Patent ID: 8720613

Claim:
A drill bit ( 10 ) for a rock drilling tool ( 12 ), which drill bit ( 10 ) has a drilling surface ( 10 b ) that is arranged to contact rock during drilling, wherein a longitudinal cross section ( 10 t ) of the drill bit ( 10 ) through the drilling surface ( 10 b ) exhibits the following relationships of L tot (depth)/L tot (5.0) and H(depth)/H(5.0) at the specified depths, where H(depth)/H(5.0) is measured according to a Vickers test and L tot (depth)/L tot (5.0) is measured according to the Palmqvist method described in this document substantially along the drill bit's longitudinal axial centre line (C): depth [mm below the drilling surface L tot (depth)/L tot (5.0) × H(depth)/H(5.0) × (10b)] 100 100 0.3 max 40, max 104 preferably max 20 0.5 max 52, max 104 preferably max 32 1.0 max 75, max 104 preferably max 56 2.0 max 94, Max 104 preferably max 80 5.0 100 100 if the drill bit ( 10 ) has a length (L) of 10 mm or greater; and a longitudinal cross section ( 10 t ) of the drill bit ( 10 ) through the drilling surface ( 10 b ) exhibits the following relationships of L tot (depth)/L tot (3.5) and H(depth)/H(3.5) at the specified depths, where H(depth)/H(3.5) is measured according to a Vickers test and L tot (depth)/L tot (3.5) is measured according to the Palmqvist method described in this document, substantially along the drill bit's longitudinal axial centre line (C): depth [mm below the drilling surface L tot (depth)/L tot (3.5) × H(depth)/H(3.5) × (10b)] 100 100 0.3 max 40, max 104 preferably max 20 0.5 max 52, max 104 preferably max 32 1.0 max 75, max 104 preferably max 56 2.0 max 94, Max 104 preferably max 80 3.5 100 100 if the drill bit ( 10 ) has a length (L) less than 10 mm, wherein the drill bit is modified to achieve the aforementioned values subsequent to a sintering process.