Talking "feeds and speeds", 7 feet per minute (1.4"/s) as a feed rate would obviously be crazy fast, so I presume this is the "speed", the linear reciprocating

Talking "feeds and speeds", 7 feet per minute (1.4"/s) as a feed rate would obviously be crazy fast, so I presume this is the "speed", the linear reciprocating speed of the chain. It's less "cutting" and more "crunching" its way through. Sheer brute force plastic deformation.