| 摘要 |
A drill bit includes a generally cylindrical central blank and a matrix portion mounted on the lower end of the blank which includes the crown and gage of the drill bit. Exceptionally deep junk slots are defined in the matrix portion. The lower end of the blank includes a radially inwardly tapering portion having matrix material formed thereover which defines an upper end of the junk slot. The matrix material is formed from powdered matrix material and a ductile filler which provides a matrix with a relatively high ductility. Also disclosed is a steel bit constructed in accordance with the present invention. <IMAGE> |
