Can I sharpen a hand saw, or should I just replace it?

Two entirely different products are sold as hand saws. Hardpoint saws have teeth hardened by induction so they hold an edge several times longer than plain steel, at the price of being unsharpenable — a file will not touch them and will be ruined trying. Traditional saws have soft-steel teeth that go blunt sooner and can be brought back indefinitely. Neither is wrong; knowing which you own decides everything.

What you'll need

• Saw vice or two boards and a bench vice (optional)
• Triangular saw file of the right size (optional)
• Saw set (plier-type) (optional)
• Flat file for jointing (optional)
• Light machine oil or camellia oil
• Blade guard or a slotted batten

Step by step

1. Identify which saw you have.Hold the blade to the light and look at the tips. A distinct darker band along the teeth means hardpoint. Bright steel all the way to the tips, and often a visible file finish between teeth, means a sharpenable saw.
2. If it is hardpoint, decide on the cut quality, not the sharpness.Hardpoint saws blunt gradually and it is easy not to notice. If it needs pushing, wanders, burnishes rather than cuts, or leaves a torn edge in clean dry timber, replace it. They are inexpensive enough that struggling with a blunt one is a false economy.
3. If it is sharpenable, joint the teeth first.Run a flat file along the tips of the teeth, held square, until every tooth shows a small flat. That makes all the teeth the same height, which is what stops a saw juddering. The flats are your guide for the filing that follows.
4. Set the teeth.A plier-type saw set bends each tooth outward by a fixed amount. Work along one side setting every alternate tooth, then turn the saw round and do the others. Set before filing, and only when the set has genuinely been lost — resetting every time removes metal for nothing.
5. File the teeth.Hold the saw low in a vice between two boards so the teeth barely project, which stops the blade screaming. Use a triangular saw file sized to the teeth. Work into every second gullet along the length, keeping the file angle consistent, until half of each jointed flat has gone. Turn the saw around and do the alternate gullets from the other side.
6. Check your work.Sight down the tooth line: the tips should form a straight line and the set should look even from both sides. Test in scrap — a correctly sharpened saw starts easily and pulls itself into the cut rather than needing pressure.
7. Protect the teeth in storage.Teeth are ruined by contact with other tools far more often than by use. Keep a plastic guard on, or cut a saw kerf down a length of scrap batten and slide it over the teeth. Hang saws rather than dropping them in a drawer.
8. Keep the plate from rusting.Wipe the blade with an oily rag after use, particularly after cutting damp or treated timber. Rust pits the plate, and a pitted plate drags in the kerf however sharp the teeth are.

Alternatives

• Professional saw sharpening: Saw doctors still exist and will joint, set and sharpen a traditional saw properly for a modest fee. Worth it for an inherited or high-quality saw, or a first sharpen you can then copy.
• Replace with a hardpoint: For construction and general site work, a new hardpoint panel saw every couple of years is cheaper and quicker than maintaining a traditional saw, and it cuts faster when new.
• Switch to a pull saw: Japanese-pattern saws have replaceable blades that clip into the handle. You get a very fine cut and simply swap the blade when it dulls, with no sharpening skill required.

Keeping on top of it

• Wipe the plate with an oiled rag after use (Every session)
• Check and refit the tooth guard (Every time it goes away)
• Check teeth for damage after cutting reclaimed timber (After each such job)
• Joint, set and file a traditional saw (When it stops starting easily)

Questions people ask