JP5103077B2 - drill - Google Patents

Description

  The present invention relates to a drill for making a hole in, for example, an engine component.

  As a drill for drilling a metal part such as an engine part, for example, Patent Document 1 discloses that the full length or a part of the twist angle of the blade part is continuously changed and the twist angle on the tip side of the blade part is changed. A drill having a larger twist angle on the rear end side is disclosed. It is described that this improves the sharpness of the drill and further increases the rigidity of the drill.

  That is, in this type of drill, the strength of the drill, such as bending strength, so-called rigidity, cutting resistance (cutting reaction force), chip shape, dischargeability, and the like vary depending on the size of the twist angle.

Japanese Utility Model Publication No. 53-38953

  By the way, for example, in the case of continuously producing engine parts made of aluminum casting, holes formed by casting in the engine parts, so-called cast holes, may vary in formation positions depending on the casting accuracy. is there. For this reason, when such a hole is cut with a drill, a displacement occurs between the cutting direction (cutting position) of the drill and the hole, resulting in a large load on the drill, tool life and There is a possibility that the processing accuracy is lowered.

  Therefore, as a drill used for machining such a cast hole, by optimizing the setting condition of the torsion angle, even if the above-mentioned positional deviation or the like occurs, the drill is damaged or the processing accuracy is improved. There is a need to avoid the decline.

  The present invention has been made in consideration of the above-described conventional problems, for example, even when cutting a punched hole, it is possible to reduce the load applied to the drill and maintain a long tool life, An object is to provide a drill capable of improving machining accuracy.

  A drill according to the present invention includes a blade portion in which a cutting edge is formed along a cutting direction from the front end side toward the rear end side, and a shank portion formed continuously on the rear end side of the blade portion. The blade portion is provided along the cutting direction from the tip of the blade portion, and has a tip-side cutting edge formed at a constant first twist angle, and the tip-side cutting blade in the cutting direction. An intermediate groove formed with a twist angle gradually changing from the first twist angle to the second twist angle along the cutting direction, and continuous along the cutting direction from the intermediate groove, A rear end side groove formed at the second twist angle, the rear end groove is set to be longer in the cutting direction than the front end side cutting edge, and the second twist angle is The angle is set to be smaller than the first twist angle.

  According to such a configuration, the front end side cutting edge is set to have a larger twist angle than the rear end side groove, so that it can be cut into the workpiece with a low cutting resistance. Therefore, for example, in the case of cutting a core hole formed in a workpiece, even if there is a positional deviation between the axial direction of the drill and the axial direction of the core hole, The drill can be cut straight along its axial direction with little influence on the position. For this reason, even if the casting accuracy of the cast hole is low, it is possible to reliably perform drilling at a desired position and to obtain high processing accuracy. In addition, it is possible to effectively prevent the drill from being inserted into the casting hole in an oblique direction due to the displacement and causing bending, breakage, and the like, so that the tool life can be maintained long.

  Furthermore, it is preferable that diamond is provided at the tip of the blade portion because chip dischargeability is further improved and wear resistance of the blade edge is also improved.

  According to the present invention, in the blade portion that performs cutting on the workpiece, the front end side cutting edge is set to have a larger twist angle than the rear end side groove. Therefore, it is possible to reduce the cutting resistance of the cutting edge at the time of cutting into the workpiece, and in particular, when cutting a punched hole, the drill is not affected by the positional accuracy of the punched hole. A straight cut can be made along the axial direction. For this reason, it is possible to reliably perform drilling at a desired position and to obtain high processing accuracy. In addition, it is possible to effectively prevent the drill from being inserted into the casting hole in an oblique direction due to the displacement and causing bending, breakage, and the like, so that the tool life can be maintained long.

  Hereinafter, preferred embodiments of the drill according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a perspective view of a drill 10 according to an embodiment of the present invention, FIG. 2A is a side view of the drill 10 shown in FIG. 1, and FIG. 2B is a blade portion of the drill 10 shown in FIG. It is explanatory drawing which shows the change of a twist angle. The drill 10 according to the present embodiment can be suitably used, for example, when cutting a punched hole previously formed in a cast part as a work, and the work is, for example, an engine part made of aluminum casting. A cylinder block or the like is exemplified. Needless to say, the drill 10 can be used effectively other than such a cast hole, for example, when drilling a metal part from scratch.

  As shown in FIGS. 1 and 2A, a drill 10 according to the present embodiment includes a blade portion 12 that performs a cutting process on a workpiece, and a shank portion 14 provided on the rear end side of the blade portion 12. Yes. The shank portion 14 is a portion that is gripped by a chuck or the like of a rotational drive source provided in a machine tool (not shown) when the drill 10 is used.

  In the blade portion 12, two cutting blades 16 and 18 are spiral along the cutting direction (axial direction) from the front end side to the rear end side of the drill 10 (in the case of this embodiment, substantially straight from the middle). Is formed. As shown in FIGS. 1, 3A and 3C, the cutting edges 16 and 18 extend from the front end side to the rear end side in a state of being symmetrically arranged with respect to the axial direction of the drill 10. . In this case, one cutting blade 16 is continuous with the blade surface 17a located on the front side in the rotation direction of the drill 10 (the direction of arrow A in FIG. 3A) and the rear side of the blade surface 17a. A projecting surface 17b constituting a radial surface, a first inclined surface 17c continuous from the projecting surface 17b, and a second inclined surface continuing from the first inclined surface 17c and constituting the outer diameter surface of the drill 10 together with the projecting surface 17b. It is comprised from the inclined surface 17d and the wall surface 17e which continues from this 2nd inclined surface 17d to the blade surface 19a of the other cutting blade 18. FIG. Similarly, the other cutting edge 18 includes a blade surface 19a, a protruding surface 19b, a first inclined surface 19c, a second inclined surface 19d, and a wall surface 19e.

  As can be understood from FIG. 3A, in the cutting edges 16 and 18, rake angles are provided on the blade surfaces 17 a and 19 a that are actually cut into the workpiece. Further, in the drill 10, the width in the circumferential direction of the projecting surfaces 17 b and 19 b, so-called margin width, is set smaller than that of the drill according to the conventional configuration, whereby the rotation direction of the drill 10 (arrow A in FIG. 3A). Cutting force (cutting torque) generated in the direction) is reduced. In addition, since the second inclined surfaces 17d and 19d function as a second margin portion following the projecting surfaces 17b and 19b, the straight traveling stability of the drill 10 is further improved.

  The tip surface 20 of the blade portion 12 has a conical shape centering on the apex (chisel point) 20a that is the foremost end of the drill 10 (see FIGS. 3B and 3C), and in the side view shown in FIG. It has a fan shape having a predetermined angle θ (for example, 166 °) centered on 20a. Thus, when the angle θ is an obtuse angle, the cutting reaction force (radial reaction force) in the rotation direction of the drill 10 can be reduced. 3A and 3C, the tip surface 20 includes a first tip inclined surface 22a and a second tip inclined surface 22b that are inclined from the apex 20a toward the one cutting edge 16, and the other cutting edge. The first tip inclined surface 24a and the second tip inclined surface 24b inclined in 18 directions are formed into the above-described cone shape. Each of the tip inclined surfaces 22a, 22b, 24a, and 24b is continuous to the cutting edges 16 and 18 at a predetermined angle.

  In such a tip surface 20, openings 26a and 26b are formed in the first tip inclined surfaces 22a and 24a provided at symmetrical positions with the vertex 20a in between (see FIGS. 3A and 3C). These openings 26 a and 26 b are openings on the front end side of the oil passage 28 that penetrates from the front end to the rear end along the axial direction of the drill 10. That is, as shown in FIG. 2A, the oil passage 28 penetrates through the drill 10 from the opening on the rear end surface of the shank portion 14 along the axial direction, and is 1 at a branch point 28a provided near the tip. After branching from the book into two (Y-shaped), it communicates with the openings 26a and 26b.

  Further, in the blade portion 12, between the cutting blades 16 and 18 extending spirally as described above, workpiece chips cut by the blade surfaces 17a and 19a of the cutting blades 16 and 18 are transferred to the blade portion. Chip discharge grooves 30 and 32 for transferring to the shank portion 14 side, which is the rear end side of 12, are formed. That is, as shown in FIG. 3A, the chip discharge groove 30 is formed by the blade surface 17a of the cutting blade 16 and the wall surface 19e of the cutting blade 18, and discharges chips cut mainly by the blade surface 17a. 32 is formed by the blade surface 19a of the cutting blade 18 and the wall surface 17e of the cutting blade 16, and discharges chips cut mainly by the blade surface 19a.

  By the way, as described above, in such a drill 10, the strength (rigidity) such as the bending strength of the drill 10 and the shape of chips (depending on the inclination angle of the cutting edge 16 (18) with respect to the axial direction, that is, the so-called twist angle. Size) and its emissions will change. That is, when the twist angle is small, for example, about 0 to 15 ° (hereinafter also referred to as a weak angle), the rigidity is high, but the cutting resistance tends to be large, and the chip is small but the discharge property is small. Lower. On the other hand, when the twist angle is large, for example, about 25 to 45 ° (hereinafter also referred to as a strong angle), the rigidity is low, but the cutting resistance tends to be small, and the chips are large (long). Its emissions are high.

  Therefore, in the drill 10 according to the present embodiment, as shown in FIGS. 2A and 2B, the tip side in which the portion of the distance L1 is formed at a constant first twist angle α1 along the cutting direction from the tip of the blade portion 12. Cutting blades 16a and 18a are used, and the portion of distance L2 on the rear end side is a variable twist angle αx that gradually changes from the first twist angle α1 to the second twist angle α2 (an angle different from the first twist angle α1). The formed intermediate grooves 16b and 18b are configured as rear end side grooves 16c and 18c formed with a constant second twist angle α2 at a distance L3 on the rear end side. As can be understood from FIG. 2A, the rear end side grooves 16 c and 18 c form the rear end of the blade portion 12 connected to the shank portion 14. Therefore, the cutting edge 16 includes a front end side cutting edge 16a formed with a constant first helix angle α1, a rear end side groove 16c formed with a constant second helix angle α2, and a variable connecting between them. It is comprised from the intermediate groove 16b formed with the twist angle (alpha) x, and the cutting blade 18 is comprised similarly.

  That is, in the drill 10 according to the present embodiment, the first twist angle α1 is a strong angle of about 25 to 45 ° (in the case of the present embodiment) as understood from the graph showing the change in the twist angle in FIG. 2B. 35 °), the second twist angle α2 is set to a weak angle of about 0 to 15 ° (0 ° in this embodiment), and the twist angle αx is about 45 to 0 °. The changing angle is set to a so-called variable angle (35 to 0 ° in the case of the present embodiment). Further, in the drill 10, the distance L1 where the front end side cutting edges 16a and 18a are formed, the distance L2 where the intermediate grooves 16b and 18b are formed, and the distance L3 where the rear end side grooves 16c and 18c are formed are L1. For example, the distance L2 is about 2 to 3 times the distance L1, and the distance L3 is about 15 times the distance L1.

  As shown in FIG. 2A, the branch point 28a of the oil passage 28 is set, for example, in a region of a distance L2 where the intermediate grooves 16b and 18b are formed. Naturally, the branch point 28a can be set in the region of the distance L1 where the front end side cutting edges 16a and 18a are formed or at other positions, and the oil passage 28 is all one or two from the front end to the rear end. It is also possible to form with a book.

  Next, the operation and effect of the drill 10 according to the present embodiment configured basically as described above will be described.

  First, as shown in FIG. 4, a cylinder block made of, for example, aluminum casting is disposed as a workpiece W on a machine tool (not shown), and the shank of the drill 10 is connected to the rotation drive source 40 of the machine tool via a chuck. The part 14 is fixed. Thereafter, the rotational drive source 40 is started to rotate the drill 10 at a high speed in the direction of arrow A in FIG. 3A. Next, by cutting the tip surface 20 of the drill 10 toward the core hole 42 formed in the workpiece W along the axial direction thereof, the workpiece W starts to be cut by the blade portion 12.

  In the drill 10 according to the present embodiment, of the cutting blades 16 and 18 formed on the blade portion 12, cutting to the core hole 42 is started by the tip-side cutting blades 16a and 18a formed on the tip side, and gradually. The intermediate grooves 16 b and 18 b and the rear end side grooves 16 c and 18 c are inserted into the workpiece W while being inserted into holes having a predetermined diameter centered on the cast hole 42.

  In this case, in the drill 10, the distal end side cutting edges 16 a and 18 a are set at a strong first twist angle α 1 and have a rake angle, so that the cutting hole 42 can be formed with a low cutting resistance. It is possible to cut reliably and stably. Therefore, as shown in FIG. 4, even if there is a positional deviation G between the axial direction D of the drill 10 and the axial direction H of the core hole 42 within a predetermined allowable range, the drill 10 can be cut straight along the axial direction H with almost no influence on the position of the punched hole 42. For this reason, even if the casting accuracy of the cast hole 42 is low, it is possible to reliably perform drilling at a desired position, and it is possible to obtain high processing (position) accuracy. In addition, since the drill 10 can be effectively prevented from being inserted into the casting hole 42 in an oblique direction due to the positional deviation G as described above and causing bending or breakage, the tool life can be maintained long. It becomes possible.

  On the other hand, the chips of the workpiece W cut by the tip side cutting edges 16a and 18a having such a strong first twist angle α1 tend to be relatively long and large as described above. Since the amount of chips generated in the processing of the punched hole 42 is small, it can be easily transferred to the intermediate grooves 16b and 18b by the synergistic effect with the high chip discharging performance, and the rear end side grooves 16c and It can be reliably discharged from the hole 18c.

  That is, in the drill 10, since the rear end side grooves 16c and 18c are formed with the weak second twist angle α2 as compared with the tip side cutting edges 16a and 18a having high chip discharging performance, the chip discharging performance is slightly low. It will be. However, since the chip amount itself is small in the cast hole 42, the chip is reliably discharged to the outside without causing clogging or the like. In addition, since the tip-side cutting edges 16a and 18a have high chip discharge efficiency, it is possible to effectively avoid clogging of chips in the deep part of the hole being cut and breakage of the drill 10, and the load on the drill 10 can be effectively avoided. Thus, the tool life can be maintained longer.

  In addition, the rear end side grooves 16c and 18c have a constant second twist angle α2, which is constant at a weak angle, in particular, in the case of the present embodiment, the second twist angle α2 is set to 0 °. Since 18c is formed as what is called a straight blade drill, it has high rigidity. For this reason, even when the positional deviation G occurs during the cutting of the punched hole 42, the root portion of the drill 10, that is, the rear end side grooves 16 c and 18 c are formed in the vicinity of the opening of the hole during the cutting. It is possible to effectively avoid deformation and damage caused by collision with W. In practice, most of the cutting of the punched hole 42 is performed by the front end side cutting blades 16a and 18a, and in the deep state, most of the hole is in contact with the rear end side grooves 16c and 18c.

  Further, the twist angle αx of the intermediate grooves 16b and 18b is gradually increased in a direction that gradually eliminates the angle difference between the first twist angle α1 of the front end side cutting edges 16a and 18a and the second twist angle α2 of the rear end side grooves 16c and 18c. It is set to change (see FIG. 2B). For this reason, it can suppress effectively that the blade part 12 produces an abrupt characteristic change in the axial direction due to the difference in the twist angle, and as a result, the load during cutting of the drill 10 is suppressed, and the tool life of the drill 10 is reduced. It can be further extended.

  In the drill 10, it may be necessary to re-polish the tip end side of the blade portion 12 by cutting a plurality of times or cutting a hard material. In this case, in the drill 10, since the distal end side cutting edges 16a and 18a constituting the distal end side of the cutting edges 16 and 18 are set to be constant at the first twist angle α1, and the sufficient distance L1 is set, By re-grinding, it is possible to effectively prevent changes in the characteristics of the leading edge side cutting edges 16a and 18a, that is, the cutting resistance, the shape of chips at the time of cutting, etc., and always obtain stable cutting characteristics. it can.

  Further, in the oil passage 28 in the drill 10, the branch point 28a is set at a portion where the intermediate grooves 16b and 18b are located as described above. That is, in most of the axial direction of the drill 10 from the shank portion 14 to the rear end side grooves 16c and 18c and a part of the intermediate grooves 16b and 18b, the oil passage 28 passes through one axial center position of the drill 10. Has been. For this reason, it becomes possible to reduce the flow resistance (passage resistance) of the cutting oil in the oil passage 28, and to form a twist shape in the rear end side grooves 16c and 18c having the second twist angle α2. Such restrictions can be eliminated and a free twist can be set. Furthermore, since the branch point 28a is set at the portion where the intermediate grooves 16b and 18b are located as described above, the positions of the openings 26a and 26b on the front end side of the oil passage 28 are hardly changed even by the re-polishing. In other words, it is possible to effectively prevent the oil supply characteristics from the openings 26a and 26b from being changed to the cutting portion, thereby enabling more stable cutting.

  Moreover, in the drill 10, a diamond cutting edge can be fixed to the front end side cutting edges 16a and 18a, or a diamond coating can be applied. Thereby, chip discharge | emission property improves further and the abrasion resistance of a blade edge | tip improves.

  As described above, the present invention has been described with the embodiments. However, the present invention is not limited to this, and it is naturally possible to adopt various configurations without departing from the gist of the present invention.

It is a perspective view of a drill concerning one embodiment of the present invention. 2A is a side view of the drill shown in FIG. 1, and FIG. 2B is an explanatory view showing a change in the twist angle of the blade portion of the drill shown in FIG. 3A is a front view of the drill shown in FIG. 2, FIG. 3B is a partially omitted side view in which the tip side of the drill shown in FIG. 2 is enlarged, and FIG. 3C is the tip side of the drill shown in FIG. FIG. It is explanatory drawing which shows the state which cuts into the core hole of the workpiece | work W with the drill shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Drill 12 ... Blade part 14 ... Shank part 16, 18 ... Cutting blade 16a, 18a ... Front end side cutting blade 16b, 18b ... Intermediate groove 16c, 18c ... Rear end side groove 17a, 19a ... Blade surface 20 ... Tip surface 28 ... Oil passages 30, 32 ... chip discharge grooves

Claims (2)

A drill comprising a blade portion in which a cutting blade is formed along a cutting direction from the front end side toward the rear end side, and a shank portion formed continuously on the rear end side of the blade portion,
The blade part is provided along the cutting direction from the tip of the blade part, and a tip-side cutting blade formed at a constant first twist angle;
An intermediate groove formed along the cutting direction from the tip side cutting edge and formed with a twist angle that gradually changes from the first twist angle to the second twist angle along the cutting direction;
The length in the cutting direction is set to be larger than the leading edge side cutting blade while being continuous from the intermediate groove along the cutting direction , and is set to a constant angle smaller than the first twist angle. and the rear end groove formed in the second twist angle are include those having a
The drill is formed with an oil passage penetrating from the front end to the rear end along the axial direction,
The oil passage is formed by one from the shank portion side to the position where the intermediate groove is formed, and after branching into two at the position where the intermediate groove is formed, the oil passage is formed on the tip surface of the blade portion. A drill characterized by being opened at two locations . The drill according to claim 1, wherein
The drill characterized by the diamond provided in the front-end | tip of the said blade part.

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