I have a Stihl 260 chainsaw, with a 3/8" chain and a 20" bar. What criteria do I need to apply when picking a second chainsaw chain?
I'll defer to the experts but personally, I wouldn't mix brands of chainsaw chains.
I seem to recall that Stihl chain designs help reduce/prevent kick-back and binding (which presumably explains why they're more expensive). Plus, they use a green and yellow color-coding system to help you select a powerhead, bar and chain combination that complies with kickback requirements of various safety standards (e.g. ANSI Standard B175.1).
But again, I'm no expert -- just paranoid about safety. =)
Mixing brands of chains is no problem, provided you use compatible chains. I'm no longer able to buy "original" chains for my old Homelite so I buy it off the roll at the local mower/chainsaw dealer, who also joins it up for me. It's worth noting that this particular dealer won't sell you a chain unless you know exactly what to ask for or bring in an old one for comparison.
The wrong type of chain can be inefficient or even downright dangerous, so get some expert advise before buying a non-genuine chain. If you have an doubts err on the safe side - always.
Oregon (http://www.oregonchain.com/) makes chainsaw accessories, including chains that would fit my chainsaw.
Stihl chains are pre-stretched, so you won't get as much initial stretch on the saw.
I heard that Stihl chains are built to closer tolerances, but nothing authoritative.
It looks like the Oregon chain needs a slightly different sized sharpening file. I don't want to have to sort out which file goes with which chain.
As @Mike B pointed out, there color-codings on Stihl saws, which is convenient.
I compared the price of a Stihl chain at my Stihl dealer to the price of an Oregon chain at my local hardware store, and the difference wasn't very big.
I decided to stick with Stihl chains.
You have to pay attention to pitch (distance between drive links) to match the sprocket (and bar tip sprocket if you're using a roller nose) and thickness of the drive tang on the drive link must match to the groove on the bar with proper established clearances.
If you pay attention to those dimensions, you can use other brands.
The loggers I grew up with used Oregon Chain by the spool. Time is money and time spent in the field sharpening anything was a waste, so you made up multiple chains, often for several saws with different bar lengths, changed them out and when you had enough, fired up your sharpening grinder (files? psh!) and processed all your dull chains for angle, depth of cut per species of tree you were felling.
stihl chains have oil groves that keep you bar and chain oiled as well as having 2 diff types of chains for kick back the green label is for less kick back for less experienced wood cutters and the yellow for pro wood cutters with bigger hp saws. my advice is stick with the stihl chains they are desighned for your saw