David, hopefully I can help Neil Macnaughtan in September's Scribe a line regarding chainsaw sharpening. The trouble with a file and guide is a lot of filing has to be done if the link is damaged but it is ideal, if stuck in a forest, just to touch up the links. It undercuts the cutting edge diameter B on the sketch which also gives a weak cutting edge. With filing you can file too much off and cause the chain to pull over to the highest side. Neil mentioned he had purchased a grinder but does not say which kind. The hand held ones are of no use as you can easily alter the angles of the cutters, even ruin a brand new chain and have to bin it. Chain saw sharpeners are reasonably cheap these days, you can pay anything from £50-£150. Rather than make one, it is better to stick with the commercially available ones. Most machines sit on a bench and you sit down to sharpen the chain. When a chain is sharpened with a machine the face angle is set at 25 degrees with a hook angle of 5 degrees (tilt of the grindstone). Try and take the same amount off each cutter as the chain will pull over to the highest side causing undue wear to the bar.
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