You got it, Rajan and Dave. Sorry... don't know why the heck I abbreviated that since a "double-bevel" file is, for most arborists a rather esoteric--and maybe rightly so!--little instrument to begin with. Maddening, but fun. Rips!
Yeah Kevin: That's interesting. If you try it on a little 200T, its WAY tricky cause you tend to dig your tie straps too much. I actually broke a chain by dinking around that way, and had to repair it in the field... Don't ask! I've come up with a way of doing it now, though, that I've been pretty happy with the results of. Ya just angle the file a lot shallower--so as to not dig the straps so hard--but, at the same time, angle the flat face of the file steeper--so as to build-in a more durable (less acute) angle into the actual chisel edge. I actually sharpened my foreman's saw that way last week, and he acknowledged how much faster it cut. Can't wait till the new full corner chain is dull, so I can see if it will cut yet better.
I am a nerd.