Most dull chains just need sharpening.

You can sharpen a dull chain several times before it really needs replacing. The trick is knowing which one you’re dealing with.

A dull chain is obvious: it throws sawdust instead of nice clean chips. You have to lean into the cut, and it leaves a rough, burned-looking surface. Sometimes it even smokes or pulls to one side. That’s all fixable with a file or a sharpener—usually takes five minutes.

But a chain that needs replacement has physical wear you can see. The drive links (the little teeth that ride in the bar groove) are worn down. The cutters themselves have been filed so many times they’re too short to cut properly. Or you’ve broken a tooth or two. Also look for wear on the tie straps between cutters—those are a sign the chain is stretched or fatigued.

The easiest test: if you sharpen it and it still cuts poorly, it’s done. Don’t overthink it. A new chain costs twenty bucks and lasts for dozens of sharpenings.

Don’t keep running a chain that’s past its life. That’s how you burn up a bar or break a chain at speed—and that’s no joke.