A drill according to an embodiment of the present invention has a pair of main cutting edges positioned at a front end of a drill body, a pair of first chisel edges each extending from the pair of main cutting edges toward a rotation axis, and a second chisel edge positioned between the pair of first chisel edges and intersecting with the rotation axis of the drill body. When viewing a locus of rotation of the pair of first chisel edges and a locus of rotation of the second chisel edge in a cross section taken so as to include the rotation axis, the respective locus of rotation of the pair of first chisel edges have a rectilinear shape, and respective imaginary straight lines obtained by extending the locus of rotation of the pair of first chisel edges toward the rotation axis are positioned further to a rear end side of the drill body than the locus of rotation of the second chisel edge.

A drill bit for drilling into bone, including at least a first, second and third longitudinally extending substantially straight flute blades, wherein the drill bit has an extrapolated outer profile established by rotation of the first, second and third flute blades 360 degrees about a longitudinal axis thereof, the extrapolated outer profile includes a first surface having tangents more perpendicular than parallel to the longitudinal axis, and the extrapolated outer profile includes a second surface having tangents more parallel than perpendicular to the longitudinal axis.

A blade section has two lands and two flutes in an alternating manner and also has a linear chisel edge. The lands are each provided with: a margin section that is continuous with a cutting blade; a clearance section that is continuous with the margin section and that has a smaller diameter than the margin section; and a pad that is continuous with the clearance section and that has the same width as the width of the margin section.

The present invention relates to a drilling tool and method for modifying a blind hole in a blade root insert of a wind turbine. The invention further relates to an apparatus and method for cleaning a blind hole. The method for modifying a blind hole comprises: removing a blade screw located in the blind hole, inserting a drilling tool into the blind hole, fixing the drilling tool in a drill, recessing the blind hole by a predetermined depth, with a maximum diameter of the end section and of the hole bottom after recessing being smaller than or equal to a diameter of the end section prior to recessing and a transition from the end section to the hole bottom being round after recessing, removing the drilling tool and the drill, mounting the blade screw in the modified blind hole.

In the drill, each of the thinning edges extends beyond an intersection point with the chisel; an axial rake angle is in a range of +5 to +15; and a ratio of a length of each of the thinning edges to a length of each of the cutting edges in a direction, in which the main cutting edge extends as viewed from the front side of the axial direction, is in a range of 20% to 50%. Intersecting ridges between: second thinning wall surfaces facing an opposite side of the drill rotation direction; and the tip flank faces, are disposed that: they are spaced apart in a direction orthogonal to the intersecting ridges; they are positioned on one diameter line passing the axis; or they mutually pass over in a passing over amount of 0.03D or less with respect to a diameter of the cutting edges.

A drilling tool includes at least two chip flutes and a chisel edge with a thinned region. The thinned region merges continuously into the chip flutes in such a way that the thinned region forms the end of the respective chip flute in the region of the chisel edge.

A drill structure includes a shank part and a flute part arranged on one end of the shank part. A chisel edge is formed on the front end of the flute part and two drill blades with tilt directions toward the shank part are formed on the two sides of the chisel edge. Every drill blade includes a primary relief surface with a cutting edge and a secondary relief surface with a knife-back edge. At least one assist relief surfaces is formed on the inner wall of one of the two helical grooves and an included angle is between the assist relief surface and the horizontal plane. The assist relief surface is connected with the cutting edge of one drill blade and portion of the knife-back edge of another drill blade.

A drill has a central axis, a front side, a circumferential surface, at least two main edges on the front side, which reach up to the circumferential surface and merge there with secondary edges, at least two central edges extending from the end of the main edge facing away from the circumferential surface, cutting surfaces associated with the main edges and central edges, chip flutes associated with the main edges and central edges and introduced into the circumferential surface, at least one cross edge adjoined by the ends of the central edges facing away from the main edges which passes through the central axis, a point thinning and chip run-up shoulders associated with at least the cutting surfaces of the central edges. An angle of the chip run-up shoulder decreases in the region of the point thinning towards the central axis as the distance from the front side increases.

A bottom cutting step up reamer incorporates a shaft having a first end with attachment features adapted to be received in a chuck. A plurality of bottom cutting edges substantially perpendicular to the shaft are located at a second end distal from the first end. At least one step up land is provided proximate the plurality of bottom cutting edges and spaced toward the first end with a plurality of parallel cutting edges substantially parallel to the shaft.

A drill structure includes a shank part and a flute part arranged on one end of the shank part. A chisel edge is formed on the front end of the flute part and two drill blades with tilt directions toward the shank part are symmetrically formed on the two sides of the chisel edge. Every drill blade includes: a primary relief surface with a cutting edge, a first connecting edge and a first chamfering edge, a secondary relief surface with a knife-back edge, a second connecting edge, a second chamfering edge and an outer edge, and an assist relief surface. The second connecting edge joins to the first connecting edge, and the second chamfering edge connects with the first chamfering edge. The assist relief surface, which tilts toward the shank part the, is extend from the first chamfering edge and the second chamfering edge. This drill structure can improve the surface finish of the drilling hole.