Below are two pictures of an Oregon chain that is on my MS311 that I bought as a loop from Bailey's. The drive links have 72 stamped on them, and the depth gage is stamped 25, indicating it should be filed so it is .025 below the cutting edge.
What is this chain? I know the difference between chisel and semi-chisel but looking in Bailey's old print catalog (2016) I don't understand the difference between a chisel and square chisel cutter. Yes they explain in text the difference, but visually I see little or no difference. The 72 chains come with a variety of letter suffixes. What do the letters mean?
I understand that a semi-skip chain will have more widely spaced cutters than a standard chain, and a skip tooth has even fewer cutters on the loop. These increase cutting speed, I'm guessing, because the saw can spin the chain faster? There must be a point of diminishing returns, or we would see chains with only two cutters on them. Is a skip tooth chain the fastest cutting?
I would guess that different species of trees call for different chains. Are there any general rules of thumb for cutting hardwoods (oak, maple) vs softer pine, spruce trees? What would softer deciduous wood like cottonwood require in a chain?
The pro's I've watched seem to just pull their saws off the truck and go to work. Either the chain does not matter so much or they had a heads up on the kind of tree before coming to the job site.
Pics of my chain:
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