{HEAD ~ The sharpened edge} 148 performs {TAIL ~ the major portion} of the cutting during a cutting operation and is periodically sharpened by the sharpening mechanism 78 
performs
{ HEAD ~ The sharpened edge } 148 performs { TAIL ~ the major portion } of the cutting during a cutting operation and is periodically sharpened by the sharpening mechanism 78
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH