Specifications include, but are not limited to: Knee Mill - Spindle Speeds (VSF) 60-550-4500 rpm (VSF Freq drive model). Spindle Speeds (HS) 60-6000* rpm (HS head option on Freq drive model). 3 HP spindle motor, variable speed milling head with AC-Frequency drive head, digital RPM display, spindle load meter, and automatic spindle direction reversal when switching between high & low speed ranges.