Bormax prima with exchangeable centre point and pre-drill bit. Two in reverse order staggered, grooved main cutting edges, a circumferencial cutting edge with longitudinal grooves - both effecting that a clear less feed force is necessary. Also they minimize the friction and the growth of heat. The pre-drill bit is ideal for drilling at an angle which is not 90° in workpieces surface, which occurs for example in the construction of staircases.
