The grinding wheel has {TAIL ~ a generally frusto conical configuration} and an outer periphery defined by first and second axially distinct helical grinding ribs having {HEAD ~ different contours} 
The grinding wheel has { TAIL ~ a generally frusto conical configuration } and an outer periphery defined by first and second axially distinct helical grinding ribs having { HEAD ~ different contours }
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD