I always thought that knee mills were mills and non-knee were mill/drills i see references to PM940s as Mill/Drills. and that mill/Drills were divided up into round column, square column and subset of minis. come to think of it is the inclusion of a quill the dividing line between mill and mill/drill? ok thanks now i have a migraine. the one mill that is not a mill/drill would be the horizontal mill. OOOOOW where's the aspirin.