The insert has a cross section forming {TAIL ~ a mount portion} 50 with six straight locating sides 51 56 lying on {HEAD ~ the sides} of an imaginary bisymmetrical polygon 58, and forming a radially outwardly extending arm 60, 62 at each corner of the polygon 
The insert has a cross section forming { TAIL ~ a mount portion } 50 with six straight locating sides 51 56 lying on { HEAD ~ the sides } of an imaginary bisymmetrical polygon 58 , and forming a radially outwardly extending arm 60 , 62 at each corner of the polygon
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH