Use the right size file for your 3/8 pitch chain. There is a "standard" 3/8 and a "low profile" size. Larger saws use standard 3/8 pitch, while smaller ones--like those used by most homeowners--use low profile. Pitch refers to the distance in inches between three consecutive rivets, divided by two. Refer to your owner's manual for the proper file size if your saw did not come with a file. Most low profile 3/8 pitch chains use a 5/32-inch round file.
Get a good sharpening guide if one was not included with your saw. Some fasten to the chain bar, others have guides marked on them to show filing angles. The best type clamps onto the bar and has a swivel, which can be set to the proper filing angle. Check the owner's manual to be certain of the filing angle, which will vary among saws. Set the angle to match the existing angle on the teeth if you cannot locate the correct angle. Put the saw on a solid surface, preferably with the bar clamped in a vise. Make sure the chain can move freely.
File from back to front on each tooth. Make a full stroke with the file each time, remove the file and start over; don't saw back and forth with the file because it only cuts in one direction. Be sure the file stays in firm contact with the tooth the entire stroke. Use only two or three strokes per tooth and keep the number consistent throughout the process. Test it with the first tooth; if two strokes make a shiny, sharp edge, that's enough.
Sharpen all teeth in one direction first, then switch the sharpening guide and sharpen the teeth on the other angle. Examine all of the teeth after sharpening to make sure there are no nicks or other damage to the tops of them. Check the depth gauge, which controls the slope or angle of the tooth, to make sure the cutting edge is always at the top. You can adjust the depth gauge with a guide and a flat file but it's usually best to get a professional sharpening, which will include that touch up.
Things You Will Need
- Sharpening guide
- Disconnect the spark plug before sharpening the chain to ensure safety.