Get a Sharpening Guide
While you can sharpen a chain saw by eyeing the way the file lines up, a sharpening guide tuned for your particular brand of saw takes out the guesswork. Cutter angles vary, typically between 25 and 35 degrees. Being off by a few degrees makes a difference in chain saw performance. A sharpening guide is inscribed with marks that indicate the sharpening angle for your saw. A sharpening guide kit also includes properly sized files for honing cutters and for filing down depth gauges. The guide or kit packaging lists all the chain saw makes and models for which it was designed. Match the right kit for your chain saw.
A Strong Vise
A vise comes in handy since you’d like your saw stationary when sharpening. When working on a saw in your shop, use a bench-mounted vise. In the field, where you will likely need to sharpen your saw while ripping through a large pile of wood, carry along a stump vise. This type of vise acts as a third hand, holding the saw firmly in place, freeing up both your hands for the sharpening tasks. Mount the chain saw into either vise and clamp down only on the cutter bar, which allows free movement of the chain itself.
Honing the Cutters
Some sharpening guides fix to the chain saw bar with bolts, others are hand held and rest on the chain. Place a dab of paint or marker on the first cutter so you know where you began sharpening. You’ll notice that the chain has two sets of cutters -- one set faces left, the other right. Use the round file on cutters, and sharpen one set at a time. Push the file away from you with each stroke, treating each individual cutter to between three and five strokes. Then, flip the saw end-to-end and sharpen the next set of cutters the same way.
Filing Depth Gauges
Depth gauges face each cutter. They control how deep the cutters bite into the wood. Use the flat file to grind these down, since the tops of the cutters wear down over time. The sharpening guide has a slot that slips over each depth gauge. Any part of the depth gauge that sticks up above the sharpening guide is filed down flush with the guide. While cutters wear rapidly, depth gauges last longer before needing attention. Address them about every third or fourth time you sharpen the cutters or about every fourth tank of fuel put in the chain saw.
Always take a moment to disconnect the spark plug before sharpening the saw or when performing any maintenance. This prevents accidental startups from occurring while your hands are on the chain. While they may not cut well through wood, even dulled cutters can slice a hand or finger. Wear heavy-duty work gloves during sharpening.