Rock drill bit having retrac teeth and method for its manufacturing

A rock drill bit for percussive drilling comprising a head defining a longitudinal center axis, the head including an axially forward rock-crushing surface and a skirt extending axially rearwardly from the rock-crushing surface, a circumferential outer surface of the skirt formed with circumferentially spaced apart grooves forming lands therebetween, the grooves and the lands extending at least generally in an axial direction, an axial rear portion of at least some of the lands forming retrac teeth for crushing rock during withdrawal of the bit from a hole, each retrac tooth including a cutting edge extending along an outer circumference of the skirt;

• each retrac tooth further including an axially rearwardly facing surface disposed radially inside of the respective cutting edge and forming an angle less than 180 degrees with an imaginary plane extending perpendicular to the axis;
• the head further including an internal recess extending along the axis and opening in an axially rearward direction, a surface of the recess having a female screw thread formed thereon;
• the recess terminating at a location axially rearwardly of the rock-crushing surface, wherein the head forms an axially rearwardly facing front abutment surface that defines a front end of the recess;
• the axially rearwardly facing surface constituting a first axially rearwardly facing surface, the head further including a second axially rearwardly facing surface extending radially inwardly from the first axially rearwardly facing surface, the second axially rearwardly facing surface defining a rear abutment surface.

A method for manufacturing a rock drill bit, comprising the steps of:

• A) a machining a recess in a cylindrical blank, such that a surface of the recess has a female screw thread formed thereon, the recess terminating short of a front end of the blank and extending through a rear end of the blank, the recess defining an axis;
• B) machining, in the rear end, an axially rearwardly facing surface forming an angle less than 180 degrees with an imaginary plane oriented perpendicular to the axis;
• and
• C) machining, in an outer cylindrical surface of the blank, a plurality of grooves, the grooves extending generally in the axial direction and spaced-apart circumferentially about the axis, to form circumferentially spaced-apart lands in the blank, the grooves extending through the front end of the blank and through the axially rearwardly facing surface, wherein the axially rearwardly facing surface is divided into surface portions, each surface portion forming part of a respective retrac tooth defined by a rear portion of a respective land, each retrac tooth having a cutting edge extending along an outer circumference of the blank.