02 September 2015

Sharpening the Saw

If you lived through the 90s, you probably read Stephen Covey's "The 7 Habits of Highly Effective People". It was one of the biggest book of the era and Bill Clinton even invited Covey to Camp David to talk about how the President could use the ideas to improve the function of the government.

Well, that didn't work out too well, but I still remember the book positively and hope that I have absorbed at least a few of its lessons, at least a little bit.

The final habit, if you recall, is of continuous improvement.  He called the habit Sharpening the Saw. The idea was to create a positive spiral of growth, change, and improvement by constantly building upon what you'd already learned. By renewing yourself constantly through education, you would propel your self ever upwards along the path of personal freedom, security, wisdom and power.

Lofty goals. So it struck me as odd the other night, as I was sitting at my work bench, that Covey called the habit 'Sharpening the Saw'. One of the first things you learn as a newbie woodworker is that no one with any sense sharpens their own saws. Planes, chisels, even drill bits, sure! But saws? No. That's too hard for mere mortals.

This prejudice was introduced to my mind when I read the bible of old tools: Michael Dunbar's "Restoring, Tuning, & Using Classic Woodworking Tools". In the section on restoring saws, Dunbar says, "As a woodworker, I have a bench grinder and other sharpening equipment, and I sharpen my own edge tools. I will occasionally touch up my saws with a file, especially in the case of a minor accident. However, it requires a lot of time to completely joint, file, and then set each tooth. This is one job I leave to the professionals."

This bias against sharpening saws was confirmed by Christopher Schwartz's excellent book, "The Joiner and the Cabinet Maker". In the section (I can't find it at the moment, so pardon me if I don't get this exactly right) where the book describes how things were done in a professional cabinet maker's shop, back in the day when such places were common, he says that even in a shop filled with master craftsmen with apprentices to do the dirty work, no one sharpened their own saws. A professional sharpener would come along every couple weeks and sharpen all the saws in the shop.

Frankly, not being able to sharpen my own hand saws wasn't a big problem for me until fairly recently, when I decided I'd had enough of the billowing clouds of fine saw dust created by power tools. During the course of this summer, I've pared my power tools down to the minimum -- bandsaw, planer, and drill press -- and gradually taught myself how tune up my hand tools. I went around the shop tuning and sharpening everything in sight, until finally my eyes finally fell on my saws. In particular, two ancient Disston rip saws that were so dull you couldn't cut your way out of a cardboard box with either one.

The first, and by far the oldest, was an old Disston I'd inherited from my grandfather. I'd actually been dumb enough to think it was sharp, back when I used it on my very first woodworking project -- fixing a bedroom door. But it was dull. Really dull. And bent. Oh, and the handle was broken.

The second was a much younger Disston that had been given to me by my Uncle Marty. This had a straight blade and a handle that was intact, even if it didn't have the charm and workmanship of the much earlier saw. But it was also quite dull.

"Simple," I thought. "I'll just send it out to be sharpened."

Ha!

Now, maybe there are still professional saw sharpeners in the hills of North Carolina, or Maine, or Oregon, but not on Long Island. Not anyone I'd trust the job to, anyway. I quickly figured out I'd have to mail my saws to someone I found on the Internet, and hope they came back properly sharpened. This would be time consuming and costly. Needless to say, I never got around to it. The saws hung on my shop wall as idle decorations.

That wouldn't do in the long run, of course. Almost without thinking about it, I gradually accumulated a saw file and even an old Disston saw set that I spotted at a garage sale hosted by a lady who had no idea what it was. I enlightened her, and she was happy to let it go for a dollar.

But I had no idea how to use these tools and didn't have the nerve to experiment.

Finally, I stumbled across a video by Paul Sellers, a 'lifestyle woodworker'. The video was a revelation.



"That looks easy!", was my first thought after watching the video, which you should watch before reading further. And last night, I finally worked up my nerve to sharpen my saw.

The first thing I did was to make a simple saw clamp. This is nothing more than a strip of scrap wood with a cut down the middle and a hole bored at the end of the cut to keep the wood from splitting.

Saw held in saw clamp
You just slide this over the blade and clamp the whole works into your bench vise. Unlike Paul, I like to sit down while I work, so this style clamp fit my budge and legs.

5 1/2 Teeth per Inch Rip Cut
With the teeth held up to the light, it was easy to see why the saw wouldn't cut: the teeth were pitted and even looked dull. After battling a moment of fear and hesitation, I plunged forward with the next -- and most drastic -- step in the process: filing (or 'jointing') the teeth to an even height.

'Jointing' the teeth to an even height
To work smoothly, all the teeth of a saw need to be the same height. It's easy to understand how a particularly tall tooth could cause the saw to catch or jam on every stroke. Having tested the dull saw on a piece of pine before starting, I knew this saw caught badly about 2/3rd of the way down the blade.

To joint the teeth, you file them down with a flat file, as shown above. In essence, the first step is to make the saw less sharp!

I tried to file the teeth with an old half-round file in my tool box, but only for two strokes. By now, I've learned that files are nearly as disposable as sand paper, and this file was dull, dull, dull. I dashed down to Home Depot to complete my toolset with a new flat file -- a flat bastard (seriously, thats it's real name.)

All the tools required - saw clamp, medium flat file, 3-sided saw file, and saw set.
This new file made quick work of filing the teeth down to the same size. It only took a few firm strokes, and they were all the same hight. Don't waste your time with worn out files. Bin them!

Then it was time to sharpen the teeth with a sharp 3-sided saw file. Paul has a specific technique for filing the teeth and I won't try to improve on his method. If you want to learn how to do this, just watch his video. My only comment is that his estimate of time is about right: it took me about 4 minutes to sharpen all the teeth. It is not rocket science.

Putting a sharp edge on one tooth
After examining each tooth, I decided I'd been a little too gentle with the file, and sharpened each tooth for a second time, a little less fearful, a little firmer, and a little more focused on the final shape and look of each individual tooth. It still took about 4 minutes to sharpen each one.

At that point, I decided to do a test cut with my newly sharpened saw. Clamping a piece of pine in the vise, I gave the saw a try. It was already much sharper than before, but it was still catching about 2/3rds of the way down the blade. Also, the saw kerf seemed too thin. The saw was binding in the cut a bit. It was time to try my saw set.

A saw set is a tool used to push saw teeth over at a slight angle. First you push every other tooth over to the right, then turn the saw around, and push the remaining teeth over to the left. Again, it was a fairly simple process, at least on a saw with enormous teeth.

Setting the teeth
Again I tested the saw and again it caught in that one spot. I tested the saw with several strokes, and each time it hesitated or caught at the same spot. I studied the one tooth that seemed to catch each time and, sure enough, it looked different from the others. It didn't have quite the same vertical rake.

I quickly filed that one tooth into shape, then continued to test and tune the saw until it sawed smoothly. The final step was to use Paul's trick to slightly close up the set of the teeth, so the kerf was wide enough to prevent binding, but no wider than necessary. See video for this step, which involves whacking the teeth gently with a ball peen hammer.

Then I used some 000 steel wool and linseed oil to remove the old grime and rust from the handle and saw blade. The result? A beautiful old saw that cuts as well as it looks.

Disston D12
As far as I can tell, this is a Disston D12, from the late 40s or early 50s. The etching on the blade isn't readable enough to be sure. Here is the information page on the D12, if you are curious about such things: http://www.disstonianinstitute.com/12page.html#d12

Bottom line: I'm now convinced old masters didn't sharpen their own saws not because they lacked the skill, but because it was cheaper to have a lower-skilled sharpener do the job for them. It just wasn't worth their time to do it themselves. I've never read this theory anywhere else, so take it with a grain of salt, but it makes sense to me.

Anyway, if I can figure out how to straighten its blade, I intend to file all the teeth off my really old Disston, and turn it into a 10 or 12 point saw. That should take some real nerve!



Next Up:  The Big Refit

8 comments:

  1. Congratulations on your saw sharpening John! Yes, Paul Sellers (pity you got his name wrong) has inspired many of us to jump in and attempt this task. I've now sharpened all my hand saws, rip cut style (I have tried in the past to do fleam with bad results). I have even re-toothed a 12 TPI 'gents' saw of 6" length to 16 TPI, for small stuff, starting by filing it smooth and then using an old hacksaw blade as measure for the new teeth.
    Starting with a large toothed saw (mine is a Disston 4 point (3 TPI!) rip saw that now runs so smooth and straight I even astounded myself) is a good idea, but don't be afraid to try your smaller saws as well.

    Rip cut pattern teeth work acceptably well for cross-cutting, if the teeth are not too aggressive in rake or over set, especially on the finer teeth of say a tenon saw.

    I agree, in the old days it was so cheap and convenient to pay a saw sharpening specialist, that few craftsman bothered to practice the art themselves. Since the advent of hardened teeth, and the mass production of throw-away saws, the saw sharpeners have all died out. The last one I knew of was an old man of 80+ when I was in my early 30's - more than 35 years ago.

    Maybe, with more practice, I'll get to filing in fleam and get a dedicated cross-cut.

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    1. Dang! I corrected Paul's name and added a link to his website. Thanks for the head's up.

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  2. <<<...off my really old Disston, and turn it into a 10 or 12 point saw. That should take some real nerve!>>>
    Comeon! Ya built a boat fer Christmas sake! Messin' with a saw gives you pause? I suspect a bit of drama. You are not deflowering the bishop's maiden aunt. It's just a piece of steel and some wood. Take it from one who has casually destroyed complex machinery-cars, trucks, week-whackers! I fired two pieces of sculpture-two weeks worth of my limited artistic tallent- in a raging bonfire last week just to see what it would do. They blew up and it was fabulous! A saw is on this earth to satisfy you, my man. Cut that sucka.

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  3. BTW John, I have almost successfully straightened a saw blade as well. There is some guidance on the internet, but there is no substitute to 'biting the bullet' and having a go at it. If the blade is bent the saw is useless, then there is little to lose, so just have a go. Remember though, that it is not intuitive, you have to hit the blade with a hammer over an anvil, or another hammer face, to spread the metal and tension the edge. This often means hitting it on the 'wrong' side. Have a read about it before you start, but don't be afraid to have a go.
    I'm not sure that this can help if the blade has been kinked though, mine just had a curve near one third the way up from the tip which always made it bend there when the teeth caught. It can still happen, but like you I paid attention to the teeth in that area to stop them catching.

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    1. Yes, I'm definitely going to give it a try. I could use a finer rip saw and I'd love to restore my older saw to a good user. Nothing ventured...

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  4. I've always found sharpening a saw very rewarding. It's a fairly straightforward job that takes less than half an hour and produces immediate results.

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