fearofpavement
Trying them all
I think that sometimes chain filing/grinding can get to the point of ridiculousness. I don't check the air pressure in my truck tires every time I leave the driveway. I'm sure NASCAR truck drivers know exactly what their air pressure is. The correlation is that if a chainsaw operator knows how a sharp chain cuts, then they know when it's NOT sharp and something needs to be done. Whether my chain was sharpened on a grinder, with a file, by a strong stare or whatever, if it isn't cutting to my satisfaction I either sharpen it or replace it. I don't lie in bed at night and calculate techniques to improve the edge on a chain. I have a number of measuring tools in the shop and the only precision tool I use on chain is a dial caliper to measure gauge if unknown. I never have measured the length of a tooth. Don't really care how long it is as long as it is sharp.
By the way, I don't think that you can have a productive day in the woods if you don't file chains at all. I usually touch mine up every couple tanks of gas and can't imagine taking enough chains to the woods to change it out every time it needs a light touch up. So even if your chains are ground with the best grinder out there and have a razor edge, it doesn't take too long before they would really like to see a few strokes of a file.
For someone that is learning filing, I recommend they run a file on a new chain. If the chain is all dull and misshapen, it will be hard for them to know what it should look like. Start with a new one and get a grasp of what it should look like and then sharpen the dull ones. It isn't rocket science but does take some practice. Even in clean wood a chain will dull. A file costs about $2.00. Get some and use them.
By the way, I don't think that you can have a productive day in the woods if you don't file chains at all. I usually touch mine up every couple tanks of gas and can't imagine taking enough chains to the woods to change it out every time it needs a light touch up. So even if your chains are ground with the best grinder out there and have a razor edge, it doesn't take too long before they would really like to see a few strokes of a file.
For someone that is learning filing, I recommend they run a file on a new chain. If the chain is all dull and misshapen, it will be hard for them to know what it should look like. Start with a new one and get a grasp of what it should look like and then sharpen the dull ones. It isn't rocket science but does take some practice. Even in clean wood a chain will dull. A file costs about $2.00. Get some and use them.