I use a flat file to dress my bars. I usually check it every time I change the chain. I have a bench mounted grinder and 4 chains for every size bar so I only file when I have to. I find it easier and less time consuming to have my employees change chains then to try and teach all of them to file. I go over my saws once a week and check for loose parts or broken/missing pieces. It's been my experience that every time a saw has cut a half moon it was do to the chain. My smallest bar is 10" and the largest is 56" and unless they receive an "employee modification" they cut straight as an arrow. Your friend that borrowed your saw owes you a sharpening or a chain. Don't loan chainsaws! I rent my father one from Home Depot. It comes with a new chain, eye, head and ear protection, a pair of chaps, and gasoline. I pay the $2.50 damage waiver and for <$30 I have no worries. A underqualified person can do hundreds of dollars damage to a saw in less than an hour. A friend of mine let someone borrow his 044 one weekend and the moron used it to cut a trench in his yard for a cable line. Ruined the bar, chain, sprocket, etc. Most people who really know how to use a chainsaw own one.
As always my $.02
