JP2003025125A - Drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drill capable of smoothly and stably drilling while preventing the shortening of the serviceable life of a tool and exhibiting superior chip disposing performance under severe machining conditions such as a high- speed and dry type cutting. SOLUTION: This drill is so formed that a chip discharge groove 3 extending toward a rear end side is formed in the outer circumference in the tip part of a drill body 1 rotated about an axis O, and a cutting edge 5 is formed in an intersectional ridge line part between the internal wall surface 4 facing to the drill rotating direction T of the chip discharge groove 3 and a tip flank 2 of the drill body 1. A projecting curved cutting edge part 16 formed into a curve projecting in the drill rotating direction T is formed in the side of the outer circumferential end 15 of the cutting edge 5 and a recessed curved cutting edge part 17 formed into a curve recessed rearward in the drill rotating direction T and smoothly continuing to the projecting curved cutting edge part 16 is formed in the internal circumferential side of the projecting curved cutting edge part 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill capable of smooth and stable drilling even under severe working conditions such as high speed dry cutting.

[0002]

2. Description of the Related Art For example, Japanese Unexamined Patent Publication No. 2000-198011 discloses a drill intended to cope with harsh machining conditions in which only a dry type or a very small amount of cutting oil is used.
The one described in Japanese Patent Publication has been proposed. That is, in the drill described in this publication, on the outer peripheral side of the cutting edge formed at the tip of the drill body, an outer corner cutting edge is formed that recedes in the drill rotation direction at an angle from the intermediate portion of the cutting edge, Since the crossing angle between the outer corner cutting edge and the margin of the outer periphery of the drill body can be made obtuse,
It is possible to prevent the occurrence of chipping at the outer peripheral edge of the cutting edge even under the processing conditions described above. Further, as a drill in which the outer peripheral end side of the cutting edge is bent rearward in the drill rotation direction as described above, for example, as described in JP-B-4-46690, the first and second secondary sides on the outer peripheral side of the cutting edge are disclosed. It is also proposed that the linear ridge has a substantially V-shaped convex shape, and in the drill described in this publication, the inner peripheral side of the secondary linear ridge is further made concave with roundness. Further, as a drill having a concave cutting edge as described above, for example, Japanese Patent Publication No. 61-58246.
In the gazette, etc., the radial rake angle of the cutting edge portion on the outer peripheral side is 0
There are also proposals that connect a concave curve so that the angle becomes positive.

[0003]

[Problems to be Solved by the Invention]
Although the cutting edge portion on the outer peripheral side has a concave curve as described in JP-A-58246, under normal processing conditions, although the processing by curling of chips is smooth and stable drilling is possible, the outer circumference of the cutting edge is Since the crossing angle with the margin on the end side is acute and the strength is insufficient, chipping and chipping will occur immediately on the outer peripheral end side of this cutting edge under severe conditions such as high speed dry cutting, It has a very short life and costs. On the other hand, as described in Japanese Patent Application Laid-Open No. 2000-198011 and Japanese Patent Publication No. 4-46690, in which the outer peripheral end side of the cutting edge is formed into a V-shaped convex shape and is bent at an angle to the rear side in the drill rotation direction, Although the intersection angle with the margin part can be made obtuse and the occurrence of chipping and chipping can be suppressed, the chips generated by the cutting edge are divided at this bending point, so these were divided in high-speed cutting. The chips are entangled with each other to cause chip clogging, and especially the chips generated at the outer peripheral end side of the bending point try to flow out to the outer peripheral side, so the curling property is poor and wear is accelerated because it gives great resistance to the drill body. Or, there is a possibility that the driving force for rotating the drill during machining may increase.

The present invention has been made against such a background, and prevents the shortening of the tool life even under severe machining conditions such as high-speed dry cutting, and has excellent chip disposability, which enables smooth and stable drilling. It is intended to provide a drill that can be processed.

[0005]

In order to solve the above-mentioned problems and to achieve such an object, the present invention extends toward the rear end side on the outer periphery of the front end portion of a drill body rotated around an axis. A drill having a chip discharge groove formed, and a cutting blade formed at an intersecting ridge portion between an inner wall surface of the chip discharge groove facing the drill rotation direction and a tip flank of the drill body, wherein an outer peripheral end side of the cutting blade is formed. In, while forming a convex curvilinear cutting edge portion having a curved shape that is convex in the drill rotation direction, on the inner peripheral side of the convex curving cutting edge portion, a curve that is concave toward the rear side in the drill rotation direction It is characterized in that a concave curved cutting edge portion is formed so as to be smoothly connected to the convex curved cutting edge portion. Therefore, in the drill configured in this way, since the convex curved cutting edge portion that is convex in the drill rotation direction is formed on the outer peripheral end side of the cutting edge, the outer peripheral side of the convex curved cutting edge portion, That is, at the intersection with the margin portion on the outer periphery of the drill body, the intersection angle can be increased to secure sufficient strength,
It is possible to prevent the occurrence of chipping and chipping even under the above processing conditions. And, on the inner peripheral side of this convex curved cutting edge portion, a concave curved cutting edge portion that is concave toward the rear side in the drill rotation direction is connected, and from this concave curved cutting edge portion to the convex curved cutting edge portion. Since the cutting edge is formed in a smooth curved line up to the outer peripheral edge, the chip is not divided at the inner and outer circumferences, and the concave curved cutting edge part wraps the chip inward. In this way, it becomes possible to curl sufficiently and process smoothly.

Here, in order to secure the strength at the intersecting portion more reliably, it is desirable to set the radial rake angle on the outer peripheral end side of the cutting edge to the negative angle side. Further, on the tip side of the inner wall surface of the chip discharge groove, a thinning portion that is continuous with the inner peripheral end side of the cutting edge is formed, and this thinning portion has a concave curved valley shape, and the valley bottom portion is the inner wall surface. On the other hand, by providing the first thinning portion that extends toward the inner peripheral end of the cutting edge while retracting toward the inner peripheral side of the drill body, the inner peripheral end side portion of the chip is formed by the first thinning portion. By guiding to the curved surface, it becomes possible to more surely roll up the entire chip on the inner peripheral side and curl it. Further, the thinning portion is provided with a second thinning portion which is formed at a tip end side of the first thinning portion and which is further retracted toward the inner peripheral side with respect to the valley bottom portion and reaches the inner peripheral end of the cutting edge. As a result, the width of the chisel at the tip of the drill body can be reduced by the second thinning portion to improve the biteability to the work piece. Also, in order to ensure sufficient rigidity of the drill body while promoting smooth discharge of the curled chips in this way, the core thickness of the drill body is
It is desirable to set the range of 0.15 × D to 0.3 × D with respect to the outer diameter D of the cutting edge.

On the other hand, when the cutting edge shape as described above is formed at the ridge line intersecting the inner wall surface of the chip discharge groove facing the drill rotation direction and the tip flank of the drill body, the drill rotation direction of the chip discharge groove On the inner wall surface facing the convex curved cutting edge portion, and the first curved surface extending to the concave curved cutting edge portion.
Since the concave curved surface portion is formed, the chips generated by the concave curved cutting edge portion as described above to be rolled into the inner peripheral side are slidably brought into contact with the first concave curved surface portion to curl more reliably. You can On the inner wall surface of the chip discharge groove facing the rear side in the drill rotation direction, a second concave curved surface portion having a concave shape in the drill rotation direction may be formed so as to be smoothly connected to the first concave curved surface portion. For example, the smooth discharge can be promoted without obstructing the flow of the chips curled by the first concave curved surface portion.

In this case, however, if the recess of the first concave curved surface portion toward the rear side in the direction of drill rotation is too small, sufficient curling may not be achieved due to sliding contact of the chips, but on the contrary, this recess may occur. If it is too large, the braking action due to the sliding contact of chips becomes too strong, and the chips may be crushed and the dischargeability may be impaired or the drill driving force may be increased. Also, with respect to the second concave curved surface portion, if the depression in the drill rotation direction is too small, the chips flowing from the first concave curved surface portion may be strongly pressed against the second concave curved surface portion, resulting in a large braking action. On the other hand, on the contrary, if the recess is too large, the chips are curled only by the sliding contact with the first concave curved surface portion, and there is a fear that the chips will not be sufficiently curled. Therefore, in the above case, in the cross section orthogonal to the axis, the recess amount L1 of the first concave curved surface portion from the first virtual straight line connecting the axis and the outer peripheral end of the inner wall surface facing the drill rotation direction. To
A recess of the second concave curved surface portion from a second virtual straight line that intersects the first virtual straight line at the axis line while being set in the range of −0.06 × D to 0 with respect to the outer diameter D of the cutting edge. It is desirable to set the amount L2 in the range of −0.06 × D to 0.06 × D.

Further, the convex curved surface portion and the first concave curved surface portion are formed on the inner wall surface of the chip discharge groove facing the drill rotation direction, and the first concave surface portion is formed on the inner wall surface of the chip discharge groove facing the drill rotation direction rear side. When the second concave curved surface portion that smoothly connects to the curved surface portion is formed,
In the cross section orthogonal to the axis, the radius of curvature of the concave curve formed by the second concave curved surface portion is made larger than the radius of curvature of the concave curve formed by the first concave curved surface portion, so that the first concave curved surface having a small radius of curvature. It is possible to curl the chip with a sufficient curl due to the portion, and by making the curl thus curled, the radius of curvature of the second concave curved surface portion is larger than that of the first concave curved surface portion. It is possible to discharge more smoothly without pressing it too strongly. At this time, the radii of curvature of these first and second concave curved surface portions may be constant, that is, in the above-mentioned cross section, the first and second concave curved surface portions may smoothly contact circular arcs having different radii at one contact point. The shape may be
Further, the radius of curvature is gradually increased from the first concave curved surface side toward the second concave curved surface side, for example, various curved shapes such as an ellipse, a trochoid, a cycloid, an involute, etc. are exhibited in the cross section. Good.

Furthermore, in the case where the first concave curved surface portion and the second concave curved surface portion are smoothly connected in this way, a cross section perpendicular to the axis line is formed between the first concave curved surface portion and the second concave curved surface portion. In, a tangential connection surface is formed that is in contact with both the concave curve formed by the first concave curved surface portion and the concave curve formed by the second concave curved surface portion, and the first and second concave curved surfaces are formed through this connection surface. The parts may be connected. In this case, the groove width of the chip discharge groove can be secured without being limited by the radius of curvature of the concave curve formed by the first and second concave curved surface portions, and the curling property and the discharging property of the chip can be improved. At the same time, it is possible to improve it, and since a space can be provided between the first concave curved surface portion and the second concave curved surface portion by the connection surface, the chips curled in the first concave curved surface portion can form the second concave concave portion. It is possible to more reliably prevent the surface from being pressed against the curved surface portion, achieve smooth discharge, and promote reduction of the drill rotation driving force. It should be noted that such a connecting surface is formed between the convex curved surface portion and the first concave curved surface portion,
It may be formed on the outer peripheral side of the second concave curved surface portion. Also,
A linear cutting edge portion may be interposed between the uneven curved cutting edge portions to smoothly connect the curved cutting edge portions.

When the smoothly curved convex curved surface portion and the first and second concave curved surface portions are formed on the inner wall surface of the chip discharge groove, the convex curved line formed by the convex curved surface portion is first formed in the cross section orthogonal to the axis. If the radius of curvature of the cutting edge is too large, the width of the concave curved cutting edge of the cutting edge may be relatively small and curling of chips may be insufficient. Since the width of the portion becomes smaller and sufficient strength may not be ensured at the intersection with the margin portion, 0.1 × D with respect to the outer diameter D of the cutting edge.
It is desirable to set it in the range of 0.8 × D. Also,
Regarding the radius of curvature of the concave curve formed by the first concave curved surface portion in the cross section orthogonal to the axis, if it is too large, it may not be possible to sufficiently curl the chips by sliding contact, but it is too small on the contrary. Since the chips may be rapidly curled and the braking action may become too large, the cutting edge may have an outer diameter D of 0.1 or less.
It is desirable to set in the range of 8 × D to 0.35 × D. Further, regarding the radius of curvature of the concave curve formed by the second concave curved surface portion in the cross section orthogonal to the axis, if this is too large, the chips will not slide on the second concave curved surface portion and will be curled only by the first concave curved surface portion. On the other hand, on the contrary, if it is too small, the sliding contact of the chips with the second concave curved surface portion becomes too strong, and a large braking action is also generated. Therefore, with respect to the outer diameter D of the cutting edge. 0.2 × D ~
It is desirable to set it in the range of 0.5 × D. Furthermore, TiN, at least on the surface of the tip of the drill body,
By coating a hard coating such as TiCN or TiAlN, the wear resistance of the tip of the drill body can be improved.

[0012]

1 to 3 show an embodiment of the present invention. In the present embodiment, the drill body 1 is formed of a hard material such as cemented carbide into a substantially cylindrical shape centered on the axis O, and its tip portion is constant from the tip flank 2 toward the rear end side. A pair of chip discharge grooves 3 and 3 which are twisted rearward in the drill rotation direction T at a twist angle of are formed symmetrically with respect to the axis O. The cutting edges 5 and 5 are respectively formed on the ridges where the inner wall surfaces 4 and 4 facing each other and the above flank 2 intersect.
Are formed. In addition, at the tip of the drill body 1, the outer peripheral surface, the tip flank 2, the chip discharge groove 3, Ti
A hard coating such as N, TiCN, TiAlN is coated.

Here, the inner wall surface 4 has a convex curve which is located on the outer peripheral side thereof, intersects with the margin portion 6, and is convex in the drill rotation direction T as shown in FIG. 2 in a cross section orthogonal to the axis O. The first convex curved surface portion 7 to be formed and the inner peripheral side of the first convex curved surface portion 7, and in the cross section, the drill rotation direction T
And a first concave curved surface portion 8 having a concave curved shape which is concave toward the rear side of the concave convex curved surface portion 7, and the convex and concave curved surfaces formed by the cross sections of the first convex and concave curved surface portions 7 and 8 are connected so as to be smoothly in contact with each other at a contact point P1. Has been. Further, in the present embodiment, the inner wall surface 9 of the chip discharge groove 3 facing the rear side in the drill rotation direction T is also positioned on the outer peripheral side thereof and reaches the heel portion 10, and the above-mentioned cross section is convex in the rear side in the drill rotation direction T. From the second convex curved surface portion 11 forming a convex curve and the second concave curved surface portion 12 located on the inner peripheral side of the second convex curved surface portion 11 and having a concave curved shape whose cross section is concave in the drill rotation direction T side. The second uneven curved surface portion 1 is configured.
The above-mentioned concave and convex curves formed by 1 and 12 are also connected so as to be in contact with each other smoothly at the contact point P2, and the concave curves formed by the cross sections of the first and second concave curved surface portions 8 and 12 of both inner wall surfaces 4 and 9 are contact points. At P3, they are smoothly contacted and continuous. The outer peripheral surface of the land portion, which extends from the margin portion 6 to the rear side in the drill rotation direction T to the heel portion 10, is formed in a cylindrical surface shape receding from the margin portion 6 toward the inner peripheral side by one step.

Further, in the present embodiment, in the above-mentioned cross section, the convex-concave curves formed by the first and second convex-concave curved surface portions 7, 8, 11, 12 respectively have radii R1 centered on points C1 to C4.
The center C1 of the convex arc formed by the first convex curved surface portion 7 is the intersection of the first convex curved surface portion 7 and the margin portion 6, that is, the outer circumference of the inner wall surface 4. It is located on the inner circumference side of the straight line Q1 in contact with the margin portion 6 at the end 13, and the center C3 of the arc formed by the second convex curved surface portion 11 is the circle formed by the outer circumference end 13 around the axis O and the second. At the intersection 14 with the extension line of the arc formed by the convex curved surface portion 11, it is also positioned on the inner peripheral side of the straight line Q2 tangent to the circle. Therefore, the first convex curved surface portion 7
Is convex to the drill rotation direction T side with respect to the first virtual straight line S1 connecting the axis O and the outer peripheral end 13 of the inner wall surface 4, and the tangent line of the first convex curved surface portion 7 at the outer peripheral end 13 is the outer peripheral side. So that it extends toward the rear side of the drill rotation direction T toward
While being inclined with respect to the virtual straight line S1, the straight line Q1 orthogonal to the first virtual straight line S1 intersects the straight line Q1 at an obtuse angle. The second convex curved surface portion 11 is also convex toward the rear side in the drill rotation direction T with respect to the straight line connecting the intersection with the heel portion 10 and the axis O. On the other hand, the centers C2 and C4 of the arc formed by the first and second concave curved surface portions 8 and 12
Since these arcs are in contact with each other at the contact point P3, both of them are located on an extension line of a straight line passing through the contact point P3 from the axis O. Further, since the contact point P3 serves as the groove bottom of the chip discharge groove 3, in the present embodiment, the circle passing through the contact point P3 with the axis O as the center is the core thickness circle of the drill body 1, and the diameter of the core thickness circle, The core thickness d of the drill body 1 is 0.15 × D to the diameter of the circle formed by the outer peripheral end 15 of the cutting edge 5 around the axis O, that is, the outer diameter D of the cutting edge 5.
It is set in the range of 0.3 × D.

The contact point P1 of the convex-concave curve formed by the first convex-concave curved surface portions 7 and 8 is located on the outer peripheral side of the circle having the diameter of 2/3 of the outer diameter D of the cutting edge 5 about the axis O. More preferably, it is located on the outer peripheral side of a circle having a diameter of 5/6 of the outer diameter D about the axis O. Further, the size of the recess of the first recessed curved surface portion 8 toward the rear side in the drill rotation direction T is such that the recess amount L1 from the first virtual straight line S1 is −0.06 × with respect to the outer diameter D of the cutting edge 5. It is set in the range of D to 0, and the size of the recess of the second recessed curved surface portion 12 toward the drill rotation direction T is the first in the above cross section.
The dent amount L2 from the second virtual straight line S2 orthogonal to the virtual straight line S1 with the axis O is set to fall within the range of −0.06 × D to 0.06 × D. However, the amount of these recesses L
1 and L2 are straight lines parallel to the first and second virtual straight lines S1 and S2, respectively, and a straight line which is in contact with the concave curve formed by the first and second concave curved surface portions 8 and 12 and the first and second virtual straight lines S1 and S1, respectively. S
2 and the distance between the two, as shown in FIG.
Regarding the recess amount L1 of the first concave curved surface portion 8, the first virtual straight line S
1, the drill rotation direction T side is positive, the rear side is negative, and conversely, with respect to the recess amount L2 of the second concave curved surface portion 12, the drill rotation direction T side is negative and the rear side is positive from the second virtual straight line S2. . Therefore, in the present embodiment, the entire first concave curved surface portion 8 is not located on the drill rotation direction T side with respect to the first virtual straight line S1.

Further, in the above section, the radii R1 to R4 of the arc formed by the first and second curved surface portions 7, 8, 11, 12 are formed.
Is the radius R1 of the first convex curved surface portion 7 with respect to the outer diameter D of the cutting edge 5.
Is in the range of 0.1 to 0.8 × D, the radius R2 of the first concave curved surface portion 8 is in the range of 0.18 to 0.35 × D, and the radius R3 of the second convex curved surface portion 11 is 0.1. To 0.8 × D, the radius R4 of the second concave curved surface portion 12 is 0.2 to 0.5 × D,
Each is set. In this embodiment, the radius R4 of the second concave curved surface portion 12 is the first concave curved surface portion 8 among them.
Is larger than the radius R2. The groove width ratio of the chip discharge groove 3 thus formed is 0.
The range is 8 to 1.2: 1.

In the cutting edge 5 formed at the intersection ridge of the inner wall surface 4 of the chip discharge groove 3 and the tip flank 2 as described above, the inner wall surface 4 is formed by the first curved surface portions 7 and 8. By being formed, on the outer peripheral end 15 side thereof, a convex curved cutting edge portion 1 having a curved shape that is convex in the drill rotation direction T is formed.
6 is formed and the first convex curved surface portion 7 is connected to the rear end side thereof, and the inner peripheral side of the convex curved cutting edge portion 16 has a curved shape that is concave toward the rear side in the drill rotation direction T. The concave curved cutting edge portion 17 is formed so as to be in smooth contact with the convex curved cutting edge portion 16 and is continuous, and the first concave curved surface portion 8 is continuous at the rear end side thereof. 16, 17
In the meantime, the cutting edge 5 has an S-shape that gently curves when viewed from the front end in the direction of the axis O. However, the cutting edge 5 has a tip angle because the tip flank 2 is inclined toward the rear end side of the drill body 1 from the inner peripheral side toward the outer peripheral side. Since the groove 3 is spirally twisted, the concave and convex curved cutting edge portions 16 and 1 of the cutting edge 5 are formed.
The S-shaped concave-convex curve formed by 7 in the tip view in the direction of the axis O is a concave-convex curve formed by the first convex-concave curved surface portions 7 and 8 of the inner wall surface 4 in a cross section orthogonal to the axis O. The shape gradually shifts toward the rotation direction T side. Therefore, in the tip view in the direction of the axis O, the tangent line at the outer peripheral end 15 of the convex curved cutting edge portion 16 is larger than the tangent line at the outer peripheral end 13 of the convex curve formed by the first convex curved surface portion 7 in the cross section. And the crossing angle with the margin portion 6 is made larger than the obtuse angle formed by the first convex curved surface portion 7 as it goes toward the outer peripheral side toward the rear in the drill rotation direction T. The radial rake angle α formed at 15 is set to the negative angle side.

On the other hand, on the tip side of the inner wall surfaces 4 and 9 of the chip discharge groove 3, the tip escape from the inner peripheral side of the first concave curved surface portion 8 to the second concave curved surface portion 12 and the second convex curved surface portion 11. A thinning portion 18 reaching the heel portion 10 is formed by notching the ridge line portion intersecting with the surface 2 toward the rear end side of the drill body 1 toward the inside of the chip discharge groove 3, and thus the cutting portion 18 is formed. The inner peripheral end side of the blade 5 is formed at an intersecting ridge line portion between the thinning portion 18 and the tip flank 2, and the axis line of the center of the tip flank 2 from the inner peripheral end of the concave curved cutting edge portion 17 is formed. O
It is a thinning cutting edge portion 19 extending toward. In the cutting edge 5, the portion where the thinning cutting edge portion 19 and the concave curved cutting edge portion 17 intersect is smoothly connected by a curved line or a straight line which is convex in the drill rotation direction T when viewed from the tip of the axis O direction. ing.

Here, a portion of the thinning portion 18 that intersects the inner wall surfaces 4 and 9 of the chip discharge groove 3 and extends toward the tip side is referred to as a first thinning portion 20, and the first thinning portion 20 is formed. The portion extending to the heel portion 10 side intersecting the inner wall surface 9 of the chip discharge groove 3 facing the drill rotation direction T rear side is formed in a flat shape, while facing the inner wall surface 9 and the drill rotation direction T side. The part where the inner wall surface 4 intersects,
That is, the portion extending from the contact point P3 portion of the first and second concave curved surface portions 8 and 12 toward the center of the tip flank 2 is seen from the direction toward the center of the tip flank 2 as shown in FIG. In this case, it is formed to have a concave curved valley shape, and the concave valley bottom portion 21 is inclined so as to recede toward the inner peripheral side of the drill body 1 with respect to the inner wall surfaces 4 and 9. Meanwhile, it is formed so as to extend toward the tip side toward the inner peripheral end of the cutting blade 5, that is, the inner peripheral end of the thinning cutting blade portion 19. The radius of curvature of the concave curve formed by the concavely curved valley bottom portion 21 of the first thinning portion 20 is 0.1 to 0.1.
It is set within the range of 0.5 mm. In addition, this valley bottom 2
The radius of curvature of the concave curve formed by the cross section of 1 may be increased toward the rear end side.

Further, in the portion where the above-mentioned valley bottom portion 21 at the extreme end of the first thinning portion 20 is about to reach the inner peripheral edge of the cutting edge 5, the drill main body 1 is further added to the valley bottom portion 21.
A second valley-shaped thinning portion 22 that extends toward the inner peripheral end side of the cutting edge 5 while being inclined one step so as to recede toward the inner peripheral side is formed, and in the vicinity of the axis O at the center of the tip flank 2 The second thinning portion 22 intersects the tip flank 2 and the inner peripheral edge of the cutting edge 5 is formed on the intersecting ridge line portion. Here, the radius of curvature of the valley bottom of the second thinning portion 22 is
The radius of curvature is smaller than the radius of curvature of the valley bottom portion 21 of the first thinning portion 20 and less than 0.1 mm. In some cases, the radius of curvature is 0, that is, the valley bottom portion is formed in a V-shaped valley shape without concave curvature. Also, the first thinning section 20
Like the valley bottom portion 21 of the above, it may be formed so as to become larger toward the rear end side of the drill body 1. In addition, the inner peripheral edge of the cutting blade 5 is formed at the ridge line portion where the second thinning portion 22 and the tip flank 2 that are inclined further than the first thinning portion 20 in this way are formed, and thus the tip of the drill main body 1 is formed. The distance between the pair of cutting blades 5 and 5, that is, the width of the chisel defined at the center of the tip flank 2 is the first thinning portion 20.
Is narrower than that in which the inner peripheral end of the cutting edge 5 is formed by intersecting the tip flank 2 as it is, and this chisel width is in the range of 0 to 0.2 mm in the present embodiment. The inner peripheral ends of the blades 5 and 5 may be aligned on the axis O.

In the drill constructed as described above,
First, a convex curved cutting edge portion 16 which is convex in the drill rotation direction T is formed on the outer peripheral edge 15 side of the cutting edge 5, and accordingly, the convex curved cutting edge portion at the outer peripheral edge 15 in the axial direction O direction tip view. The angle of intersection between 16 and the margin portion 6 can be set to a large angle as described above, and can also be set to an angle larger than the angle of intersection between the first convex curved surface portion 7 and the strength of the drill body 1 in the vicinity of the outer peripheral end 15. Can be sufficiently secured. Therefore, the cutting speed is the highest because it is located on the outer periphery of the drill body 1, and the amount of chips produced is also the largest, so that excessive load is likely to occur, and chipping or chipping occurs at the outer peripheral end 15 of the cutting blade 5. Can be prevented, and the tool life can be extended even under severe processing conditions such as high-speed dry cutting. Moreover, in this embodiment, the convex curved cutting edge portion 16 is formed so as to be more convex in the drill rotation direction T than the straight line connecting the outer peripheral end 15 of the cutting edge 5 and the axis O in the end view in the direction of the axis O. As a result, as described above, the radial rake angle α is a negative angle, so that the intersection angle with the margin portion 6 is an obtuse angle, and the strength of the drill body 1 around the outer peripheral end 15 is more reliably ensured. Can be secured.

The convex curved cutting edge portion 16 thus has a curved shape that is convex in the drill rotation direction T, and the cutting edge 5 is bent into an V shape at an angle as in the conventional case. A bending point is not formed, and a concave curved cutting edge portion 17 that is concave toward the rear side in the drill rotation direction T is smoothly connected to the convex curved cutting edge portion 16 on the inner peripheral side thereof. Therefore, the chips generated by the cutting edge 5 flow out toward the inner peripheral side of the portion generated by the concave curved cutting edge portion 17 without being divided at the bending point as described above. As a result, the curl is smoothly curled so as to be entirely caught in the inner peripheral side. For this reason,
The separated chips do not become entangled with each other to cause chip clogging, and the chips on the outer peripheral end 15 side flow out to the outer peripheral side to increase resistance and accelerate wear of the drill body 1. Nonetheless, it is possible to promote smooth and stable processing of chips to reduce the driving force of the drill rotation during drilling, and to suppress wear to further extend the tool life. Further, since the tip of the drill body 1 including the cutting edge 5 is coated with a hard coating such as TiN, TiCN, TiAlN, the wear resistance of the drill body 1 can be further improved. .

Further, in this embodiment, the thinning portion 18 is formed on the tip end side of the chip discharge groove 3, so that the inner peripheral end side of the cutting edge 5 is directed toward the center of the tip flank surface 2. 19, the intersection of the thinning cutting edge portion 19 and the concave curved cutting edge portion 17 is formed into a convex curved line or a straight line smoothly connecting to both cutting edge portions 17 and 19, and thinning is also performed. First connected to the cutting edge 19
Since the thinning portion 20 has a valley shape in which the valley bottom portion 21 is concavely curved, the above-described bending point is not formed over the entire length of the cutting blade 5, and the thinning cutting blade portion 1
The inner peripheral side portion of the chips generated by 9 also includes the valley bottom portion 2 of the first thinning portion 20 as shown by a black arrow in FIG.
It can be curled so as to be rolled inward along the concave curve formed by one cross section. Therefore, in combination with the fact that the concave curved cutting edge portion 17 causes the chips to be caught on the inner peripheral side, the chip disposability can be further improved, which is particularly effective in processing difficult-to-cut materials. is there. In addition, in the present embodiment, the radius of curvature of the concave curve formed by the valley bottom portion 21 of the first thinning portion 20 is 0.1 to 0.5 mm.
If the radius of curvature is larger than this, there is a possibility that the inner peripheral side portion of the chip cannot be sufficiently rolled up and curled. On the contrary, if it is smaller than this, the inner peripheral side portion of the chip is thinned portion 18. This is because there is a risk of clogging inside.

At the tip of the thinning portion 18,
A second thinning portion 22 is formed to reach the tip flank 2 by further inclining one step from the valley bottom portion 21 of the first thinning portion 20, and on the ridge line portion where the second thinning portion 22 and the tip flank 2 intersect. Since the inner peripheral edge of the cutting edge 5 is formed on the cutting edge 5 and the radius of curvature of the groove bottom of the second thinning portion 22 is less than 0.1 mm, which is smaller than that of the valley bottom portion 21, the cutting edge 5 The inner circumference end of the chisel is located closer to the inner circumference side, so that the width of the chisel is 0 to 0.2.
The width is very short, mm. Therefore, when the drill bites into the workpiece, the biting property and straight running stability can be improved to perform more stable and highly accurate machining, and the thrust acting on the drill body 1 in the axial direction thereof can be achieved. The force can be suppressed, and it becomes possible to promote further reduction of the drill driving force. Moreover, since the thinning portion 18 is formed by the first and second plurality of thinning portions 20 and 22 having a large inclination toward the inner peripheral edge of the cutting edge 5 in this manner, the second thinning portion 22 at the tip is formed. The tip angle of the drill body 1 in the cross section along the groove bottom of
Since the groove bottom of a single thinning portion becomes larger than that in the case where the groove bottom is inclined so as to have the same chisel width, according to the present embodiment, sufficient strength is secured around the rotation center of the tip of the drill body 1. It is possible to provide a drill that is not damaged by an impact load when biting. However, the second thinning portion 22 may be omitted as long as the biting property of the drill body 1 and the straight running stability and strength can be secured only by the first thinning portion 20.

On the other hand, such an uneven curved cutting edge portion 16,
In order to form the cutting edge 5 provided with 17, in the present embodiment,
On the inner wall surface 4 of the chip discharge groove 3 which faces the drill rotation direction T, first concave and convex curved surface portions 7 and 8 which are respectively continuous with the concave and convex curved cutting edge portions 16 and 17 are formed, and are thus divided by the cutting edge 5. The chips that are continuously generated in the width direction without being rolled up are curled further by being rolled up on the inner peripheral side and pressed against the first concave curved surface portion 8 while slidingly contacted, and the rotation of the drill body 1 is increased. Along with that, it is pushed out to the rear end side and discharged. Further, on the inner peripheral side of the first concave curved surface portion 7, the second concave curved surface portion 12 of the inner wall surface 9 of the chip discharge groove 3 facing the rear side in the drill rotation direction T is smooth with the first concave curved surface portion 7. Since the second concave curved surface portion 12 is formed so as to be recessed in the drill rotation direction T contrary to the first concave curved surface portion 8, the second concave curved surface portion 12 is further reduced by the first concave curved surface portion 8. The curled chips are smoothly discharged as described above without obstructing the flow of the chips. Moreover, in the present embodiment, the second convex curved surface portion 11 is formed on the outer peripheral side of the second concave curved surface portion 12 so as to be smoothly continuous,
Therefore, the flow of chips is not blocked on the heel portion 10 side, and the strength of the drill body 1 at the heel portion 10 can be secured.

Further, in the present embodiment, the depression amounts L1 and L2 of the first and second concave curved surface portions 8 and 12 are set to the first
Regarding the concave curved surface portion 8, from the first virtual straight line S1 connecting the axis O and the outer peripheral end 13 of the inner wall surface 4 to the outer diameter D of the cutting edge 5 −
The second imaginary straight line orthogonal to the first imaginary straight line S1 on the axis O of the second concave curved surface portion 12 so as to be in the range of 0.06 × D to 0 (however, the rear side in the drill rotation direction T is negative). S2 is set to be in the range of -0.06xD to 0.06xD (however, the drill rotation direction T side is negative), so that the chips are not too strong and not too weak. By making sliding contact with the second concave curved surface portions 8 and 12, an appropriate braking action can be given. For this reason,
However, the chips can be reliably curled and processed without causing the chips to be crushed by the excessive braking action to impair the smooth discharging property or to increase the drill rotation driving force. It should be noted that, in order to more reliably bring out such an action and effect, as in the present embodiment, the axis O
In a cross section orthogonal to, the radius of curvature R2 of the concave curve (concave arc) formed by the first concave curved surface portion 8 is in the range of 0.18 to 0.35 × D with respect to the outer diameter D of the cutting edge 5, and 2 concave curved surface 1
The radius of curvature R4 of 2 is preferably set in the range of 0.2 to 0.5 × D.

Further, in the present embodiment, these first and second
Even between the concave curved surface portions 8 and 12, the radius of curvature of the concave curve formed by the second concave curved surface portion 12, that is, the radius R4 in the cross section orthogonal to the axis O, is the radius of curvature of the concave curve formed by the first concave curved surface portion 8, that is, It is designed to be larger than the radius R2, so that the chips generated by the cutting blade 5 are first slidably contacted with the first concave curved surface portion 8 having the relatively small radius R2, so that the chips are sufficiently wound. By curling with a habit and allowing the curled chips to flow out toward the second concave curved surface portion 12 side having a relatively large radius R4, the chips may be pressed too strongly in the second concave curved surface portion 12. It is possible to promote smoother discharge and further reduce the driving force for rotating the drill. Moreover, in the present embodiment, the concave curve formed by the first and second concave curved surface portions 8 and 12 is designed to draw a continuous concave curve in contact with the contact point P3 of 1. It becomes possible to make the flow of the chips from the second concave curved surface portion 12 smoother to promote smoother chip discharge.

However, instead of forming the first and second concave curved surface portions 8 and 12 in such a manner that the concave curves formed by the cross sections thereof are in contact with each other at the contact point P3 of 1 and are smoothly continuous, for example, shown in FIG. As described above, between the first and second concave curved surface portions 8 and 12, both the concave curve formed by the first concave curved surface portion 8 and the concave curve formed by the second concave curved surface portion 12 in the cross section orthogonal to the axis O. It is also possible to form a tangential connecting surface 23 that is in contact with the contact points P4 and P5 and smoothly connect the biconcave curved surface portions 8 and 12 via the connecting surface 23. Also in this case, the chips having the curl due to the first concave curved surface portion 8 are not impaired in the flow thereof, and further, the chips are not strongly pressed against the connection surface 23 and the drill rotation driving force is not increased. Thus, it is possible to send out to the second concave curved surface portion 12 side and smoothly discharge. On the other hand, when such a connecting surface 23 is interposed between the first and second concave curved surface portions 8 and 12, the radius of curvature R of the first and second concave curved surface portions 8 and 12 is
Since the groove width of the chip discharge groove 3 can be set without being limited to 2 and R4, for example, contrary to the above, depending on the material of the workpiece, the second concave curved surface portion 12 can be sufficiently chipped. Even if the radius of curvature R4 is made small when it must be slidably contacted and curled, it is possible to secure a sufficiently large groove width and maintain a smooth discharge property.

Further, in this embodiment, the first and second
The radii of curvature R1 and R3 of the convex curve (convex arc) formed by the convex curved surface portions 7 and 11 in the above cross section are set in the range of 0.1 to 0.8 × D with respect to the outer diameter D of the cutting edge 5, respectively. And
As a result, the strength around the margin portion 6 and the strength around the heel portion 10 at the inner wall surface 4 of the drill body 1 and the outer peripheral ends 13 and 15 of the cutting edge 5 and the strength around the heel portion 10 are sufficiently secured, and
It is possible to prevent the radial widths of the concave curved surface portions 8 and 12 from becoming too small, and to reliably improve the chip disposability.
Even under conditions such as high-speed dry cutting, in order to more reliably ensure the strength of the drill body 1 and the improvement of the chip disposability in this way, the first uneven curved surface in the cross section as in the present embodiment is used. The contact point P1 of the uneven curve formed by the parts 7 and 8 is
The cutting edge 5 is positioned on the outer peripheral side of a circle having a diameter of ⅔ of the outer diameter D, more preferably on the outer peripheral side of a circle having a diameter of 5/6 of the outer diameter D, and the chip discharge groove 3 The groove width ratio of 0.8
It is desirable to set the range to 1.2: 1.

Furthermore, in the present embodiment, as the chip disposability is improved and the drill rotation driving force is reduced, the load that the drill body 1 itself receives during processing is also reduced, and as a result, The core thickness d can also be set to a relatively small range of 0.15 × D to 0.3 × D with respect to the outer diameter D of the cutting edge 5. Therefore, particularly the thrust force of the load received by the drill main body 1 is reduced, and the cross-sectional area of the chip discharge groove 3 is increased to promote smoother chip discharge, thereby further increasing the power for drilling. Can be reduced. On the other hand, the cross-sectional area of the drill main body 1 is large on the outer peripheral side by the curvature radii R1 to R4 being set in an appropriate range as described above, and particularly by the first and second convex curved surface portions 7 and 11. By doing so, it is possible to ensure the necessary and sufficient level, and therefore the rigidity of the drill body 1 can be maintained, and in addition to the fact that the machining power can be further reduced as described above,
It is also possible to prevent a situation in which the drill life is consumed due to breakage during processing.

Table 1 below shows the drill of the embodiment shown in FIGS. 1 to 3 and the radius R1 of the first convex curved surface portion 7, respectively.
The cutting speed is changed with the comparative drills 1 to 5 which are similar to this embodiment except that the size of the first and second concave curved surface portions 8 and 12 and the size of the core thickness d are different. In addition, it shows the results of a dry drilling processing test, and the processing conditions and evaluations are as shown in the table below.

[0032]

[Table 1]

From the results shown in Table 1, first, the first convex curved surface portion 7
In the comparative drill 1 whose radius R1 is less than 0.1 × D with respect to the outer diameter D of the cutting edge 5, as the width of the first convex curved surface section 7 decreases, the convex curved cutting edge section 16 at the tip end And the convex curved cutting edge portion 16 causes chipping at the shoulder of the cutting edge 5, that is, at the outer peripheral end 15 portion, and conversely, the radius R1 exceeds 0.8 × D. In 2,
The first convex curved surface portion 7 and the convex curved cutting edge portion 16 are widened, and the first concave curved surface portion 8 and the concave curved cutting edge portion 17 are relatively narrow, whereby the curling property of chips is improved. The chips were damaged and the chips were strongly pressed against the inner wall surfaces 4 and 9 of the chip discharge groove 3, resulting in large wear. Also,
Contrary to the above embodiment, the radius R2 of the first concave curved surface portion 8 is set to the second radius R2.
Comparative drill 3 having a radius larger than the radius R4 of the concave curved surface portion 12
Then, when the chips were strongly pressed against the second concave curved surface portion 12, crushing occurred as shown in FIG. 5B, and the second concave curved surface portion 12 was significantly worn. Further, in the comparative drill 4 in which the core thickness d is larger than 0.3 × D, the cross-sectional area of the chip discharge groove 3 is small, the abrasion due to the scraping of the chips is also large, and the thrust force is increased and the drill driving force is also increased. On the contrary, the core thickness d is 0.15
In the comparative drill 5 having a size smaller than × D, the thrust force was small, but the rigidity was insufficient, and breakage occurred.

In contrast to these comparative drills 1 to 5, in the drills 1 to 3 of the above-described embodiment, the discharged chips are all curled small as shown in FIG. 5A without being crushed. Also, the tool wear on the inner wall surfaces 4, 9 of the chip discharge groove 3 is normal, and particularly in the embodiment drill 2 in which the core thickness d is 0.23 × D, both the thrust force and the horizontal component force are small. It was possible to perform more stable drilling. On the other hand, in the embodiment drill 3 in which the core thickness d is slightly smaller than 0.20 × D, the rigidity is also reduced accordingly, and the horizontal component force tends to increase. There was no breakage, and a practically sufficient life could be obtained.

[0035]

As described above, according to the present invention,
By forming a convex curved cutting edge portion on the outer peripheral end side of the cutting edge, it is possible to secure the strength of the drill main body at the outer peripheral edge of the cutting edge to prevent chipping and chipping and By forming the concave curved cutting edge portion smoothly connected to the cutting edge portion on the inner peripheral side, it is possible to curl the entire chip as if it were rolled up on the inner peripheral side, and an efficient treatment can be achieved. . Therefore, even under severe processing conditions such as dry type and high-speed cutting, the drill life can be extended and smooth and stable drilling can be performed.

[Brief description of drawings]

FIG. 1 is a front view of an embodiment of the present invention as viewed from the front end in the direction of an axis O. FIG.

2 is a cross-sectional view orthogonal to the axis O of the embodiment shown in FIG.

3 is a perspective view of a tip portion of the drill body 1 showing a thinning portion 18 of the embodiment shown in FIG. 1. FIG.

FIG. 4 is a connection surface 23 between the first and second concave curved surface portions 8 and 12.
It is sectional drawing which shows the case where it forms.

5A is a diagram showing chips produced by a drill according to an embodiment of the present invention, and FIG. 5B is a diagram showing a radius R2, R4 of the first and second concave curved surface portions 8, 12 in the embodiment. It is a figure which shows the chip | tip by the comparative drill 3 with which the magnitude of was made opposite.

[Explanation of symbols]

1 Drill Main Body 2 Tip Relief Surface 3 Chip Discharge Groove 4, 9 Inner Wall Surface 5 of Chip Discharge Groove 3 Cutting Edge 7 First Convex Curved Surface Section 8 First Recessed Curved Surface Section 11 Second Convex Curved Surface Section 12 Second Recessed Curved Surface Section 13 Outer peripheral end 15 of the wall surface 4 Outer peripheral end 16 of the cutting edge 5 Convex curved cutting edge portion 17 Concave curved cutting edge portion 18 Thinning portion 19 Thinning cutting edge portion 20 First thinning portion 21 Valley bottom portion of the first thinning portion 20 2 Thinning portion 23 Connection surface O Axis T of the drill body 1 Drill rotation directions R1 to R4 First and second curved surface portions 7, 8, 11, 12
Curvature radii S1 and S2 of curves formed in a cross section orthogonal to the axis O are the dent amount d of the first and second imaginary straight lines L1 and L2 first and second concave curved surface portions 8 and 12 Core thickness α of the drill body 1 Cutting edge Rake angle on the outer peripheral edge 15 side of No. 5

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takeshi Inoue             1528, Nakashinden, Yokoi, Kobe-cho, Anpachi-gun, Gifu Prefecture             Address Mitsubishi Materials Corporation Gifu Factory             Within F-term (reference) 3C037 BB04 BB08 BB13 CC00 DD01

Claims (12)

[Claims] 1. A chip discharge groove extending toward the rear end is formed on the outer periphery of the front end of a drill body rotated about an axis.
A drill in which a cutting edge is formed at the ridge line intersecting the inner wall surface of the chip discharge groove facing the drill rotation direction and the tip flank of the drill body, and the drill is provided on the outer peripheral end side of the cutting edge. A convex curved cutting edge that forms a curved shape that is convex in the rotation direction is formed, and a curved shape that is concave on the rear side in the drill rotation direction is formed on the inner peripheral side of this convex curved cutting edge. And a concave curved cutting edge portion smoothly connecting to the convex curved cutting edge portion. 2. The drill according to claim 1, wherein a radial rake angle on the outer peripheral end side of the cutting edge is set to a negative angle side. 3. The tip end side of the inner wall surface of the chip discharge groove is
A thinning portion that is continuous with the inner peripheral end side of the cutting edge is formed, and this thinning portion forms a concave curved valley shape, and the valley bottom portion is on the inner peripheral side of the drill body with respect to the inner wall surface. The drill according to claim 1 or 2, further comprising a first thinning portion that extends toward the inner peripheral end of the cutting edge while retracting. 4. The second thinning portion is formed on the tip side of the first thinning portion and reaches the inner circumferential end of the cutting edge while retracting further toward the inner circumferential side with respect to the valley bottom portion. The drill according to claim 3, further comprising: 5. The core thickness of the drill body is set in a range of 0.15 × D to 0.3 × D with respect to an outer diameter D of the cutting edge. The drill according to claim 4. 6. A convex curved surface portion continuous with the convex curved cutting edge portion is formed on an inner wall surface of the chip discharge groove facing the rotation direction of the drill,
A first concave curved surface portion continuous with the concave curved cutting edge portion is formed, and the inner wall surface of the chip discharge groove facing the rear side in the drill rotation direction is smoothly connected to the first concave curved surface portion and drilled. A second concave curved surface portion having a curved surface shape that is concave in the rotation direction is formed, and in a cross section orthogonal to the axis line, a first virtual straight line connecting the axis line and the outer peripheral end of the inner wall surface facing the drill rotation direction. From the above-mentioned first concave curved surface portion L1
Is set in a range of −0.06 × D to 0 with respect to the outer diameter D of the cutting edge, and the second concave curved surface from a second virtual straight line that intersects the first virtual straight line at the axis line. 6. The drill according to claim 1, wherein the dent amount L2 of the portion is set in the range of −0.06 × D to 0.06 × D. 7. A convex curved surface portion continuous with the convex curved cutting edge portion is formed on an inner wall surface of the chip discharging groove facing the drill rotation direction,
A first concave curved surface portion continuous with the concave curved cutting edge portion is formed, and the inner wall surface of the chip discharge groove facing the rear side in the drill rotation direction is smoothly connected to the first concave curved surface portion and drilled. A second concave curved surface portion having a curved surface shape that is concave in the rotational direction is formed, and in a cross section orthogonal to the axis, the radius of curvature of the concave curve formed by the second concave curved surface portion is the first concave curved surface portion. 7. The drill according to claim 1, wherein the radius of curvature of the concave curve formed by is larger. 8. A convex curved surface portion continuous with the convex curved cutting edge portion is formed on an inner wall surface of the chip discharging groove facing the drill rotation direction,
A first concave curved surface portion that is continuous with the concave curved cutting edge portion is formed, and a second curved surface that is concave in the drill rotation direction is formed on the inner wall surface of the chip discharge groove facing the rear side in the drill rotation direction. A concave curved surface portion is formed, and between these first and second concave curved surface portions, a concave curve formed by the first concave curved surface portion and a concave curve formed by the second concave curved surface portion in a cross section orthogonal to the axis. 2. A tangential connecting surface that is in contact with both of the first concave curved surface portion and the second concave curved surface portion is smoothly connected via the connection surface. A drill according to claim 7. 9. A radius of curvature of a convex curve formed by the convex curved surface portion in a cross section orthogonal to the axis is set to a range of 0.1 × D to 0.8 × D with respect to an outer diameter D of the cutting edge. The drill according to any one of claims 6 to 8, characterized in that it is provided. 10. The radius of curvature of the concave curve formed by the first concave curved surface portion in the cross section orthogonal to the axis is in the range of 0.18 × D to 0.35 × D with respect to the outer diameter D of the cutting edge. The drill according to any one of claims 6 to 9, wherein the drill is set to. 11. A radius of curvature of a concave curve formed by the second concave curved surface portion in a cross section orthogonal to the axis is in a range of 0.2 × D to 0.5 × D with respect to an outer diameter D of the cutting edge. The drill according to any one of claims 6 to 10, wherein the drill is set to. 12. The drill according to claim 1, wherein at least a surface of a tip portion of the drill body is coated with a hard coating.