When you get time sit and do a lot research. There is all kind of designs out there. Really you got to know what you working with and what the customer is trying to do. Enough make your head spin at first but with experience you will know what you are looking for. Most times I am dealing home owners so it is a lot simpler than when a pro comes in.
As for the Rotary bar numbers they are
9532520 20" 3/8" .050 72dl
9533520 20" 3/8" .058 72dl
And I highly recommend using a safety chain as the non safety are dangerous in the hands of non professional.
Both are Pro Sprocket versions with replaceable sprocket tips. Although I yet to replace one as most time the rest of the bar is shot too.
And it comes to chains it is the same thing about styles. You got safety and non safety, different types of bumper links; standard, semi skip, and full skip cutter sequence; semi chisel, chisel, and square face cutters; single and dual rakers. And even got a choice between cross cut and rip cut versions. Head spinning yet?
Most chains you will come across will be cross cut (25-35 degree cutters). Stihl chains are usually file at 25 degrees and most others either 25 or 30 degrees. Rip cut (10 degree cutters) are mostly for milling operation where you are making planks (lumber). This is where you want to break up the shavings more as they are very long otherwise and clog the clutch housings.
I even have a few rare 3/8lp full skip chains here that one particular insists on buying. Oregon has quit making them so when what I got is gone he will have take a standard chain or move up to a larger saw that skip chains are still available for. Normally you will not find skip in a 3/8lp chain.
And just found out a week ago the Rotary has the style of 3/8lp chain I have been looking for my customers that do plunge cuts. I got a 100' roll on the wish list Rotary PO. The particular bumper link style makes it where the bar tip is a lot easier to cut with. I personally do plunge cuts to install wedges for splitting on wood that wedges just don't want to get started. Most chains the bar tip can have a lot of kickback, even the safety ones; although, safety one has less of a kickback.
As Bert said paper catalogs have a lot more info in them than the online stuff. And most of your vendors sales reps have even less knowledge about these specs.
I am old hand filer that finally gave in and brought me a good chain grinder. I actually tried the HF piece of junk grinder. It became so sloppy after a few chains that I disassemble it and threw it in the recycle bin. Kinda had to after a batch of eight chains took over 6 files to sharpen and I had blisters for over a week. Still trying to figure out who made those chains as the customer doesn't remember where he got them.
Last week I got a customer that says he has lots of chains that he needs sharpen so it looks I be sharping a few chains in the near future. He just didn't know I had the equipment to do them or knew more about saw chain than he does.
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