| 摘要 |
PCT No. PCT/SU85/00020 Sec. 371 Date Oct. 27, 1986 Sec. 102(e) Date Oct. 27, 1986 PCT Filed Mar. 13, 1985 PCT Pub. No. WO86/05426 PCT Pub. Date Sep. 25, 1986.A drill comprises a holder (1) and a cutting member in the form of a pair of discs (2,3). Each disc (2,3) has at least five facets (11,12) arranged along its periphery and symmetrically with respect to its center line (13, 14), the discs (2, 3) being mounted in such a manner that angles ( phi ) of inclination of their facets (11, 12) with respect to an axis (4) of the holder (1) are equal to one another. |
