Patent ID: 7882908

Claim:
A drill, comprising: a stem ( 8 ); and a one-piece drilling head ( 10 ; 20 ; 30 ) formed of a hard material and provided, at a first end ( 5 ) thereof, with at least one main bit having a tip ( 4 ) and at least one cutting structure ( 3 ) integral to the one-piece drilling head ( 10 ; 20 ; 30 ), and at a second end ( 6 ), located opposite the first end ( 5 ), with a bottom surface ( 7 ) for mounting the drilling head ( 10 ; 20 ; 30 ) on the stem ( 8 ), and having a plurality of axially extending through-grooves ( 11 ; 21 ; 31 ) for removing drillings produced during a drilling process and having a cross-section which increases, at least regionwise, in a direction toward the bottom surface ( 7 ) of the drilling head ( 10 ; 20 ; 30 ); wherein a cross-section of each of the through-grooves ( 11 ; 21 ; 31 ) has a respective tangential transition edge ( 12 ; 22 ; 32 ) spaced from the bottom surface ( 7 ) by a respective distance (a; b; d) corresponding to about from 10% to 40% of a distance (D) from the tip ( 4 ) to the bottom surface ( 7 ).