JPH0938816A - Drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce cutting resistance in drill working, and also prevent damage in the drill rotation center in particular to prolong the life of a drill. SOLUTION: A cutting blade 4, extending toward a drill outer peripheral side from the drill rotation center C, is formed on the tip of a drill main body 1 rotated around an axis O. The blade 4 is constituted of a first cutting blade part 4A positioned on the drill outer peripheral side to linearly extend in tip view in an axis O direction, a second protrudedly curved cutting blade part 4B ranging with the inner peripheral side of the blade part 4A to expand to a drill rotation direction side, and a third recessedly curved cutting blade part 4C ranging with the more inner peripheral side of the blade part 4B to be recessed to the rear side in a drill rotation direction in the vicinity of the center C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill in which a cutting edge is formed at the tip of a drill body and used for drilling.

[0002]

2. Description of the Related Art In drilling with such a drill, at the center of the drill rotation at the tip of the drill body,
It is known that the peripheral speed becomes 0 regardless of the rotation of the drill body, and therefore the cutting speed becomes 0, and theoretically no cutting is performed. For this reason, cutting at the center of rotation of the drill is rather than scraping off the work material, rather, the drill body is pushed into the work material, and the part crushed by the work material is crushed near the center of rotation of the drill. It becomes a cutting form that is cut by a blade.

[0003]

However, in such a cutting form, it is unavoidable that the cutting resistance increases due to the pushing force for pushing the drill body into the work material. In the vicinity of the center of rotation of the drill, as described above, the drill body crushes the work material, so flank wear is significantly accelerated on the drill body side, and excessive cutting load acts. By doing so, microchipping may occur and the drill life may be impaired.

In view of such circumstances, the present invention provides a drill capable of reducing the cutting resistance during drilling and preventing damage to the center of rotation of the drill and extending its life. It was made for the purpose.

[0005]

In order to solve the above problems and to achieve the above object, the present invention is directed to the outer periphery of a drill body rotated around an axis, from the tip of the drill body to the base end side. A chip discharge groove extending toward is formed, at the ridge line intersecting the wall surface of the chip discharge groove facing the drill rotation direction side and the tip flank of the drill body, from the drill rotation center at the tip of the drill body to the drill outer peripheral side. In a drill in which a cutting edge extending toward the cutting edge is formed, a first cutting edge portion linearly located on the outer peripheral side of the drill and extending linearly in the axial tip end view in the cutting edge, and the first cutting edge. A second part that is formed in a convex curve that is continuous with the inner peripheral side of the portion and expands toward the drill rotation direction
And a third cutting edge portion which is connected to the inner peripheral side of the second cutting edge portion and has a concave curved shape that is recessed rearward in the drill rotation direction in the vicinity of the drill rotation center. Characterized by the fact that

In the drill having such a structure, when viewed from the tip end in the axial direction of the drill main body, the cutting edge is bent rearward in the drill rotation direction by the third cutting edge portion from the drill rotation center toward the outer peripheral side. , Is formed so as to be continuous with the second cutting edge portion, reversely convexly curved in the drill rotation direction side, and further connected to the linear first cutting edge portion. Therefore, the processed material portion crushed by the vicinity of the center of rotation of the drill is promptly pushed out to the outer peripheral side so as to be guided by the third curved cutting edge portion, and is cut by the second cutting edge portion. Since it is scraped off and generated as chips, the force required to push the center of rotation of the drill into the work material can be reduced to reduce cutting resistance, and the cutting load acting near the center of rotation of the drill It is possible to reduce and suppress chipping and flank wear.

If the radius of curvature of the concave curve formed by the third cutting edge portion in the axial direction front end view is too large, the third cutting edge portion approaches a linear shape and the above-described action is sufficiently exerted. If it is not effective, and if it is too small, on the contrary, when the work material scooped by the center of rotation of the drill is guided by the third cutting edge part, its direction can be suddenly changed, and the reaction force causes the cutting edge to move. There is a possibility that inconvenience may occur, such as an increase in the load acting on. For this reason, it is desirable that the radius of curvature of the concave curve formed by the third cutting edge portion is set within the range of 0.1 × D to 0.3 × D with respect to the outer diameter D of the cutting edge.

Further, if the third cutting edge portion is too short, the above-mentioned effect is not sufficiently achieved, but the radial rake angle is set to the regular angle side. There is a possibility that the strength of the cutting edge is deteriorated near the center. For this reason, the third cutting edge portion may be formed only in the vicinity of the center of rotation of the drill, and specifically, in the axial direction tip view, the third cutting edge portion and the third cutting edge portion may be formed.
The diameter d of the circle formed around the center of rotation of the drill at the intersection with the cutting edge part is set to a range of 0.15 × D to 0.3 × D with respect to the outer diameter D of the cutting edge. It is desirable to be done.

Furthermore, the convex curved second cutting blade portion and the linear first cutting blade portion connected to the outer peripheral side of the third cutting blade portion are the first cutting blade portion in the axial direction when viewed from the first end. The cutting edge portion may be formed so as to be in contact with a convex curve formed by the second cutting edge portion and extend in the tangential direction thereof, and the second cutting edge portion may have an inner circumference of the first cutting edge portion. It may be formed so as to project to the drill rotation direction side with respect to a virtual extension line to the side. In the former case, since the first and second cutting edge portions are smoothly connected to form a cutting edge, it is possible to prevent the chips from being excessively divided with respect to the work material in which sheared chips are generated. On the other hand, in the case of the latter, in the latter case, since the second cutting edge portion has a raised mountain shape with respect to the first cutting edge portion, especially for a processed material in which chips that tend to extend are generated, Appropriate stress can be applied to the chips to promote effective division during curling, and in any case, smooth chip disposal can be achieved.

Further, in the cutting edge, in a side view from the radial direction with respect to the axis, at least a portion from the third cutting edge portion to the second cutting edge portion is directed toward the inner peripheral side toward the axial tip end. It is preferably formed in a convex curve shape that swells to the side. By adopting such a configuration, the tip angles of the second and third cutting edge portions gradually increase from the outer peripheral side of the drill toward the inner peripheral side, and become the maximum at the center of rotation of the drill. The strength of the cutting edge can be secured in the third cutting edge portion near the center of rotation of the drill, and the occurrence of chipping or the like can be prevented more reliably.

In the case of adopting such a structure, if the radius of curvature of the convex curve formed by the second and third cutting edge portions in the side view is too large, the cutting edge portions become almost linear. If the radius of curvature is too small, the convex curved portion of the cutting edge becomes too small and the above effect cannot be reliably obtained. There is a fear. For this reason,
The radius of curvature of the convex curve formed by these cutting edges in side view is preferably set in the range of 0.1 × D to 3.0 × D with respect to the outer diameter D of the cutting edges.

[0012]

FIG. 1 to FIG. 3 show an embodiment of the present invention. In these drawings, on the outer periphery of the drill body 1, a pair of twists are formed from the tip flank 2 facing the tip side toward the rear side in the drill rotation direction (counterclockwise direction in FIG. 1) toward the base end side. The chip discharge grooves 3 and 3 are formed symmetrically with respect to the rotation axis O of the drill body 1. Then, the wall surfaces 3A, 3A facing the drill rotation direction side of the chip discharge grooves 3, 3 and the tip flank 2
Cutting edges 4 and 4 extending from the drill rotation center C at the tip of the drill body 1 to the outer circumference of the drill are formed at the intersection of the tip flank 2 and the axis O.

However, in this embodiment, the cutting edge 4 is
It is composed of first, second, and third three cutting edge portions 4A, 4B, 4C which are continuous from the outer peripheral side toward the drill rotation center C. Of these, the first located on the outer peripheral side of the drill
The cutting edge portion 4A is linearly formed as shown in FIG.
It is arranged slightly above the center. In addition, the second cutting edge portion 4B connected to the inner peripheral side of the first cutting edge portion 4A.
In the present embodiment, when viewed from the front end in the direction of the axis O, it is formed in a convex curve shape protruding toward the drill rotation direction side with respect to the virtual extension line L to the inner peripheral side of the first cutting edge portion 4A, That is, it is formed so as to face the inner circumference side from the first cutting edge portion 4A and then to rise toward the drill rotation center C in the shape of an arcuate mountain. In the present embodiment, this second
The curvature radius R ₂ of the convex curve formed by the cutting edge portion 4B of
The diameter of the circle formed by the outer peripheral edge of the cutting edge portion 4A around the drill rotation center C, that is, with respect to the outer diameter D of the cutting edge 4 of the drill, is set in the range of 0.5 × D to 4.0 × D. Has been done.

The third cutting edge portion 4C formed further on the inner peripheral side of the second cutting edge portion 4B is the second cutting edge portion 4
Contrary to B, it is formed so as to draw a concave curve dented rearward in the drill rotation direction in the end view in the direction of the axis O, and extends from the intersection point P with the second cutting edge portion 4B to the drill rotation center C. The third cutting edge portions 4C and 4C of the pair of cutting edges 4 and 4 formed at the tip of the drill body 1 are smoothly continuous so that the tangent lines at the drill rotation center C coincide with each other. . Here, the third cutting edge portion 4C has the axis O
The curvature radius R ₃ of the concave curve formed in the front end view in the direction is 0.1 × D to 0.1 with respect to the outer diameter D of the cutting edge 4 in the present embodiment.
It is set in the range of 3 × D. Further, the range in which the third cutting edge portion 4C is formed is only in the very vicinity of the drill rotation center C, and in the present embodiment, the intersection point P is around the drill rotation center C in the axial line O direction tip view. The diameter d of the circle (see FIG. 3) is set to be in the range of 0.15 × D to 0.30 × D with respect to the outer diameter D of the cutting edge 4.

In this embodiment, the second cutting edge portion 4 is used.
B and the third cutting edge portion 4C are formed smoothly and continuously so that the tangents to each other at the intersection point P coincide with each other. Further, the first cutting edge portion 4A and the second cutting edge portion 4B are
They are connected via a concave curved portion 4D that is in contact with both cutting edge portions 4A and 4B. Further, on the outer circumference of the drill body 1, along the ridge line portion on the outer circumference side of the wall surface 3A of the chip discharge groove 3 which faces the drill rotation direction, on a cylindrical surface having an outer diameter equal to the outer diameter D of the cutting blade. A margin 5 is formed so as to extend. Further, the portion from the margin 5 to the heel on the rear side in the drill rotation direction is an outer peripheral flank 6 slightly recessed inward from the cylindrical surface.

On the other hand, in a side view from a radial direction (arrow X direction in FIG. 1) with respect to the axis O, which is orthogonal to a plane parallel to the axis O including the linear first cutting edge portion 4A, FIG.
As shown in FIG. 3, the cutting edge 4 projects so that the second and third cutting edge portions 4A, 4B on the inner peripheral side of the cutting edge 4 form an arc toward the tip side in the axis O direction toward the drill rotation center C side. It is formed in a convex curve shape. On the other hand, the first
The cutting edge portion 4A is formed in a linear shape that inclines toward the base end side in the direction of the axis O as it goes toward the outer peripheral side of the drill even in a side view. Here, in the present embodiment, the second,
The curvature radius R _S of the convex curve formed by the third cutting edge portions 4B and 4C in the side view is 0.1 × D to the outer diameter D of the cutting edge 4.
It is set in the range of 3.0 × D. Further, both third cutting edge portions 4C, 4C of the pair of cutting edges 4, 4 are formed so as to be in smooth contact with each other at the drill rotation center C in this side view, and therefore, the cutting at the drill rotation center C is performed. The tangent line of the blade 4 will be orthogonal to the axis O.

In this way, the second and third cutting edge portions 4 are
By making B and 4C have a convex curved shape in a side view, these cutting edge portions 4B and 4 of the tip flank 2 of the drill body 1 are formed.
The portion of C that is continuous with the drill rotation direction side is also formed in a convex curved surface shape that bulges so as to project in the direction of the axis O toward the drill rotation center C side. However, since the flank 2 is provided with a clearance angle, this convex curved surface does not have a spherical shape centered on the axis O, and the cutting edge portions 4B, 4
As it goes away from C and goes rearward in the direction of rotation of the drill, it gradually recedes toward the base end side in the direction of the axis O, and the clearance angle is gradually increased.

However, in the thus constructed drill, the third cutting edge portion 4C located on the inner circumference side of the cutting edge 4 and connected to the drill rotation center C is recessed rearward in the drill rotation direction. Since it is formed in a curved shape, the work material portion scooped by pushing the drill rotation center C at which the peripheral speed becomes 0 at the time of drilling is cut into this concave curved third cutting edge portion 4C. As it is guided, it quickly flows out to the outer peripheral side, reaches the second cutting edge portion 4B, and is generated and discharged as chips. Therefore, it is possible to prevent a situation in which the cut work material portion stays in the vicinity of the drill rotation center C and resists the pushing of the tip of the drill body 1, thereby reducing the force required for pushing and reducing the cutting resistance. It becomes possible. Further, since it becomes possible to quickly remove the work material portion scooped near the drill rotation center C, it is possible to reduce the cutting load acting near the drill rotation center C, This makes it possible to effectively prevent the occurrence of chipping and the promotion of flank wear. Therefore, according to the drill having the above structure, damage to the drill body 1, particularly near the drill rotation center C at the tip, can be prevented and the life of the drill body 1 can be extended.

By the way, in the third cutting edge portion 4C thus formed in a concave curve shape, if the radius of curvature R ₃ of this concave curve is too large, the third cutting edge portion 4C will move in the direction of the axis O. When viewed from the tip, the shape becomes close to a straight line, which may impair the guideability when guiding the processed material portion scooped at the drill rotation center C to the outer peripheral side. On the other hand, if this radius of curvature R ₃ is too small, when the above-mentioned scooped portion is guided by the third cutting edge portion 4c and flows out, its outflow direction can be rapidly changed, and its reaction force On the contrary, there is a possibility that the load acting on the cutting edge portion 4C may be increased. However, in contrast, in this embodiment,
By setting the radius of curvature R ₃ in the range of 0.1 × D to 0.3 × D with respect to the outer diameter D of the cutting edge 4 as described above,
By preventing such an inconvenience from occurring, the cutting resistance is reliably suppressed, and the drill body 1 is prevented from being damaged.

In addition, even if the radius of curvature R ₃ is appropriately set as described above, if the third cutting edge portion 4C is too short, the guideability may not be sufficiently achieved. Even if the third cutting edge portion 4C is too long, since the radial rake angle of the third cutting edge portion 4C is set to the regular angle side, the cutting edge strength of the cutting edge 4 may be impaired. Occurs. However, in the present embodiment, on the other hand, the third cutting edge portion 4C and the second cutting edge portion 4 in the front end view in the direction of the axis O.
The diameter d of the circle that the intersection point P with B makes around the drill rotation center C
Is set to be in the range of 0.15 × D to 0.3 × D with respect to the outer diameter D of the cutting edge 4, and the length of the third cutting edge portion 4C is optimized to provide sufficient guideability. While ensuring the above, the deterioration of the cutting edge strength of the cutting edge 4 is prevented, and the life of the drill is extended more reliably.

Further, in the present embodiment, the second cutting edge portion 4B connected to the outer peripheral side of the third cutting edge portion 4C has a linear cutting edge portion 4A further on the outer peripheral side. When viewed from the front end in the direction of the axis O, it is formed in a convex curve shape projecting toward the drill rotation direction side with respect to the virtual extension line L to the inner peripheral side of the first cutting edge portion 4A, and the second cutting edge portion 4B is the first. It is formed so as to rise in a mountain shape from the first cutting edge portion 4A. This allows
When chips are generated by these cutting blade portions 4A and 4B, appropriate stress is applied to the chips, and when the chips are sent into the chip discharge groove 2 and curled, the stress is generated. It becomes possible to divide the chips into an appropriate length. For this reason, according to the present embodiment, it is possible to smoothly perform processing of chips, for example, for a processed material in which chips tend to be elongated, such as an aluminum material, and to prevent occurrence of chip clogging and the like. It is possible to promote further reduction of cutting resistance.

However, in the present embodiment, the second cutting edge portion 4B is thus projected with respect to the extension line L of the first cutting edge portion 4A to obtain the above effect. As shown in FIG. 4, the first cutting edge portion 4A may be formed so as to contact the second cutting edge portion 4B having a convex curve shape and extend in the tangential direction thereof. However, when such a configuration is adopted, the stress acting on the chips at the time of chip generation can be suppressed as compared with the case of the above-described embodiment, so that, for example, when performing drilling on cast iron, it is easy to be divided. When sheared chips are generated, it is possible to prevent the chips from being excessively divided and the dischargeability of chips being impaired.

On the other hand, in the present embodiment, in the side view with respect to the axis O, the cutting blades 4 are arranged from the third cutting blade portion 4C to the second cutting blade portion 4C.
Is formed in a convex curved shape protruding toward the tip side in the direction of the axis O, whereby the tip angles of the second and third cutting edge portions 4B and 4C are from the outer peripheral side of the drill. It gradually increases toward the inner peripheral side, and reaches the maximum at the drill rotation center C. Therefore, according to the present embodiment,
In the third cutting edge portion 4C near the drill rotation center C, it is possible to obtain the advantage that the edge strength can be secured and chipping and the like can be more reliably prevented.

Further, since the cutting blade portions 4B and 4C are formed in a curved shape even in a side view as described above, it is possible to give a larger stress to the chips produced by these, In particular, in the case where the above-mentioned chips that tend to stretch are generated, it is possible to reliably control the division, and there is an advantage that a smoother chip disposal can be promoted. Moreover, in the present embodiment, the second and third cutting edge portions 4B and 4C are thus formed.
Is formed in a convex curve shape, the first cutting edge portion 4
Since A is formed in a straight line even in a side view, it is possible to apply stress to the chips even between them, and it is also possible to obtain the advantage that more reliable control of chip disposal can be achieved. it can.

Incidentally, these second and third cutting edge portions 4B, 4
If the curvature radius R _S of the convex curve formed by C in the side view is too large, the cutting edge portions 4B and 4C may become nearly linear and the above effect may not be obtained. The tip angles of the parts 4B and 4C are especially the center of rotation C of the drill.
In the vicinity, the cutting edge 4 may become excessively large and the biting of the cutting edge 4 may become unstable, or the pushing force may rather increase, which is not preferable. On the other hand, if the radius of curvature R _S is too small, the convex curved portion in side view becomes too small, and the above effect may not be obtained. Therefore, the curvature radius R _S of the convex curve formed by the cutting edge 4 in a side view is set in the range of 0.1 × D to 3.0 × D with respect to the outer diameter D of the cutting edge as described above. Is desirable.

Further, in the present embodiment, as described above, the pair of cutting blades 4 and 4 are formed at the tip of the drill body 1 symmetrically with respect to the axis O, and the chip discharge grooves 3 and 3 are twisted around the axis O. The case where the present invention is applied to the formed so-called two-blade twist drill has been described, but the shape of the cutting edge of the present invention can also be applied to a drill having one cutting edge. Further, the chip discharge groove may be formed in parallel with the axis O without being twisted. Therefore, the present invention can be applied to, for example, a conventionally known single-blade or straight groove gun drill. It is possible.

[0027]

As described above, according to the present invention,
The part that has been scooped by pushing the drill rotation center at the tip of the drill body into the work material is promptly guided to the outer peripheral side by the third cutting edge part formed on the drill rotation center side of the cutting edge, and eliminated as chips. By doing so, it is possible to reduce the force required to push in the drill body, reduce the cutting load acting on the cutting edge, and suppress chipping and flank wear. For this reason, it is possible to reliably prevent damage to the tip of the drill body, especially near the center of rotation of the drill, and to extend the life of the drill.

[Brief description of drawings]

FIG. 1 is a front view from the front end side showing an embodiment of the present invention.

FIG. 2 is a side view of the embodiment shown in FIG. 1 as viewed in the direction of the arrow X.

FIG. 3 is an enlarged view of the vicinity of a drill rotation center C of the embodiment shown in FIG.

FIG. 4 is a front view from the tip side showing another embodiment of the present invention.

[Explanation of symbols]

1 Drill main body 2 Tip flank surface 3 Chip discharge groove 4 Cutting edge 4A First cutting edge section 4B Second cutting edge section 4C Third cutting edge section O Rotation axis of drill main body C Drill rotation center D Cutting edge 4 Outer diameter P of the intersection of the second and third cutting edge portions 4B and 4C d the diameter of the circle drawn by the intersection point P around the drill rotation center C R ₂ the radius of curvature of the second cutting edge portion 4B R ₃ the third cutting edge Curvature radius of blade 4C

Claims (7)

[Claims] 1. A chip discharge groove extending from a tip of the drill body toward a base end is formed on an outer periphery of a drill body rotated around an axis, and a wall surface facing the drill rotation direction side of the chip discharge groove. In a drill in which a cutting edge extending from the drill rotation center of the drill body toward the outer peripheral side of the drill is formed at a ridge line portion intersecting with a tip flank of the drill body, the cutting edge is viewed in the axial tip direction. In the first cutting edge portion, which is located on the outer peripheral side of the drill and extends linearly,
Second cutting edge portion which is continuous to the inner peripheral side of the cutting edge portion and bulges in the drill rotation direction side and which has a convex curved shape, and is further continuous to the inner peripheral side of the second cutting edge portion, and which is the drill rotation center. A drill having a third cutting edge portion having a concave curved shape that is recessed toward the rear side in the drill rotation direction in the vicinity thereof. 2. The radius of curvature of the concave curve formed by the third cutting edge portion in the axial direction distal end view is in the range of 0.1 × D to 0.3 × D with respect to the outer diameter D of the cutting edge. The drill according to claim 1, wherein the drill is set to. 3. In the axial direction tip end view, the second
The diameter d of the circle formed by the intersection of the cutting edge portion and the third cutting edge portion around the rotation center of the drill is 0.15 × D to 0.3 × D with respect to the outer diameter D of the cutting edge. The drill according to claim 1 or 2, wherein the drill is set in a range. 4. The first portion as viewed in the axial direction end.
4. The drill according to claim 1, wherein the cutting edge portion of the second cutting edge portion is formed so as to contact a convex curve formed by the second cutting edge portion and extend in a tangential direction thereof. . 5. The second portion as viewed in the axial direction end.
4. The cutting edge portion of the first cutting edge portion is formed so as to project toward the drill rotation direction side with respect to an imaginary extension line of the first cutting edge portion toward the inner peripheral side. A drill described in any one of. 6. In a side view from the radial direction with respect to the axis, at least from the third cutting edge portion to the second cutting edge portion, a convex curved shape that swells toward the tip end side in the axial direction toward the inner peripheral side. The drill according to any one of claims 1 to 5, wherein the drill is formed in a circular shape. 7. The radius of curvature of the convex curve formed by the third cutting edge portion in the side view is set in a range of 0.1 × D to 3.0 × D with respect to the outer diameter D of the cutting edge. The drill according to claim 6, wherein the drill is provided.