How to Sharpen a Chainsaw: File vs Electric Sharpener

To sharpen a chainsaw chain, file each cutter with a round file whose size matches the chain’s pitch, held in a file guide at the angle marked for that chain, which is usually 30°. File every cutter from the inside of the cutter outward with the same number of strokes, do all the cutters on one side, then turn the saw and do the other side. Every few sharpenings, check the depth gauges in front of each cutter and lower them with a flat file if they stand too high. An electric sharpener does the same job faster and more evenly, but it removes more metal and needs the right grinding wheel for the chain.

File size by chain pitch

Chain pitch	Round file size	Common on
1/4 in	5/32 in (4.0 mm)	Small top-handle and pole saws
3/8 in low profile	5/32 in (4.0 mm)	Homeowner and battery saws
.325 in	3/16 in (4.8 mm)	Mid-size gas saws
3/8 in (full)	7/32 in (5.5 mm)	Larger gas saws
.404 in	7/32 in (5.5 mm)	Heavy professional saws

The pitch is usually stamped on the drive links or the guide bar; how to measure a chainsaw bar and chain shows how to find it. Some chains in the same pitch use a slightly different file, so the chain maker’s chart is the final word.

How to sharpen with a file

1. Make the saw safe: engine off and cool (or battery out), chain brake on.
2. Clamp the bar in a vise or a stump vise so the saw can’t move, and tension the chain so it doesn’t wobble.
3. Mark the first cutter with a marker, so you know where you started.
4. Fit the file in a file guide, which holds it at the right height, and line up the angle marks with the chain (usually 30°; some chains are 25° or 35°).
5. File from the inside of the cutter outward, with smooth, firm forward strokes. Lift the file on the return stroke.
6. Give every cutter on that side the same number of strokes, usually 3 to 5, so they stay the same length.
7. Turn the saw round and repeat on the cutters facing the other way.
8. Check the depth gauges (the small tabs in front of each cutter) with a depth gauge tool every few sharpenings. File down any that stick up above the tool with a flat file, to the depth the chain maker specifies.

File or electric sharpener?

	Round file	Electric sharpener
Where	On the saw, in the field	On the bench, chain removed
Speed	Slower	Faster
Evenness	Depends on your technique	Very even once set up
Metal removed	Little	More; chains wear out sooner
Cost	Low	Higher
Best for	Regular touch-ups	Badly dulled or damaged chains, many chains

Many people file in the field and use a bench sharpener, or a saw shop, when a chain has hit dirt or a stone.

Signs a chain needs sharpening

• It makes fine dust instead of thick chips.
• You have to push the saw into the wood.
• The saw pulls to one side, a sign the cutters on one side are shorter or duller.
• It smokes or the bar gets hot, even with plenty of oil.

Keeping the bar and chain oiled matters as much as sharpness; can you use used motor oil for chainsaw bar oil explains why the right oil matters, and 16 vs 18 inch chainsaw helps with bar length if you’re replacing the bar and chain.

Wear cut-resistant gloves when filing: chain cutters are sharp even when they’re too dull to cut wood well.

Related guides

• How to Measure a Chainsaw Bar and Chain
• 16 vs 18 Inch Chainsaw: Which Bar Length Do You Need?
• Can You Use Used Motor Oil for Chainsaw Bar Oil?