A hand saw rarely fails all at once. It dulls quietly: the first sign is a wayward cut, then a hard push, then a tired shoulder. Most of us assume the blade is worn out. It is not. The teeth have only lost their even points and their slight outward lean. Both can be restored with a jointer, a triangular file, a saw set, and a few careful passes.
Photo by Jean-Baptiste D. on Unsplash.
What You Need
- A saw jointer, or a flat mill file held in a straight block
- A slim triangular saw file
- A saw set
- A bench vise; a saw vise is better, but wood pads work
- A marker
- A wood offcut for the test cut
Work with the saw clamped firmly. The teeth should be just above the jaws, not buried. A wobbly blade makes a bad file stroke and a worse temper.
1. Joint the Tooth Tips
Jointing evens the teeth so that every tip rises to the same line. Without this step, a file will follow the low spots and leave some teeth unsharpened.
Clamp the saw with the handle to your right. Hold a saw jointer or a flat mill file level along the tops of the teeth. Use light push strokes, and cover the whole row at once. Stop as soon as every tooth shows a small bright flat. If you colour the tips with a marker first, these flats are easier to see.
Do not joint until the tooth line looks polished. Each flat is a target for the triangular file; once the flat is there, you have enough reference. More jointing removes metal that should stay in the tooth.
2. Shape the Teeth
The jointed flats are now the tops of blunt little posts. A triangular saw file restores the points by cutting the gullets between them.
Place the file in the first gullet and use a firm push stroke. The file should bear on the back of one tooth and the face of the next, so it cuts both sides of the gullet at the same time. Work along the saw, moving one gullet at a time. On a second pass, return to any gullet that still leaves a flat on the tooth tip.
For a crosscut saw, you can keep this shaping pass square to the blade. The bevels that make it a crosscut saw are added later. At this stage the goal is simply a row of sharp, even points with clean gullets.
Photo by Alexander Andrews on Unsplash.
3. Set the Teeth
A saw with no set makes a kerf no wider than the plate, and the plate will bind in its own cut. Setting bends the top portion of each tooth alternately left and right, so the kerf becomes a little wider than the blade.
Work from one end to the other. Adjust the saw set so it grips the tooth near the tip. Bend every other tooth away from you, then bend the teeth in between toward you. A useful amount for most work is a bend equal to about one third of the thickness of the blade. Use a little less set for dry hardwood and a little more for green or soft wood.
Set only the upper part of the tooth. If the saw set presses too low, the root of the tooth can crack. If you cannot see the lean clearly, wipe the teeth with a marker and look along the blade; the set teeth should catch light at their tips.
4. File the Teeth
Filing is where the saw becomes sharp. Use a triangular saw file that fits comfortably in the gullet without rubbing against the next gullet. A six inch slim file is a good place to start for an ordinary eight to ten point hand saw; use a smaller file for finer teeth.
Push the file across the teeth on the forward stroke, then lift it clear. Pulling the file backwards only dulls it. Let the file cut at its own pace; force is not the point.
Filing a Rip Saw
For a rip saw, hold the file square to the saw plate. In plan, the file points straight across the blade. Keep the handle end a few degrees lower than the tip to give the tooth a small rake. Work through every gullet from one end to the other. Because the file is square, each pass gives the tooth on one side of the gullet a chisel point and the tooth on the other side a matching back. You should be able to file the whole saw without turning it around.
Filing a Crosscut Saw
For a crosscut saw, hold the file at about 75 degrees to the saw plate, not square to it. This slant, often called fleam, is what makes the teeth slice across the wood grain instead of chiselling it. File the teeth that lean away from you first, working systematically along the saw. Then turn the saw around in the vise and file the teeth that lean toward you. Keep the same file angle on the second pass. The edges should come up as fine points that meet like small knife blades.
Photo by Austin Ramsey on Unsplash.
Test the Saw
Before you put the saw away, make a test cut in a wood offcut. Mark a straight line and start carefully with short pull strokes. If the saw is sharp, it will stay on the line without extra pressure. The kerf should be clean and the sawdust even.
If the saw binds, it needs a little more set. If it cuts roughly and the kerf looks ragged, the set is too large. If one side of the cut is polished or the saw refuses to bite, you have probably filed one side at a different angle. Check the file angle and repeat only the questionable side, taking light strokes.
A saw that pulls itself into the wood and leaves a straight kerf has been brought back. The handle may still show fifty years of use, but the teeth will feel new.