PERCUSSION DRILL BIT, AN INSERT, A USE AND A METHOD OF MAINTAINING THE DRILL BIT DIAMETER

摘要

The present invention relates to a percussion drill bit (10) for drilling bores, comprising a steel body (12), means at one end of the steel body for connecting the bit to a percussive unit such as a down-the-hole hammer or a drill string for a jack hammer, a plurality of inserts embedded in the other end of the steel body. At least the peripheral inserts or gauge row inserts comprise a cemented carbide body having a rear mounting portion embedded in the steel body and a front end protruding from the steel body. A polycristalline diamond layer is provided on the front end of the carbide body. The layer has an edge along a border in the vicinity of the maximum diameter of the insert. The edge (22) is kept away a first distance (L1) from the wall of the bore during drilling by tilting the gauge row insert (16) an acute angle (a) of 41 DEG to 51 DEG relative to the rotational axis (11) of the drill bit (10). The invention further relates to a gauge insert, use of a diamond-coated insert as a gauge insert in a drill bit and a method of maintaining the diameter of a drill bit during percussive drilling of a bore in a rock material.