the top of the main cutting element 20 are provided two secondary cutting edges 23 23 u2032 which branch off in v shaped manner from the longitudinal cutting edge 22 the secondary cutting edges 23 23 u2032 run outwards at right angles to the main cutting direction 60 on its rear side remote from the longitudinal cutting edge 22 the main cutting element 20 is supported by a cutting edge support area 14 whose height decreases with increasing spacing from the main cutting element 20 behind the frontally positioned main cutting element 20 two reaming elements 30 30 u2032 are provided on the top on dedendum 10 as shown in fig1 and 4 relative to the reaming element 30 reaming elements 30 30 u2032 in each case have a round shaft bit 33 with a conical tip area a conical carbide pin type cutting edge 32 is provided on the tip of the round shaft bit 33 two reception sleeves 37 37 u2032 are provided in the rear portion of the cutting edge support area 14 on the top of dedendum 10 for holding the reaming elements 30 30 u2032 the round shaft bits 33 of the reaming elements 30 30 u2032 are inserted in the reception sleeves 37 37 u2032 which can in particular have a round or elliptical internal cross section the reaming elements 30 30 u2032 are positioned in such a way that their pin type.