Throwaway insert
 An improved throwaway insert is proposed which has a cutting edge, a land extending along and inside of the cutting edge, a breaker groove extending along and inside of the land, a flat central area enclosed by the breaker groove, and a plurality of semicircular projections arranged in a chip breaker groove at its corners and its straight portions to enable chip to be satisfactorily broken over wide ranges of the depth of cut and the feed. These projections rise from midway of the breaker groove until they become even with the central area enclosed by the breaker groove. 
Sumitomo Electric Industries Ltd.
Y B Y Y
Y10T B23B Y10T Y10T
additional inventional additional additional
Yoshikatsu Jun
Mori Maeda