Patent ID: 6450273
Filing Date: 2002-09-17
Classification: B23B,E21B

Abstract:
A drilling tool for drilling a hard material comprising an axially extending shaft (2,22) having a first cutting end and an opposite second end, each of said second end and said first end having a surface extending transversely of said shaft axis, a drilling head (5,25) at said first end having at least three cutting members (7, 8 and 9; 26) formed of a hard metal, said drilling head having an axially extending radially outer circumferential surface, at least two adjacent cutting members having bases spaced axially inward of said drilling head; said at least two adjacent cutting members projecting radially outwardly from said circumferential surface with an angle between said adjacent cutting members in the range of about 100 degrees to about 150 degrees and being separated by at least one of a plurality of axially extending drilled material grooves (10, 11 and 12; 27, 28 and 29) discharging at least into one discharging groove (4) extending helically around said shaft towards said second end, at least one of said two adjacent cutting members projecting radially outwardly from said circumferential surface and having a radially outer edge lying on an enveloping circle (E) and said circle having a diameter (e) at least equal to 15 mm, said two adjacent cutting members extending axially, said drilled material grooves (10, 11 and 12; 27, 28 and 29) located between said edges of said cutting members projecting outwardly from said circumferential surface (14, 15) and defining alternating guiding regions (14) extending axially from said bases of said two adjacent cutting members and co-extending sections (15) of said circumferential surface adjoining said guiding regions and extending axially; said co-extending sections (15) containing said drilled material grooves (10; 11 and 12; 27, 28 and 29) and having an opening to said drilled material grooves in said circumferential surface with an aperture angle &agr; measured from said shaft axis and an axial extent (f) greater than 0, wherein the value of &agr;&lE;100âˆ’e and wherein two tangents located at transitions of the drilling head circumference to the outer edges of one of said drilled material grooves (29) encloses an angle (&ggr;) with one another with the angle between said tangents being smaller than 45Â°.