Boring tool for making borings in solid metal material of workpieces

A boring tool comprising a shaft and at least two cutting bits, each said bit being hexagonal with its cutting edges equally long and arranged in pairs, said cutting bits being exchangeable and each arranged in a respective recess facing in the direction of rotation of said shaft, each said cutting bit having one said pair of its said cutting edges arranged for simultaneous effective engagement with a workpiece, said pair of effective cutting edges of every cutting bit forming an obtuse angle (.alpha.) therebetween straddling a line parallel to the shaft axis and each defining substantially the same angle (.alpha./2) with said line parallel to the shaft axis, wherein said cutting bits are circumferentially spaced at equal angular distances on said shaft, said cutting bits being located at different radial distances from the axis of said shaft and such that the operative region of the effective cutting edges of each cutting bit somewhat radially overlaps the operative region of the effective cutting edges of the radially adjacent cutting bit, and one effective cutting edge of the radially inner cutting bit borders directly on said shaft axis or slightly overlaps same, the radially outermost cutting bit having its radially outermost effective cutting edge of its pair of effective cutting edges extending radially outward beyond the shaft periphery and meeting the adjacent cutting edge of the adjacent cutting edge pair in a further angle less than said obtuse angle (.alpha.) such that said adjacent cutting edge angles away from and does not engage the peripheral wall of a hole bored by said tool and converges toward the axis of the shaft.