How do you sharpen a bow saw blade?
Most bow saw blades are made to be replaced rather than sharpened, because their teeth are induction-hardened — often blued or blackened — and a fresh blade costs little while cutting better than a hand-filed hardened one. Sharpening only makes sense for softer, silver-toothed peg blades.
How can you tell if a blade is hardened or filable?
Tell a hardened blade from a filable one by the colour and feel of the teeth: hardened teeth are usually blued, blackened, or grey and skate a file across their surface, while filable teeth are bright silver steel that a file bites into. A quick, light touch of a file tells you within a stroke or two.
Manufacturers often state it on the packaging or the blade — terms like "hard point", "induction hardened", or "for replacement" mean the teeth cannot be filed. If the blade is bright, uniform steel with no dark tooth tips, it is likely a traditional peg blade that will take a file. When in doubt, treat a dark-toothed blade as disposable and a silver-toothed one as sharpenable.
Can hardened bow saw blades be sharpened?
Hardened blades cannot practically be filed. The heat-treated teeth are too hard for a standard file to bite, and attempting it wears the file without restoring the edge. If your blade has dark, factory-hardened teeth, the right move is to fit a new one. Keep a spare so a dull blade never stops the job.
What tools do you need to sharpen a peg blade?
Sharpening a peg blade needs only three things: a triangular saw file sized to the teeth, a saw set to bend the teeth, and a vice or clamp to hold the blade steady. A pair of wooden strips protects the blade in the vice and dampens the ringing as you file.
You can find files and setting tools in the sharpening files and tools range. Match the file size to the tooth pitch — too large a file rounds the gullets, too small a file chatters — and keep the file angle consistent so every tooth ends up the same height and bevel.
How do you sharpen a softer peg-tooth blade?
Softer peg-tooth blades can be sharpened with care:
- Clamp the blade firmly in a vice between two wood strips.
- File each tooth with a triangular saw file matched to the original tooth angle.
- Set the teeth lightly with a saw set so they cut a clearing kerf.
- Check the tops are even so the blade tracks straight.
How do you keep a blade sharp for longer?
Keep a blade sharp longer by keeping it out of the dirt, clear of nails and wire, and clean of sap between jobs. Most blades are dulled or wrecked not by honest cutting but by a single strike on soil, stone, or an embedded nail, which rounds or chips a whole run of teeth at once.
Cut on a sawhorse or log stand rather than on the ground, and stop before the blade reaches the earth on a ground log. Wipe sap off the teeth with a rag or solvent so the gullets keep clearing, and store the saw dry and lightly oiled with the guard fitted. These habits stretch a blade's working life far more than any amount of sharpening.
How do you set the teeth after filing?
Set the teeth after filing by bending each alternate tooth very slightly outward with a saw set, so the row cuts a kerf a little wider than the blade itself. Without set, the blade binds in its own cut; with the right set, it clears sawdust and runs free.
Work along the blade setting every other tooth to one side, then turn the blade and set the remaining teeth to the other side, keeping the amount even. Green-wood blades take a touch more set than dry-wood blades because wet fibres swell and grip the blade. Keep the set modest — over-setting cuts a ragged, slow kerf and wastes effort — and sight down the blade afterward to check the teeth splay evenly left and right.
Is sharpening worth it?
For most owners, sharpening is not worth the effort. Replacement blades are inexpensive and widely stocked, so fitting a fresh blade when cutting slows is faster and gives a better cut. Spend your time keeping the blade clean, lightly oiled against rust, and correctly tensioned instead. For more on blades and tension, see our bow saw blades guide.
