| 摘要 |
A driver or dogging element adapted to transfer torsion forces between a rotating outer tube ( 10 ) and a drill bit ( 1 ) of a down-the-hole hammer, wherein the dogging element ( 7 ) is made of a softer material than those parts ( 3, 4 ) of the drill bit ( 1 ) that co-act with the dogging element ( 7, 8 ).
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