A core drill bit 1 includes a tubular shaft 12, a mounting platform 31 provided on a proximal end of the tubular shaft 12 for mounting the core drill bit on a power tool 26, and an annular cutting section 2 provided with abrasive cutting segments 3 arranged at a distal end of the tubular shaft 12. A first transponder 24 is provided at the distal end of the tubular shaft 12. A repeater 28 is provided comprising a second transponder 29 at the proximal end of the tubular shaft 12, an antenna 33 facing the first transponder 24, and a wired connection 34 between the antenna 33 and the repeater 28.

The negative land includes: a first region in which a space between the upper cutting edge and the lower cutting edge becomes wider toward the outer circumferential surface; and a second region which is continuous to the first region and in which the space becomes wider toward the rotation axis. In a cross section perpendicular to the rotation axis, the rake face includes a return face continuous to the outer circumferential surface, the return face being recessed opposite to a rotation direction of the drill. When a first boundary represents a boundary between the outer circumferential surface and the first region and a second boundary represents a boundary between the first region and the second region, a length of the first boundary is larger than a length of the second boundary in a direction parallel to the rotation axis. The second boundary is continuous to the return face.

The drill comprises a base body, which extends in the axial direction along an axis of rotation and rotates about the axis of rotation in a direction of rotation during operation. Into the base body are incorporated flutes and between consecutive flutes is formed a rear surface, which extends, in relation to the direction of rotation, from a leading flute to a trailing flute. On the rear surface in the region of the leading flute, a guide chamfer and a support chamfer spaced apart from it in the direction opposite the direction of rotation are formed, wherein the support chamfer, as radially outermost region, forms a support edge for a merely linear support.

A drill including: a chip discharge groove formed in an outer periphery of an edge portion serving as a leading end side portion of a drill body; and a cutting edge formed in an intersecting edge between a rake surface of a leading end side region and a leading end flank of the edge portion. The drill having a margin portion, a shoulder portion and a web thinning portion. The cutting edge includes, in order from a rotation center, first cutting edge, second cutting edge, shoulder cutting edge, and margin cutting edge portions. Honing widths of the second cutting edge, the margin cutting edge, and the shoulder cutting edge portions satisfy a relation represented by expression (1), as follows: honing width of the shoulder cutting edge portion>honing width of the margin cutting edge portionhoning width of the second cutting edge portion.

The negative land includes: a first region in which a space between the upper cutting edge and the lower cutting edge becomes wider toward the outer circumferential surface; and a second region which is continuous to the first region and in which the space becomes wider toward the rotation axis. In a cross section perpendicular to the rotation axis, the rake face includes a return face continuous to the outer circumferential surface, the return face being recessed opposite to a rotation direction of the drill. When a first boundary represents a boundary between the outer circumferential surface and the first region and a second boundary represents a boundary between the first region and the second region, a length of the first boundary is larger than a length of the second boundary in a direction parallel to the rotation axis. The second boundary is continuous to the return face.

The present disclosure provides a multi-groove pagoda drill bit. A circumferential wall of a tapered body is provided with a diameter-expanding step increasing in diameter from front to back. A plurality of primary helical grooves extending from a rear end to a front end and a plurality of secondary helical grooves extending from the rear end to close to the front end are opened on the circumferential wall of the tapered body. An axial cutting blade same as a cutting trajectory is disposed on groove mouths of the primary helical grooves and the secondary helical grooves. On a radial section of the tapered body, a front recess segment located at a side of a line connecting an edge tip and an axis and close to the edge tip is disposed in the groove mouths of the primary helical grooves and the secondary helical grooves.

A drill in which: a chip discharge groove is formed in an outer periphery of an edge portion serving as a leading end side portion of a drill body; and a cutting edge is formed in an intersecting edge between a rake surface of a leading end side region and a leading end flank of the edge portion, the drill comprising a margin portion, a shoulder portion and a web thinning portion, wherein: the cutting edge comprises, in order from a rotation center, a first cutting edge portion, a second cutting edge portion, a shoulder cutting edge portion, and a margin cutting edge portion; the honing width gradually decreases from the boundary P1 toward the position P2; and the conditions represented by expression (1): honing width of second cutting edge portion?R1 and expression (2): 2.0<R1/R2<5.0 are satisfied.

An instrument comprising a shank and a working portion, the working portion having a tip and a plurality of flutes being defined by at least two lands having a land margin; wherein the working portion has a parabolic cross-section defining opposing convexed surfaces extending between at least two opposing land margins.

A cutting head rotatable about a central axis, includes a tip portion and an intermediate portion. The tip portion has an axially forwardmost tip point contained in the central axis and at least two axially forward-facing front surfaces, each front surface having a radially extending cutting edge. The intermediate portion has at least two head lands circumferentially alternating with at least two chip evacuation passages, each head land having a leading edge extending axially rearwardly from the tip portion. The cutting edges are contained in an imaginary annular ring surface, and a first imaginary radial plane containing the central axis intersects the imaginary annular ring surface to form two imaginary radial cutting profiles. Each imaginary radial cutting profile has consecutively radially outward extending first, second, and third cutting profile portions, and the second cutting profile portion includes first and second concave sub-portions spaced apart by a first convex sub-portion.

The drill includes a main blade having a wicking amount, a thinning blade, a thinning back portion, and an oil hole. The thinning bottom is along the first radius. The thinning back portion is along the second radius. The pair of thinning bottoms includes a thinning separation amount. (1) The first radius for the wicking amount ranges from 0.5?f to 1.2?f, and f represents the wicking amount. (2) The second radius ranges from 5.5 mm to 7.5 mm. (3) The thinning separation amount ranges from 0.5 mm to 1.2 mm. (4) The thinning-oil hole distance ranges from 0.1 mm to 0.8 mm (5) The thinning range from the first thinning end to the second thinning end is in the range from (D/2?1.5 mm) to (D/2?0.2 mm) with respect to the diameter, and D represents the diameter.