Sandvik Intellectual Property Ab

Bo Carlström

Per-Olof Liljebrand

Jens Sundin

Christer Lundberg

Susanne Lejon

Anders Brungs

Johan Lindén

The invention relates to a drill bit () for percussive rock drilling, which comprises: &#x2014;a drill head (); &#x2014;a skirt (), which has a first end and an opposite second end, the skirt being connected to the drill head at said first end; &#x2014;a recess () extending axially through the skirt from the second end of the skirt towards the first end thereof, the recess being provided with an internal, cylindrical female thread (); and &#x2014;an impact surface () at the bottom of the recess. Every cross-section of the recess () between the impact surface and the part of the recess where the female thread has its full thread profile has a cross-sectional area which is smaller than the cross-sectional area of a cross-section of the recess at the part of the recess where the female thread has its full thread profile.

Drill bit for percussive rock drilling

A drill bit intended for percussive rock drilling is formed to reduce the occurrence of cavitation during percussive drilling. The drill bit includes an integral skirt and at least one channel for transport of flush medium, such as water. The drill bit has a front face provided with buttons, which define a greatest first external diameter (D). A recess with a female thread, such as a rope or trapezoid thread for percussive drilling, extends into the drill bit from a rear end face of the drill bit. The recess has an axial depth (L). The external surface of the skirt includes a conical portion having an axial extension that is greater than one-eighth of the depth (L) of the recess but smaller than the depth (L) of the recess.

Rock drill bit and a thread joint therefor

A male portion for percussive rock drilling includes sections of reduced cross-sectional area. At least one thread for percussive rock drilling is provided at an end of the male portion. The end of the male portion comprises an abutment surface for the transfer of impact waves. The length of the portion is defined as the length of an imaginary cylinder from a plane of the impact surface to a point where the plane ceases to contact a crest of the thread, wherein the length divided by the external diameter of the cylinder lies within a range of 1&#x2013;2.

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Sandviken, Sweden

Bo Carlström