JP2007105801A - Composite drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite drill including a cutting blade member, whose rear end is inserted in a mounting hole of a shank and fixed and fitted by an adhesive, achieving stable high-accuracy boring by restraining displacement of the position of the cutting blade even if the adhesive is softened due to heat of cutting. <P>SOLUTION: In this composite drill, the rear end 17 of the cutting blade member 16 having a cutting blade part 15 at the tip is inserted in the mounting hole 12 formed at the tip of the shank 11 and fixed and fitted by the adhesive 18. An abut member 22 projected from a hole bottom 14 to abut on the rear end face 21 of the cutting blade member 16 is interposed between the hole bottom 14 of the mounting hole 12 and the rear end face 21 of the cutting blade member 16. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a composite drill in which a shank formed separately and a cutting blade member are fixed by an adhesive and assembled.

For example, in a drill with a small cutting edge diameter used for drilling a printed circuit board, a mounting hole is formed at the tip of a steel shank that is larger than the cutting edge diameter. A composite drill in which a rear end portion of a cutting blade member made of cemented carbide or the like having a cutting blade portion provided on the side is inserted and attached is used. In this type of composite drill, for example, as described in Patent Documents 1 to 3, the rear end portion of the cutting blade member inserted into the mounting hole is fixed with an adhesive and integrated with the shank. Things have been proposed. The cutting blade portion of such a cutting blade member is formed by bonding the cutting blade member to the shank in this way and then forming an outer diameter polishing, a chip discharge groove, and a cutting blade, with the shank axis as the center. It is supposed to be.
Japanese translation of PCT publication No. 2002-501836 JP 2002-210607 A US Pat. No. 3,751,176

  By the way, even in drilling of a printed circuit board with such a small-diameter composite drill, in recent years, there has been a demand for high-efficiency processing, and the rotational speed of the drill during processing tends to increase, When the drill rotation speed at the time of machining is increased in this way, the generated cutting heat also increases, which propagates from the cutting edge portion to the cutting blade member having high thermal conductivity, and between the mounting hole and the rear end portion of the cutting blade member. The adhesive may be softened and the adhesive strength may be reduced. If the adhesive strength is reduced in this way, the cutting blade member tends to move to the rear end side in the axial direction of the shank due to the feed force at the time of drilling, so that stable machining becomes difficult. For example, even if an attempt is made to drill a blind hole having a predetermined depth, the position of the cutting edge at the tip of the cutting edge portion changes, and the accuracy of the hole depth and the like may be reduced.

  On the other hand, the mounting hole at the tip of the shank is usually formed by drilling with a drill, but the cutting edge of a normal drill is attached with a tip angle, and the rotation trajectory has a convex conical surface shape. Thus, the hole bottom 3 of the mounting hole 2 of the shank 1 has a concave conical surface (see, for example, FIGS. 1 and 3 of Patent Document 2). However, the rear end portion 5 of the cylindrical cutting blade member 4 as described in Patent Document 2 is inserted into the mounting hole 2 having the hole bottom portion 3 having such a shape and adhered by the adhesive 6. In this case, as described above, when the adhesive 6 is softened by propagation of cutting heat and the cutting blade member 4 is pushed into the mounting hole 2 toward the rear end side in the axis O direction of the shank 1, the central axis of the concave conical surface is obtained. That is, when the axis O and the center axis X of the cylinder of the rear end portion 5 of the cutting blade member 4 do not coincide with each other with high accuracy, the rear end of the cutting blade member 4 is formed in a part of the hole bottom 3 in the circumferential direction. A portion of the circumference of the periphery of the rear end surface 7 in the portion 5 hits first, so that it is in a so-called one-sided state, and further, the cutting blade member 4 is pushed in, so that the inclination of the concave conical surface formed by the hole bottom portion 3 The central axis X is inclined with respect to the axis O of the shank 1. . As a result, the position of the cutting edge 9 in the cutting edge portion 8 on the distal end side of the cutting edge member 4 is also greatly displaced from the axis O of the shank 1, that is, the rotation axis of the composite drill, and the accuracy of the drilling hole is significantly deteriorated. In some cases, the cutting edge 8 may be broken.

  The present invention has been made under such a background. In the composite drill in which the rear end portion of the cutting blade member is inserted into the mounting hole of the shank and fixed by an adhesive as described above, the composite drill is attached by cutting heat. An object of the present invention is to provide a composite drill capable of stable and highly accurate drilling by suppressing the displacement of the cutting edge even when the adhesive is softened.

  In order to solve the above-described problems and achieve such an object, the present invention provides a rear end portion of a cutting blade member in which a cutting blade portion is provided on the front end side in a mounting hole formed in the front end portion of the shank. Is inserted and fixed by an adhesive, the composite drill is attached between the hole bottom portion of the mounting hole and the rear end surface of the cutting blade member at the center portion of the hole bottom portion from the hole bottom portion. A contact member that protrudes and can contact the rear end surface of the cutting blade member is interposed.

  Therefore, in the composite drill configured as described above, even if the cutting blade member is pushed into the hole bottom side of the mounting hole due to the softening of the adhesive due to the cutting heat, the gap between the rear end surface of the cutting blade member and the hole bottom portion is reduced. Since the abutting member is interposed so as to protrude from the bottom of the hole, the rear end surface of the cutting blade member is further in contact with the bottom of the mounting hole via the abutting member. Since the cutting blade member does not move to the hole bottom side, that is, the rear end side in the axial direction of the shank, stable drilling can be performed. Further, since the cutting blade member is positioned in contact with the bottom of the mounting hole via the contact member, the position of the cutting blade at the tip of the cutting blade member does not fluctuate, and therefore a blind hole with a predetermined depth is obtained. Can be drilled with high accuracy.

  Further, since this contact member is interposed so as to be able to contact the rear end surface of the cutting blade member at the center portion of the hole bottom portion, even if the hole bottom portion of the mounting hole has a concave conical surface shape, The rear end surface of the blade member comes into contact with the contact member before the peripheral edge comes into contact with the hole bottom. For this reason, since the rear end surface does not come into contact with the bottom of the hole and the inclination of the cutting blade member can be suppressed, according to the composite drill having the above configuration, the position of the cutting edge due to the inclination of the cutting blade member can be suppressed. Displacement can also be prevented, and more accurate drilling can be promoted.

  Here, when the hole bottom portion of the mounting hole of the shank has a concave conical surface, the spherical abutting member contacts the concave conical surface by making the abutting member spherical. When contacting, the corresponding contact member is surely positioned at the center of the concave conical surface, and one plane perpendicular to the central axis of the concave conical surface intersects with the concave conical surface. I will meet you. And since the rear end surface of the cutting blade member comes into contact with the spherical contact member in contact with the hole bottom in this way and is positioned, it is possible to more stably support the cutting blade member and prevent displacement of the cutting blade position. it can.

  The outer diameter of the abutting member (or the diameter when the abutting member is spherical) is in the range of 0.3 to 1.0 of the outer diameter of the rear end portion of the cutting blade member. Is desirable. That is, if the outer diameter is smaller than this, the rear end surface of the cutting blade member comes into contact with the hole bottom earlier than the contact member, particularly when the bottom of the mounting hole has a concave conical surface as described above. Conversely, if the outer diameter of the contact member is larger than this, there is a large gap between the rear end surface of the cutting blade member and the bottom of the mounting hole, and more adhesive is required. Or the stability of the cutting blade member may be impaired.

  FIG. 1 is a sectional view showing a composite drill according to an embodiment of the present invention. In this embodiment, the shank 11 is formed in a substantially cylindrical shape centered on the axis O by a steel material such as stainless steel, for example, and a tip portion of the shank 11 gradually decreases in diameter toward the tip side (left side in FIG. 1). 12 and a mounting hole 13 is formed from the center of the front end portion toward the rear end side along the axis O. The mounting hole 13 is formed in a circular cross section having a constant inner diameter A with the axis O as the center, and is drilled by a normal drill in the present embodiment. Therefore, the hole bottom 14 has an axis O. And a concave conical surface that is recessed toward the rear end side (right side in FIG. 1). Note that the taper angle θ of the concave conical surface is equal to the tip angle of the cutting edge of the drill that drills the attachment hole 13, and is usually an obtuse angle of about 110 ° to 150 °.

  A rear end portion 17 of a cutting blade member 16 having a cutting edge portion 15 formed on the front end side is inserted into the mounting hole 13 and fixed by an adhesive 18. The cutting blade member 16 is formed of a hard material such as a cemented carbide having a hardness higher than that of the shank 11, and the rear end portion 17 has a slightly smaller diameter (for example, 0. 0 mm) than the inner diameter A of the mounting hole 13. 90 to 0.99 × A) is formed in a substantially cylindrical shape having an outer diameter B, and the cutting edge portion 15 has an outer diameter corresponding to the outer diameter C of the cutting edge 19 formed at the tip thereof. A tapered portion that is formed in a substantially cylindrical shaft shape having a smaller diameter than the portion 17 and that is continuous between the cutting edge portion 15 and the rear end portion 17 at a taper angle equal to the tapered portion 12 of the shank 11. 20 is formed.

  The outer diameter C of the cutting blade 19 is about 0.1 to 1.6 mm when the composite drill is for drilling a printed circuit board as described above. However, in the present embodiment, the cutting blade 19 is simplified in illustration, and a chip discharge groove (not shown) that is usually a twisted groove connected to the cutting blade 19 is formed on the outer periphery of the cutting blade portion 15. . In the cylindrical rear end portion 17, the rear end surface 21 is a flat circle orthogonal to the central axis X of the rear end portion 17.

  Here, such a cutting edge portion 15 is formed by inserting a cylindrical member made of a cemented carbide having the same diameter as the rear end portion 17 into the mounting hole 13 of the shank 11 and fixing it with an adhesive 18. It is formed by reducing the diameter of the columnar member projecting toward the tip of the shank 11 to the outer diameter C by grinding or the like, forming the tapered portion 20, and further sharpening the chip discharge groove and the cutting edge 19. The Therefore, as shown in FIG. 1, even if the center axis X of the rear end portion 17 of the cutting blade member 16 is slightly decentered from the axis O of the shank 11, the cutting blade portion 15 is formed with the axis O as the center. Can do. Further, as the adhesive 18, for example, an anaerobic fixing agent or the like is preferably used.

  A shank between the rear end surface 21 of the rear end portion 17 of the cutting blade member 16 fixed by the adhesive 18 and the hole bottom portion 14 of the mounting hole 13 of the shank 11 is formed in the center portion of the hole bottom portion 14. 11, an abutting member 22 is interposed. The abutting member 22 is formed of a metal material such as a cemented carbide or a steel material. In this embodiment, the contact member 22 has a diameter of 0. 0 with respect to the outer diameter B of the rear end portion 17 having a columnar shape. It is a spherical shape having a diameter D in the range of 3 to 1.0 × B, and its tip side portion protrudes further to the tip side than the hole bottom portion 14 in contact with the hole bottom portion 14, that is, this hole It protrudes to the front end side in the axis O direction from the intersecting ridge line portion between the concave conical surface formed by the bottom portion 14 and the cylindrical inner peripheral surface of the mounting hole 13. The adhesive 18 is filled in the hole bottom portion 14 so as to fill the periphery of the abutting member 22, and is also entirely between the outer periphery of the rear end portion 17 of the cutting blade member 16 and the inner periphery of the mounting hole 13. It is filled so as to be interposed between the two over the circumference.

  In the composite drill configured as described above, the cutting heat at the time of drilling propagates from the cutting blade portion 15 to the entire cutting blade member 16, so that the adhesive 18 is softened, and the cutting blade member 16 is fed by the feed force. The contact member between the hole bottom 14 of the mounting hole 13 and the rear end surface 21 at the rear end 17 of the cutting blade member 16 even if it tries to move so as to be pushed into the rear end side in the axis O direction in the mounting hole 13 22 is interposed, the cutting edge member 16 is positioned in the direction of the axis O in the state where the rear end surface 21 abuts against the abutting member 22 and the corresponding abutting member 22 abuts against the hole bottom portion 14, and the rear end Movement to the side is restricted. In addition, since the contact member 22 is formed of a relatively hard metal material as described above, the contact member 22 may be crushed even if it receives a pressing force so that the cutting blade member 16 is pushed to the rear end side. There is nothing. Therefore, no displacement occurs in the position of the cutting edge portion 15 at the tip of the cutting edge member 16 in the direction of the axis O, and high-precision machining is performed even when, for example, a blind hole having a predetermined depth is formed. It is possible to prompt.

  Further, the contact member 22 is disposed at the center of the hole bottom portion 14 of the mounting hole 13 and is interposed between the rear end surface 21 of the cutting blade member 16. Is also brought into contact with the central portion. Therefore, as described above, even if the center axis X of the rear end portion 17 of the cutting blade member 16 is slightly decentered from the axis O of the shank 11 and is fixed by the adhesive 18, it is cut at the peripheral edge of the rear end surface as in the prior art. Compared to the case where the blade member comes into contact with the bottom of the hole, when the adhesive 18 is softened, the cutting blade member 16 is pressed against the axis O when the cutting blade member 16 is pressed to be pushed to the rear end side. Accordingly, it is possible to prevent the cutting blade 19 at the tip of the cutting blade member 16 from being displaced in the radial direction. Therefore, according to the composite drill having the above-described configuration, it is possible to ensure high accuracy in terms of the inner diameter accuracy and roundness of the processed hole, and since an excessive force does not act on the cutting edge portion 15, breakage occurs. It is possible to reliably prevent the occurrence of the above.

  Moreover, in the present embodiment, the mounting hole 13 is formed by being drilled by a normal drill as described above, and the bottom 14 of the hole has a concave conical surface shape, whereas the contact member 22 is formed. When the abutting member 22 abuts against the hole bottom 14, the abutting member 12 is surely positioned at the most bottom side, that is, the center of the hole bottom 14, and the hole bottom 14 is The abutting member 12 comes into contact with the hole bottom 14 on the entire circumference where the plane perpendicular to the central axis of the concave conical surface and the concave conical surface intersect. Accordingly, when the rear end surface 21 of the rear end portion 17 of the cutting blade member 16 contacts the spherical contact member 22 that contacts the hole bottom portion 14 in this manner, the cutting blade member 16 has a rear end in the axis O direction. Therefore, according to the present embodiment, it is possible to prevent the cutting blade 19 from being displaced more reliably and to perform high-precision drilling.

  However, in this embodiment, the bottom 14 of the mounting hole 13 has a concave conical surface, whereas the contact member 22 has a spherical shape. For example, the mounting hole 13 is formed by electric discharge machining or the like. When the hole bottom 14 of the mounting hole 13 is formed in a planar shape perpendicular to the axis O as in the modification shown in FIG. 2, the contact member 22 is connected to the hole bottom 14 and the cutting edge. For example, a cylindrical shape, a disk shape, a cubic shape, or a rectangular parallelepiped shape may be used in which both end surfaces that contact the rear end surface 21 of the member 16 are formed in parallel planes. Further, even if the mounting hole 13 has a flat shape as described above, if the contact member 22 can be reliably interposed between the cutting blade member 16 in the center portion thereof, Such a spherical contact member 22 may be used.

  If the contact member 22 interposed in this way is too small, the contact of the attachment hole 13 with the hole bottom 14 or the rear end surface 21 of the cutting blade member 16 becomes unstable, and the cutting blade member The support of 16 may also become unstable, and particularly when the hole bottom 14 has a concave conical surface shape as in the above embodiment, the rear end 17 may be rearward depending on the taper angle θ. There is also a possibility that the peripheral edge of the end surface 21 may easily hit the concave conical surface of the hole bottom 14. On the other hand, even if the contact member 22 is too large, there is a large space in the direction of the axis O between the hole bottom portion 14 and the rear end surface 21, and more adhesive 18 is used to fill this space. If it is necessary to fill or the adhesive 18 is insufficient, the contact member 22 cannot be reliably held at the center of the hole bottom portion 14, and the support of the cutting blade member 16 may also become unstable. is there.

  For this reason, the size of the contact member 22 is the outer diameter thereof, that is, the diameter D when the contact member 22 is spherical as in the embodiment, the cutting edge member 16 as described above. It is desirable to be within a range of 0.3 to 1.0 × B with respect to the outer diameter B of the rear end portion 17. In addition, when the contact member 22 has a cylindrical shape, a disk shape, a cubic shape, or a rectangular parallelepiped shape having both planar end faces parallel to each other as in the modification shown in FIG. It is desirable that the distance and the outer dimension of the end face be within the above range. Further, when the contact member 22 is spherical as in the above-described embodiment, the center thereof may not be disposed in the center of the hole bottom portion 14 so as to be strictly located on the axis O, for example, What is necessary is just to interpose between the cutting blade member 16 in the center part of the hole bottom part 14 so that at least one part of the contact member 22 may be located on the axis line O.

It is sectional drawing which shows one Embodiment of this invention. It is sectional drawing which shows the modification of embodiment shown in FIG. It is sectional drawing which shows the conventional composite drill.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Shank 13 Mounting hole 14 Hole bottom part of the mounting hole 15 Cutting blade part 16 Cutting blade member 17 Rear end part of the cutting blade member 16 Adhesive 19 Cutting blade 21 Rear end surface 22 of the cutting blade member 16 Contact member A Mounting hole 13 inner diameter B outer diameter of rear end 17 C outer diameter of cutting edge 19 D outer diameter of abutting member 22 O axis of shank 11 X central axis of rear end 17

Claims (3)

  In the composite drill in which the rear end portion of the cutting blade member provided with the cutting edge portion on the front end side is inserted into the mounting hole formed in the front end portion of the shank and fixed by an adhesive, the mounting hole An abutting member that protrudes from the bottom of the hole and can abut on the rear end surface of the cutting blade member is interposed between the bottom of the hole and the rear end surface of the cutting blade member. A composite drill characterized by   The composite drill according to claim 1, wherein the bottom of the mounting hole has a concave conical surface shape, and the contact member is spherical. 3. The composite according to claim 1, wherein an outer diameter of the contact member is in a range of 0.3 to 1.0 of an outer diameter of a rear end portion of the cutting blade member. Drill.

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