Percussion rock drill bit

A rock drill bit for percussive drilling, comprising a head and a shank connected to the head, the shank having a central boring in which a thread is provided;

• the thread adapted to cooperate with a corresponding thread in a drill string driven by a top hammer;
• the boring connected to at least one fluid passage which emerges at least in the vicinity of a front face of the head;
• the fluid passage connecting to a radially extending first groove formed in the front face;
• a radially outer end of each first groove connecting to a second groove which extends generally axially rearwardly;
• wherein at least three of the second grooves are provided and form lands between one another, each land carrying a gauge insert;
• wherein the gauge inserts are asymmetrically positioned relative to a center axis of the drill bit;
• and wherein each second groove extends radially inwards at least as far as an imaginary circle which touches radially innermost points of the gauge inserts as viewed in a direction parallel to the axis, wherein a radius line of each gauge insert forms a first angle with a radius line of a first adjacent gauge insert and a second angle with a radius line of a second adjacent gauge insert, the first angle being different from the second angle;
• each gauge insert having a diameter which is 10-30% of an outer diameter of the rock drill bit, the second groove being substantially V-shaped as viewed in the direction parallel to the axis.