JP2021088007A - Drill - Google Patents

Abstract

To prevent damage and chipping of a cutting edge by preventing occurrence of crater wear in a part very close to a cutting edge of a rake face without dulling sharpness of the cutting edge or impairing the strength of the cutting edge.SOLUTION: A cutting edge 5 is formed at a ridge line part of an intersection of a tip clearance surface 8 and a wall surface, facing a drill rotation direction T of a chip discharge groove 6, of a drill body 1 rotated in a drill rotation direction T about an axis. The cutting edge 5 has a main cutting-edge part 5a on an outer peripheral side of the drill body 1. Honing is performed on at least part of this main cutting-edge part 5a to form a plurality of steps of honing surfaces 10 forming a straight line in a cross-section orthogonal to the main cutting-edge part 5a as viewed from an axial tip side. In the plurality of steps of honing surfaces 10, the nearer the plurality of steps of honing surfaces 10 to the tip clearance surface 8, the larger an axial rake angle α toward a negative angle side.SELECTED DRAWING: Figure 4

Description

In the present invention, a chip discharge groove that opens to the tip flank surface of the drill body and extends to the rear end side is formed on the outer periphery of the tip portion of the drill body that is rotated in the direction of rotation of the drill around the axis, and the drill of this chip discharge groove It relates to a drill in which a cutting edge is formed at an intersecting ridgeline portion between a wall surface facing the rotation direction and a tip flank surface.

As such a drill, for example, in Patent Document 1, a chip discharge groove is formed on the outer periphery of the tip portion of the drill body rotated around the axis, and the wall surface of the chip discharge groove facing the drill rotation direction and the tip escape of the drill body. A drill in which a cutting edge is formed at the intersection ridge with the surface, and this cutting edge is a main cutting edge extending from the outer peripheral end of the cutting edge to the inner peripheral side and a wall surface facing the drill rotation direction of the chip discharge groove. A thinning blade formed so as to cut out the inner peripheral portion on the axis side is provided with a thinning blade formed at the intersecting ridgeline portion between the thinning surface facing the drill rotation direction of the thinning portion and the tip flank surface and connected to the inner circumference of the main cutting edge. Is listed.

The thinning blade in the drill described in Patent Document 1 is mainly via a connecting portion having a convex curved shape or a convex curved line formed by a plurality of straight lines in contact with the main cutting blade when viewed from the tip side in the axial direction. Along with being connected to the cutting edge, honing is applied to at least the connecting portion side of the main cutting edge to form a honing surface.

Further, the honing angle of the honing surface is equal to the rake angle of the thinning blade by the thinning surface, and the honing surface and the thinning surface are smoothly continuous. Furthermore, Patent Document 1 also describes that a minute chamfer having a convex cross section with a radius of about 0.01 mm to 0.02 mm is applied to the intersecting ridge line portion between the honing surface and the tip flank surface.

Japanese Unexamined Patent Publication No. 2014-193513

However, in the drill described in Patent Document 1, the honing surface is set to one step as shown in FIG. 3 of Patent Document 1, and if the width of the honing surface is narrow, it is on the honing surface at the time of drilling. The built-up edge generated in the patent becomes smaller, and the chips that have passed over the built-up edge scrape the rake face very close to the intersection ridge with the honing surface. For this reason, crater wear occurs in a portion of the rake face that is extremely close to the cutting edge, which makes it easy for the cutting edge to be chipped or chipped.

Further, in the drill described in Patent Document 1, the axial rake angle (honing angle) of the honing surface is set to 0 ° or a negative angle, but the width of the honing surface is set in such a one-step honing surface. When the width is wide, if the axial rake angle of the honing surface is a negative angle, the sharpness of the cutting edge becomes dull.

On the other hand, when the width of the honing surface is also widened in the same one-step honing surface, if the axial rake angle of the honing surface is 0 ° or an angle close to 0 °, the space between the honing surface and the tip flank surface is reached. The cutting edge angle of the cutting edge becomes smaller, and even if a minute chamfer with a convex cross section is applied to the intersection ridgeline between the honing surface and the tip flank as described above, the cutting edge strength is impaired. Defects and chipping are likely to occur.

The present invention has been made under such a background, and crater wear occurs in a portion of the rake face very close to the cutting edge without dullness of the cutting edge or impairing the cutting edge strength. It is an object of the present invention to provide a drill capable of preventing the cutting edge from being chipped or chipping.

In order to solve the above problems and achieve such an object, the present invention opens an opening on the outer periphery of the tip portion of the drill body which is rotated in the drill rotation direction around the axis and on the tip flank surface of the drill body. A drill in which a chip discharge groove extending to the rear end side is formed, and a cutting edge is formed at an intersection ridge line portion between the wall surface of the chip discharge groove facing the drill rotation direction and the tip flank surface. A main cutting edge portion is provided on the outer peripheral side of the drill body, and at least a part of the main cutting edge portion is honed so as to be orthogonal to the main cutting edge portion when viewed from the tip side in the axial direction. A plurality of steps of honing surfaces forming a straight line in the cross section are formed, and these multiple steps of honing surfaces are formed so that the rake angle in the axial direction becomes larger toward the negative angle side as the honing surface is closer to the tip flank surface. It is characterized by being.

In the drill configured in this way, by honing at least a part of the main cutting edge portion of the cutting edge, a straight line is formed in a cross section orthogonal to the main cutting edge portion when viewed from the tip side in the axial direction. A plurality of horning surfaces having a shape are formed. Since these multi-stage honing surfaces are formed so that the axial rake angle becomes larger toward the negative angle side as the honing surface is closer to the tip flank surface, at least a part of the main cutting edge portion is honed. The blade angle between the honing surface on the most tip flank side and the tip flank can be increased, and the cutting edge strength can be ensured.

On the other hand, the honing surface on the rear end side of the drill body is larger than the honing surface on the most tip flank side, because the axial rake angle is larger on the conformal side than the honing surface on the most tip flank side. The sharpness of the cutting edge can be sharpened in at least a part of the cutting edge portion that has been honed. Therefore, the cutting resistance can be reduced.

Further, in the drill having the above configuration, by forming the honing surface in a plurality of stages in this way, the width in the cross section orthogonal to the main cutting edge portion when viewed from the tip side in the axial direction of the entire honing surface can be obtained. It can be secured large. Therefore, it is possible to increase the built-up edge generated on the honing surface during drilling, and the chips that have run on the built-up edge are separated from the intersecting ridge of the rake face with the honing surface toward the rear end side of the drill body. You can guide to the position.

Therefore, even if crater wear occurs due to such chips scraping the rake face, the position where the crater wear occurs is separated from the intersecting ridge of the rake face with the honing surface to the rear end side of the drill body. It is possible to prevent chipping and chipping in the honed portion of the main cutting edge portion. Therefore, according to the drill having the above configuration, it is possible to perform stable drilling for a long period of time.

Further, by making the width of the honing surface of the plurality of stages in the cross section orthogonal to the main cutting edge portion when viewed from the tip side in the axial direction wider as the honing surface is farther from the tip flank surface, the axial direction is obtained. The built-up edge generated on the honing surface away from the tip flank with a large rake angle on the conformal side can be made larger.

Therefore, the chips that have passed over the built-up edge can be guided to a position further away from the intersecting ridge of the rake face with the honing surface to the rear end side of the drill body, so that the honing of the main cutting edge can be performed. It is possible to more reliably prevent defects and chipping in the applied portion.

On the other hand, a thinning portion is formed by applying thinning to the inner peripheral portion of the tip of the chip discharge groove, and the cutting edge has a thinning rake surface facing the drill rotation direction of the thinning portion and the tip relief. When a thinning blade portion connected to the inner peripheral side of the main cutting blade portion is formed at the intersecting ridge line portion with the surface, the axial rake angle of the thinning rake face is either positive or negative. Although it may be present, it is larger on the conformal side than the axial rake angle of the honing surface closest to the tip flank surface among the multiple-stage honing surfaces, and is larger than the axial rake angle of the rake surface of the main cutting edge portion. Is desirable to be large on the negative angle side.

If the axial rake angle of this thinning rake face is larger than the axial rake angle of the honing surface closest to the tip flank surface among the multiple-stage honing surfaces, the cutting resistance due to the thinning blade becomes too large. Therefore, even if a thinning portion is formed on the inner peripheral portion of the tip of the chip discharge groove, the thrust load may increase significantly. Further, if the axial rake angle of the thinning rake face is larger on the conformal side than the axial rake angle of the rake face of the main cutting edge portion, the cutting edge angle of the thinning cutting edge may become too small and cause a defect. is there.

Further, at the outer peripheral end of the main cutting edge portion, the direction of rotation of the drill is the rake surface of the main cutting edge portion, and the direction of rotation of the drill with respect to the rake face of the main cutting edge portion toward the outer peripheral side of the tip of the drill body. By forming the chamfered portion that is inclined to the opposite side, it is possible to prevent the main cutting edge portion from being chipped at the outer peripheral end portion that is the edge of the main cutting edge portion.

As described above, according to the present invention, in the honed portion of the main cutting edge portion of the cutting edge, sharp sharpness is given to reduce cutting resistance, and the cutting edge angle is secured to ensure the cutting edge. The strength can be maintained, and the crater wear due to scraping of chips can be set at a position away from the cutting edge of the rake face, and it is possible to prevent the cutting edge from being chipped or chipped.

It is a side view which shows the 1st Embodiment of this invention. It is an enlarged side view of the tip part of the embodiment shown in FIG. It is an enlarged front view which looked at the embodiment shown in FIG. 1 from the tip side in the axial direction. FIG. 3 is a cross-sectional view of YY in FIG. 3 (a cross-sectional view orthogonal to the main cutting edge portion when viewed from the tip side in the axial direction of the drill body). FIG. 3 is a ZZ cross-sectional view (cross-sectional view orthogonal to the thinning blade portion when viewed from the tip side in the axial direction of the drill body) in FIG. FIG. 5 is a cross-sectional view corresponding to the YY cross-sectional view in FIG. 3 in the first modification of the first embodiment of the present invention. FIG. 5 is a cross-sectional view corresponding to the ZZ cross-sectional view in FIG. 3 in the second modification of the first embodiment of the present invention. It is an enlarged side view of the tip part of the 3rd modification of the 1st Embodiment of this invention. FIG. 8 is an enlarged front view of a modified example shown in FIG. 8 as viewed from the tip side in the axial direction. It is an enlarged side view of the tip part of the 4th modification of the 1st Embodiment of this invention. It is an enlarged front view seen from the tip side in the axial direction of the modification shown in FIG. It is a side view which shows the 2nd Embodiment of this invention. It is an enlarged side view of the tip part of the embodiment shown in FIG. It is an enlarged front view which looked at the embodiment shown in FIG. 12 from the tip side in the axial direction.

1 to 5 show a first embodiment of the present invention. In the present embodiment, the drill body 1 is integrally formed of a hard material such as cemented carbide in a substantially multi-stage columnar shape centered on the axis O. Of the drill body 1, the rear end portion (the right portion in FIG. 1) having a large outer diameter is a shank portion 2 having a columnar outer shape, and has an outer diameter larger than that of the shank portion 2. The tip portion (the left portion in FIG. 1) formed to have a smaller diameter is the cutting edge portion 3.

Further, in the present embodiment, the portion between the shank portion 2 and the cutting edge portion 3 of the drill body 1 is centered on the axis O whose outer diameter gradually decreases at a constant rate toward the tip end side of the drill body 1. The tapered neck portion 4 has a truncated cone shape. 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 causing the cutting edge portion. The work material is drilled by the cutting edge 5 formed in 3.

A chip discharge groove 6 is formed on the outer periphery of the cutting edge portion 3 at the tip of the drill body 1 so as to open in the tip surface of the drill body 1 and twist in the direction opposite to the drill rotation direction T toward the rear end side. Is formed symmetrically with respect to the axis O. The cutting edge 5 is formed on the tip side edge portion of the inner wall surface of these chip discharge grooves 6 facing the drill rotation direction T. Therefore, the tip of the wall surface of the chip discharge groove 6 facing the drill rotation direction T is the rake face 7 of the cutting edge 5, and the tip surface of the drill body 1 connected to the rake face 7 is the tip relief of the cutting edge 5. It is designated as surface 8. The drill body 1 is 180 ° rotationally symmetric with respect to the axis O.

The tip flank surface 8 includes first and second tip flank surfaces 8a and 8b in which the clearance angle gradually increases from the cutting edge 5 toward the side opposite to the drill rotation direction T. Further, the tip flank surface 8 is inclined toward the rear end side toward the outer peripheral side of the drill body 1, whereby the cutting edge 5 is provided with a tip angle of 180 ° or less in the present embodiment. .. Further, on the outer peripheral surface of the cutting edge portion 3, two margin portions 3a connected to the drill rotation direction T side and the side opposite to the rotation direction T of the chip discharge groove 6 are formed, and these two margin portions 3a are formed. An outer peripheral flank surface (second surface) 3b is formed between the two.

Further, in the present embodiment, two coolant holes 1a are formed in the drill body 1 from the rear end surface of the shank portion 2 toward the tip end side in the same number as the chip discharge groove 6. These coolant holes 1a are twisted in the direction opposite to the drill rotation direction T toward the rear end side of the drill body 1 with a lead equal to the chip discharge groove 6, and are also symmetrical with respect to the axis O like the chip discharge groove 6. It is formed. These coolant holes 1a extend between the two chip discharge grooves 6 in the cutting edge portion 3, respectively, and open in the second tip flank surface 8b of the tip flank surfaces 8 in the tip surface of the drill body 1. doing.

Further, the inner peripheral portion of the tip of the chip discharge groove 6 is thinned so that the inner peripheral portion of the rake face 7 of the cutting edge 5 is cut out toward the axis O side, and the concave groove-shaped thinning portion 9 is formed. Is formed. The thinning portion 9 extends from the inner peripheral portion of the tip of the rake face 7 by cutting out the tip portion of the wall surface facing the side opposite to the drill rotation direction T of the chip discharge groove 6 so as to reach the outer periphery of the cutting edge portion 3. ing.

Furthermore, the cutting edge 5 includes a main cutting edge portion 5a on the outer peripheral portion of the drill body 1 and a thinning blade portion 5b on the inner peripheral portion. In the present embodiment, the main cutting edge portion 5a extends in a straight line as shown in FIG. 3 when viewed from the tip side in the O direction of the axis line, and the portion of the rake face 7 connected to the main cutting edge portion 5a is the main cutting edge rake. It is the surface 7a. As shown in FIG. 3, the straight line formed by the main cutting edge portion 5a when viewed from the tip side in the axis O direction is formed so as to be located on the drill rotation direction T side of the straight line parallel to this straight line and passing through the axis O. ..

Further, the thinning blade portions 5b are connected in a convex curve on the inner peripheral portion of the main cutting blade portion 5a as shown in FIG. 3 when viewed from the tip side in the O-direction of the axis, and move toward the inner peripheral side toward the axis O side. It extends straight toward you. The wall surface of the thinning portion 9 facing the drill rotation direction T is a thinning rake surface 7b connected to the thinning blade portion 5b.

Then, by applying honing to at least a part of the main cutting edge portion 5a, the cross section orthogonal to the main cutting edge portion 5a when viewed from the tip side in the O direction of the axis is linear as shown in FIG. A plurality of stages of honing surfaces 10 are formed. In the present embodiment, the entire length of the main cutting edge portion 5a is honed, and the first and second two-stage honing surfaces 10a and 10b are formed. In the cross-sectional view shown in FIG. 4 and the cross-sectional view shown in FIGS. 5 to 7 described later, the reference numeral O1 is shown in the cross-sectional view showing the reference of the axial rake angles α, β, γ, δ, and θ. It is a straight line parallel to the axis O.

Further, in these multi-stage honing surfaces 10, the axial rake angle α of the first honing surface 10a closer to the tip flank surface 8 is the axial rake angle of the second honing surface 10b away from the tip flank surface 8. It is formed so as to be larger on the negative angle side than β. In the present embodiment, the axial rake angles α and β of the first and second honing surfaces 10a and 10b are both negative angles, that is, the first and second honing surfaces 10a and 10b are the drill body 1. It is inclined toward the T side in the drill rotation direction toward the rear end side. The axial rake angle γ of the main cutting edge rake face 7a is a conformal angle.

The axial rake angle α of the first honing surface 10a is preferably in the range of 5 ° to 30 °, and the axial rake angle β of the second honing surface 10b is preferably in the range of −5 ° to 20 °. The axial rake angle γ of the main cutting edge rake face 7a on the outermost peripheral portion of the cutting edge portion 5a is preferably in the range of 10 ° to 40 °.

Further, the width of these plurality of honing surfaces 10 in the cross section orthogonal to the main cutting edge portion 5a when viewed from the tip side in the O-direction of the axis is larger than the width W1 of the first honing surface 10a close to the tip flank surface 8. The width W2 of the second honing surface 10b away from the tip flank surface 8 is wide.

The width W1 in the direction parallel to the axis O of the first honing surface 10a (the direction of the straight line O1 in FIG. 4) is the diameter of the cutting edge 5 (the diameter of the circle formed by the outer peripheral end of the cutting edge 5 around the axis O). It is desirable that the range is 0.002 × D to 0.05 × D with respect to D, and the width W2 in the direction parallel to the axis O of the second honing surface 10b is also with respect to the diameter D of the cutting edge 5. It is desirable that the range is 0.002 × D to 0.05 × D.

Further, the thinning blade portion 5b is also honed to form a thinning honing surface 10c. The thinning honing surface 10c has one step in the present embodiment, and the axial rake angle δ of the thinning honing surface 10c is a negative angle. The axial rake angle θ of the thinning rake face 7b may be either a positive angle or a negative angle, but in the present embodiment, it is a negative angle as shown in FIG.

However, the axial rake angle θ of the thinning rake face 7b is the axial direction of the first honing surface 10a closest to the tip flank surface 8 among the plurality of honing surfaces 10 regardless of whether the angle is positive or negative. It is desirable that the rake angle α is made larger on the conformal side and the main cutting edge rake surface 7a is made larger on the negative angle side than the axial rake angle γ. That is, it is desirable that α <θ <γ.

In the present embodiment, the thinning rake face 7b of the thinning blade portion 5b is continuous with the second honing surface 10b of the main cutting blade portion 5a. Further, the thinning honing surface 10c of the thinning blade portion 5b is continuous with the first honing surface 10a of the main cutting blade portion 5a.

In the drill configured as described above, when at least a part (total length in the present embodiment) of the main cutting edge portion 5a of the cutting edge 5 is honed, when viewed from the tip side in the O-direction of the axis line. As shown in FIG. 5, a plurality of stages of honing surfaces 10 forming a straight line are formed in a cross section orthogonal to the main cutting edge portion 5a of the above, and these multi-stage honing surfaces 10 are close to the tip flank surface 8. The honing surface 10a of No. 1 is formed so that the axial rake angle α becomes larger on the negative angle side.

Therefore, it is possible to increase the blade angle between the first honing surface 10a on the most tip flank 8 side and the tip flank 8 in at least a part of the main cutting edge portion 5a that has been honed. Therefore, it is possible to secure the cutting edge strength of at least a part of the main cutting edge portion 5a, and it is possible to prevent the occurrence of chipping and chipping.

On the other hand, the second honing surface 10b on the rear end side of the drill body 1 with respect to the first honing surface 10a on the most tip flank 8 side has an axial rake angle β on the most tip flank 8 side. It becomes larger on the conformal side than the honing surface 10a of 1. Therefore, the sharpness of the cutting edge 5 can be sharpened in at least a part of the main cutting edge portion 5a that has been honed, so that the cutting resistance can be reduced.

Further, in the drill having the above configuration, by forming the first and second plurality of honing surfaces 10a and 10b in this way, when viewed from the tip side of the entire honing surface 10 in the axial direction O direction. It is possible to secure a large width in the cross section orthogonal to the main cutting edge portion 5a.

Therefore, since the built-up edge generated on the honing surface 10 at the time of drilling can be increased, the chips that have run on the built-up edge can be used as the main cutting edge rake face 7a and the honing surface 10 (second honing surface). It is possible to guide the drill body 1 to a position away from the intersecting ridge line portion of 10b) toward the rear end side.

Therefore, even if crater wear occurs due to the chips that have passed over the constituent cutting edges scraping the main cutting edge rake face 7a, the positions where this crater wear occurs are the main cutting edge rake face 7a and the honing surface 10. It is a position away from the crossing ridge line portion of the drill body 1 toward the rear end side. For this reason, it is possible to prevent chipping and chipping in the honed cutting edge portion of the main cutting edge portion 5a due to such crater wear, so that stable drilling can be performed over a long period of time. It will be possible.

Further, in the present embodiment, the widths W1 and W2 of the first and second plurality of honing surfaces 10 in the cross section orthogonal to the main cutting edge portion 5a when viewed from the tip side in the O-direction of the axis are the tip flanks 8. It is said to be as wide as the second honing surface 10b away from. Therefore, the built-up edge generated on the second honing surface 10b in which the axial rake angle β away from the tip flank surface 8 is large on the conformal side can be made larger.

Therefore, the chips that have passed over the built-up edge can be guided to a position further away from the intersecting ridge line portion of the main cutting edge rake face 7a with the honing surface 10 toward the rear end side of the drill body 1, and thus this embodiment. According to the above, it is possible to more reliably prevent chipping and chipping in the honed portion of the main cutting edge portion 5a.

On the other hand, in the present embodiment, the thinning portion 9 is formed by applying thinning to the inner peripheral portion of the tip of the chip discharge groove 6, and the cutting edge 5 is provided with the drill rotation direction T of the thinning portion 9. A thinning blade portion 5b connected to the inner peripheral side of the main cutting blade portion 5a is formed at the intersecting ridge line portion between the facing thinning rake surface 7b and the tip flank surface 8.

Then, the axial rake angle θ of the thinning rake surface 7b is more regular than the axial rake angle α of the first honing surface 10a closest to the tip flank surface 8 of the plurality of stages of honing surfaces 10 as described above. By making it larger on the side and larger on the negative angle side than the axial rake angle γ of the main cutting edge rake face 7a, it is possible to reliably reduce the thrust load while preventing the thinning blade portion 5b from being damaged.

That is, when the axial rake angle θ of the thinning rake face 7b is larger than the axial rake angle α of the first honing surface 10a closest to the tip flank surface 8 among the plurality of honing surfaces 10 on the negative angle side. The cutting resistance of the thinning blade portion 5b becomes too large, and even if the thinning portion 9 is formed on the inner peripheral portion of the tip of the chip discharge groove 6, the thrust load may increase remarkably.

On the other hand, conversely, if the axial rake angle θ of the thinning rake face 7b is larger than the axial rake angle γ of the main cutting edge rake face 7a of the main cutting edge portion 5a on the conformal side, the thinning blade portion 5b The blade angle may become too small. Therefore, the thinning blade portion 5b may be defective.

Next, FIG. 6 shows a first modification of the first embodiment shown in FIGS. 1 to 5, and is a cross-sectional view corresponding to the YY cross-sectional view in FIG. In the first embodiment, the axial rake angles α and β of the first and second honing surfaces 10a and 10b of the plurality of honing surfaces 10 are both negative angles, whereas this first modification Then, the axial rake angle β of the second honing surface 10b is set to 0 °. In the first modification, the second to fourth modifications described later, and the second embodiment, the same reference numerals are given to the parts common to the first embodiment, and the description thereof will be omitted. ..

FIG. 7 shows a second modification of the first embodiment shown in FIGS. 1 to 5, and is a cross-sectional view corresponding to the ZZ cross-sectional view in FIG. In the first embodiment, the axial rake angle θ of the thinning rake face 7b is set to a negative angle, whereas in this second modification, the axial rake angle θ of the thinning rake face 7b is set to 0 °. ing. Also in these first and second modifications, the multi-stage honing surface 10 is formed so that the axial rake angle α becomes larger toward the negative angle side as the first honing surface 10a closer to the tip flank surface 8. Thereby, the same effect as that of the first embodiment can be obtained.

The multi-stage honing surface 10 of the main cutting edge portion 5a may have any number of stages as long as it is formed so that the rake angle in the axial direction becomes larger toward the negative angle side as it is closer to the tip flank surface 8. However, if the number of steps is increased, the honing surface 10 may become close to an arc shape in the cross section, and the above-mentioned effect may not be sufficiently obtained. Therefore, the number of stages of the plurality of honing surfaces 10 is limited to about 2 or 3 as in the first embodiment shown in FIG. 4 and the first modification shown in FIG. desirable.

8 and 9 show a third modification of the first embodiment. In the first embodiment shown in FIGS. 1 to 5, a coolant hole 1a is formed in the drill body 1 and is opened in the second tip flank surface 8b of the tip flank 8. In the third modification, the coolant hole 1a is not formed.

Further, FIGS. 10 and 11 show a fourth modification of the first embodiment. In the first embodiment, the main cutting edge portion 5a of the cutting edge 5 extends in a straight line as shown in FIG. 3 when viewed from the tip side in the O-direction of the axis, whereas in this fourth modification, the main cutting edge portion 5a extends in a straight line. As shown in FIG. 10, a chamfer 11 is formed on the main cutting edge rake face 7a at the outer peripheral end of the main cutting edge 5a so as to be inclined in the direction opposite to the drill rotation direction T toward the outer peripheral side of the tip of the drill body 1. As a result, the main cutting edge portion 5a is also on the side opposite to the drill rotation direction T with respect to the main cutting edge rake face 7a as the outer peripheral end portion thereof faces the outer peripheral side of the drill body 1 as shown in FIG. It is characterized in that it is formed in the shape of a fold line that slopes toward.

In the drill of the fourth modified example configured in this way, the main cutting edge portion 5a extending linearly by the plurality of stages of honing surfaces 10 formed on at least a part of the main cutting edge portion 5a is chipped or chipped. Of course, the chamfered portion 11 formed at the outer peripheral end portion of the main cutting edge portion 5a can surely prevent the chipping and chipping of the outer peripheral end portion.

At the outer peripheral end of the main cutting edge portion 5a on which the chamfered portion 11 is formed, the chamfered portion 11 can prevent defects and chipping in this way, so that the honing surface 10 in a plurality of stages is not formed. May be good. In this case, the multi-stage honing surface 10 is formed on a part of the main cutting edge portion 5a.

Furthermore, FIGS. 12 to 13 show a second embodiment of the present invention. In the first embodiment shown in FIGS. 1 to 5, the tip flank surface 8 is inclined toward the rear end side toward the outer peripheral side of the drill body 1, and is less than 180 ° on the cutting edge 5. Whereas the tip angle was given, in this second embodiment, the tip angle of the cutting edge 5 is approximately 180 °, indicating a case where the present invention is applied to a drill for counterbore drilling. ing.

Also in this second embodiment, the coolant hole 1a is not formed as in the third modification. Further, in the second embodiment, the chamfered portion 11 is formed at the outer peripheral end portion of the main cutting edge portion 5a as in the fourth modification. However, as shown in FIG. 14, the main cutting edge portion 5a and the main cutting edge rake face 7a of the second embodiment are formed so as to be concave in the direction opposite to the drill rotation direction T, and are chamfered portions. Reference numeral 11 denotes a flat surface parallel to the axis O, which is inclined to the side opposite to the drill rotation direction T with respect to the main cutting edge rake face 7a.

Even in such a drill of the second embodiment, at least a part of the main cutting edge portion 5a has a plurality of stages in which the axial rake angle α is larger toward the negative angle side as the first honing surface 10a closer to the tip flank surface 8. By forming the honing surface 10, it is possible to prevent the main cutting edge portion 5a from being chipped or chipped.

In particular, in a drill for counterbore drilling as in the second embodiment, the tip angle of the main cutting edge portion 5a is set to approximately 180 °, and the main cutting edge portion 5a and the thinning blade portion 5b are machined at once. Since it bites into the material, it is effective against the fact that chipping and chipping are likely to occur due to the action of an impact load. The tip angle of the main cutting edge portion 5a of such a counterbore drill may be in the range of 160 ° to 180 °.

1 Drill body 1a Coolant hole 2 Shank part 3 Cutting edge part 3a Margin part 3b Outer peripheral relief surface 4 Tapered neck part 5 Cutting edge 5a Main cutting edge part 5b Thinning blade part 6 Chip discharge groove 7 Squeeze surface 7a Main cutting edge rake surface 7b Thinning rake face 8 Tip flank surface 9 Thinning part 10 Honing surface 10a First honing surface 10b Second honing surface 10c Thinning honing surface 11 Chamfering part O Axis of drill body 1 T Drill rotation direction α First honing surface 10a Axial rake angle β Axial rake angle of the second honing surface 10b γ Axial rake angle of the main cutting edge rake surface 7a δ Axial rake angle of the thinning honing surface 10c θ Axial rake angle of the thinning rake surface 7b W1 Axial line Width in the direction parallel to the axis O of the first honing surface 10a in the cross section orthogonal to the main cutting edge portion 5a when viewed from the tip side in the O direction W2 The main cutting edge portion 5a when viewed from the tip side in the O direction of the axis. Width in the direction parallel to the axis O of the second honing surface 10b in a cross section orthogonal to

Claims (4)

A chip discharge groove that opens to the tip flank surface of the drill body and extends to the rear end side is formed on the outer periphery of the tip portion of the drill body that is rotated in the direction of drill rotation around the axis, and the drill rotation direction of this chip discharge groove is defined. A drill in which a cutting edge is formed at the intersection ridgeline between the facing wall surface and the tip flank surface.
The cutting edge is provided with a main cutting edge portion on the outer peripheral side of the drill body, and at least a part of the main cutting edge portion is honed so that the main cutting edge is viewed from the tip side in the axial direction. A multi-stage honing surface forming a straight line is formed in a cross section orthogonal to the blade portion.
The drill is characterized in that these multi-stage honing surfaces are formed so that the rake angle in the axial direction becomes larger toward the negative angle side as the honing surface is closer to the tip flank surface. The claim is characterized in that the width of the honing surface of the plurality of stages in the cross section orthogonal to the main cutting edge portion when viewed from the tip side in the axial direction is wider as the honing surface is farther from the tip flank surface. The drill according to 1. A thinning portion is formed by applying thinning to the inner peripheral portion of the tip of the chip discharge groove.
In the cutting edge, a thinning blade portion connected to the inner peripheral side of the main cutting edge portion is formed at an intersecting ridge line portion between the thinning rake surface facing the drill rotation direction of the thinning portion and the tip flank surface.
The axial rake angle of the thinning rake face is larger on the conformal side than the axial rake angle of the honing surface closest to the tip flank surface among the plurality of stages of honing surfaces, and the rake angle of the main cutting edge portion The drill according to claim 1 or 2, wherein the drill is larger on the negative angle side than the axial rake angle. On the outer peripheral end of the main cutting edge portion, the rake surface of the main cutting edge portion is on the side opposite to the drill rotation direction with respect to the rake surface of the main cutting edge portion toward the outer peripheral side of the tip of the drill body. The drill according to any one of claims 1 to 3, wherein a chamfered portion inclined to the surface is formed.

Images