I use the Husqvarna/Oregon Precision Bar-Mount Filing Guide Sharpener. I have sharpened some really awfully dull chains with it and it gives good results if you are patient and work on one cutter at a time and don't rush. Because it is a hand sharpener you will get better as far as feeling the bite of the file the more you use it. It dials in all the correct angles. You attach it with thumb screws to the bar and move it down from one cutter to the next as you complete the sharpening.
Anyone else use one?
I used to use one of these filers from Oregon for a long time. 6 years ago I purchased a TecoMec FL-136 grinding machine, and I love it. You can't beat that grinder. Don't get me wrong, I still use the Bar mount filer, to cut down one raker, and use the grinder for the rest.
Prior to the grinder, I used to take 1 hour to sharpen 4, 20" chains. With the grinder, I can sharpen 8, 20" chains in an hour. If I do the rakers at the same time, I can do 4 chains in an hour. The edge from the grinder for some reason, dont know why, but seams to last longer than with the file.
Just my thoughts on the subject. Bruce.