Robit Oyj

Robit Plc

Mika Koskinen

Kimmo Ala-kanto

A drill assembly for percussive drilling, includes a drill bit having a downhole portion and an attachment portion having a cylindrical male coupling thread, and a drill string element for transferring impacts from a percussion device to the drill bit and having a female coupling thread for threadedly coupling with the male coupling thread. The drill bit includes a first annular impact surface arranged on an uphole-side end the downhole portion, the first annular impact surface surrounding the attachment portion, and the drill string element includes, at a downhole-side end thereof, a second annular impact surface. The first and second impact surfaces are inclined with respect to a plane perpendicular to the longitudinal direction. A drill bit and drill string element are also disclosed.

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Tampere, Finland

Mika Koskinen