Patent ID: 7059432
Filing Date: 2006-06-13
Classification: E21B

Abstract:
1. A cup-shaped drill head having an axis with a leading end and a trailing end and an inner space extending axially from the trailing end toward the leading end with an inner axially extending conical surface ( 2 ) extending from the trailing end for force-locking connection to an outer axially extending conical surface ( 3 ) of a driving drill shank ( 4 ), said inner space having a cup base ( 5 ) having a variable curvature (K) with a center point (P) of said variable curvature located on said drill head axis adjacent said leading end and said variable curvature extending toward said inner conical surface ( 2 ), wherein at a transition from said cup base ( 5 ) to said inner conical surface ( 2 ) the curvature (K) of said cup base ( 5 ) is smaller than the curvature at the center point (P).