Monday, June 14, 2010

Class Report - Saw Sharpening at St. Roy's School

Short version: I took a one-day class on Saturday at the Woodwright's School in Pittsboro, NC. The topic of the class was Saw Sharpening. It was great and I finally figured out what all this fleam and rake and gullets and such really meant. I recommend for anyone who wants to learn.

Much longer version:

Now I hear some of you snickering at the n00b, but it is a skill that while simple in its foundation, is, for me at least, best learned by example rather than trial and error.

The class was taught by one of Roy's local teachers, Bill Andersen, who has been teaching classes in the area for some time now. Bill did a great job introducing us to the various tools and implements used for saw sharpening. We each had a bench with an old saw vise and we brought our own saws, but there were plenty there that needed sharpening.

We were just able to get through doing a rip saw before lunch, and a cross cut after lunch. I finished early enough to then re-tooth one of his back saws which looked like it hadn't been touched in 50 years.

We started on the rip saw because it is much easier to learn on than the crosscut. I had brought two Simmonds, a 6-point rip and an 8-point cross cut. Both had been re-toothed and sharpened quite a while ago when I first came to NC (2003) by a saw sharpening service in Raleigh. I was under the impression that these saws worked fine but only needed a quick touch-up.

We began with jointing the saw, filing with a larger, flat file held perpendicular to the teeth, and run straight down the tops of the saw teeth. Boy, was that an eye-opening experience. This saw was not so beautifully toothed as I thought. I had to take a fair amount to touch most of the teeth. I ended up with about four teeth down the length of the saw that were still just too short for me to reach. Bill said that was fine, you'll get them eventually as you sharpen it, either next time or the time after.

We then re-shaped the teeth to get the right rake. I began at the heel of the saw, down by the handle, and there's a good reason to do so, because when you screw up there, it doesn't really matter too much since you almost never saw with those teeth. Good thing too. I made my first big mistake, and was grateful for having someone there who knew what they were doing. First mistake was thinking I could keep my file at the right angle without a help. I got about six teeth down when Bill came by and gently pointed out my very common mistake, I was filing my teeth with a 30-degree rake because I was following the natural reaction to have the top face of the file become more and more flat as I filed. He suggested I use on of the very simple, but extremely useful, wooden blocks he had made that help give you a reference face for the right angle. Stick the block on the end of the file, and keep the block horizontal and you'll be ok. Big difference. You can see one of these very simple devises on Pete Taran's saw filing page.

This is where a teacher-led class can more than pay for itself. Bill showed me what I was doing wrong before I had ruined all the teeth, and he showed me how to fix it.

I got my money's worth again a short time later when I made my second big mistake. I was getting the angle right, but this time, because I was trying to "fix" the teeth that I had filed at too sharp of an angle, I was getting a bit aggressive with the file. I was trying to shape AND sharpen at the same time (without really knowing that's what I was doing) and as a result every other gullet was way deeper than the one I hadn't done. Again, Bill was able to come to the rescue and help me figure out that I was doing it wrong, and how to fix it before I did too much damage.

After that, things went more smoothly. I ended up having to re-joint the teeth a couple more times before I got them shaped like I wanted. I then did a light jointing, set them, and did a final sharpening. Bill showed us how much to stone the side of the saw to adjust the set and I was done.

We had each tested our saws at the beginning for the "before" cut. We tried cutting to a line and see how far ten strokes took us through the wood. After sharpening, we tested the "after". My saw had too much set at the beginning, which is why, I found out, that it had a tendency to vibrate a lot in the cut. Afterwards, I cut about a third longer in the same number of strokes, the kerf was cleaner and I didn't have nearly the vibration I had before.

The crosscut saw after lunch went much more smoothly, even with the added complexity of also filing the fleam into the teeth. We shaped the teeth like it was a rip saw, except the rake this time was 25-degrees instead of 8-degrees. Then finished shaping with adding the fleam. This time I was a much lighter touch with the file, and kept a rhythm while also watching each tooth carefully. This saw also had way too much set that graduated with almost no set by the heel and way wide set by the toe. It had so much that I actually didn't need to set it at all. The filing had taken off just enough set that it seemed fine.

I finished early enough that I thought I'd try my hand at a backsaw. In the pile of saws that needed sharpening was a nice brass-backed 19th-century British saw that had teeth but they were in a sorry state. By getting good light, and using a light, consistent touch, I was able to get it re-toothed as a rip quite quickly and easily. That was extremely satisfying to see those old, raggedy, nasty teeth turn into shiny, consistent teeth. The saw was so nasty that the teeth were already black with crud and age I didn't need to blacken them. For the other saws, we had used an alcohol based carbon blacking spray which worked like a spray paint. That was really easy to spray and mark each tooth to make sure you knew which one you'd done, and which ones you hadn't. It cleaned up with alcohol.

So, if you're interested in learning how to sharpen, this is a great class. And I'm so glad I've finally gotten a chance to learn how it's done, and had it de-mystified for me. It's now time to make a couple of those jigs to help me keep a good angle, and find my saw vise in the dust and I'm in business.