JP2006326752A - Drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drill which can avoid trouble due to chips by facilitating discharge of chips from a machined hole, and prevent breakage of the drill due to insufficient rigidity or deterioration of dimension accuracy of the machined hole by ensuring the rigidity of the drill body. <P>SOLUTION: In the drill, a chip discharge groove 20 which is twisted around the axis O and extends toward the rear end side is formed on the outer periphery of a cutting blade part 12 formed at the tip end side of the drill body 10 rotated around the axis O, and a cutting blade 30 is formed at the intersection edge line part of the inner wall surface facing the front side of the drill rotation direction of the chip discharge groove 20 and the tip end flank 13 of the cutting blade part 12. The cutting blade part 12 is provided with a groove expansion part 16 which is formed so that the cross section area on the section orthogonal to the direction of the axis O of the chip discharge groove 20 gradually becomes large as it advances toward the rear end side of the cutting blade part 12, and the helix angle α of the chip discharge groove 20 gradually becomes small as it advances toward the rear end side of the cutting blade part 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a drill used for drilling to form a processed hole in a workpiece, and more particularly to a drill used for processing a deep hole.

Conventionally, as such a drill, a cutting edge portion is formed at a tip portion of a drill body rotated about an axis, and a pair of chip discharge grooves extending toward a rear end side are formed on an outer periphery of the cutting blade portion. A drill is known in which a cutting edge is formed at an intersecting ridge line portion between an inner wall surface facing the front side in the drill rotation direction of the chip discharge groove and a tip flank surface of the cutting edge portion. (See Patent Document 1)
In such a drill, the drill body is rotated around the axis and fed in the axial direction, and pressed against the material to be cut, so that the material to be cut is cut with a cutting blade to have a predetermined inner diameter. A hole is formed.

  In the case of cutting with a drill having such a configuration, if chips generated during cutting accumulate inside the processing hole, the cutting resistance increases due to the chips, and the drill breaks, or the chips become cutting edges. It has been known that various troubles occur such as the fact that welding cannot be performed due to welding, and the inner wall surface of the processing hole is damaged by chips. In particular, in deep hole machining, it is necessary to discharge chips from the deep position of the processed hole to the surface of the workpiece, so that the chips cannot be discharged sufficiently and accumulate in the processed holes. There was a problem that the possibility that a trouble would occur increased.

Therefore, in order to promote chip discharge from the machining hole, the groove width of the chip discharge groove formed on the outer peripheral surface of the cutting edge portion is increased to increase the groove width ratio in the cross section orthogonal to the axis, or to the groove depth. There is provided a drill in which the cross-sectional area of the chip discharge groove is increased by increasing the depth of the core to reduce the core thickness of the cutting edge.
JP 2003-25125 A

  However, in the conventional drill, if the cross-sectional area of the chip discharge groove is increased, the drill body is notched greatly, the rigidity of the drill body is insufficient, chattering and resonance occur during cutting, and the dimensional accuracy of the processed hole deteriorates. Or the drill body may break due to cutting resistance. In particular, in a drill used for processing a deep hole having a hole depth exceeding 3 × D with respect to the diameter D of the drill's cutting edge, the drill length with respect to the outer diameter of the drill increases, and chatter and resonance due to insufficient rigidity occur. There is a problem that the drill is easily generated and the drill is easily broken.

Thus, in conventional drills, particularly drills used for deep hole processing, when chip discharge is promoted, troubles such as drill breakage due to insufficient rigidity of the drill body are likely to occur, When the rigidity of the drill body is secured, chip discharge is not promoted, and troubles such as chip clogging are likely to occur due to defective chip discharge. It was very difficult.
Therefore, when forming a deep hole, after inserting the drill into the machining hole and cutting it slightly, the drill is extracted from the machining hole, the chips are discharged to the surface of the workpiece, and the drill is inserted into the machining hole again. It is necessary to perform so-called step processing, and there is a problem that the processing efficiency by the drill is remarkably lowered.

  The present invention has been made in consideration of such circumstances, and can facilitate the discharge of chips from a machining hole to avoid trouble due to defective chip discharge, and ensure the rigidity of the drill body to ensure rigidity. An object of the present invention is to provide a drill that can prevent breakage of a drill and deterioration of dimensional accuracy of a drilled hole due to shortage, and can form a deep hole efficiently.

  In order to solve this problem, the present invention provides a chip discharge groove that extends toward the rear end side while being twisted around the axis on the outer periphery of a cutting edge portion formed on the front end side of a drill main body rotated about the axis. In the drill in which the cutting edge is formed at the intersection ridge line portion between the inner wall surface facing the front side of the drill rotation direction of the chip discharge groove and the tip flank of the cutting blade portion, the cutting blade portion includes the The chip discharge groove is formed such that a cross-sectional area in a cross section perpendicular to the axial direction of the chip discharge groove is gradually increased as it goes toward the rear end side of the cutting edge portion, and the twist angle of the chip discharge groove is A groove enlarged portion formed so as to gradually become smaller toward the rear end side of the cutting blade portion is provided.

  In the drill having this configuration, the cross-sectional area in the cross section perpendicular to the drill body axis of the chip discharge groove is formed so as to gradually increase toward the rear end side of the cutting edge portion. Chips formed at the tip of the drill can be discharged to the surface of the workpiece through the chip discharge grooves formed on the outer peripheral surface of the cutting blade, and troubles due to defective chip discharge can be prevented. Here, since chip discharge is promoted, it is not necessary to perform step processing when performing deep hole processing, and the processing efficiency during deep hole processing can be greatly improved.

  Furthermore, since the twist angle of the chip discharge groove is formed so as to gradually become smaller toward the rear end side of the cutting edge portion, the twist angle on the rear end side of the cutting edge portion becomes smaller, and in the axial direction. When drilling, the drill body's notched portion only needs to be small, so the rigidity of the drill body can be secured, the drill body's chatter and resonance can be suppressed, and machining holes can be formed with high dimensional accuracy, Drill breakage can be prevented.

Further, the chip discharge groove in the groove enlarged portion is formed such that a groove width ratio in a cross section perpendicular to the axial direction of the cutting blade portion gradually increases as it goes toward the rear end side of the cutting blade portion. As a result, the discharge of chips is surely promoted and the size of the notched portion of the drill body is gradually changed.For example, compared to the case where the groove width ratio is suddenly changed at one place, There is no portion where stress is concentrated, and breakage of the drill body due to cutting resistance can be prevented.
Here, when the groove width ratio is smaller than 0.6: 1, the groove width of the chip discharge groove may be narrowed and the chips may not be discharged. On the other hand, when the groove width ratio is larger than 0.83: 1, the drill is removed. There is a possibility that the rigidity of the main body is lowered and the drill is broken by the cutting resistance. Therefore, it is preferable to change the groove width ratio within the range of 0.6: 1 to 0.83: 1.

  Further, by forming the chip discharge groove in the groove enlarged portion so that the core thickness in the cross section perpendicular to the axial direction of the cutting blade portion gradually decreases as it goes to the rear end side of the cutting blade portion. The depth of the chip discharge groove is increased and the chip discharge is surely promoted, and the size of the notched portion of the drill body is gradually changed. Compared with the case where it is changed, there is no portion where stress is concentrated on the drill body, and breakage of the drill body due to cutting resistance can be prevented.

  Here, when the diameter of the cutting edge is D, if the core thickness is smaller than 0.275 × D, the rigidity of the drill body is lowered and the drill may be broken due to cutting resistance, while the core thickness is 0. If it is larger than 3 × D, the depth of the chip discharge groove becomes shallow, and there is a possibility that the chip cannot be discharged smoothly. Therefore, it is preferable to change the core thickness within a range of 0.3 × D to 0.275 × D. Of course, both the groove width ratio and the core thickness may be gradually changed in the groove enlarged portion.

  In addition, by changing the twist angle of the chip discharge groove within the range of 30 ° to 10 °, the twist angle can be formed in the drill tip side portion to 30 ° or less according to the cutting conditions, By setting the twist angle to 10 ° or more at the rear end portion of the drill, it is possible to prevent the portion where the drill body is cut out from being displaced in the axial direction and forming a portion where stress is concentrated on the drill body.

  Further, when the diameter of the cutting edge is D, the length from the outer peripheral end of the cutting edge to the tip of the groove enlarged portion is set to 1.5 × D or more, whereby the groove shape of the drill tip is changed. The shape can be made according to the cutting conditions, and the cutting resistance when cutting the workpiece with the cutting edge at the tip of the drill can be suppressed to smoothly perform the cutting with the drill. Further, by setting the length from the outer peripheral end of the cutting blade to the tip of the groove enlarged portion to be 3 × D or less, the groove enlarged portion is sufficiently formed, and a deep hole that is 8 times or more the diameter D of the cutting blade Even in the case of forming, the chips can be discharged well and the rigidity of the drill body can be ensured.

  Further, by providing the cutting blade on a cutting blade member made of a hard material and joined to the tip of the drill main body, a chip discharge groove is formed on the outer peripheral surface of the drill main body before mounting the cutting blade member. It can be processed using a general cutting tool such as a ball end mill without interfering with the cutting edge. Therefore, the manufacturing cost of the drill can be greatly reduced, and the chip discharge groove can be formed with high dimensional accuracy.

  As described above, according to the present invention, it is possible to promote chip discharge from the machining hole to avoid trouble due to defective chip discharge, and to ensure the rigidity of the drill body and to break the drill due to insufficient rigidity or the size of the machining hole. It is possible to provide a drill capable of preventing deterioration of accuracy and forming a deep hole with high processing efficiency.

A drill according to an embodiment of the present invention will be described with reference to the accompanying drawings. 1 to 3 show a drill according to an embodiment of the present invention.
As shown in FIG. 1, the drill body 10 of this drill is formed in a substantially cylindrical shape centering on the axis O, and the rear end side (upper side in FIG. 1) of the drill body 10 serves as a rotating shaft of the machine tool. The shank portion 11 is gripped, and the distal end side (lower side in FIG. 1) of the drill body 10 is a cutting blade portion 12.

On the outer periphery of the cutting edge portion 12, a pair of chip discharge grooves 20, 20 that are twisted toward the rear side in the drill rotation direction T from the tip flank 13 toward the rear end side in the axis O direction are formed symmetrically with respect to the axis O. The cutting edges 30 and 30 are respectively formed at the intersecting ridge line portions of the inner wall surfaces 21 and 21 and the tip flank 13 facing the front side of the drill rotation direction T of the chip discharge grooves 20 and 20.
As shown in FIG. 2, the tip flank 13 of the cutting edge portion 12 is formed by forming the cutting edges 30, 30 at the ridge line portion on the front side of the drill rotation direction T when the chip discharge grooves 20, 20 intersect. The flank surfaces 13A, 13A and the second flank surfaces 13B, 13B connected to the rear side of the drill rotation direction T of the first flank surfaces 13A, 13A have a multi-step surface shape. Is provided with a relief that increases in a multi-step manner as it goes backward in the drill rotation direction T.

  Further, the tip flank 13 is inclined toward the rear end side of the cutting edge portion 12 as it goes from the inner circumference side to the outer circumference side, so that a predetermined tip angle is given to the cutting edges 30 and 30. It has become. Note that a coolant hole 14 is provided in the drill body 10 along the axis O from the shank portion 11 toward the tip in the axis O direction, and a supply hole extending from the coolant hole 14 toward the tip of the drill. 14A and 14A are respectively opened at the intersecting ridge line portion between the tip flank 13 and the outer peripheral surface of the cutting edge portion 12, and in the cutting process, the cutting site is passed through the coolant hole 14 and the supply holes 14A and 14A. Coolant is supplied toward

The cutting edge portion 12 is a first cutting edge portion in which the core thickness d1 is substantially constant in the axis O direction and the groove width W and the twist angle α of the chip discharge groove 20 are also substantially constant in the axis O direction. 15 and the rear end of the first cutting edge 15, and the core thickness d2 and the groove width W and the twist angle α of the chip discharge groove 20 are gradually increased toward the rear end of the cutting edge 12 in the axis O direction. The second cutting blade portion 16 is changed, and the second cutting blade portion 16 is a groove expanding portion. The core thickness of the cutting edge portion 12 is centered on the axis O inscribed in the cross section of the cutting edge portion 12 as shown in FIG. 2 when the cutting edge portion 12 is viewed in a cross section orthogonal to the axis O direction. The outer diameter of a circle (circle indicated by a broken line in FIG. 2).
Here, when the diameter of the cutting edge 30 of the drill is D, the length of the first cutting edge portion 15 in the direction of the axis O is 1.5 × D to 3.0 × D from the outer peripheral end of the cutting edge 30. Within the range, in this embodiment, 2 × D. That is, the second cutting edge portion 16 is formed on the rear end side of 2 × D from the outer peripheral end of the cutting edge 30.

  In addition, a cutting edge member 17 made of a hard material such as cemented carbide and brazed to the leading end surface of the drill main body 10 is provided at the tip side portion of the first cutting edge portion 15. The cutting blade member 17 is provided with a back taper so that the outer diameter gradually decreases as it goes toward the rear end side of the cutting blade portion 12. In this embodiment, the back taper amount of the cutting blade member 17 is 0. .8 / 100 to 1.0 / 100. Further, the joint portion between the cutting blade member 17 and the drill body 10 is chamfered so as to be smoothly connected.

The inner wall surface 21 facing the front side of the drill rotation direction T of the chip discharge groove 20 of the cutting blade member 17 is located on the outer peripheral surface thereof, intersects the land portion 50 of the cutting blade member 17, and is a cross section orthogonal to the axis O. As shown in FIG. 2, the first convex curved surface portion 22 having a convex curve shape that protrudes forward in the drill rotation direction T, and the axial line O is located on the inner peripheral side of the first convex curved surface portion 22. The first concave curved surface portion 23 having a concave curve shape recessed toward the rear side in the drill rotation direction T in the cross section orthogonal to FIG.
Furthermore, the inner wall surface 24 facing the rear side of the drill rotation direction T of the chip discharge groove 20 of the cutting blade member 17 is located on the outer peripheral side and reaches the heel portion 51 (crosses the land portion 50 of the cutting blade portion 12). In the cross section perpendicular to the axis O, the second concave curved surface portion 25 is formed in a concave curve shape that is concave in the drill rotation direction T front side.

The cutting blade 30 formed at the intersecting ridge line portion between the inner wall surface 21 facing the front side of the drill rotation direction T of the chip discharge groove 20 and the tip flank 13 has the inner wall surface 21 connected to the first convex curved surface portion 22. Since it is composed of the first concave curved surface portion 23, as shown in FIG. 2, a convex curved cutting edge 31 is formed on the outer peripheral side thereof, forming a curved shape that is convex forward in the drill rotation direction T. The first convex curved surface portion 22 is connected to the rear end side, and the convex curved cutting edge 31 is formed on the inner peripheral side of the convex curved cutting edge 31 so as to form a concave curve on the rear side in the drill rotation direction T. A concave curved cutting edge 32 that is in smooth contact and continuous is formed, and the first concave curved surface portion 23 is continuous on the rear end side.
As a result, between the convex curved cutting edge 31 and the concave curved cutting edge 32, the cutting edge 30 exhibits an S-shape that is gently curved when viewed from the front end side in the axis O direction. In addition, since the outer peripheral side part of the cutting blade 30 is the convex curved cutting edge 31, the radial rake angle which the cutting blade 30 makes at the outer peripheral end is set to the negative angle side.

Further, from the inner peripheral side of the first concave curved surface portion 23 to the second concave curved surface portion 25 on the front end side of the inner wall surface 21 facing the front side of the drill rotation direction T of the chip discharging groove 20 and the inner wall surface 24 facing the rear side. The crossing ridge line portion with the tip flank 13 (the first flank 13A and the second flank 13B) is notched toward the inside of the chip discharge groove 20 toward the rear end side of the cutting edge portion 12. Thus, a thinning portion 40 that reaches the land portion 50 including the heel portion 51 is formed.
Therefore, the inner peripheral end side of the cutting edge 30 is formed at the intersecting ridge line portion of the thinning portion 40 and the first flank 13A, and extends from the inner peripheral end of the concave curved cutting edge 32 to the center of the tip flank 13. The thinning cutting edge 33 extends toward the axis O located.

Here, the outer peripheral surface excluding the pair of chip discharge grooves 20, 20 in the cutting blade member 17 of the cutting blade portion 12, that is, the land portion 50 in the cutting blade member 17, as shown in FIG. 2, in a cross section orthogonal to the axis O. And a margin part 52 having a substantially arc shape centering on the axis O, intersecting with the outer peripheral side ridge line part of the first convex curved surface part 22 on the inner wall surface 21 facing the front side of the drill rotation direction T of the chip discharge groove 20. The margin portion 52 is connected to the rear side of the drill rotation direction T, and is constituted by a second rounding surface 53 having a substantially arc shape centering on an axis O having an outer shape one step smaller than the arc formed by the margin portion 52. .
Further, like the chip discharge groove 20, the margin portion 52 and the second picking surface 53 are formed on the rear side of the drill rotation direction T from the portion intersecting the tip flank 13 toward the rear end side in the axis O direction. The cutting blade member 17 is formed over substantially the entire length in the direction of the axis O so as to be twisted.

  When the rear end side portion (the portion other than the cutting blade member 17) and the second cutting edge portion 16 of the first cutting edge portion 15 and the second cutting edge portion 16 are viewed in a cross section orthogonal to the axis O, as shown in FIG. A wall surface 21 facing the front side of the drill rotation direction T of the discharge groove 20 is configured by a third concave curved surface portion 26 having a concave curved surface shape recessed toward the rear side of the drill rotation direction T, and the drill rotation direction T rear side of the chip discharge groove 20 The facing wall surface 24 is constituted by a fourth concave curved surface portion 27 having a concave curve shape that is recessed forward in the drill rotation direction T.

  Further, in the second cutting edge portion 16, the core thickness d2 is gradually reduced at a constant rate toward the rear end side of the axis O, and the core thickness d1 in the cutting blade member 17 shown in FIG. 3 and the core thickness d2 at the second cutting edge portion 16 shown in FIG. 3, as the groove depth of the chip discharge groove 20 heads toward the rear end side of the cutting edge portion 12 so that d1> d2. It is formed so as to become gradually deeper. In this embodiment, the core thickness is formed so as to gradually change between 0.275 × D and 0.3 × D, where D is the diameter of the cutting blade 30 of the drill.

  Further, in the second cutting edge portion 16, the groove width ratio W / M in the cross section orthogonal to the axis O is gradually increased toward the rear end side of the cutting edge portion 12, that is, as shown in FIG. The groove width of the chip discharge groove 20 is such that the groove width W1 at the cutting blade member 17 and the groove width W2 at the second cutting edge portion 16 shown in FIG. 3 are in the relationship of W1 <W2. 12 is formed so as to gradually become wider toward the rear end side. In the present embodiment, the groove width ratio W / M is formed so as to gradually change between 0.6 and 0.83.

  In the second cutting edge portion 16, the twist angle of the chip discharge groove 20, that is, the angle α formed by the axis O and the center line of the chip discharge groove 20 is directed toward the rear end side of the cutting edge portion 12. It is formed so as to become gradually smaller. More specifically, the twist angle α is within a range of 20 ° to 30 ° (25 ° in the present embodiment) at the most distal end side of the second cutting edge portion 16, that is, at the connection portion with the first cutting edge portion 15. It is set to be gradually smaller as it goes to the rear end side of the second cutting edge portion 16 and is set to 10 ° on the most rear end side of the second cutting edge portion 16.

  Such a chip discharge groove 20 is formed as follows. First, the first ball end mill is cut into the outer peripheral surface of the cylindrical drill material, and the drill material is adjusted so that the ball end mill has a predetermined twist angle from the front end side to the rear end side of the drill material. Is moved while rotating around the axis O relative to the cutting line. Here, the outer diameter of the first ball end mill constitutes a wall surface 21 that faces the rear end side portion of the first cutting edge portion 15 and the drill rotation direction T front side of the chip discharge groove 20 in the second cutting edge portion 16. It is made the same as the diameter of the circular arc formed by the third concave curved surface portion 26, and the ball end mill is sent once along the rear end side portion of the first cutting edge portion 15 and the second cutting edge portion 16 to discharge chips. A wall surface 21 facing the front side in the drill rotation direction T of the groove 20 is formed.

  Next, the second ball end mill is cut in front of the drill rotation direction T of the wall surface 21 formed on the drill material in this way, and is similarly moved to perform cutting. The outer diameter of the second ball end mill is a fourth wall surface 24 that faces the rear end portion of the first cutting edge portion 15 and the drill rotation direction T rear side of the chip discharge groove 20 in the second cutting edge portion 16. The diameter of the arc formed by the concave curved surface portion 27 is the same, and the ball end mill is sent once along the rear end side portion of the first cutting edge portion 15 and the second cutting edge portion 16 to thereby generate the chip discharge groove 20. A wall surface 24 facing the rear side of the drill rotation direction T is formed.

When the chip discharge groove 20 is formed in the second cutting edge portion 16, the cutting amount in the radial direction of the drill material by the first and second ball end mills and the rotational movement amount with respect to the drill material are set on the tip side. , The groove width ratio W / M, the torsion angle α, and the core thickness d of the chip discharge groove 20 can be gradually changed.
After forming the chip discharge groove 20 in this way, the cutting blade member 17 is joined to the tip of the drill body 10 by brazing.

Further, in the present embodiment, the surface of the cutting edge portion 12 in the drill body 10, that is, the land portion 50 that is the outer peripheral surface of the cutting edge portion 12, the tip flank 13, the inner wall surfaces 21 and 24 of the chip discharge groove 20, and A hard coating such as TiN, TiCN, or TiAlN is coated on the surface of the thinning portion 40 or the like.
Then, over the entire surface of the cutting edge portion 12 coated with the hard film, a polishing process is performed by applying a brush containing hard particles such as diamond particles to the brush, and polishing. The surface roughness Ra (arithmetic average roughness defined in JIS B 0601-1994) is set in the range of Ra = 0.1 μm to 0.3 μm.

  In the drill configured as described above, the shank portion 11 formed at the rear end of the drill body 10 is gripped by the rotating shaft of the machine tool and rotated around the axis O, and at the front end side in the axis O direction. It is sent toward and pressed against the material to be cut to form a processed hole having a predetermined inner diameter in the material to be cut. Here, the coolant is supplied from the machine tool side through the coolant hole 14 and the supply hole 14A so that the cutting can be performed smoothly.

  In the drill having this configuration, the core thickness d2 is gradually decreased and the groove width ratio W / M of the chip discharge groove 20 is gradually increased as the second cutting edge portion 16 moves toward the rear end side of the cutting edge portion 12. Therefore, the chip discharge groove 20 is formed so that the cross-sectional area in the cross section orthogonal to the axis O of the chip discharge groove 20 gradually increases as it goes toward the rear end side of the cutting edge portion 12. To the surface of the workpiece can be promoted.

  In addition, since the twist angle of the chip discharge groove 20 in the second cutting edge portion 16 is gradually reduced toward the rear end side of the cutting edge portion 12, the drill can be secured while ensuring the cross-sectional area of the chip discharge groove 20. The portion of the main body 10 that is notched can be reduced, the rigidity of the drill main body 10 can be secured, the chatter and resonance of the drill main body 10 can be suppressed, and the machining hole can be formed with high dimensional accuracy. Breakage can be prevented.

Further, the groove width ratio W / M is formed so as to gradually change between 0.6 and 0.83, and the core thickness d is changed between 0.3 × D and 0.275 × D. On the other hand, since the twist angle α is formed so as to gradually decrease between 25 ° and 10 °, the cross-sectional area of the chip discharge groove 20 can be increased to facilitate chip discharge, and the drill body 10 Can be secured, and troubles due to defective chip discharge or problems due to insufficient rigidity can be prevented.
Further, since the twist angle α is set to be within a range of 20 ° to 30 ° at the most distal end side of the second cutting edge portion 16, that is, at the connection portion with the first cutting edge portion 15, the first The twist angle of the cutting edge portion 15 can be set according to the cutting conditions.

Further, since the cross-sectional area of the chip discharge groove 20 in the second cutting edge portion 16 is gradually changed, there is no portion where stress is concentrated on the drill body 10, and the breakage of the drill body 10 due to cutting resistance is surely prevented. Can do.
Further, the length L1 of the first cutting edge portion 15 is 2 × D, and the second cutting edge portion 16 connected to the rear end side of the first cutting edge portion 15 is rear end of 2 × D from the outer peripheral end of the cutting edge 30. Therefore, the cutting force can be reduced by making the shape of the first cutting edge portion 15 in accordance with the cutting conditions, and a deep hole that is 8 times or more the diameter D of the cutting edge 30 can be formed. Even when it is formed, chips can be discharged well and the rigidity of the drill body 10 can be ensured.

  Further, in the present embodiment, the cutting blade member 17 is joined to the tip side of the drill body 10 by brazing, so that the outer peripheral surface of the drill body 10 is joined before joining the cutting blade member 17 as described above. On the other hand, the chip discharge groove 20 can be formed by cutting with a ball end mill. Therefore, the machining cost of the drill can be greatly reduced, and the shape of the chip discharge groove 20 can be formed with high dimensional accuracy.

Further, in the present embodiment, since the entire surface of the cutting edge portion 12 coated with the hard film is polished, the inner wall surfaces 21 and 24 of the chip discharge groove 20 are also polished. The surface roughness Ra is set as small as Ra = 0.1 μm to 0.3 μm.
For this reason, when the chips generated by the cutting blade 30 are guided to the rear end side of the cutting blade portion 12 by the chip discharging groove 20, when they are in sliding contact with the inner wall surfaces 21 and 24 of the chip discharging groove 20. It is possible to reduce the frictional resistance of the chip, to promote chip discharge and to suppress the occurrence of chip clogging, and to prevent troubles (for example, breakage of the cutting edge 12 or inability to drill holes) caused by chip discharge failure. Can do.

Furthermore, after the hard coating is coated on the surface of the cutting edge part 12, the surface of the margin part 52 (in this embodiment, the entire surface of the cutting edge part 12) is polished, and the surface Since the roughness Ra is set as small as Ra = 0.1 μm to 0.3 μm, it is possible to prevent the inner peripheral surface of the processing hole from being roughened by the margin portion 52 that contacts the inner peripheral surface of the processing hole.
That is, while the surface of the cutting edge portion 12 is coated with a hard film to improve wear resistance, the hard film is polished on the margin portion 52 that tends to have a relatively large surface roughness. In this way, the inner peripheral surface of the processed hole is not roughened, and the processed hole is formed even in the initial stage of cutting where the surface roughness of the margin portion 52 is not reduced by friction with the inner peripheral surface of the processed hole. The surface roughness of the inner peripheral surface can be improved.

  In addition, although this embodiment demonstrated the brazing type drill which formed the cutting blade in the cutting blade member brazed to the drill front end side, it is not limited to this, The insert in which the cutting blade was formed It is also possible to use an insert type drill having a drill body mounted on the tip of the drill body or a solid type drill in which a cutting blade is directly formed on the drill body. However, in the case of solid type drills, when a cutting tool such as a ball end mill is used when forming a chip discharge groove, the present invention is applied to brazing type drills and insert type drills. It is effective to apply

  Moreover, although the hard film | membrane was coat | covered with respect to the surface of the cutting-blade part 12, and it demonstrated by what polished this hard film | membrane surface, it is not limited to this, What applied polish process It may not be, and it may not be coated with a hard film. However, it is preferable to use a hard coating to improve the wear resistance and to polish the surface of the inner wall surface of the processing hole.

It is a side view of the drill which is embodiment of this invention. It is an A direction arrow directional view in FIG. It is XX sectional drawing in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Drill main body 12 Cutting blade part 13 Tip flank 16 2nd cutting blade part (groove expansion part)
17 Cutting blade member 20 Chip discharge groove 30 Cutting blade

Claims (8)

A chip discharge groove extending toward the rear end side while being twisted around the axis is formed on the outer periphery of the cutting edge portion formed on the tip side of the drill body rotated about the axis, and the drill rotation direction of the chip discharge groove In the drill in which the cutting edge is formed at the intersecting ridge line part of the inner wall surface facing the front side and the tip flank of the cutting edge part,
In the cutting blade portion, the chip discharge groove has a cross-sectional area in a cross section orthogonal to the axial direction of the chip discharge groove gradually increasing toward the rear end side of the cutting blade portion, and A drill having a groove enlargement portion formed such that a twist angle of a chip discharge groove gradually decreases as it goes toward a rear end side of the cutting blade portion.   The chip discharge groove in the groove enlarged portion is formed such that a groove width ratio in a cross section perpendicular to the axial direction of the cutting blade portion gradually increases as it goes toward the rear end side of the cutting blade portion. The drill according to claim 1.   The drill according to claim 2, wherein the groove width ratio is changed within a range of 0.6: 1 to 0.83: 1.   The chip discharge groove in the groove enlarged portion is formed such that the core thickness in a cross section perpendicular to the axial direction of the cutting edge portion gradually decreases as it goes toward the rear end side of the cutting edge portion. The drill according to any one of claims 1 to 3, wherein the drill is characterized.   The drill according to claim 4, wherein the core thickness is changed within a range of 0.3 × D to 0.275 × D, where D is a diameter of the cutting edge.   The drill according to any one of claims 1 to 5, wherein the twist angle of the chip discharge groove is changed within a range of 30 ° to 10 °.   When the diameter of the cutting blade is D, the length from the outer peripheral end of the cutting blade to the tip of the groove enlarged portion is set within a range of 1.5 × D to 3 × D. The drill according to any one of claims 1 to 6, wherein the drill is characterized.   The drill according to any one of claims 1 to 7, wherein the cutting blade is provided on a cutting blade member made of a hard material and joined to a tip portion of the drill body.

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