JP2009000806A - Drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drill with high machining accuracy by effectively preventing generation of riding up P of a front surface layer and whisker burrs Q of a rear surface layer to be a problem of a composite material including a difficult-to-cut material such as a CFRP (carbon fiber reinforced plastic). <P>SOLUTION: In this drill, a torsional flute 3 having a prescribed lead angle β is formed on an outer peripheral surface of a drill main body 1, and a cutting blade 5 formed by a point angle α on a tip end surface is provided. Each tip end lead part 3a in which a tip end lead angle βa of the torsional flute 3 is set to be a fixed value in the range of an angle of -10° to +10° smaller than the lead angle β is formed in each of tip end head portions 10 and 20 of the drill main body 1. By setting an outer peripheral rake angle θ, an outer peripheral blade part 5a having a sharp cutting edge shape is formed in the cutting blade 5, and a ridge line of the cutting blade 5 is formed into a recessed curved line shape. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a drill, and more particularly to a drill useful for application to a composite material in which materials including difficult-to-cut materials such as carbon fiber reinforced resin (CFRP), which are frequently used as aircraft materials, are laminated. The present invention relates to an improvement in a twist drill having a twisted lead groove formed on a surface and a cutting blade formed on a tip surface with a tip angle.

In general, when drilling with a composite material W containing a difficult-to-cut material such as CFRP, which is frequently used as a major part of an aircraft, as a workpiece (material to be drilled), the fluffing of carbon fibers causes the problem in FIG. As shown, there were problems in processing accuracy and quality, such as a state P in which the periphery of the hole on the front surface was rolled up and a state Q in which the burrs were protruded around the hole on the back surface.
In order to solve the above problems, conventionally, a back taper portion that changes the outer diameter of the drill body is formed, and an improvement in which the tip angle is changed in two steps with respect to the lead angle of the twisted lead groove (Patent Document 1), or A substantially crescent-shaped main cutting edge is formed on the circumferential surface of both sides around the centering cutting edge, the tip of which forms an arc with respect to the drilled surface, and a cutting edge is formed between the centering cutting edge and the main cutting edge. The improvement (patent document 2) etc. etc. in which they became a substantially M-shaped blade-tip shape seeing from the front etc. were seen.

Further, the inventors of the present application have developed and filed a drill particularly suitable for drilling a high-strength fiber composite material, for example, an antenna substrate of a millimeter wave radar antenna (Patent Document 3: Japanese Patent Application No. 2005-338841). ).
The basic structure of this prior application drill is that a pair of cutting blades and a flank formed by the tip angle are formed at the tip of the drill body. The outer peripheral shoulder of the flank is a curved surface with a rounded chamfer. The blade and the torsion lead groove near the shoulder are provided with a scooping portion, and the ridge line of the cutting blade is formed in a concave curve shape from the tip portion toward the outer peripheral end and a curved shape subsequent thereto, and the cutting blade as a whole is an S-curve in side view. In this way, the surface layer is rolled up to prevent wrinkles remaining in the holes and lower burrs from occurring on the back layer.

Japanese Utility Model Publication No.59-33546 JP-A-8-71824 Japanese Patent Application No. 2005-338841

  However, in the prior arts of Patent Document 1 and Patent Document 2 described above, a sufficiently effective solution can be obtained for the occurrence of the bulging P and the burrs Q of tough fibers when the CFRP material W is drilled. Even when the prior art of Patent Document 3 is adopted, when applied to the CFRP material W, it is possible to prevent the generation of wrinkles remaining in the holes and wrinkle burrs Q on the back surface layer, but the surface layer is swollen. It was not enough to prevent P.

In view of the above-described conventional circumstances, the present invention is based on the further improvement of the drill disclosed in Patent Document 3, and the surface layer bulge P and the back surface burrs, which were problems with composite materials containing difficult-to-cut materials such as CFRP. An object is to provide a drill with high machining accuracy by effectively preventing the generation of Q.
Another object of the present invention is to improve the manufacturability and durability of the drill by improving the structure and material of the tip head portion of the drill body.

The present invention provides a drill having a torsional lead groove having a predetermined lead angle β on the outer peripheral surface of the drill body and a cutting edge formed by the tip angle on the tip surface. A tip lead portion having a tip lead angle βa of the torsion lead groove set to a constant value in a range of −10 ° to + 10 ° smaller than the lead angle β is formed, and the cutting edge is set on the cutting edge by setting an outer peripheral scooping angle. An outer peripheral blade portion having a sharp shape is formed, and a ridge line of the cutting blade is formed in a concave curve shape (Claim 1). That is, the general twist lead groove is constant up to the tip, and the lead angle β is 20 ° to 30 °, and the tip lead angle βa is changed to an angle of −10 ° to + 10 °. The second feature is that the outer edge portion is sharpened and the cutting edge ridge is formed into a concave curve.
The second feature is a configuration in which the prior application invention of Patent Document 3 is substantially applied, and the first feature is a configuration in which the prior application invention is improved or changed.

  According to the first feature, since the force component acting in the radial direction of the tip lead portion 3a in the initial stage of the drilling process is oriented toward the thrust direction, the rounding up by the outer peripheral blade portion and the subsequent tip lead portion is suppressed. In addition, according to the second feature, the chip remains in a ring shape in the concave curve of the cutting edge ridgeline immediately before drilling, and is maintained in a substantially intact state. Since it is cut off at or immediately after that, the fiber member at the hole exit portion is surely cut.

And as for the concrete structure of the said outer periphery blade part, a sharp blade edge | tip shape is formed by setting an outer periphery scoop angle to 20 degrees-40 degrees (Claim 2). This sharp outer peripheral blade portion may be either formed by scooping using a grindstone, or formed by molding, such as an edge head with a replaceable blade tip described later. However, when the outer peripheral edge is formed by the former scooping process, the concave curve of the tip cutting edge ridge line is necessarily formed simultaneously.
In addition, the tip cutting blade may have a two-blade structure in which the cutting blades are respectively disposed at diametrically opposed positions, but it is preferably a three-blade capable of stable drilling by centripetalness compared to the two-blade structure. (Claim 3).
Further, the tip angle forming the tip cutting edge of the drill body is typically 118 ° to 130 °, but in order to make the concave curve of the cutting edge ridge line more effective, the tip angle is 140 °. It is preferable to set it as (degree)-150 degrees (Claim 4). However, in the case of a three-blade structure, the cutting resistance in the thrust direction is increased, so in order to reduce the resistance, the central portion of the tip is set to about 120 °, and the outer periphery thereof is changed in two steps from 140 ° to 150 °. Good (Claim 5).

The drill body is preferably provided with a structure for cooling the tip cutting edge.
As the cooling structure, a coolant path is drilled in the center of the axis of the drill body, a cooling hole branched from the coolant path is opened at the front part in each of the lead grooves, and the coolant injected from the opening of the cooling hole is It is made to inject toward the ridgeline of a front-end cutting blade (Claim 6).
Further, the drill body may have a blade tip exchange type, that is, the tip head portion may be formed separately from the drill body and detachably attached to the tip of the drill body (Claim 7). In the case of the blade tip exchange type, the tip head is generally cut and ground with a cemented carbide material with a grindstone, or an ultra-high pressure sintered body or a diamond blade tip is attached, or the surface is coated with a hard film such as diamond. However, it is preferable to use a mold that can handle complex shapes. Especially, the entire head is a molded product that is sintered at high pressure using diamond powder or high-density powder of superhard material. It is preferable that it is present (claim 8).

  Furthermore, it is preferable that the tip head is a ceramic molded article such as silicon carbide, silicon nitride, or alumina (Claim 9), or that a diamond coating is formed thereon (Claim 10).

According to the present invention, at the initial stage of drilling, since the cutting by the outer peripheral blade portion and the leading end lead portion thereafter is suppressed and reliable cutting is started, the composite material containing difficult-to-cut material such as CFRP is drilled as a workpiece. Even when processing, the surface layer is prevented from curling P, and the concave curved ridge line formed on the sharp outer peripheral edge portion reliably cuts the fiber member at the perforation outlet portion. Generation of burrs Q can also be prevented. In addition, if the tip cutting blade has a three-blade structure, a drill with high processing accuracy can be provided, such as ensuring a perfect circular perforation in combination with prevention of the above-mentioned curling and wrinkle burr (claim 1). ~ 5).
In addition, a coolant such as air is directly sprayed from the inside of the twisted lead groove in the tip head portion toward the cutting edge ridge line through the coolant passage provided in the drill body, so that a high cooling effect of the cutting edge can be obtained and Durability can be improved and the chip discharge effect is further improved by the refrigerant flow reversed at the tip in the lead groove (claim 6).

Further, if the tip end portion is detachable from the drill body as in claim 7, even if the tip end portion such as CFRP material is likely to be worn, the tip head is replaced or re-polished to always obtain the best cutting. Sex can be secured.
Moreover, since the tip head part can be molded as described in claim 8 by the blade tip replacement method, a tip head having a complicated structure and shape that cannot be obtained by conventional grinding / polishing is obtained. A functional drill can be provided.
Further, the toughness of the tip head portion can be increased by forming the tip head portion as a ceramic molded body as in claim 9, and further, the wear resistance can be increased by forming a diamond coating layer as in claim 10. Thus, it is possible to provide a drill particularly suitable for difficult-to-cut materials such as CFRP.

The embodiment of the present invention will be described with reference to the drawings. FIGS. 1 to 4 illustrate the basic form of the drill A of the present invention, FIG. 1 is a side view, FIG. These are sectional views which follow a (3)-(3) line.
The drill body 1 is made of a super hard material such as cemented carbide or high-speed steel, and includes a shank 2 on one side (rear side) of a substantially columnar shape rotated around an axis, and for chip discharge on the front side. The land portion 4 in which the three twisted lead grooves 3, 3 and 3 are formed is provided, and the head portion 10 at the tip includes cutting blades 5, 5, and 5 formed by the tip angle α, and each cutting blade. And a thinning 7 for facilitating discharge of chips and a chisel edge 8 formed by thinning.
Further, the drill body 1 has a coolant passage 9 opened in the center of the shaft from the end face of the shank 2 toward the tip head portion 10.

  The cutting blades 5, 5, 5 exemplify a three-blade structure arranged at a central angle of 120 ° by the three twisted lead grooves 3, 3, 3, and each cutting blade 5 has the chisel edge 8, the chisel edge 8 functions as a primary cutting blade, and the cutting blade 5 functions as a secondary cutting blade.

Each of the torsional lead grooves 3 is generally opened from the tip head portion 10 toward the shank 2 at a constant lead angle (twisting angle) β in the range of 20 ° to 30 °. However, in the present invention, the lead angle (tip lead angle) βa of only the tip head portion 10 is set to an angle (5 ° in the illustrated example) smaller than the lead angle β as shown in FIG. The tip lead portion 3 a is formed on the substrate 10. That is, the torsion lead groove 3 has a tip lead portion 3a having a lead angle βa of 5 ° in the tip head portion 10, and changes from there to a predetermined lead angle β (not particularly limited, but 20 ° to 30 °). It is.
The tip lead angle βa is not limited to 5 °, but is effective at a constant value in the range of −10 ° to + 10 ° corresponding to the lead angle of the torsional lead groove 3 and the material of the workpiece. Yes (see FIG. 4). That is, if the lead angle βa exceeds 10 °, the function of preventing the rolling-up P cannot be achieved, and if it is less than −10 °, the machinability itself is deteriorated. Furthermore, the preferable range of the tip lead angle βa is −5 ° to + 5 °.

2 and 3, the tip head portion 10 has an outer periphery having a sharp cutting edge shape on the outer periphery of the tip cutting edge 5 by setting the torsion lead groove 3 to a large outer peripheral chamfer angle θ. The blade part 5a is formed.
This outer peripheral scoop angle θ is set to a constant value of 20 ° to 40 °, preferably 30 ° to 40 ° in consideration of the machinability and the strength of the cutting edge of the outer peripheral blade portion 5a. This is because if the outer peripheral scoop angle θ is less than 20 °, the desired machinability cannot be obtained, and if it exceeds 40 °, the edge strength is low and durability cannot be obtained.

Further, by forming a scooping surface having the outer peripheral scooping angle θ, each cutting blade 5 is not only formed with the sharp outer peripheral cutting portion 5a, but also from each end of the chisel edge 8 toward the outer peripheral cutting portion 5a. The cutting edge ridge line is formed in a concave curve shape.
The concave curve shape of the cutting edge ridge line changes depending on the tip angle α when the outer peripheral scoop angle θ is the same. Specifically, since the standard tip angle α is 118 ° to 130 °, FIG. 1 illustrates the case where the tip angle α is 120 °, but the tip angle α is set to 140 ° as shown in FIG. Then, the concave curvature depth of the cutting edge ridgeline is larger than that in the case of FIG. 1, that is, the concave curve depth becomes deeper as the tip angle α is larger.
In the processing of the CFRP material W, considering that it is important to quickly discharge a large volume of chips because the chips become very hard and powdery, the concave curve depth of the cutting edge ridge line is deep. It is preferable.

On the other hand, in the drill A having a three-blade structure, considering that the cutting resistance in the thrust direction (drilling direction) increases as the tip angle α increases, even when the tip angle α is larger than the standard angle, 140 ° to Set in the range of 150 °.
In order to further reduce the cutting resistance, even if the tip angle is in the range of 140 ° to 150 °, the tip angle is changed in two steps, that is, the tip angle of the central portion is set to around 120 °, and the outer peripheral tip What is necessary is just to set an angle to the range of 140 degrees-150 degrees (FIG. 14). In FIG. 14, the blade tip replaceable tip head 20 is illustrated, but it is needless to say that it can be applied to the tip head portion 10.

The refrigerant path 9 has a rear end opened to the rear end face of the shank 2 and extends to the center of the axis of the drill main body 1, and a front end in the vicinity of the tip lead portion 3 a of the tip head portion 10, specifically, A cooling hole 9a is formed at a position slightly behind the tip lead portion 3a and branched into three at the tip, and the tip of each cooling hole 9a is opened into the twisted lead groove 3.
Refrigerant is supplied to each cooling hole 9a through the refrigerant path 9 when drilling, and the refrigerant is twisted from the inside of the lead groove 3 toward the ridge line of the tip cutting edge 5, more preferably the cutting edge 5. The outer peripheral blade portion 5a and the tip lead portion 3a are sprayed to cool the portion, and the cut chips are twisted and discharged to the rear in the lead groove 3.

  Note that air, water, oil, etc. are used as the refrigerant. However, when the CFRP material W is drilled, the chips are very hard and powdery. In consideration of this, it is preferable to use air having a high cooling rate due to expansion.

Thus, the operation in the case of drilling the CFRP material W using the drill A (the tip angle α is exemplified by 140 ° in FIG. 5) will be described with reference to FIG.
First, the drill A is rotated at a high speed while supplying air to the refrigerant path 9 to start drilling the CFRP material W. At the initial stage, the center of the tip head portion 10 abuts and is cut by each chisel edge 8. Centering is performed, and immediately after that, the sharp outer peripheral blade portion 5a starts cutting while pushing down the surface of the CFRP material W with the tip lead portion 3a (see FIG. 6 (1)). In the initial stage of cutting, the outer peripheral blade portion 5a is cut while drawing a circle, and the force component acting in the radial direction of the distal end lead portion 3a is thrust by setting the distal end lead angle βa of the distal end lead portion 3a following the outer circumferential blade portion 5a. The direction closer to the direction, that is, the cutting force of the carbon fiber by the outer peripheral blade part 5a acts downward rather than acting upward with respect to the traveling direction of the drill. As a result, the surface curling P as shown in FIG. 16 can be prevented.

Next, during drilling in which the drill A advances, cutting is performed with the sharp cutting edge shape of the outer peripheral blade portion 5a, so that the carbon fiber can be reliably cut to prevent wrinkles remaining in the hole and the drilling penetrates. Immediately before, as shown in FIG. 6 (2), the chips remain in a ring shape in the concave curve portion formed by the ridge line of the cutting blade 5, and the chips are cut off in a substantially intact state when penetrating (see FIG. 6). 6 (3)), it is possible to prevent wrinkle burrs Q on the back surface as shown in FIG.
Note that the chips supplied by the air supplied to the refrigerant passage 9 during the drilling process are twisted and discharged rearward through the lead groove 3, and are injected and cooled toward the outer peripheral blade portion 5a and the tip lead portion 3a of the tip cutting blade 5. Of course, it acts. In particular, as described above, it is possible to quickly discharge a large amount of chips in the processing of the CFRP material W due to the supply of air as a refrigerant and the concave curve depth of the cutting edge ridgeline.

Next, FIGS. 7 to 12 show another embodiment of the present invention. Specifically, the tip head 20 corresponding to the tip head portion 10 described above is formed separately from the drill body 11, and the drill head is drilled. This is a case where the blade tip is replaceable with respect to the main body 11.
The drill main body 11 has the three twisted lead grooves 13, 13, 13 and the land portions 14, 14, 14 and is made of a cemented carbide or the like in the same manner as the drill main body 1 described above.
The drill body 11 forms a coolant passage 19 that penetrates the axial center portion thereof, and is provided with attachment grooves 21 that radially extend from the center to the land portions 4 on the end face, that is, the end face to which the tip head 20 is joined, The engagement protrusion 22 of the tip head 20 is fitted into the mounting groove 21.
Further, in the drill body 11, a cooling hole 19 a is opened in each twist lead groove 3 on the outer peripheral surface of the tip of the refrigerant passage 19, and the refrigerant (air) supplied to the refrigerant passage 19 is cut by the cutting edge 15 of the tip head 20. Inject toward

The tip head 20 forms a cutting edge 15 having a concave curved ridgeline, a sharp outer peripheral edge 15a is formed on the outer periphery thereof, and is smaller than the lead angle β of the twisted lead groove 13 The formation of the tip lead portion 13a having an angled tip lead angle βa is the same as that of the tip tip head portion 10 shown together with the functions thereof, and thus detailed description thereof is omitted.
The tip lead portion 13a of FIG. 7 is formed in an area extending from the outer peripheral blade portion 15a to the back surface or rear surface of the tip head 20, that is, the zone is formed at a constant tip lead angle βa, and the drill body at the rear end thereof. 11 illustrates a case in which it is connected to the 11 twisted lead grooves 13, that is, displaced to the lead angle β. In addition, at the displacement point, in order to improve manufacturability and durability, an R connection is made so that the angle changes smoothly.

  The tip head 20 has engaging projections 22 that fit into the mounting grooves 21 of the drill body 11 on the back surface thereof. Each mounting groove 21 is a substantially V-shaped groove, and each engaging protrusion 22 is approximately V-shaped. As a shape, both are fitted and positioned without backlash. That is, by fitting the mounting grooves 21 and the engaging protrusions 22, the twist lead grooves 13 of the drill body 11 can be joined to the tip head 20 so as to be continuous. Further, the fitting structure between the mounting grooves 21 and the engaging protrusions 22 supports the rotational torque of the tip head 20.

The tip head 20 can be integrally coupled by brazing to the tip surface of the drill body 11, and can be removed from the drill body 11 by melting the wax if necessary, such as during re-polishing. Further, when the drill diameter is large, instead of brazing, as shown in FIG. 13, it is optional to attach the tip head 20 to the drill body 11 detachably by bolting 23 at three locations. is there.
In addition, since it is easily understood that the above-described action for preventing the rolling-up P and the flashing burr Q can be obtained by using this blade-tip-exchangeable drill, details are omitted for the sake of explanation.

14 and 15 show another embodiment in which the tip head 20 is improved.
As described above, the tip head 20a of FIG. 14 is a case where the tip angle α is changed in two steps, specifically, the central portion is set to 120 ° and the outer peripheral portion thereof is set to 140 °. Thereby, the cutting resistance at the time of cutting by the tip head 20 is reduced, and the concave curve depth of the cutting edge ridge line is secured, and the occurrence of the rolling-up P and wrinkle burrs Q of the CFRP material W is more reliably prevented. It is a thing.

The tip head 20b in FIG. 15 is a case where the length of the tip lead portion 13a is shortened. That is, in the tip head 20 of FIG. 7, the tip lead portion 13a is an area from the outer peripheral blade portion 15a to the back surface of the tip head 20, but the tip head 20b is formed by shortening the area. .
Specifically, the tip lead portion 13a is formed to have a length of about 1/5 of the area from the outer peripheral blade portion 15a to the back surface of the tip head 20b, and the lead angle β that is the same as that of the twisted lead groove 13 behind the tip lead portion 13a. The connection lead part 13b which has is interposed. According to the tip head 20b, the length of the tip lead portion 13a is short, so that the machining operation is facilitated when the edge portion is re-polished.

Further, in the tip head 20b, the case where the tip lead angle βa is a negative angle (−5 °) is illustrated, and the tip head of FIG. 7 is at the displacement point where the tip lead portion 13a and the lead portion 13b are connected. In the same manner as described in FIG.
The case where the lead angle of the connecting lead portion 13b is the same as the lead angle β of the twisted lead groove 13 on the rear side thereof has been described. However, the lead angle βa of the tip lead portion 13a and the lead angle β of the twisted lead groove 13 are The lead angle of the connecting lead portion 13b is larger than the leading end lead angle βa and smaller than the lead angle β of the twisted lead groove 13, that is, by interposing the connecting lead portion 13b. The twisted lead groove 13 may be smoothly connected from the lead portion 13a.
Of course, the configuration of the tip head 20b can be applied to the tip head portion 10 of FIG.

The method of forming the drill main body 11 and the tip head 20 or 20a, 20b will be described. The drill main body 11 is ground and polished on the three twisted lead grooves 13 using a rotating grindstone, as in the case of normal drill forming. A method of grinding and polishing the groove 21 or a method of extruding the twisted lead groove 13 is employed.
The tip head 20 or 20a, 20b may be formed by grinding / polishing using a rotating grindstone as in the case of the drill body 11, but preferably a high-density powder such as diamond powder or super hard material is used as the material. The entire tip head 20 is sintered and formed by molding the powder material at ultrahigh pressure and high temperature, or by performing additional processing such as electric discharge machining or grinding in addition to that. It may be a form.
According to this mold forming method, it becomes possible to produce complicated and dense scooping parts and tip lead grooves that cannot be formed due to interference by the grindstone, and especially when using diamond powder as the material, the cutting edge part The drill with high durability (lifetime) can be obtained by increasing the strength.

Further, the tip head 20 or 20a, 20b is formed as a ceramic molded body. Specifically, silicon carbide (SiC), silicon nitride (SiN), alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), boron carbide (B ₄ C), a ceramic powder material such as boron nitride (CBN) may be formed by, for example, applying a hydrostatic pressure (CIP, HIP) treatment.
Furthermore, a diamond coating layer may be formed on the surface of the ceramic molded body, and preferably a coating layer using diamond nanoparticles may be used. And when forming a diamond coating layer, in order to raise the adhesive strength of a diamond coating layer, it is preferable to form the intermediate | middle layer which adjusts to both materials mutually between a ceramic molded body and a diamond coating layer.

In the case of adopting the above-mentioned sintered compact by molding, or in the case of a ceramic compact or a tip head on which a diamond coating layer is formed, it is limited to the structure and shape of the tip head disclosed in the above description. Without limitation, the present invention can also be applied to a conventional blade tip replaceable tip head.

  In the description of the above-described embodiment, the tip lead portions 3a and 13a shown in FIGS. 1, 4, 7, 14 and 15 are exemplified by the case where the entire length is linearly formed. However, the present invention is not limited thereto. For example, a smooth convex shape (convex R shape) or a concave shape (concave R shape) is also optional.

In the description of the above embodiment, the change in the core thickness of the drill body and the groove width and groove depth of the twisted lead groove are not particularly described, but they are not limited thereto. That is, the core thickness is constant, increases, or decreases from the tip toward the shank side, and the lead groove also has a constant or variable groove width and depth, or the lead angle β changes from the middle. Either can be applied to the present invention.
If the specific values of the dimensions of each part are illustrated, the drill diameter is 1/8 to 1 inch (about 3.175 to 25.4 mm), the drill A in the illustrated example is about 6 mm, and the length of the tip lead part 3a is CFRP material. It is 50% or less (1 to 1.5 mm in the illustrated example) of the thickness of the work material such as W.
Moreover, it is as Table 1 if the groove width ratio, core thickness, and axial groove ratio in FIGS. 9-11 are illustrated.

  Further, in the above-described embodiment, the case of the CFRP material as the composite material including the difficult-to-cut material has been described. However, the present invention is not limited to this, and the present invention can be applied to a composite material having the same degree of hard-cutability. Of course, it is applicable to composite materials and other workpieces that are easier to cut.

It is a side view of this invention drill. It is a front-end enlarged front view of the drill. It is an expanded sectional view which follows the (3)-(3) line of FIG. It is a side view which shows the range of the tip lead angle applied in this invention. It is a side view when the tip angle is 140 ° in the present invention. It is sectional drawing explaining the effect | action of this invention. It is a partial expanded side view which shows the drill of other embodiment of this invention. It is a front view of the tip of the drill. It is sectional drawing which follows the (9)-(9) line | wire of FIG. It is sectional drawing which follows the same (10)-(10) line. It is sectional drawing which follows the same (11)-(11) line. 8 is a perspective view of the drill of FIG. 7, in which (1) is an assembled state, (2) is a rear perspective view of the disassembled tip head, and (3) is an exploded drill body. It is a front view of the front end of an embodiment in which the front end head is attached by bolting. It is a side view of other examples of a tip head which changed a tip angle two steps. It is a side view of the further another Example of the front-end | tip head which improved the front-end | tip lead part. It is sectional drawing which shows the problem at the time of processing with a conventional drill.

Explanation of symbols

1: Drill body 3: Twisted lead groove 3a: Tip lead portion 5: Tip cutting edge 5a: Outer peripheral blade portion 9: Refrigerant passage 9a: Cooling hole 10: Tip head portion β: Lead angle of twist lead groove βa: Tip lead angle θ: outer peripheral scooping angle 11: drill main body 13: twist lead groove 13a: tip lead portion 15: tip cutting edge 15a: outer peripheral blade portion 19: refrigerant path 19a: cooling hole port 20: tip head 20a: tip head 20b: tip head 21: Mounting groove 22: Engagement protrusion 23: Bolt fixing

Claims (10)

  In a drill having a torsion lead groove having a predetermined lead angle β on the outer peripheral surface of the drill body and a cutting edge formed by a tip angle on the tip surface, the tip head portion of the drill body has the twist lead groove on the tip body. An outer periphery in which the tip lead angle βa is set to a constant value in a range of −10 ° to + 10 ° smaller than the lead angle β, and the cutting edge is sharpened by setting the outer peripheral rake angle. A drill characterized by forming a blade portion and forming a ridge line of the cutting blade into a concave curve.   The drill according to claim 1, wherein the outer peripheral scoop angle is 20 ° to 40 °.   The drill according to claim 1 or 2, wherein the tip cutting edge is a three-blade arranged at a central angle of 120 ° by three twisted lead grooves.   The drill according to any one of claims 1 to 3, wherein a tip angle of the tip head portion is set to 140 ° to 150 °.   The drill according to claim 4, wherein the tip angle is about 120 ° at the center of the tip and 140 ° to 150 ° on the outer periphery.   A coolant path is drilled in the center of the axis of the drill body, and a cooling hole branched from the coolant path is opened at the tip of each of the lead grooves, and the coolant sprayed from the opening of the cooling hole reaches the ridgeline of the tip cutting edge. The drill according to any one of claims 1 to 5, wherein the drill is jetted toward.   The drill according to any one of claims 1 to 6, wherein the tip head portion is a blade tip exchange type that is separate from the drill body and is detachably attached to the tip of the drill body.   8. The drill according to claim 7, wherein the tip head portion is a sintered compact formed by molding a powder material.   9. The drill according to claim 8, wherein the tip head portion is a ceramic molded body such as silicon carbide, silicon nitride, or alumina.   10. The drill according to claim 9, wherein the tip head portion has a diamond coating layer formed on the surface of the ceramic molded body.

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