The process 6, wherein the angle of {HEAD ~ movement} about {TAIL ~ the pivot} is about 60° 
about
The process 6 , wherein the angle of { HEAD ~ movement } about { TAIL ~ the pivot } is about 60 °
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH