by Bob Smalser
This article first appeared as a thread on theWoodNet woodworking forum. It was compiled and reproduced here for easier public consumption. All Text and Images are the property of Bob Smalser.
Youngest son Jake heads down to Central America next week on a two-week church mission to build a stick frame house for a poor family. He'll go with a dozen other teenagers in his youth fellowship group .to an area with no electricity and no generators. Hand tool country..so I figure it's time to teach the lad how to sharpen saws, something sure to raise his value to the locals. The best treatise I've seen on this is by Pete Taran, another sawyer's son over at Vintage Saws.it'll help to pull it up in a separate browser window as you read my article:
Saw Filing - A Beginner's Primer by Pete Taran
The problem with written rather than hands-on instruction is that it sounds a lot more complicated that it is, making it intimidating for the beginner. That's a shame, because sending your saws out to commercial sharpening services shortens their life.the first thing the commercial shops generally do is shear in a new set of teeth by machine, which reduces your remaining blade depth by anywhere from 3/16th's to a quarter inch. Touching up your saws as it is needed, in contrast, is dead simple and only takes off a few thousands of an inch, as you will soon see. For the price of a couple commercial sharpenings, you can buy all the simple tools you need and fabricate a filing horse like ours..your saws will thank you.
I print off Pete's Beginner's Primer and have Jake puzzle through it alone in the shop.Jake has some experience in milling logs and basic wood shop skills and I'd call him an advanced beginner.then we go through the process so I can understand what wasn't clear to him so I can emphasize it here.
Pete shows how to make a guide block to keep the rake angle consistent. There are two angles to deal with."rake" and "fleam". Rake is the vertical angle of the leading edge of the tooth, as shown in the drawing above.. generally from 12-15 degrees past vertical in crosscut teeth. 12 degrees is steeper and harder to start the saw, so I choose 15 degrees for beginners. The guide block is drilled to fit the tip of the slim tapered triangular files, and an index line is drawn off of vertical to line up one edge of the file. 15 degrees past vertical comes to 105 degrees on the protractor, and I mark that angle on the guide block with reference marks for which side is up. As every other tooth is filed from one side of the saw and then the saw turned to file the remaining teeth, the mirror images of the marks are drawn on the opposite side of the block. This will be crystal clear when you turn the saw to file from the other side.
Fleam is merely the angle of the bevel filed into the teeth horizontally. These can run from 15 to 24 degrees. The steep 15-degree angle produces a durable edge but a coarse cut, and the sharper 24-degree angle slices fast and smooth but the teeth dull quickly. 20 degrees is a common compromise and that's what we'll put on this 9tpi Disston 12 crosscut today..the angle transferred to a bevel gage to use as a guide.
As the teeth on this saw are is decent shape, our first step is to joint them..bringing them down to an even height.with an unhandled single-cut mill file held square to the sawblade.
.you can see the small flat mark the file puts on each tooth..stop when each tooth has a faint mark. The more jointing required, the more filing required, so use a light hand in good light and wear dime store reading glasses for some magnification. A couple pair of different strengths live in the bin of the filing horse with the files, sawset and chalk.
Jake then sets the teeth using a sawset. This can be done before or after filing, but setting the teeth before insures the sawset doesn't damage the freshly sharpened edges. If you sharpen your saws regularly, you don't need the amount of set in the teeth specified by the tool.I use half the tpi setting specified on the sawset.today the sawset's adjustment wheel is indexed for 4.5tpi to set a 9tpi saw. Sight down your saw, first.if the teeth look uniformly set, you may not have to mess with it at all.
Every other tooth on one side of the saw is sharpened..the bevel gage guides the fleam angle and keeping the rake angle guide block level guides the rake. Before starting, look at the bevels that already exist on the teeth and lay the file in a few of them at the correct angles.it will be clear that the file fits neatly in every other tooth when working from one side of the saw and memorizing that correct picture now will prevent you from making a mistake should filing tedium set in and you lose track of where you are.
To file equal sized teeth, Jake begins with his flattest tooth and counts the number of strokes it takes to halve the size of the flat spot made by the jointing file. As I had him joint this saw heavily today to be sure he could see the flats clearly and understand the principle, he'll do 8 filing strokes on every other tooth, then move to the other side of the saw and do 8 strokes on the remaining teeth. Were I doing this saw alone, I probably would have been able to get away with 4 strokes. The above photo shows the teeth after only one side of the saw has been filed and every other tooth is at full depth from those 8 file strokes.
Jake switches sides, reversing his rake guide block on the file. By the time he arrived at this spot half way through the opposite side of the saw his consistency and speed become as good as I can do. Later, he did an excellent job on the more difficult 14tpi dovetail saw laying on the Workmate in the first photo all by himself.filing saws was my first real job in Uncle Paul's boatyard beginning at age 11.to read about saw filing still makes my head hurt.but actually doing it is child's play.
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