Each end surface includes {HEAD ~ an upper portion} connected to {TAIL ~ the cutting edge}, and a lower portion connected to the upper portion by a concave transition portion 
connected to
Each end surface includes { HEAD ~ an upper portion } connected to { TAIL ~ the cutting edge } , and a lower portion connected to the upper portion by a concave transition portion
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH