Drill bit structure

A drill bit structure, comprising a drill bit body having lands with a given first circumferential width (a) and, between the lands, flutes with a second circumferential width (b), said lands being interconnected by a web having a thickness (c), said drill bit body further having a diameter (d), a shank at one end thereof and a tip at the other end of said drill bit body, a groove in said drill bit tip, a hard tip member fitted and fixed in said groove, said web thickness (c) corresponding to 25 to 35% of said drill bit diameter (d), said drill bit body further having a flute width ratio in the range of 0.4:1 to 0.8:1, whereby said flute width ratio is defined as said flute width (b) divided by said land width (a), and wherein said drill bit body tip including said hard tip member is formed so that its radial rake angle of an outer peripheral cutting lip, as measured at positions spaced at least 2/3 of the drill bit diameter radially outwardly from a central drill bit axis, is in the range of -5.degree. to positive values, and wherein said drill bit tip including said hard tip member forms a rake surface (23) the axial length of which is zero at said central drill bit axis, to provide rotational symmetry with respect to a center of rotation defined by said central drill bit axis.