Just heat treat the cutting edges and never worry about sharpening. I bought a house in the woods that previous home owner never removed any dead trees that fell. I went through three chains this spring (cutting rotten trees on the ground) and took the old chain to work to test it on the Hardness tester. The Oregon chains (cutting edge) are heat treated to Rockwell 38. This is very soft compare to Carbide with Rockwell 88-95 that you will find on most table saws or commercial lumber mills saws. They do this on purpose so you keep on buying chains. I bought micro torch that runs on propane and heated just the edges of each tooth till they were glowing red, then pressed ice cubes into them. Been cutting for the entire summer and fall without ever needing to sharpen. And I've been cutting only nasty stuff laying on the ground with grass growing on top. I have six cords of wood from rotten trees and probably another 4 cords of waste I cut off that was all moldy and completely rotten. My chain finally fell apart (broke chain ling) right before Thanksgiving. The chain was just worn down all over the place and bar groove was all messed up. That's how long the chain lasted. Got new bar and chain and heat treated the edges right away. I have two more trees that are few years old on the ground and then I get to cut some nice clean fresh wood for a change. I'm tried of cutting this garbage but I have to clean up what is laying around first.