? I think I’m going to give it a shot. It’s about 16% thicker on its cutting edge than the original that I’m working with, but that doesn’t seem that bad (and some of this thickness may be lacquer). The thickness of the original is a little unusual anyway; full-size saws are about 33% thicker. The only blade I have that’s close is my frame saw blade (0.029″), and, er, that’s not gonna work.

Then there’s the matter of taper-grinding. Should I try this? I’ve got sort of an idea of how I can do it without a power tool (although if I were sane, I’d ask to use someone’s belt sander). Would that warp the plate? Hmm.

Frankensaw; Saw Sharpening Guides

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I’m finally done with sharpening the last saw on my to-do list. This and the one in my previous post were both acquired at an estate sale over in the Sunset district last year. They’re both Disston No. 7s, but both have been rehandled. The first one I worked on had some sort of modernish handle on it. The one I just finished has a No. 12 handle.

Someone must have liked these saws. They were both rust-free and had pretty good visible etches. Unfortunately, the sharpening on them was crap. The No. 7/12 Frankensaw needed serious jointing (and therefore, serious tooth reshaping) before it could be pointed.

But once at the pointing stage, things went pretty quickly in spite of it being a 26″ saw with 8 teeth per inch. I used a 10 degree fleam angle this time, and used a roughly 10 degree slope on the gullets as well. Here’s a shot of the sharpening in progress:

This picture shows one of the issues that often comes up when sharpening crosscut saws that I’ve been talking about recently, and that is, that the shape that the tooth appears to be can be misleading. Look at the teeth on the right side of the saw in the preceding image. See how they look kind of spindly? It’s a trick of the reflected light. Here’s a close-up, where you can see the reflections and the full tooth profile:

Obviously, there are some uneven spots here, too, like the second-to-left gullet, but those were taken care of on a second pass. but the point is that you have to be careful about what you see. Just be consistent with the angles you work at, look at the tops of the teeth to see when you’re done.

Here is the saw in its finished state:

You can see my fleam guide in the photo of the work in progress. I worked a little on the code for this before starting this saw. My previous version required you to use two different cutouts to sharpen each side of the teeth. That was kind of stupid, because you can see only one side of it at a time. So I reworked it.

Update: I now recommend that you use the versions that are on the Plans and Guides page rather than the following, but I’m not going to remove these any time soon.

Here are PDF versions for:

  • 10 degree fleam (fleam10)
  • 15 degree fleam (fleam15)
  • 20 degree fleam (fleam20) (whoops, need to regenerate that sometime)

If you know how to use PostScript, ask me for the source code; you can put in any fleam angle you like. (I haven’t figured out how to trick WordPress into letting me upload a .ps file without doing something stupid like archiving yet, sigh.)

Also, I have a PDF tooth pitch gauge (toothgauge) that you might be able to use at some point.

My Sloped Gullets

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Leif over at Norse Woodsmith did a recent post on sloped gullets. Strangely enough, I’ve been working on restoring a couple of saws lately, and about the time he posted, I was starting to sharpen one of them, an old Disston No. 7. I finished this morning and decided to take a photo of the result. Unfortunately, I don’t have a macro lens, so I can’t get much better than the following shot, and also unfortunately, I don’t think the angle is very good, because you can’t really see the bottom of the gullets too well:

In any case, take a look at the bottom of the brightly reflected edges, and you’ll see that the rear is higher than the front, especially on that tooth all the way to the left. This shot was taken straight from the saw coming off the file, so you can see some burr here and there. You can also see how difficult it is to judge the height and shape of the teeth here. In this shot, it looks like the teeth set towards the camera (the all-dark ones) are a little bit lower than the ones set away, but in reality, they’re all the same. It really is easier to tell by jointing the teeth and filing until the flats are gone.

I’d mentioned in a comment on Leif’s post that the angle I used for fleam and slope was not that great. On further inspection, it seems to be moderate. The fleam angle is 20 degrees and the slope is about the same. I think a 10-15 degree fleam and slope would be easier to file, and I plan to try it out on the other saw I need to sharpen.

All of this theory is useless if it doesn’t work in practice. Here is a test cut in beech:

It’s about what you would expect from a 6TPI saw that’s 26″ long. The important part is that it belches sawdust profusely when sawing, and with a controlled cut, you don’t get much tearout. And it’s always nice to get a 110+ year old tool working again.