JP2021053783A - Drill - Google Patents

Abstract

To prevent the degradation of surface roughness of an inner peripheral surface of a drilling hole, and the generation of chipping or the like in a margin part.SOLUTION: A drill in which a first margin part 8 and a second margin part are formed in an outer peripheral surface of a cutting blade part 3 of a drill body 1 to be rotated in a drill rotation direction T is such that: in a cross section orthogonal to a shaft line of the drill body 1, a crossing ridge line part between a first margin front wall surface 8a facing the drill rotation direction T of the first margin part 8, and a first margin outer peripheral surface 8c facing an outer peripheral side and forming a circular arc shape around the shaft line is used as a first margin front chamfering part 8d chamfered in a convex curve shape, and a crossing ridge line part between a second margin front wall surface facing the drill rotation direction T of the second margin part, and a second margin outer peripheral surface facing an outer peripheral side and forming a circular arc shape around the shaft line of a radius equal to that of the first margin outer peripheral surface 8c is used as a second margin front chamfering part chamfered in a convex curve shape.SELECTED DRAWING: Figure 4

Description

The present invention particularly relates to a drill used for drilling counterbore holes on an inclined surface or a curved surface of a work material.

As such a drill, for example, Patent Document 1 describes a drill having a tip angle of 180 ° to 181 °, and this drill has a curved cutting edge, from the cutting edge toward the outer peripheral corner. The angle between the extending straight line and the straight line extending from the chisel edge to the outer corner is 18 ° to 22 °, and the land is described with two margins. The drill described in Patent Document 1 is a two-flute drill.

Further, Patent Document 1 also describes that the groove length is twice or more and five times or less the diameter of the drill, and the shank length is five times or more and 20 times or less the diameter of the drill. Patent Document 1 describes that such a drill can suppress the runout of the drill even in counterbore drilling of a work material having an inclined surface or a curved surface while maintaining the strength of the cutting edge.

Japanese Unexamined Patent Publication No. 2014-034080

By the way, in such a drill having a substantially flat tip angle of 180 ° to 181 °, the above-mentioned runout of the drill occurs when the cutting edge bites the inclined surface or curved surface of the work material. easy. On the other hand, in the drill described in Patent Document 1, as shown in FIGS. 1 and 2 of Patent Document 1, the first margin located in the drill rotation direction out of the two margins provided on the land. The wall surface facing the drill rotation direction and the outer peripheral surface facing the outer peripheral side intersect at an angle, and the drill rotation direction of the second margin portion located on the side opposite to the drill rotation direction from the first margin portion. The wall surface facing the surface and the outer surface facing the outer peripheral side also intersect at an angle.

However, in such a drill described in Patent Document 1, if the above-mentioned runout of the drill occurs when the cutting edge bites, the wall surface and the outer peripheral surface of the angular first margin portion facing the drill rotation direction The intersecting ridgeline between the wall surface facing the drill rotation direction of the intersection ridge and the second margin and the outer peripheral surface bites into the inner peripheral surface of the drilled hole as the drill rotates, damaging the inner peripheral surface of the drilled hole. There is a risk of deteriorating the surface roughness and causing damage such as chipping at the angular crossing ridges.

The present invention has been made under such a background, and in a drill for counterbore hole drilling in which the tip angle of the cutting edge is close to 180 °, the cutting edge portion of the tip of the drill body is formed when the cutting edge bites. Even if runout occurs, the surface roughness of the inner peripheral surface of the machined hole deteriorates, and the intersection ridgeline between the wall surface facing the drill rotation direction of the margin portion and the outer peripheral surface facing the outer peripheral side may be chipped. The purpose is to provide a drill that can prevent this.

In order to solve the above problems and achieve such an object, the present invention presents the tip escape of the drill body on the outer periphery of the cutting edge portion on the tip side of the drill body which is rotated in the direction of rotation of the drill around the axis. Two chip discharge grooves that open on the surface and extend to the rear end side are formed at intervals in the circumferential direction, and are formed at the intersection ridge line portion between the wall surface of these chip discharge grooves facing the drill rotation direction and the tip flank surface. A drill having a cutting edge having a tip angle in the range of 178 ° to 182 °, and on the outer peripheral surface of the cutting edge portion between the two chip discharge grooves, on the outer peripheral edge of the cutting edge. A first margin portion that protrudes to the outer peripheral side of the drill body in a row, and a second margin portion that protrudes from the first margin portion to the outer peripheral side of the drill body at intervals on the side opposite to the drill rotation direction. Is formed, and in a cross section orthogonal to the axis line, a circle centered on the axis line facing the front wall surface of the first margin facing the drill rotation direction of the first margin portion and the outer peripheral side of the first margin portion. The intersecting ridge line portion with the arc-shaped first margin outer peripheral surface is a first margin front surface portion chamfered in a convex curve shape, and the second margin front wall surface of the second margin portion facing the drill rotation direction. The intersecting ridge line portion with the outer peripheral surface of the second margin, which faces the outer peripheral side of the second margin portion and forms an arc shape centered on the axis having the same radius as the outer peripheral surface of the first margin, is chamfered in a convex curve shape. It is characterized by having a two-margin front surface portion.

In the drill configured as described above, in the cross section orthogonal to the axis line, the intersecting ridge line portion between the first margin front wall surface and the first margin outer peripheral surface is chamfered in a convex curve shape. In addition, the intersecting ridge line portion between the front wall surface of the second margin and the outer peripheral surface of the second margin is a second margin front surface portion chamfered in a convex curve shape. It is formed so that the front wall surfaces of the first and second margins facing the drill rotation direction of the first and second margin portions and the outer peripheral surfaces of the first and second margins do not intersect at an angle.

For this reason, even if the cutting edge portion swings when it bites into the inclined surface or curved surface of the cutting edge work material whose tip angle is within the range of 178 ° to 182 °, it is in front of the angular first margin. The intersecting ridgeline portion between the wall surface and the outer peripheral surface of the first margin and the intersecting ridgeline portion between the front wall surface of the second margin and the outer peripheral surface of the second margin do not bite into the inner peripheral surface of the machined hole. Therefore, the inner peripheral surface of the drilled hole is damaged and the surface roughness deteriorates, or the intersection ridgeline portion between the first margin front wall surface and the first margin outer peripheral surface and the second margin front wall surface and the second margin outer peripheral surface It is possible to prevent damage such as chipping at the crossed ridge line portion, perform high-quality counterbore drilling with high accuracy, and extend the drill life.

Here, of these first and second margin front trimming portions, the first margin front trimming portion located on the drill rotation direction side is the one that first slides into the machined hole of the work material as the drill body rotates. Therefore, in the cross section orthogonal to the axis, the radius of curvature of the first margin front surface portion is made larger than the radius of curvature of the second margin front surface portion, so that the machined hole of the work material is first rubbed. It is possible to reliably prevent the first margin front surface portion in contact from biting into the inner peripheral surface of the machined hole.

In the cross section orthogonal to the axis, it is desirable that the radius of curvature of the first margin front surface portion and the radius of curvature of the second margin front surface portion are within the range of 10 μm to 50 μm. If the radius of curvature of the front surface of the first and second margins is smaller than this range, the intersecting ridges of the front wall surfaces of the first and second margins and the outer peripheral surfaces of the first and second margins become sharp and bite into the surface. There is a risk that chipping cannot be prevented. On the contrary, if the radius of curvature of the front surface of the first and second margins is larger than this range, the outer circumferences of the first and second margins that are in sliding contact with the inner peripheral surface of the machined hole. The first and second margin widths W1 and W2 of the surface become smaller, and there is a possibility that the cutting edge portion cannot be reliably supported.

On the other hand, in the cross section orthogonal to the axis, the intersecting ridge line portion between the rear wall surface of the first margin facing the opposite side of the drill rotation direction of the first margin portion and the outer peripheral surface of the first margin is chamfered in a convex curve shape. The first margin rear chamfering portion is formed, and the intersecting ridge portion between the second margin rear wall surface facing the opposite side of the drill rotation direction of the second margin portion and the second margin outer peripheral surface has a convex curve shape. It may be a chamfered second margin rear chamfered portion. As a result, the intersecting ridges between the rear wall surfaces of the first and second margins and the outer peripheral surfaces of the first and second margins may bite into the inner peripheral surface of the machined hole, or the intersecting ridges may be chipped. Can be prevented.

In this case, the first and second margin front chamfering portions may bite into or chip the inner peripheral surface of the machined hole rather than the first and second margin rear chamfering portions. Since it is high, it is desirable that the radius of curvature of the first margin frontal portion is larger than the radius of curvature of the first margin rear chamfer in the cross section orthogonal to the axis, and the radius of curvature of the second margin frontal portion is It is desirable that it is larger than the radius of curvature of the second margin rear chamfered portion.

Further, in particular, when the second margin width W2 is made smaller than the first margin width W1 as described below, in order to secure the width in the circumferential direction of the outer peripheral surface of the second margin that is in sliding contact with the inner peripheral surface of the machined hole. Similarly, in a cross section orthogonal to the axis, it is desirable that the radius of curvature of the second margin rear chamfering portion is smaller than the radius of curvature of the first margin rear chamfering portion. For the same reason as described above, the radius of curvature of the first margin rear chamfered portion and the radius of curvature of the second margin rear chamfered portion are within the range of 10 μm to 50 μm in the cross section orthogonal to the axis. Is desirable.

Further, in the cross section orthogonal to the axis, the width along the arc chord formed by the second margin outer peripheral surface is larger than the first margin width W1 which is the width along the arc chord formed by the first margin outer peripheral surface. If a certain second margin width W2 is too large, the resistance due to the outer peripheral surfaces of the first and second margins sliding in contact with the inner peripheral surface of the machined hole becomes large, and the cutting edge portion tends to swing around. The driving force for rotating the drill body may increase, or high frictional heat may be generated.

On the other hand, if the second margin width W2 is too small with respect to the first margin width W1, the cutting edge portion cannot be reliably supported due to the sliding contact of the second margin portion with the inner peripheral surface of the machined hole, resulting in runout. There is a risk that the rotation cannot be suppressed. Therefore, when viewed from the tip side in the axial direction, the second margin width W2 is within the range of 0.2 × W1 to 0.6 × W1 with respect to the first margin width W1. desirable.

Furthermore, the runout of the cutting edge portion as described above occurs when the length L of the chip discharge groove in the axial direction is longer than the diameter D of the cutting edge, that is, when the length of the cutting edge portion is long. Although it is likely to occur, if the length of the cutting edge portion is too short, it becomes impossible to perform counterbore hole processing with a hole depth deeper than the length of the cutting edge portion, and the versatility is impaired. Therefore, it is desirable that the length L of the chip discharge groove in the axial direction is within the range of 1 × D to 3 × D with respect to the diameter D of the cutting edge.

As described above, according to the present invention, when the tip angle of the cutting edge is in the range of 178 ° to 182 ° and the counterbore is formed on the inclined surface or curved surface of the work material, the cutting edge is formed. Prevents the intersecting ridgeline between the front wall surface of the first and second margins and the outer peripheral surface of the first and second margins from biting into the inner peripheral surface of the machined hole even if the cutting edge portion swings around when the cutting edge is bitten. It is possible to prevent the surface roughness of the inner peripheral surface of the machined hole from deteriorating and damage such as chipping at these intersecting ridges, resulting in high accuracy and high quality. Counterbore can be machined and the drill life can be extended.

It is a perspective view which shows one Embodiment of this invention. It is an enlarged front view of the embodiment shown in FIG. It is a side view of the tip part of the embodiment shown in FIG. FIG. 5 is an enlarged cross-sectional view orthogonal to the axis showing the first margin portion of the embodiment shown in FIG. FIG. 5 is an enlarged cross-sectional view orthogonal to the axis showing the second margin portion of the embodiment shown in FIG. FIG. 5 is an enlarged cross-sectional view orthogonal to the axis showing the outer peripheral surface of the land portion in the cutting edge portion of the embodiment shown in FIG.

1 to 6 show an embodiment of the drill of the present invention. In the present embodiment, the drill body 1 is formed of a hard material such as cemented carbide in a substantially columnar shape centered on the axis O, and has a rear end portion (upper right portion in FIG. 1; upper portion in FIG. 3). ) Is a shank portion 2 that remains cylindrical, and a tip portion (lower left portion in FIG. 1; lower portion in FIG. 3) is a cutting edge portion 3.

In such a drill, the shank portion 2 is gripped by the spindle of the machine tool, and the drill body 1 is sent out to the tip side in the axis O direction while being rotated in the drill rotation direction T around the axis O, thereby reaching the cutting edge portion 3. The formed cutting edge 4 is used to drill a counterbore on an inclined surface or curved surface that is inclined with respect to the axis O of the work material.

On the outer periphery of the cutting edge portion 3, two chip discharge grooves 6 are spirally twisted so as to open to the tip flank surface 5 of the drill body 1 and extend in the direction opposite to the drill rotation direction T toward the rear end side. Are formed at intervals (equal intervals) in the circumferential direction, and the cutting edge 4 is formed at the intersecting ridge line portion between the wall surface of these chip discharge grooves 6 facing the drill rotation direction T and the tip flank surface 5. Has been done. That is, the drill of this embodiment is a two-flute twist drill. The drill body 1 is formed in a 180 ° rotationally symmetric shape with respect to the axis O.

The tip angle α of these cutting edges 4 is in the range of 178 ° to 182 °, particularly 180 ° in the present embodiment, and the bottom surface of the counterbore hole formed in the work material is the axis line. It has a flat shape perpendicular to O. In these cutting blades 4, as shown in FIG. 2 when viewed from the tip side in the O-direction of the axis, a short portion between the central portion and the outer peripheral portion around the axis O is formed in a substantially linear shape, and the central portion and the central portion thereof. The long portion between the outer peripheral portion and the outer peripheral portion is formed in a concave curved shape slightly recessed on the side opposite to the drill rotation direction T. Further, the tip inner peripheral portion of the chip discharge groove 6 is thinned, and the thinning blade 4a is formed on the inner peripheral portion of the cutting blade 4.

Further, on the outer peripheral surface of the cutting edge portion 3, a first margin portion 8 is formed so as to be connected to the outer peripheral end of the cutting edge 4 and protrude toward the outer peripheral side of the drill body 1 in the land portion 7 between the two chip discharge grooves 6. A second margin portion 9 projecting from the first margin portion 8 to the outer peripheral side of the drill body 1 at a distance opposite to the drill rotation direction T is formed.

The first and second margin portions 8 and 9 are formed in a substantially trapezoidal shape when viewed from the tip end side in the O-direction of the axis. Of these, in the first margin portion 8, the first margin front wall surface 8a facing the drill rotation direction T has a straight line along the straight line formed by the outer peripheral portion of the cutting edge 4, and is opposite to the drill rotation direction T. The rear wall surface 8b of the first margin facing the side is inclined so as to extend toward the side opposite to the drill rotation direction T toward the inner peripheral side of the drill body 1.

Further, the second margin portion 9 is formed in a substantially equal pedestal shape when viewed from the tip side in the O direction of the axis, and as the second margin front wall surface 9a facing the drill rotation direction T toward the inner peripheral side of the drill body 1. The second margin rear wall surface 9b, which is inclined so as to extend toward the drill rotation direction T and faces the side opposite to the drill rotation direction T, becomes a side opposite to the drill rotation direction T as it faces the inner peripheral side of the drill body 1. It is tilted so that it extends toward it.

The intersecting ridge line portion between the first margin front wall surface 8a facing the drill rotation direction T of the first margin portion 8 and the first margin outer peripheral surface 8c facing the outer peripheral side of the drill body 1 of the first margin portion 8 is shown in FIG. As shown in the above, in the cross section orthogonal to the axis O, the first surface is chamfered into a convex curve having a radius of curvature smaller than that of the first margin outer peripheral surface 8c in contact with the first margin front wall surface 8a and the first margin outer peripheral surface 8c. The margin front surface is 8d.

Further, the intersecting ridge portion between the second margin front wall surface 9a facing the drill rotation direction T of the second margin portion 9 and the second margin outer peripheral surface 9c facing the outer peripheral side of the drill body 1 of the second margin portion 9 is also shown in FIG. As shown in the above, in the cross section orthogonal to the axis O, the front surface of the second margin chamfered in a convex curve shape having a smaller radius of curvature than the outer peripheral surface 9c of the second margin in contact with the front wall surface 9a of the second margin and the outer peripheral surface 9c of the second margin. It is said to be a margin 9d.

The outer peripheral surfaces 8c and 9c of the first and second margins are centered on the axis O having a diameter equal to the diameter D of the cutting edge 4, that is, the diameter of the circle formed by the outer peripheral end of the cutting edge 4 around the axis O. It is formed so as to be located on one cylindrical surface, and is formed in an arc shape having a radius equal to each other centered on the axis O in a cross section viewed from the tip side in the axis O direction or orthogonal to the axis O. ..

Further, in the cross section orthogonal to the axis O, the first margin width W1 which is the width along the arc chord formed by the first margin outer peripheral surface 8c is along the arc chord formed by the second margin outer peripheral surface 9c. The second margin width W2, which is the width, is within the range of 0.2 × W1 to 0.6 × W1. Further, the chip discharge groove 6 is cut off to the outer peripheral side on the rear end side of the cutting edge portion 3, and the length L in the axis O direction from the cutting edge 4 to the portion where the chip discharge groove 6 is cut off is defined as. It is within the range of 1 × D to 3 × D with respect to the diameter D of the cutting edge.

Furthermore, in the present embodiment, in the cross section orthogonal to the axis O, the first and second margin frontal portions 8d and 9d are formed in a convex arc shape, except that the radius of curvature (radius) is the first. The radius of curvature R8d of the margin front surface portion 8d is made larger than the radius of curvature R9d of the second margin front surface removal portion 9d. In the cross section orthogonal to the axis O, the radius of curvature R8d of the first margin front surface portion 8d and the radius of curvature R9d of the second margin front surface portion 9d are within the range of 10 μm to 50 μm.

Further, in the present embodiment, as shown in FIG. 4, in a cross section orthogonal to the axis O, the first margin portion 8 faces the side opposite to the drill rotation direction T, and the first margin rear wall surface 8b faces the outer peripheral side. The intersecting ridge line portion with the 1-margin outer peripheral surface 8c is also a first margin rear chamfering portion 8e chamfered in a convex curve shape in contact with the first margin rear wall surface 8b and the first margin outer peripheral surface 8c.

Similarly, as shown in FIG. 5, in a cross section orthogonal to the axis O, the second margin rear wall surface 9b facing the side opposite to the drill rotation direction T of the second margin portion 9 and the second margin outer peripheral surface facing the outer peripheral side. The intersecting ridge line portion with 9c is also a second margin rear chamfering portion 9e chamfered in a convex curve shape in contact with the second margin rear wall surface 9b and the second margin outer peripheral surface 9c.

Further, in the cross section orthogonal to the axis O, these first and second margin rear chamfering portions 8e and 9e are also formed in a convex arc shape, but are larger than the radius of curvature (radius) R8e of the first margin rear chamfering portion 8e. The radius of curvature R8d of the first margin frontal portion 8d is increased, and the radius of curvature R9d of the second margin frontal portion 9d is larger than the radius of curvature (radius) R9e of the second margin rear chamfering portion 9e.

Furthermore, in the cross section orthogonal to the axis O, the radius of curvature R9e of the second margin rear chamfered portion 9e is smaller than the radius of curvature R8e of the first margin rear chamfered portion 8e. The radius of curvature (radius) R8e and R9e of the convex curve (arc) formed by the first margin rear chamfered portion 8e and the second margin rear chamfered portion 9e in the cross section orthogonal to the axis O is within the range of 10 μm to 50 μm. Has been done.

On the other hand, of the outer peripheral surface of the land portion 7 of the cutting edge portion 3, chips are discharged from the portion between the first and second margin portions 8 and 9 and from the second margin portion 9 to the side opposite to the drill rotation direction T. The portion of the groove 6 up to the heel 10, which is the intersection ridge with the wall surface facing the side opposite to the drill rotation direction T, is recessed from the outer peripheral surfaces 8c and 9c of the first and second margins to the inner peripheral side of the drill body 1. However, it is said to be the outer peripheral escape surface (second round surface) 11. The corners where the outer peripheral flanks 11 and the rear wall surface 8b of the first margin intersect, and the corners where the front wall surface 9a of the second margin and the rear wall surface 9b of the second margin intersect are on the axis O. It is formed in a concave curve shape in orthogonal cross sections.

Further, in the present embodiment, of the outer peripheral surface of the land portion 7 of the cutting edge portion 3, the outer peripheral relief surface 11 between the first margin portion 8 and the second margin portion 9 has a cross section orthogonal to the axis O. A concave concave portion 12 having a concave curved shape is formed on the inner peripheral side of the drill body 1. In the present embodiment, a plurality (two) of such recesses 12 are formed side by side in the circumferential direction on the outer peripheral escape surface 11 between the first margin portion 8 and the second margin portion 9.

Therefore, in the cross section orthogonal to the axis O, a chevron-shaped convex portion 13 that is convex on the outer peripheral side of the cutting edge portion 3 relative to the concave portion 12 is formed between the plurality of concave portions 12. Become. Here, in the present embodiment, the depth d in the radial direction with respect to the axis O from the protruding end 13a of the convex portion 13 to the bottom 12a of the concave portion 12 adjacent in the circumferential direction of the convex portion 13 is set to 10 μm or more. There is. The plurality of (two) recesses 12 are formed to have the same shape and the same size. Therefore, the depths d in the radial direction with respect to the axis O from the tip 13a of the convex portion 13 to the bottom 12a of these recesses 12 are mutual. equal.

As shown in FIGS. 1 and 3, the recess 12 and the first and second margin portions 8 and 9 are orthogonal to the axis O so as to form a spiral in accordance with the twist of the chip discharge groove 6. The chip discharge groove 6 is continuously formed up to the portion cut off on the outer peripheral side of the drill body 1 while maintaining the same cross section.

Further, in the present embodiment, as shown in FIGS. 4 and 5, the extension surface of the first margin front wall surface 8a to the outer peripheral side of the drill body 1 and the extension of the first margin outer peripheral surface 8c in the drill rotation direction T. The first margin straight line E1 passing through the intersection point P1 with the surface and the axis O, the extension surface of the second margin front wall surface 9a to the outer peripheral side of the drill body 1, and the second margin outer peripheral surface 9c in the drill rotation direction T. The intersection angle θ of the second margin straight line E2 passing through the intersection P2 with the extension surface and the axis O as seen from the tip side in the axis O direction shown in FIG. 2 is within the range of 30 ° to 60 °.

In the drill configured as described above, in the cross section orthogonal to the axis O, the intersecting ridge line portion between the first margin front wall surface 8a and the first margin outer peripheral surface 8c of the first margin portion 8 is chamfered in a convex curve shape. The first margin front surface portion 8d is used, and the intersection ridge portion between the second margin front wall surface 9a and the second margin outer peripheral surface 9c of the second margin portion 9 is a second margin front surface portion chamfered in a convex curve shape. It is said to be 9d.

Here, these first and second margin front chamfering portions 8d and 9d are formed by the cutting edge 4 as the first and second margin portions 8 and 9 rotate in the drill rotation direction T of the drill body 1. Since it is the part that first slides into the inner peripheral surface of the counterbore, even if such a part is chamfered in a convex curve in cross section, even if the cutting edge portion 3 swings, the first and first parts are used. As in the case where the front wall surfaces 8a and 9a of the two margins and the outer peripheral surfaces 8c and 9c of the first and second margins intersect at an angle at the intersecting ridges, the intersecting ridges bite into the inner peripheral surface of the machined hole. It is possible to prevent the surface roughness from being deteriorated and the angular crossing ridges from being chipped or the like. Therefore, it is possible to perform counterbore hole machining with high accuracy and high quality, and it is possible to extend the drill life.

Further, particularly in the present embodiment, of the first and second margin frontal portions 8d and 9d, the radius of curvature R8d of the first margin frontal portion 8d is larger than the radius of curvature R9d of the second margin frontal portion 9d. Has been done. For this reason, the first margin front surface 8d, which is located on the T side of the drill rotation direction T side of the second margin front surface 9d and comes into sliding contact with the inner peripheral surface of the drilled hole first, bites into the cutting edge portion 3 due to the runout. It is possible to more reliably prevent chipping.

Further, in the present embodiment, in the cross section orthogonal to the axis O, the radii of curvature R8d and R9d of the first and second margin frontal portions 8d and 9d are within the range of 10 μm to 50 μm, and the first and first margins are set to be within the range of 10 μm to 50 μm. The cutting edge portion 3 can be stably supported by the inner peripheral surface of the machined hole to suppress the runout while more reliably preventing the biting or chipping of the two-margin front surface portions 8d and 9d.

That is, when the radii of curvature R8d and R9d of the first and second margin front trimming portions 8d and 9d are smaller than 10 μm, the first and second margin front trimming portions 8d and 9d become sharp to prevent biting and chipping. It may not be possible to do so. On the other hand, if the radii of curvature R8d and R9d of the first and second margin frontal portions 8d and 9d are larger than 50 μm, the first and second margin portions 8 and 9 are in sliding contact with the inner peripheral surface of the machined hole. The first and second margin widths W1 and W2, which are the widths of the outer peripheral surfaces 8c and 9c of the first and second margins in the circumferential direction, may become smaller, and the cutting edge portion 3 may be reliably supported and the swing may increase.

Further, in the present embodiment, in the cross section orthogonal to the axis O, the intersecting ridge portion of the first margin rear wall surface 8b and the first margin outer peripheral surface 8c facing the side opposite to the drill rotation direction T of the first margin portion 8 is also provided. The first margin rear chamfering portion 8e is chamfered in a convex curve, and the second margin rear wall surface 9b and the second margin outer peripheral surface 9c facing the opposite side of the second margin portion 9 from the drill rotation direction T. The crossed ridge portion is also a second margin rear chamfered portion 9e that is chamfered in a convex curve shape. Therefore, due to the swing of the cutting edge portion 3, the intersecting ridge line portion between the rear wall surfaces 8b and 9b of the first and second margins and the outer peripheral surfaces 8c and 9c of the first and second margins may bite into the inner peripheral surface of the machined hole. It is possible to prevent chipping and the like, further to perform high-quality counterbore hole processing with high accuracy, and to extend the drill life.

However, the first and second margin front chamfered portions 8d and 9d located on the T side in the drill rotation direction bite into the inner peripheral surface of the drilled hole rather than the first and second margin rear chamfered portions 8e and 9e. There is a high risk that dripping or chipping will occur. Therefore, in the present embodiment, in the cross section orthogonal to the axis O, the radius of curvature R8d of the first margin front chamfering portion 8d is made larger than the radius of curvature R8e of the first margin rear chamfering portion 8e, and the second margin front surface. The radius of curvature R9d of the taking portion 9d is made larger than the radius of curvature R9e of the second margin rear chamfering portion 9e.

Further, in the present embodiment, in the cross section orthogonal to the axis O, the radius of curvature R9e of the second margin rear chamfered portion 9e is smaller than the radius of curvature R8e of the first margin rear chamfered portion 8e. Therefore, particularly when the second margin width W2 is smaller than the first margin width W1 as in the present embodiment, the second margin width W2 of the second margin outer peripheral surface 9c of the second margin portion 9 is small. It is possible to prevent the cutting edge portion 3 from becoming too large, and the second margin portion 9 can surely support the cutting edge portion 3 and prevent the runout from becoming large.

Furthermore, in the present embodiment, in the cross section orthogonal to the axis O, the radii of curvature R8e and R9e of the first and second margin rear chamfered portions 8e and 9e are within the range of 10 μm to 50 μm, so that the first In the second margin rear chamfered portions 8e and 9e, the cutting edge portion 3 can be supported by the inner peripheral surface of the machined hole to suppress the runout while more reliably preventing biting and chipping.

That is, when the radii of curvature R8e and R9e of the first and second margin rear chamfered portions 8e and 9e are smaller than 10 μm, the first and second margin rear chamfered portions 8e and 9e become sharp to prevent biting and chipping. It may not be possible to do so. On the contrary, if it is larger than 50 μm, the first and second margin widths W1 and W2 become small, and the cutting edge portion 3 cannot be reliably supported, and there is a possibility that the swing becomes large. ..

Further, in the present embodiment, in the cross section orthogonal to the axis O, the second margin outer circumference is relative to the first margin width W1 which is the width of the first margin outer peripheral surface 8c along the chord of the arc formed around the axis O. The second margin width W2, which is the width along the chord of the arc formed by the surface 9c about the axis O, is within the range of 0.2 × W1 to 0.6 × W1. The runout of the cutting edge portion 3 can be reliably suppressed without increasing the driving force for rotation or generating high frictional heat with the inner peripheral surface of the machined hole.

That is, when the second margin width W2 is larger than the first margin width W1 so as to exceed 0.6 × W1, the first and second margin outer peripheral surfaces 8c and 9c are in sliding contact with the inner peripheral surface of the drilled hole. The resistance becomes large, and the cutting edge portion 3 is likely to swing around, the rotational driving force of the drill body 1 may increase, and high frictional heat may be generated. On the other hand, if the second margin width W2 is smaller than 0.2 × W1 with respect to the first margin width W1, the cutting edge portion 3 is surely brought into contact with the inner peripheral surface of the machined hole of the second margin outer peripheral surface 9c. It becomes impossible to support the cutting edge portion 3, and the swing of the cutting edge portion 3 may increase.

In the drill having the above configuration, as described above, the first and second margin front wall surfaces 8a and 9a and the first and second margin rear wall surfaces 8b and 9b intersect with the first and second margin outer peripheral surfaces 8c and 9c. Since the first and second margin front chamfered portions 8d and 9d and the first and second margin rear chamfered portions 8e and 9e are formed on the ridge line portion, the first and second margin widths W1 and W2 are the first of these. , The width of the portion excluding the second margin front chamfered portions 8d and 9d and the first and second margin rear chamfered portions 8e and 9e.

Further, in the present embodiment, the length L of the chip discharge groove 6 in the axis O direction is within the range of 1 × D to 3 × D with respect to the diameter D of the cutting edge 4. As described above, in a drill having a long chip discharge groove 6 length L, that is, a drill having a long protrusion length of the cutting edge portion 3, the cutting edge portion 3 is particularly likely to swing around. By adopting the configuration, according to the present embodiment, it is possible to further improve the drilled hole accuracy, the hole position accuracy, and the surface roughness of the inner peripheral surface of the drilled hole. If the length L of the chip discharge groove 6 in the axis O direction is smaller than 1 × D with respect to the diameter D of the cutting edge 4, it becomes impossible to perform counterbore drilling with a deep hole depth. Versatility may be impaired.

On the other hand, in the present embodiment, the intersection angle θ between the first margin straight line E1 and the second margin straight line E2 is within the range of 30 ° to 60 ° when viewed from the tip side in the O-direction of the axis. On the other hand, in the drill described in Patent Document 1, as shown in FIGS. 1 and 2 of Patent Document 1, the intersection angle θ is about 64 °, and the present embodiment is compared with this. The intersection angle θ is small, that is, the distance between the first and second margin portions 8 and 9 in the circumferential direction is small. Therefore, the time from when the first margin outer peripheral surface 8c of the first margin portion 8 is in sliding contact with the inner peripheral surface of the machined hole to when the second margin outer peripheral surface 9c of the second margin portion 9 is in sliding contact due to the rotation of the drill body 1. Can be shortened.

Therefore, when the tip angle α of the cutting edge 4 is close to a straight line perpendicular to the axis within the range of 178 ° to 182 °, the axis O obliquely intersects the inclined surface or curved surface formed on the work material. It is possible to shorten the time during which the cutting edge portion 3 becomes unstable when the cutting edge 4 bites, and it is possible to prevent the cutting edge portion 3 from swinging even when the counterbore is drilled. be able to. Therefore, it is possible to prevent the drilled hole accuracy and the hole position accuracy from being lowered, and it is possible to perform counterbore hole drilling with higher accuracy and higher quality.

Here, when the intersection angle θ of the first and second margin straight lines E1 and E2 exceeds 60 °, the first margin outer peripheral surface 8c slides into contact with the inner peripheral surface of the machined hole, and then the second margin outer peripheral surface 9c slides. It becomes impossible to shorten the time until contact, and there is a possibility that the runout of the cutting edge portion 3 cannot be sufficiently suppressed. On the other hand, when the intersection angle θ of the first and second margin straight lines E1 and E2 is less than 30 °, the first and second margin portions 8 and 9 come too close to each other and the cutting edge portion 3 is placed at two points in the circumferential direction. Since it is in a state of being slidably contacted and supported, there is a possibility that the cutting edge portion 3 is likely to swing around when the cutting edge 4 bites.

Further, in the present embodiment, on the outer peripheral surface (outer peripheral relief surface 11) of the land portion 7 of the cutting edge portion 3, the drill body 1 has a cross section orthogonal to the axis O between the first and second margin portions 8 and 9. A concave concave portion 12 having a concave curved shape is formed on the inner peripheral side of the above. Therefore, for example, as shown in FIGS. 1 and 2 of Patent Document 1, the outer peripheral flank surface of the cutting edge portion between the two margins is recessed from the outer peripheral surface of the two margins in the cross section orthogonal to the axis. While it is formed so as to form a convex curve, in the case of wet cutting in which counterbore drilling is performed while supplying cutting fluid, the drill body is formed between the recess 12 and the inner peripheral surface of the drilled hole. Since convection of the cutting fluid can be generated with the rotation of 1, efficient cooling and lubrication of the first and second margin portions 8 and 9 and the inner peripheral surface of the machined hole can be achieved, and the first and second margins can be achieved. It is possible to prevent welding or the like from occurring in the margin portions 8 and 9.

Moreover, in the present embodiment, a plurality of (two) recesses 12 are formed side by side in the circumferential direction on the outer peripheral relief surface 11 between the first and second margin portions 8 and 9 of the cutting edge portion 3. Therefore, convection of the cutting fluid can be generated between the individual recesses 12 and the inner peripheral surface of the machined hole, so that the more efficient first and second margin portions 8 and 9 and the inner peripheral surface of the machined hole can be generated. Can be cooled and lubricated, and welding and the like can be prevented more reliably.

Furthermore, in the present embodiment, when a plurality of recesses 12 are formed side by side in the circumferential direction on the outer peripheral relief surface 11 between the first and second margin portions 8 and 9 of the cutting edge portion 3, the axis line is formed. In a cross section orthogonal to O, the depth in the radial direction with respect to the axis O from the protruding end 13a of the convex portion 13 formed between the adjacent concave portions 12 to the bottom 12a of the concave portion 12 adjacent in the circumferential direction of the convex portion 13. d is set to 10 μm or more.

Therefore, a sufficient depth d from the tip 13a of the convex portion 13 to the bottom 12a of the concave portion 12 can be sufficiently secured, and the cutting fluid can be reliably convected, and the first and second margin portions are even more efficient. It is possible to cool and lubricate the inner peripheral surfaces of 8 and 9 and the machined holes. That is, if the depth d is less than 10 μm, the concave portion 12 may become too shallow with respect to the convex portion 13 and it may be difficult to reliably convect the cutting fluid. However, if this depth d becomes too large, the rigidity and strength of the cutting edge portion 3 may be impaired, so it is desirable that the depth d be 100 μm or less.

The cutting fluid as described above can be supplied to the cutting edge portion 3 from the outside of the drill body 1 by external lubrication. For example, the tip of the cutting edge portion 3 is supplied from the rear end surface of the shank portion 2 of the drill body. A coolant hole may be formed toward the flank surface 5 or the like, and the cutting fluid may be internally supplied through the coolant hole.

1 Drill body 2 Shank part 3 Cutting edge part 4 Cutting edge 4a Thinning blade 5 Tip escape surface 6 Chip discharge groove 7 Land part 8 1st margin part 8a 1st margin front wall surface 8b 1st margin rear wall surface 8c 1st margin outer peripheral surface 8d 1st margin front surface 8e 1st margin rear surface 9 2nd margin 9a 2nd margin front wall 9b 2nd margin rear wall 9c 2nd margin outer peripheral surface 9d 2nd margin front surface 9e 2nd margin rear surface Part 10 Heel 11 Outer peripheral flank surface 12 Concave part 12a Bottom of concave part 12 13 Convex part 13a Protrusion of convex part 13 O Axis of drill body 1 T Drill rotation direction T
α Tip angle of cutting edge 4 R8d Radius of curvature of first margin front surface 8d R8e Radius of curvature of first margin rear chamfer 8e R9d Radius of curvature of second margin front surface 9d R9e Curvature of second margin front surface 9e Radius W1 1st margin width W2 2nd margin width D Diameter of cutting edge 4 L Length of chip discharge groove 6 in the axis O direction P1 Extension surface of the front wall surface 8a of the first margin to the outer peripheral side and the outer peripheral surface of the first margin 8c Intersection with the extension surface in the drill rotation direction T P2 The intersection of the extension surface of the front wall surface 9a of the second margin to the outer peripheral side and the extension surface of the outer peripheral surface 9c of the second margin in the drill rotation direction T E1 First margin straight line E2 Second margin straight line θ The intersection angle between the first margin straight line E1 and the second margin straight line E2 d The depth in the radial direction with respect to the axis O from the protruding end 13a of the convex portion 13 to the bottom 12a of the concave portion 12.

Claims (10)

On the outer circumference of the cutting edge on the tip side of the drill body, which is rotated around the axis in the direction of rotation of the drill, two chip discharge grooves that open to the tip flank surface of the drill body and extend toward the rear end are spaced apart in the circumferential direction. Formed open,
A drill in which a cutting edge having a tip angle within the range of 178 ° to 182 ° is formed at an intersecting ridgeline portion between the wall surface of these chip discharge grooves facing the direction of rotation of the drill and the tip flank surface.
On the outer peripheral surface of the cutting edge portion between the two chip discharge grooves, a first margin portion that is connected to the outer peripheral end of the cutting edge and projects toward the outer peripheral side of the drill body, and the first margin portion to the above. A second margin portion is formed so as to project to the outer peripheral side of the drill body at intervals on the side opposite to the drill rotation direction.
In a cross section orthogonal to the axis, the first margin of the first margin portion facing the drill rotation direction and the first margin facing the outer peripheral side of the first margin portion and forming an arc shape centered on the axis. The intersecting ridge line portion with the outer peripheral surface is a first margin front surface portion chamfered in a convex curve shape, and the second margin front wall surface and the second margin portion of the second margin portion facing the drill rotation direction. The intersecting ridge with the outer peripheral surface of the second margin forming an arc shape centered on the axis having the same radius as the outer peripheral surface of the first margin facing the outer peripheral side is the second margin front surface chamfered in a convex curve. A drill characterized by being made. The drill according to claim 1, wherein the radius of curvature of the first margin front surface portion is larger than the radius of curvature of the second margin front surface portion in a cross section orthogonal to the axis. Claim 1 or claim 1, wherein the radius of curvature of the first margin front surface portion and the radius of curvature of the second margin front surface portion are within the range of 10 μm to 50 μm in a cross section orthogonal to the axis line. The drill according to claim 2. In the cross section orthogonal to the axis, the intersecting ridge line portion between the rear wall surface of the first margin facing the opposite side of the drill rotation direction of the first margin portion and the outer peripheral surface of the first margin is chamfered in a convex curve shape. The 1-margin rear chamfering portion is formed, and the intersecting ridge line portion between the second margin rear wall surface facing the opposite side of the drill rotation direction of the second margin portion and the second margin outer peripheral surface is chamfered in a convex curve shape. The drill according to any one of claims 1 to 3, wherein the second margin is a rear chamfering portion. The drill according to claim 4, wherein the radius of curvature of the second margin front chamfered portion is larger than the radius of curvature of the second margin rear chamfered portion in a cross section orthogonal to the axis. The drill according to claim 4 or 5, wherein the radius of curvature of the first margin front chamfering portion is larger than the radius of curvature of the first margin rear chamfering portion in a cross section orthogonal to the axis. Any one of claims 4 to 6, characterized in that the radius of curvature of the second margin rear chamfered portion is smaller than the radius of curvature of the first margin rear chamfered portion in a cross section orthogonal to the axis. The drill described in. According to claim 4, the radius of curvature of the first margin rear chamfered portion and the radius of curvature of the second margin rear chamfered portion are within the range of 10 μm to 50 μm in the cross section orthogonal to the axis. The drill according to any one of claim 7. In the cross section orthogonal to the axis, the width along the chord of the arc formed by the outer peripheral surface of the first margin is the width of the first margin width W1 which is the width of the outer peripheral surface of the first margin along the chord of the arc. The drill according to any one of claims 1 to 8, wherein a certain second margin width W2 is within the range of 0.2 × W1 to 0.6 × W1. Claims 1 to 9, wherein the length L of the chip discharge groove in the axial direction is within the range of 1 × D to 3 × D with respect to the diameter D of the cutting edge. The drill described in any one of them.

Images