Add mmpm
Continue thoughts with Material class.

Need to determine if surface cutting speed can be automatically
determined from BHN and/or MR.

Preference is to require the minimal information from which spindle
speed and feed rate can be determined.

At this point the core parameters seem to be chip load per tooth (feed
per tooth / chip size), tool material (hss / carbide), material BHN,
cutter engagement & depth of cut.
Experiment with Machining formulas.