Over the past few years I have always bought a new chain when they got dull.
This year I needed to finish cutting up main trunk part of a maple we had cut a few years ago.
The wood was extremly hard and after purchasing 2 new chains I decided to try my hand at sharpening them myself. I had always heard stories of how diificult this was so I was worried that I would waste a lot of time trying to sharpen and end up having to get another chain anyway.
After buying two new chains without finishing the wood I decided to give sharpening a try.
I found that the angle on the sharpening guide has to match the teeth on the chain. Mine was 30 degrees. Also the diameter of the file has to match the teeth as well.
Filing should only be done in one direction... the file should be pushed in the direction toward the sharp part of the tooth.
This manual filing takes some effort and time but compared to the time it takes to run to the store and the cost of a new chain I found that it was worth it.
Happy sharpening!