Armstrong, Nikaido, Marmelstein, Kubovcik & Murray
Ball end mill with throw away insert
 A ball end mill having a plurality of throw away inserts. Its body is formed in its hemispherical portion at diametrically opposite positions with insert mounting pockets each having a plurality of insert mounting seats. In each set, an insert having an acruate cutting edge is mounted so that the cutting edges will generate a hemispherical locus with laps of more than a quarter of the length of each cutting edge. The inserts closer to the front end of the body has an axial rake of 0 to 5 degrees, whereas those at the rear have an axial rake of 4 to 8 degrees, the latter having a larger axial rake than that of the former. Further, the insert in each pocket are arranged so that the one at the rear will have the leading end of its cutting edge located on the extension line of the cutting edge of the one in front. Thus, the inserts as a whole form a substantially S-shaped line as viewed form the front of the body. 
Sumitomo Electric Industries, Ltd.
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Keiji Yoshikatsu Naohiro
Honda Mori Nakamura