JP2009184043A - Stepped twist drill and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stepped twist drill having excellent cutting performance of a large-diameter part, and reducing the machined shape error caused by the large-diameter part, and to provide a method of manufacturing the same. <P>SOLUTION: In the stepped twist drill, separate twist grooves are formed in a small-diameter part 40 and the large-diameter part 50, respectively, and the lead of the twist groove 51 of the large-diameter part is relatively small with respect to the lead of the twist groove 41 of the small-diameter groove. A wall surface 52 on the leading edge side of the twist groove of the large-diameter part constituting a rake face of a cutting edge of the large-diameter part is formed so that, from the middle part of the small-diameter part 40 in the axial direction of the drill, at least an outer peripheral edge of a wall surface 42 on the leading edge side of the twist groove of the small-diameter part is notched rearwardly in a drill rotating direction K. A depth D of the notch in the drill rotating direction K is gradually increased toward the rear end side in the axial direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a stepped twist drill for machining a stepped hole having a stepped portion in a work material and a method for manufacturing the stepped twist drill.

  Step drills used mainly in the automotive industry allow machining of stepped holes consisting of a small diameter part and a large diameter part and chamfering of the mouth of the machined hole. The advantages of shortening the number of tools and the number of tools used.

  The stepped drill disclosed in Japanese Patent Application Laid-Open No. 2002-18621 has a ratio of the drill diameter of the small diameter part to the large diameter part of 2.5 to 3.5 times, and the twist angle of the small diameter part is 15 ° or more, The twist angle of the large diameter portion is 38 ° or more. Furthermore, the step drill disclosed in Japanese Patent Application Laid-Open No. 2002-79408 has a concave arc shape with a small-diameter tip blade from the vicinity of the core thickness toward the outer periphery in addition to the above configuration.

Further, the stepped rotary cutting tool disclosed in Japanese Patent Application Laid-Open No. 2001-105216 has a multi-groove structure by providing a step in the tool rotation direction between the outer peripheral groove of the small diameter portion and the outer peripheral groove of the large diameter portion. The outer peripheral rake angle γ1 of the small diameter portion is different from each other so that it is in the range of 0 ° or more and γ2 is 0 ° or less.
JP 2002-18621 A JP 2002-79408 A JP 2001-105216 A

  However, in the above-described conventional stepped drill (stepped rotary cutting tool), generally, an arc-shaped grindstone is often used for groove processing, and in this case, the processing amount (grinding amount) is large. Since the design of the first stage cutting blade is given priority, the radial RR RR in the front end view is greatly negative in the second stage cutting edge (see FIG. 3). This tendency is particularly strong when the second stage cutting edge forms a chamfering cutting edge having a tip angle of 90 °.

  Thus, when the radial RR RR of the second stage cutting blade is a large negative, chatter vibration and cutting torque increase due to a decrease in sharpness, resulting in problems such as poor accuracy of the machining surface and a reduction in machining efficiency. Further, when the second stage cutting edge is a chamfering cutting edge, there arises a problem that the processed chamfering angle is out of order.

In order to solve this problem, the following measures have been taken, but each has its own problems and has not been put into practical use.
(1) In the case where a specially shaped grindstone having a step as an inflection point is used at the boundary between the small diameter portion and the large diameter portion so that the radial rake RR of the second stage cutting blade is increased, the position of the step Is fixed at a predetermined position, the applicable range of the diameter of the first stage cutting blade becomes very narrow (see FIG. 4A).
(2) When the second stage cutting blade and the first stage cutting blade are processed with separate grindstones, the first stage cutting blade and the second stage cutting blade must be positioned accurately in the radial direction of each grindstone. There is a problem that stress concentrates on the remaining of the small diameter portion or the large diameter portion caused by one of the two biting into the other and breaks (see FIG. 4B).

  The present invention has been made to solve the above-described problem, and has an object to provide a stepped twist drill having excellent sharpness of a large-diameter portion and a small machining shape error due to the large-diameter portion, and a manufacturing method thereof. And

  In order to solve the above-mentioned problem, the invention according to claim 1 is directed to a blade portion provided on the tip side of a drill body having a substantially round bar shape, and a large-diameter portion connected to the rear-end side of the small-diameter portion. A stepped twist drill in which a torsional groove is provided on the outer periphery of each of the small diameter portion and the large diameter portion, and a cutting blade is formed on each of the small diameter portion and the large diameter portion. And the large diameter portion is formed with a separate twist groove, and the lead of the large diameter portion of the twist groove is relatively small with respect to the lead of the small diameter portion of the twist groove. The wall surface on the leading edge side of the torsion groove of the large diameter portion constituting the surface is at least outside the wall surface on the leading edge side of the torsion groove of the small diameter portion after the intermediate portion of the small diameter portion in the axial direction of the drill body. Periphery after drill direction Notch on the side, further, the depth of the notch drill rotation direction is stepped twist drill, characterized in that it is gradually so that large, formed toward the above axial direction rear side.

  According to the stepped twist drill, the wall on the leading edge side of the torsion groove of the large diameter portion constituting the rake face of the cutting blade of the large diameter portion is at least the outer periphery of the wall on the leading edge side of the torsion groove of the small diameter portion The end is notched rearward in the drill rotation direction, and the notch depth in the rotation direction of the notch is formed so as to gradually increase toward the rear end side in the axial direction. The cutting blade as a whole moves backward in the drill rotation direction. Therefore, the radial rake RR of the cutting edge of the large diameter portion is prevented from becoming a large negative. Therefore, compared with the conventional stepped drill, which has a large negative rake RR of the cutting edge of the large diameter part, the sharpness when cutting with the cutting edge of the large diameter part is superior, so that consideration is given to reducing feed. Since it is unnecessary, the cutting efficiency is improved and the processing accuracy is improved.

  Furthermore, since the tip of the notch, that is, the connecting portion of the small-diameter torsion groove and the large-diameter torsion groove is provided in the middle portion of the small-diameter portion in the axial direction of the drill body, the small-diameter portion and the large-diameter No small diameter portion or large diameter portion remains at the boundary with the portion. Therefore, the life of the drill is extended by preventing breakage due to stress concentration at the boundary.

  Further, when the large-diameter portion is a chamfered blade, the problem that the chamfering angle of the processed chamfer becomes large, as in a conventional drill having a large negative radial rake RR, is solved.

  The invention according to claim 2 of the present invention is the stepped twist drill according to claim 1, wherein the cutting blade of the large diameter portion is a chamfering blade having a tip angle of 60 ° to 120 °. is there. Since the radial rake RR of the cutting blade of the large diameter portion is prevented from becoming a large negative by the configuration of claim 1, the chamfering in the chamfering shape of the workpiece processed by the chamfering blade of the large diameter portion. Angle deviation is reduced. Considering the practical range of the chamfering angle and the effective range of the effect of reducing the deviation of the chamfering angle, the tip angle of the cutting edge of the large diameter portion is set to a range of 60 ° to 120 °. desirable.

  In the invention according to claim 3 of the present invention, the outer circumference of the small diameter portion and the large diameter portion is such that the outer peripheral portion of the grindstone follows the torsion of the torsion groove while the disc-shaped grindstone is rotated around its axis. 3. The twist groove is formed by being cut in a surface and moving in the axial direction while rotating the drill body around the axis relative to the grindstone in the direction of the twist. The method of manufacturing the stepped twist drill according to claim 1, wherein the grindstone that forms the twisted groove of the large diameter portion includes the twisted groove of the small diameter portion at the intermediate portion of the small diameter portion in the axial direction of the drill body. It is cut into at least the outer peripheral edge of the wall on the leading edge side formed by the grinding wheel to be formed, and the drill body is rotated around the axis relative to the grinding stone in the direction of the twist. The amount of rotation of the drill body relative to the amount of movement in the axial direction is greater when the large-diameter portion twist groove is formed than when the small-diameter portion twist groove is formed. It is the manufacturing method of the stepped twist drill characterized by being set so that it may become.

  According to the invention which concerns on Claim 3, the grindstone which forms the torsion groove | channel of the said large diameter part is the grindstone which forms the torsion groove | channel of the said small diameter part in the axial direction of this drill main body after the intermediate part of the said small diameter part. By cutting into the outer peripheral edge of the formed leading edge side wall surface, the cutting edge of the large diameter portion formed with the wall surface on the leading edge side of the torsion groove of the large diameter portion as the rake face is With respect to the virtual large-diameter cutting edge formed by extending the torsional groove to the large-diameter portion, the entire blade moves backward in the rotational direction. Therefore, it becomes possible to manufacture a stepped twist drill that prevents the radial rake RR of the cutting blade of the large diameter portion from becoming a large negative.

  Furthermore, when the drill body is moved in the axial direction while rotating around the axis relative to the grindstone in the direction of twist, the amount of rotation of the drill body relative to the amount of movement in the axial direction is: The large-diameter portion cutting blade formed by the large-diameter portion twist groove is set to be larger when the large-diameter portion twist groove is formed than when the small-diameter portion twist groove is formed. Prevents the radial rake RR from becoming much negative due to the fact that the amount of retreating backward in the rotational direction as a whole becomes larger than the virtual large-diameter cutting edge formed by the small-diameter torsion groove. This makes it possible to manufacture a stepped twist drill that is extremely effective.

  From the above, according to the invention according to claim 3, the sharpness when cutting with the large-diameter portion cutting edge as compared to the conventional stepped drill, in which the radial rake RR of the large-diameter portion cutting blade is greatly negative. It becomes possible to manufacture a stepped twist drill with good cutting efficiency and processing accuracy.

  According to the invention of claim 3, the grindstone that forms the large-diameter portion twist groove is formed by the grindstone that forms the small-diameter portion twist groove after the intermediate portion of the small-diameter portion in the axial direction of the drill body. Since the outer edge of the wall on the leading edge side is cut, the small diameter portion and the large diameter portion are not left at the boundary between the small diameter portion and the large diameter portion. Therefore, it becomes possible to manufacture a stepped twist drill having a long life by preventing breakage due to stress concentration at the boundary between the small diameter portion and the large diameter portion.

  Moreover, in the axial direction of the drill body, the position where the grindstone forming the large-diameter portion twist groove is cut into the outer peripheral edge of the wall on the leading edge side formed by the grindstone forming the small-diameter portion twist groove, Provided that a radial rake RR of the cutting edge having a desired large diameter portion can be obtained, it is not particularly strictly controlled, and it suffices if it is in the middle portion of the small diameter portion, thereby providing a very easy manufacturing method. be able to.

  Moreover, a specially shaped grindstone having a step at the boundary between the small diameter portion and the large diameter portion, which has been conventionally used to improve that the radial rake RR of the cutting blade of the large diameter portion becomes large negative, is used. Compared with the method of forming twisted grooves, the shape of the grindstone is not complicated, and the applicable range of the diameter of the small diameter part or large diameter part is not narrowed. The scope of application becomes wider.

According to the first aspect of the present invention, a stepped twist drill excellent in cutting efficiency and processing accuracy is provided in order to prevent the cutting edge of the large diameter portion from becoming a large negative radial rake RR and improve sharpness. Can be provided. Furthermore, since the breakage at the boundary between the small diameter portion and the large diameter portion is suppressed, a stepped twist drill having a long life can be provided.
Further, according to the invention according to claim 3, it is possible to manufacture a stepped twist drill excellent in cutting efficiency and processing accuracy in order to prevent the radial rake RR of the cutting blade having a large diameter portion from becoming a large negative. Become.

  Hereinafter, an embodiment of a stepped twist drill according to the present invention will be described with reference to the drawings. FIG. 1 is a front view of a stepped twist drill according to the present embodiment. 2A is a cross-sectional view taken along the line AA in FIG. 1, and FIG. 2B is a cross-sectional view taken along the line BB in FIG.

  As shown in FIGS. 1 and 2, the stepped twist drill of this embodiment includes a blade portion 20 provided on the distal end side of the drill body 10 and a shank 30 connected to the rear end side of the blade portion 20. Prepare. The blade portion 20 includes a small diameter portion 40 provided on the front end side and a large diameter portion 50 connected to the rear end side of the small diameter portion 40. A pair of torsion grooves 41 and 51 formed substantially symmetrically with respect to the axial direction of the drill body 10 are formed on the outer peripheral surfaces of the small diameter portion 40 and the large diameter portion 50. Surface) to the rear end portion of the large-diameter portion 50.

  As for the twist grooves 41 and 51, the separate twist grooves 41 and 51 are formed in the small diameter part 40 and the large diameter part 50, respectively. A rake face is formed on each of the wall surfaces 42 and 52 on the leading edge side of the twist grooves 41 and 51, and a cutting edge 43 having a small diameter portion is formed on the intersecting ridge line between the rake face 42 and the tip surface of the small diameter portion 40. ing. Similarly, a cutting edge 53 having a large diameter portion is formed on the intersecting ridge line between the rake face 52 and the tip surface of the large diameter portion 50. In the embodiment illustrated in FIG. 1, the large-diameter cutting blade 53 is a chamfered blade having a tip angle α of 90 °.

  As can be seen from FIG. 1, the large-diameter portion twist groove 51 is formed on the wall surface on the leading edge side of the small-diameter portion twist groove 41 in the range after the intermediate portion of the small-diameter portion 40 in the axial direction of the drill body 10. The outer peripheral edge portion of the rake face is formed to be cut out along the outer peripheral edge portion. Furthermore, since the lead of the large-diameter portion twist groove 51 is formed to be relatively small with respect to the lead of the small-diameter portion twist groove 41, the large-diameter portion twist groove 51 causes the small-diameter portion 40 of the small-diameter portion 40 to The notch portion 60 in which the rake face after the intermediate portion is notched is a mode in which the depth D and the radial width W as viewed in the rotation direction K of the drill body gradually increase toward the rear end side in the axial direction of the drill body 10. (See (b) of FIG. 1 and FIG. 2).

  If the depth D and the radial width W of the cutout portion 60 as viewed in the rotation direction K of the drill body are formed so as to gradually increase toward the rear end side in the axial direction of the drill body, the small diameter portion and the large diameter The lead of each torsion groove of the part may be constant or may change at each position. Whether or not the web taper is applied to the web formed by the groove bottoms of the twisted grooves 41 and 51 of the small diameter part and the large diameter part is not particularly limited. Further, the wall surface 52 on the leading edge side of the large-diameter portion twist groove has at least the outer peripheral edge portion of the wall 42 on the leading edge side of the small-diameter portion twist groove in the rearward direction K to cut the large-diameter portion cutting edge 53. Therefore, the portion other than the wall surface on the leading edge side (for example, the heel side wall surface) may be formed by the large-diameter portion twist groove 51 or the small-diameter portion twist groove. It may be formed by extending 41.

  The manufacturing method of the stepped twist drill according to the present embodiment will be described below. First, the outer peripheral portion of the first grindstone is cut into the outer peripheral surface of the small-diameter portion 40 so as to follow the twist of the torsion groove 41 of the small-diameter portion, and the drill body 10 is directed toward the twist direction of the small-diameter portion 40. A twisted groove 41 having a small diameter portion is formed by moving the drill body 10 from the front end to the rear end side in the axial direction while rotating around the axis relative to the grindstone. The minimum movement amount in the axial direction may be such that at least the twist groove 41 having substantially the same cross-sectional shape is formed from the front end to the rear end of the small diameter portion 40.

  Thereafter, the outer peripheral portion of the second grindstone forming the large-diameter torsion groove 51 is at least the wall surface 42 on the leading edge side of the already formed small-diameter torsion groove in the intermediate portion of the small-diameter portion 40 in the axial direction. It is cut into the outer peripheral edge, and toward the rear end side of the drill body 10 in the axial direction while rotating the drill body 10 around the axis relative to the second grindstone toward the twisting direction of the large diameter portion 50. By moving, the large-diameter portion of the twist groove 51 is formed. Here, the amount of rotation around the axis relative to the amount by which the drill body 10 is moved in the axial direction is set to be larger than the amount of rotation around the axis relative to the amount of movement in the axial direction when forming the small-diameter torsion groove 41. Then, the outer peripheral portion of the second grindstone is cut into the outer peripheral edge portion of the wall 42 on the leading edge side of the twisted groove of the small diameter portion, and the depth D and the radial direction in the rotational direction K of the cut portion The width W gradually increases toward the rear end side in the axial direction. The first grindstone and the second grindstone may be the same shape or different shapes. Further, the amount of rotation for rotating the drill body about the axis with respect to each grindstone in the direction of twisting may be constant or may vary with respect to the amount of movement of the drill body in the axial direction. However, when the amount of rotation changes, it is desirable that the amount of rotation with respect to the second grindstone is larger than the amount of rotation with respect to the first grindstone at the portion where the outer peripheral portion of the second grindstone is cut into the twisted groove of the small diameter portion.

  The stepped twist drill described above is mounted on the main spindle of a machine tool via a holder such as a drill holder, rotated around the axis, and sent to the tip end in the axial direction to form a stepped hole in the work piece. Is processed.

  According to the stepped twist drill according to the embodiment described above, the large-diameter portion twist groove 51 is formed so as to cut out at least the outer peripheral end portion of the wall 42 on the leading edge side of the small-diameter portion twist groove, Since the depth D in the rotational direction K and the width W in the radial direction of the cutout portion 60 are formed so as to gradually increase toward the rear end side in the axial direction, the leading edge of the torsion groove of the large diameter portion The large-diameter cutting edge 53 having the side wall 52 as the rake face is moved backward as a whole in the rotational direction. Therefore, the radial rake RR of the cutting blade 53 of the large diameter portion is prevented from becoming a large negative. Therefore, in comparison with the conventional stepped twist drill in which the radial rake RR of the large-diameter portion cutting blade is greatly negative, the stepped twist drill according to the present embodiment is used for cutting with the large-diameter portion cutting blade 53. Since it is excellent in sharpness, it is not necessary to consider reducing feed, so that cutting efficiency is improved and processing accuracy is improved.

  Furthermore, the tip of the notch 60, that is, the connecting portion between the small-diameter torsion groove 41 and the large-diameter torsion groove 51 is provided in the middle of the small-diameter portion 40 in the axial direction of the drill body 10, A small diameter portion residue and a large diameter portion residue do not occur at the boundary portion 70 between the small diameter portion and the large diameter portion. Therefore, the life of the stepped twist drill is extended by preventing breakage due to stress concentration at the boundary 70.

  Furthermore, the stepped twist drill according to the present embodiment has occurred in the conventional stepped twist drill because the radial rake RR becomes large negative when the chamfering blade is formed in the large diameter portion 50. The problem that the chamfer angle of the processed chamfer is greatly out of order can be solved. Considering the practical range of the chamfer angle and the effective range of the effect of reducing the deviation of the chamfer angle, the tip angle α of the large-diameter cutting blade 53 is set to a range of 60 ° to 120 °. Is desirable.

  According to the manufacturing method of the stepped twist drill according to the present embodiment, the grindstone that forms the twisted groove 51 of the large diameter portion is the twisted groove of the small diameter portion after the intermediate portion of the small diameter portion 40 in the axial direction of the drill body 10. By cutting into the outer peripheral edge of the wall 42 on the leading edge side formed by the grindstone that forms 41, the cutting of the large diameter portion using the wall 52 on the leading edge side of the torsion groove on the large diameter portion as a rake face. The blade 53 as a whole moves backward in the rotational direction K with respect to the virtual large-diameter cutting blade 53a formed by extending the small-diameter torsion groove 41 to the large-diameter portion. Therefore, it becomes possible to manufacture a stepped twist drill that prevents the radial rake RR of the cutting blade 53 of the large diameter portion from becoming a large negative.

  Furthermore, the amount of rotation of the drill body 10 relative to the amount of movement in the axial direction when the drill body 10 is moved in the axial direction while rotating around the axis relative to the grindstone in the direction of twisting is less than that of the small diameter portion. The large-diameter portion twisted groove 51 is formed larger than the twisted groove 41 formed. Therefore, the large-diameter cutting edge 53 formed by the large-diameter portion twist groove 51 is rotated as a whole with respect to the virtual large-diameter cutting blade 53a formed by the small-diameter portion twist groove 41. Since the amount of backward movement is further increased, it becomes possible to manufacture a stepped twist drill that is extremely effective in preventing the radial rake RR from becoming a large negative. Therefore, compared with the conventional stepped drill (see FIG. 3) in which the radial rake RR of the large-diameter portion has a large negative value, the cutting efficiency and the cutting efficiency when cutting with the large-diameter portion cutting edge 53 are excellent. It becomes possible to manufacture a stepped twist drill with good machining accuracy.

  Further, the grindstone that forms the large-diameter torsion groove 51 is the wall surface on the leading edge side that is formed by the grindstone that forms the small-diameter portion torsion groove 41 in the axial direction of the drill body 10 after the intermediate portion of the small-diameter portion 40. Since it cuts into the outer peripheral edge part of 42, a small diameter part remainder and a large diameter part remainder do not arise in the boundary part 70 of a small diameter part and a large diameter part. Therefore, it becomes possible to manufacture a stepped twist drill having a long life by preventing breakage due to stress concentration on the boundary portion 70 between the small diameter portion and the large diameter portion.

  Moreover, in the axial direction of the drill body 10, a position where the grindstone forming the large-diameter portion twist groove 51 is cut into the outer peripheral edge of the wall 42 on the leading edge side formed by the grindstone forming the small-diameter portion twist groove. If the radial rake RR of the cutting edge 51 having a desired large diameter portion is obtained, it is not particularly strictly controlled, and it is only necessary to be in the middle portion of the small diameter portion 40, so that it is very easy to manufacture. A method can be provided.

  Moreover, a specially shaped grindstone having a step at the boundary between the small diameter portion and the large diameter portion, which has been conventionally used to improve that the radial rake RR of the cutting blade of the large diameter portion becomes large negative, is used. Compared with the method of forming twisted grooves, the shape of the grindstone is not complicated, and the applicable range of the diameter of the small diameter part or large diameter part is not narrowed. The scope of application becomes wider.

It is a front view of the stepped twist drill which concerns on embodiment of this invention. (A) is the sectional view on the AA line in FIG. 1, (b) is the sectional view on the BB line in FIG. It is a front view side view of the conventional stepped twist drill. It is a cross-sectional view of the conventional stepped twist drill, (a) shows what formed the torsion groove with the grindstone which has a level difference with an inflection point, (b) shows 1 step part and 2 step parts. Indicates the one formed with a different grindstone.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Drill main body 20 Blade part 30 Shank part 40 Small diameter part 41 Small diameter part twist groove 42 Wall surface (rake face) of leading edge side of small diameter part twist groove
43 Cutting Blade 50 for Small Diameter Part 50 Large Diameter Part 51 Large Diameter Torsion Groove 52 Leading Edge Side Wall (Rake Surface) of Large Diameter Torsion Groove
53 Cutting edge of large diameter part (Chamfering blade)
60 Notch 70 Boundary RR between small diameter and large diameter RR Radial rake α of large diameter cutting edge Tip angle of cutting edge of large diameter

Claims (3)

The blade portion provided on the tip side of the drill body having a substantially round bar shape is provided with a small diameter portion and a large diameter portion connected to the rear end side of the small diameter portion, and on the outer periphery of the small diameter portion and the large diameter portion, A twisted drill with stepped twist grooves each provided with a torsion groove and having a cutting edge formed in each of the small diameter portion and the large diameter portion,
Separate twist grooves are respectively formed in the small diameter portion and the large diameter portion,
The lead of the twisted groove of the large diameter portion is relatively small with respect to the lead of the twisted groove of the small diameter portion,
The wall surface on the leading edge side of the torsion groove of the large diameter portion constituting the rake face of the cutting blade of the large diameter portion is the torsion groove of the small diameter portion after the intermediate portion of the small diameter portion in the axial direction of the drill body. At least the outer peripheral edge of the wall on the leading edge side of the notch is notched to the rear side in the drill rotation direction, and further, the depth of the notch in the drill rotation direction is gradually increased toward the rear end side in the axial direction, A stepped twist drill characterized by being formed. The stepped twist drill according to claim 1, wherein the cutting blade of the large diameter portion is a chamfering blade having a tip angle of 60 ° to 120 °. While the disc-shaped grindstone is rotated about its axis, the outer peripheral portion of the grindstone is cut into the outer peripheral surfaces of the small diameter portion and the large diameter portion so as to follow the twist of the twist groove, and in the direction of the twist 3. The method of manufacturing a stepped twist drill according to claim 1, wherein the twist groove is formed by moving the drill body in the axial direction while rotating the drill body about the axis relative to the grindstone. There,
The grindstone that forms the twist groove of the large diameter portion is at least a wall on the leading edge side that is formed by the grindstone that forms the twist groove of the small diameter portion after the intermediate portion of the small diameter portion in the axial direction of the drill body. Cut into the outer periphery,
When the drill body is moved in the axial direction while rotating around the axis relative to the grindstone in the twist direction, the amount of rotation of the drill body relative to the amount of movement in the axial direction is A method for manufacturing a stepped twist drill, characterized in that it is set to be larger when the large-diameter portion twist groove is formed than when the small-diameter portion twist groove is formed.

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