The cam portion has {HEAD ~ a cam surface} that undulates from {TAIL ~ one side} of the cam plane to the other 
The cam portion has { HEAD ~ a cam surface } that undulates from { TAIL ~ one side } of the cam plane to the other
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH