Drill body
A drill body for chip removing machining, including a rotationally symmetrical envelope surface and front and rear ends between which a center axis extends, around which the envelope surface is rotatable in a predetermined direction of rotation. A head is formed in the front end that includes two cutting edges, each one of which includes a first part edge and a second part edge. The first part edge is included in a central tip part having a front end portion situated along the center axis. The second part edge extends between a peripheral end point positioned along the envelope surface and a radially inner end point where the second part edge transforms into the first part edge. The two first part edges converge at a positive nose angle (α) in an axially forward direction, and the two second part edges diverge at a negative angle (β) in the axially forward direction. Each cutting edge is delimited between a chip surface adjacent to a chip flute countersunk in the envelope surface, and a primary clearance surface that transforms into a secondary clearance surface situated rotationally behind the primary clearance surface. Each primary clearance surface includes two part surfaces which mutually form an obtuse angle (χ), and which meet each other in a first chute bottom that runs rotationally rearward from the inner end point of the second part edge. A second chute bottom extends in the extension of the first chute bottom and separates two second part surfaces included in the secondary clearance surface.
1. A drill body for chip removing machining, comprising:
a rotationally symmetrical envelope surface and front and rear ends between which a center axis extends, around which the drill body is rotatable in a predetermined direction of rotation;
a head formed in the front end that includes two cutting edges, each one of which includes a first part edge and a second part edge, the first part edge being included in a central tip part having a front end portion situated along the center axis, the second part edge extending between a peripheral end point positioned along the envelope surface and a radially inner end point where the second part edge transforms into the first part edge, the two first part edges converging at a positive nose angle (α) in an axially forward direction, and the two second part edges diverging at a negative angle (β) in the axially forward direction;
each cutting edge being delimited between a chip surface adjacent to a chip flute countersunk in the envelope surface, and a primary clearance surface that transforms into a secondary clearance surface situated rotationally behind the primary clearance surface;
each primary clearance surface including two part surfaces which mutually form an obtuse angle (χ), and which meet each other in a first chute bottom that runs rotationally rearward from the inner end point of the second part edge; and
a second chute bottom which extends in the extension of the first chute bottom and separates two second part surfaces included in the secondary clearance surface, wherein
the secondary clearance surface via a borderline transforms into a transition surface, which extends to the respective chip flute, the second chute bottom extending between the first chute bottom and a point where the borderline ends peripherally.
2. The drill body according to claim 1 , further comprising first and second fluid ducts which mouth along respective second chute bottoms.
3. The drill body according to claim 2 , wherein the two part surfaces in the primary clearance surface and the two second part surfaces in the secondary clearance surface are plane and spaced-apart by respective chute bottoms in the form of straight turning lines.
4. The drill body according to claim 1 , wherein the two part surfaces in the primary clearance surface and the two second part surfaces in the secondary clearance surface are plane and spaced-apart by respective chute bottoms in the form of straight turning lines.