| 摘要 |
A tool bit shank (11) for percussion drilling or chipping has at least three rotary entrainment grooves (13, 14, 15) extending in the axial direction and at least one locking groove (12) also extending axially. The rotary entrainment grooves (13, 14, 15) open at a free end (16) of the shank (11) so that rotary entrainment members of a tool bit chuck can be inserted axially into the rotary entrainment grooves. The locking groove is closed at its end adjacent the end face (16) to prevent ejection of the tool bit when it is engaged by a locking member of the chuck. To significantly reduce the wear of the tool bit shank and the tool bit chuck, the rotary entrainment grooves (13, 14, 15) are arranged in sequence in the circumferential direction in respect to radially outwardly facing circumferentially extending openings from the largest to the smallest opening. The locking groove (12) is located between the rotary entrainment groove (13) with the largest opening and the rotary entrainment groove (15) with the smallest opening. Similarly, the rotary entrainment members (43, 44, 45) in the tool bit chuck correspond to the size of their base cross-sections and are arranged in sequence from the largest to the smallest base cross-sections. The locking member is located between the rotary entrainment member with the largest base cross-section and the rotary entrainment member with the smallest base cross-section.
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