JP2005186247A - Twist drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress clogging of chips in a chip discharge groove by improving chip discharge property, and efficiently perform a deep hole machining in the case of drilling with a twist drill. <P>SOLUTION: The twist drill is provided with a spiral chip discharge groove 11 on the outer periphery of a drill body 10, and a first straight cutting blade 13 is formed by a tip end flank 12 and the chip discharge groove on the outer peripheral part side of the tip of the drill body. The thinning surface 14 is formed onto a central part side from the first cutting blade, and the second cutting blade 15 is formed by the thinning surface and the tip end flank surface. A gash surface 16 expanded toward the outer peripheral side is formed on the rake face 11a of the chip discharge groove relative to the first cutting blade so that the rake angle θ in the vertical direction of the first cutting blade becomes small. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a twist drill in which a spiral chip discharge groove is provided on the outer periphery of a drill body and a cutting edge is formed at the tip of the drill body, and in particular, a hole for a work piece made of metal. In processing, it is characterized in that the chip evacuation performance is improved so that deep hole processing can be performed efficiently.

  When drilling a metal workpiece, a twist drill with a spiral chip discharge groove on the outer periphery of the drill body and a cutting edge formed at the tip of the drill body is widely used. Has been.

  Then, when drilling a workpiece made of metal with such a twist drill, the twist drill is rotated and the hole is cut while cutting the workpiece with the cutting edge provided at the tip. Processing is performed, and the chips cut by the cutting blade are discharged through the chip discharge groove.

  Here, when drilling as described above, the cutting speed of the cutting edge on the outer peripheral side is faster than the center part of the twist drill, and the rake angle is increased, so that the cut chips are fan-shaped. Then, this chip curls in the above-mentioned chip discharge groove. Especially when using a twist drill made of cemented carbide as in recent years and rotating this twist drill at a high speed to drill holes at a high speed, the twist drill's center and outer peripheral sides are also used. The difference in the cutting speed of the cutting edge in the case becomes larger, and the chips are more easily curled.

  And when the depth which drills using the above twist drills is about 2 to 3 times with respect to a drill diameter, there are few cases where the chip curled as mentioned above clogs the chip discharge groove. However, when the depth of drilling is deep and drilling more than 5 times the diameter of the drill is performed, the curled chips are clogged in the chip discharge groove and cannot be discharged well. A large resistance is applied to the rotation of the twist drill, and the cutting performance is deteriorated and the drill is broken.

  On the other hand, when the chip discharge groove is enlarged to improve chip discharge, the rigidity of the drill body decreases, making it difficult to drill straight holes, and the drill is likely to break. Occurred.

  For this reason, conventionally, when deep hole machining is performed with the twist drill as described above, so-called step machining is performed in which the drill is lifted up to the middle when the hole machining is performed, chips are discharged, and the hole machining is performed again. Has been done.

  However, when hole processing is performed by step processing in this way, deep hole processing requires a lot of time, and there is a problem that work efficiency is extremely deteriorated.

  In recent years, in order to prevent the chips from curling and clogging into the chip discharge groove as described above, the chip discharge groove is formed to have a substantially L-shaped cross section. A drill having a groove depth of 0.25 to 0.3 times the diameter of the drill has been proposed (see, for example, Patent Document 1).

  However, even in the drill as described above, the difference in the cutting speed of the cutting edge between the central portion and the outer peripheral side is still large, and it has not been possible to sufficiently prevent the chips from curling and clogging into the chip discharge grooves.

  Further, in recent years, the central cutting edge side of the outer peripheral main cutting edge is formed as a straight line or a convex arc having a large R radius, and the outer peripheral edge has no inflection point and is closer to the central cutting edge. The radius of curvature is gradually reduced toward the outer periphery, the radius of R gradually decreases, and the radius of R at the outermost periphery becomes 0.25 times or more of the drill diameter. Has been proposed (for example, see Patent Document 2).

However, it is difficult to manufacture the twist drill as described above, and there are problems such as high cost.
Japanese Patent No. 2609993 JP 2003-285111 A

  An object of the present invention is to solve the above-described problems in a twist drill in which a spiral chip discharge groove is provided on the outer periphery of the drill body and a cutting blade is formed at the tip of the drill body. When drilling a workpiece made of metal using this twist drill, it is possible to improve chip discharge and suppress clogging of the chip into the chip discharge groove, thus enabling deep hole drilling efficiently. The challenge is to make it possible.

  In the twist drill according to the present invention, in order to solve the above-described problems, a spiral chip discharge groove 11 is provided on the outer periphery of the drill body 10, and the tip flank face on the outer peripheral side of the tip of the drill body 10. 12 and the chip discharge groove 11 form a linear first cutting edge 13, and a thinning surface 14 is formed closer to the center than the first cutting edge 13. In the twist drill in which the second cutting edge 15 is formed by the tip flank 12, the chip discharge groove 11 with respect to the first cutting edge 13 is set such that the vertical rake angle θ of the first cutting edge 13 is reduced. On the rake face 11a, a gash face 16 that spreads toward the outer peripheral side was formed.

  Here, in the above twist drill, when the spiral chip discharge groove 11 is provided on the outer periphery of the drill body 10, the ratio of the core thickness d of the drill body 10 to the drill diameter D of the drill body 10 (d / D ) Is in the range of 0.35 to 0.5, and the cross-sectional shape of the chip discharge groove 11 is preferably substantially L-shaped and the opening angle α is preferably in the range of 85 ° to 110 °. .

  Moreover, in said twist drill, it is preferable to coat | cover at least the front-end | tip part of said drill main body 10 with a hard film.

  In the present invention, a spiral chip discharge groove is provided on the outer periphery of the drill body, and the linear first cutting edge is formed by the tip flank and the chip discharge groove on the outer peripheral side of the drill body tip. In the twist drill in which the thinning surface is formed on the center side from the first cutting edge and the second cutting edge is formed by the thinning surface and the tip clearance surface, Since the rake angle in the vertical direction of the cutting edge is reduced, and the rake face of the chip discharge groove with respect to the first cutting edge is formed with a gash surface that extends toward the outer peripheral side, the cutting resistance against the first cutting edge is reduced. Increasing toward the outer peripheral side, the thickness of the chips cut by the first cutting edge increases toward the outer peripheral side, and the cut chips flow at the center side and the outer peripheral side of the first cutting edge. Difference in time is reduced, chips becomes to be inhibited from curling becomes a fan shape.

  As a result, when drilling is performed with this twist drill, the curl of the cut chips is reduced, and the curled pitch is increased so that the linearly extended chips are efficiently discharged through the chip discharge groove. Therefore, even when deep hole machining is performed, it is possible to prevent chips from being clogged in the chip discharge groove and reducing cutting performance or breaking the drill, as in the past. This eliminates the need for deep hole drilling.

  Further, in the twist drill according to the present invention, the chips are efficiently discharged through the chip discharge groove as described above. Therefore, it is not necessary to enlarge the chip discharge groove, and the twist thickness is increased by increasing the core thickness of the drill body. The rigidity of the drill can be increased, so that a straight hole can be drilled and the drill is prevented from being broken.

  Hereinafter, a twist drill according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings.

  In the twist drill according to this embodiment, as shown in FIGS. 1A and 1B, a pair of spiral chip discharge grooves 11 are provided on the outer periphery of the drill body 10, and the tip of the drill body 10 has a tip. On the outer peripheral portion side, the first cutting blades 13 that are linear are formed by the respective chip discharge grooves 11 and the tip flank 12 respectively.

  Further, the second flank 12a is formed on the rear side in the rotation direction of the twist drill with respect to each of the tip flank 12 above, and the shaft of the drill body 10 is disposed on the center side with respect to each of the first cutting edges 13 above. A thinning surface 14 is formed along the direction, and a second cutting edge 15 that is linear is formed by each thinning surface 14 and the tip flank 12. In addition, in this embodiment, although the 2nd cutting blade 15 was formed in linear form, it is also possible to form in the curved shape which became concave or convex.

  And as shown in FIG.1 (B) and FIG. 2, the substantially triangular-shaped gash surface 16 spread toward the outer peripheral side to the rake face 11a with respect to the 1st cutting edge 13 of each said chip discharge | emission groove | channel 11 is respectively shown. The vertical rake angle θ of the first cutting edge 13 is made smaller than the vertical rake angle θa of the rake face 11 a with respect to the first cutting edge 13.

  Here, in the twist drill in this embodiment, in providing the pair of spiral chip discharge grooves 11 on the outer periphery of the drill body 10, the core thickness d of the drill body 10 with respect to the drill diameter D of the drill body 10 is set. When the ratio (d / D) is small, the rigidity of the twist drill cannot be sufficiently increased. On the other hand, when the ratio (d / D) is excessively large, chip discharge performance is reduced. / D) is preferably in the range of 0.35 to 0.5.

  Moreover, as said chip discharge | emission groove | channel 11, as shown in FIG. 3, it is preferable to provide the thing whose cross-sectional shape is a substantially L shape, and the opening angle (alpha) is the range of 85 degrees-110 degrees. That is, when the cross-sectional shape of the chip discharge groove 11 is substantially L-shaped and the opening angle α is set to 110 ° or less, the chips cut by the first cutting blade 13 strike the wall surface of the chip discharge groove 11. It becomes easy to divide, the length of the chip is shortened, and the chip discharging property is further improved. The reason why the opening angle α of the chip discharge groove 11 is set to 85 ° or more is to facilitate the processing of the chip discharge groove 11.

  Further, in this twist drill, it is preferable to cover at least the tip of the drill body 10 with a hard coating, and as the material of this hard coating, for example, TiN, TiAlN, CrN, DLC (diamond-like carbon) or the like is used. be able to. Here, when the drill body 10 is covered with a hard coating such as TiN or TiAlN, the wear resistance and welding resistance of the twist drill are improved, and the life of the twist drill is improved. Further, when the drill body 10 is coated with a hard coating having a small friction coefficient such as CrN or DLC and having excellent lubricity, the wear resistance and welding resistance of the twist drill are improved, and chip discharge is further improved. Will also improve.

  Next, drilling is performed using the twist drill according to the embodiment of the present invention and the twist drill of the comparative example, and it is clear that the chip discharging performance is improved in the twist drill according to the embodiment of the present invention. To do.

  In the twist drill of the example, in the twist drill in the above embodiment, the drill body 10 having a drill diameter D of 10 mm is used, and the outer periphery of the drill body 10 has a spiral shape with a twist angle of 30 ° and a cross-sectional shape. Are provided with two chip discharge grooves 11 with an opening angle α of 100 °, and the ratio (d / D) of the core thickness d of the drill body 10 to the drill diameter D is 0.45. did.

  Further, as described above, the second flank 12a is formed on the rear side in the rotational direction of the twist drill with respect to the tip flank 12, and the thinning surface 14 is formed on the center side with respect to each first cutting edge 13. The second cutting edge 15 having a linear shape was formed by each thinning surface 14 and the tip flank 12. Here, in this embodiment, as shown in FIG. 4, the ratio between the length L1 of the first cutting edge 13 and the length L2 of the second cutting edge 15 in the linear direction of the first cutting edge 13. (L1: L2) was set to 3.5: 1.

  Further, as described above, the rake face 11a of each chip discharge groove 11 with respect to the first cutting edge 13 is formed with a substantially triangular gash face 16 spreading toward the outer peripheral side, and the vertical direction of the first cutting edge 13 is formed. The rake angle θ was set to + 5 °, and the axial width w of the gash surface 16 at the outer peripheral portion of the drill body 10 was set to 0.05 times the drill diameter D described above.

  And the hard film which consists of TiN was formed with respect to this twist drill by PVD method.

  On the other hand, in the twist drill of the comparative example, the twist drill was produced in the same manner as in the above example except that the gash face 16 was not formed.

  And using each twist drill of said Example and a comparative example, the cutting speed of 15.7 m / min (500 rpm) by the wet system which each supplies cutting oil with respect to the work material which consists of carbon steel of S50C. , Deep hole machining was performed in which a through hole of 100 mm having a depth 10 times the drill diameter D was provided under the condition of a feed of 0.3 mm / rev.

  As a result, when the twist drill of the comparative example is used, as shown in FIG. 5, chips are generated which are curled greatly and the pitch of the curls is reduced, and the chips are discharged in the middle of the hole processing. 11 and the torque became abnormally large, and it was necessary to interrupt the drilling.

  On the other hand, when the twist drill of the embodiment is used, as shown in FIG. 6, there is little curling, the curl pitch is increased, and appropriately cut chips are generated, and in the middle of drilling Chips were not clogged in the chip discharge groove 11 and deep hole processing could be performed at once without interrupting the hole processing.

It is the schematic side view of the front-end | tip part of the twist drill which concerns on one Embodiment of this invention, and the front view of a front end side. In the twist drill of the embodiment, it is sectional explanatory drawing which showed the state which formed the gash surface in the rake face with respect to the 1st cutting blade of a chip discharge groove. In the twist drill of the embodiment, it is sectional explanatory drawing which showed the state of the chip discharge groove. In the twist drill of the Example of this invention, it is the front view of the front end side which showed the length L1 of the 1st cutting blade, and the length L2 of the 2nd cutting blade 15 in the linear direction of a 1st cutting blade. It is a schematic diagram of the chip | tip which arose when drilling was performed with the twist drill of a comparative example. It is a schematic diagram of the chip | tip which arose when drilling was performed with the twist drill of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Drill main body 11 Chip discharge groove 11a Rake face 12 Tip flank 13 First cutting edge 14 Thinning face 15 Second cutting edge 16 Gash face D Drill diameter d Core thickness α Opening angle of chip discharge groove

Claims (4)

  A spiral chip discharge groove 11 is provided on the outer periphery of the drill body 10, and a linear first cutting edge 13 is formed by the tip flank 12 and the chip discharge groove 11 on the outer peripheral side of the tip of the drill body 10. Is formed, and a thinning surface 14 is formed on the center side of the first cutting edge 13, and the second cutting edge 15 is formed by the thinning face 14 and the tip flank 12. , The vertical rake angle θ of the first cutting edge 13 is reduced so that the gash surface 16 spreads toward the outer peripheral side on the rake face 11a of the chip discharge groove 11 with respect to the first cutting edge 13. Twist drill characterized by being formed.   The twist drill according to claim 1, wherein a ratio (d / D) of a core thickness d of the drill body 10 to a drill diameter D of the drill body 10 is in a range of 0.35 to 0.5. And twist drill.   3. The twist drill according to claim 1, wherein the chip discharge groove 11 has a substantially L-shaped cross section and an opening angle α in a range of 85 ° to 110 °. drill.   The twist drill according to any one of claims 1 to 3, wherein at least a tip portion of the drill body 10 is covered with a hard coating.

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