JP2014079814A - Boring tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boring tool capable of sufficiently increasing dimensional accuracy of a machined hole.SOLUTION: The boring tool is inserted into a prepared hole, previously formed in a workpiece, to cut the inner wall surface of the prepared hole and form a machined hole. The boring tool comprises: a tool body 2 having a shaft shape and rotated around its axis O; and a plurality of cutting edges 3 formed on an outer circumferential surface of the tool body 2 in the circumferential direction with mutual intervals, and extending along the axis O direction. The number of cutting edges 3 is an even number, and all the pairs of the cutting edges 3 disposed back-to-back by sandwiching the axis O on a cross section perpendicular to the axis O are not at the positions of 180° rotational symmetry to each other.

Description

  The present invention relates to a hole machining tool that is inserted into a prepared hole formed in advance in a workpiece and cuts an inner wall surface of the prepared hole to form a processed hole.

  Conventionally, as this type of drilling tool, for example, as shown in Patent Document 1 below, a tool body (shank portion) that has an axial shape and is rotated around the axis, and a circumferential direction on the outer peripheral surface of the tool body. A reamer is known that includes a plurality of cutting edges that are formed at intervals and extend along the axial direction. In this hole drilling tool, a plurality of cutting edges are arranged at equal intervals in the circumferential direction on the outer peripheral surface of the tool body.

JP 2002-059313 A

  However, the above-described conventional drilling tools still have room for improvement in improving the dimensional accuracy (particularly roundness and cylindricity) of the drilled holes.

  This invention is made | formed in view of such a situation, Comprising: It aims at providing the drilling tool which can fully improve the dimensional accuracy of a drilling hole.

In order to solve such problems and achieve the above object, the present invention proposes the following means.
That is, the present invention is a hole machining tool that is inserted into a prepared hole formed in a work material in advance and cuts the inner wall surface of the prepared hole to form a processed hole. A tool body that is rotated around, and a plurality of cutting edges that are formed on the outer peripheral surface of the tool body at intervals in the circumferential direction and extend along the axial direction, and the number of cutting edges is an even number. A pair of cutting blades arranged in a back direction across the axis in a cross section perpendicular to the axis are not in a rotationally symmetric position with respect to each other by 180 °.

  In the hole drilling tool of the present invention, the number (total number) of cutting edges formed on the outer peripheral surface of the tool body is an even number, and a pair of cutting edges are arranged in the back direction with the axis of the tool body sandwiched in the center. (Placed back to back). And in the cross section perpendicular to the axis of the tool main body (hereinafter referred to as a cross sectional view), all the pair of cutting edges are arranged so as not to be 180 ° rotationally symmetrical with each other. Play.

  In other words, the distance between the pair of cutting blades arranged in the back direction in a cross-sectional view of the tool body is smaller than the diameter of the circular rotation locus (the inner diameter of the machining hole) drawn by the cutting edges around the axis. And when one of the pair of cutting edges cuts into the inner wall surface (inner peripheral surface) of the prepared hole of the workpiece, the external force (reaction force) that the one cutting edge receives by cutting ) Is less likely to affect the cutting of the other cutting edge through the tool body. That is, in this cross-sectional view, since the other cutting edge is not on the straight line connecting the one cutting edge and the axis of the tool body, the cutting load generated on one cutting edge is transmitted to the other cutting edge. Hateful. In addition, since the straight line connecting the pair of cutting edges does not pass on the tool axis line, the tool body is less likely to run out.

  In this way, since the cutting edges facing each other are less likely to affect each other and the shaft runout is suppressed, the roundness and cylindricity of the processed hole formed in the workpiece are reliably increased. . Therefore, according to the drilling tool of the present invention, the dimensional accuracy of the drilled hole can be sufficiently increased.

  Further, in the drilling tool of the present invention, in the cross section perpendicular to the axis, the angles formed around the axis between the cutting edges adjacent in the circumferential direction are set to be different from each other. It is good as well.

  In this case, in the cross-sectional view of the tool body, the angles (center angles) formed around the axis line between the cutting edges adjacent in the circumferential direction are all set to be different from each other. It is easy to realize the configuration described above. In addition, the effect of preventing vibration and resonance of the tool body is remarkably enhanced, and high-precision cutting can be performed.

  Further, in the drilling tool of the present invention, the outer peripheral surface of the tool body is disposed adjacent to the rear side in the tool rotation direction of the cutting edge, and a cross section perpendicular to the axis is on the rotation locus of the cutting edge. It is good also as providing the circular land part which makes circular arc shape so that it may overlap.

  In this case, a circular land portion adjacent to the other cutting edge is arranged on a straight line passing through at least one of the cutting edges and the axis among the pair of cutting edges arranged in the back direction in the cross-sectional view of the tool body. it can. Therefore, when one of the cutting edges receives an external force by cutting, the round land portion located on the opposite side across the axis line comes into contact with the inner wall surface of the machining hole, so that the one cutting edge is radially inward. Thus, the cutting edge is prevented from being retracted from the rotation locus (that is, the machining surface). As a result, the dimensional accuracy of the processed hole is significantly increased. Such an action is difficult to obtain when the number of cutting edges is an odd number.

  According to the drilling tool of the present invention, the dimensional accuracy of the drilled hole can be sufficiently increased.

It is the (a) front view and (b) side view which show the drilling tool concerning one embodiment of the present invention. It is a cross-sectional view (cross-sectional view perpendicular to the axis) showing the main part of the hole drilling tool of FIG. It is a cross-sectional view which shows the reference example for demonstrating the drilling tool which concerns on one Embodiment of this invention. It is a cross-sectional view which shows the reference example for demonstrating the drilling tool which concerns on one Embodiment of this invention. It is a figure explaining the roundness of the processing hole cut by the hole processing tool of this invention. It is a figure explaining the roundness of the processing hole cut with the hole processing tool of the reference example.

Hereinafter, a drilling tool 1 according to an embodiment of the present invention will be described with reference to the drawings.
The hole machining tool 1 of the present embodiment is a reamer used for machining a stem guide hole through which a valve stem is inserted, for example, in a cylinder head of an automobile engine or the like.

The hole machining tool 1 is inserted into a prepared hole formed in a workpiece, and an inner wall surface (inner peripheral surface) of the prepared hole is cut to form a processed hole having a predetermined inner diameter. .
As shown in FIGS. 1A and 1B and FIG. 2, the drilling tool 1 has a shaft shape, a tool body 2 that is rotated around the axis O, and a circumferential direction on the outer peripheral surface of the tool body 2. And a plurality of cutting edges 3 extending along the axis O direction. Further, the hole machining tool 1 is disposed adjacent to the tool rotation direction T rear side of the cutting edge 3 on the outer peripheral surface of the tool body 2, and a cross section perpendicular to the axis O overlaps the rotation locus of the cutting edge 3. In this way, the circular land portion 4 having an arc shape and the circular land portion 4 are connected to the rear side in the tool rotation direction T, and the cross section perpendicular to the axis O is retracted radially inward from the circular land portion 4. And a formed flank face portion 5. Further, on the outer peripheral surface of the tool body 2, a chip discharge groove 8 is formed between the flank portion 5 and the cutting edge 3 adjacent to the flank portion 5 on the rear side in the tool rotation direction T.
This drilling tool 1 is mounted on a cutting tool (not shown) whose base end side (right side in FIG. 1B) along the axis O direction of the tool body 2 has a larger diameter than the drilling tool 1. At the same time, the cutting tool is mounted on a main shaft of a machine tool or the like, and the main shaft rotates to rotate about the axis O.

  Here, in the present specification, of the direction along the axis O of the tool body 2 (axis O direction), the cutting tool side of the tool body 2 is referred to as a base end side, and the cutting tool of the tool body 2 is In addition to being on the opposite side, the direction in which the tool body 2 is inserted into the prepared hole of the workpiece (left side in FIG. 1B) is referred to as the tip side. A direction perpendicular to the axis O (direction orthogonal to the axis O) is referred to as a radial direction, and a direction around the axis O is referred to as a circumferential direction.

  In FIG. 1B, the tool main body 2 has an axial shape (bar shape), the tip side portion of the tool main body 2 is a cutting edge portion 6, and the base end side portion is a shank portion 7. The tool body 2 is formed of a hard material such as a cemented carbide. The tool body 2 preferably has at least a cutting edge portion 6 made of a hard material such as cemented carbide, and the shank portion 7 may be a steel material other than the hard material. Further, a coolant supply hole (not shown) is formed in the tool body 2 so as to penetrate the tool body 2 along the axis O. The coolant supply hole is formed to be branched into a plurality from the axis O in the tool body 2 toward each cutting edge 3.

  An end portion on the proximal end side of the shank portion 7 of the tool main body 2 is a mounting portion for mounting the drilling tool 1 on the cutting tool.

  As shown in FIG. 1B, in the present embodiment, the cutting edge 3 extends in a spiral shape gradually toward the front side in the tool rotation direction T from the tip end in the axis O direction toward the base end side. Yes. Note that the cutting edge 3 may gradually extend toward the rear side in the tool rotation direction T from the tip end in the axis O direction toward the base end side, or may be formed to extend in parallel to the axis O. Good. Further, the tip 3a of the cutting edge 3 is different from the portion other than the tip 3a, and gradually extends inward in the radial direction toward the tip. The tip 3a is a bite blade (pilot blade). ).

  In FIG. 2, in the present embodiment, the cutting edge 3 is formed on the outer peripheral surface of the cutting edge portion 6 of the tool body 2 so as to have an even number of cutting edges 3 at intervals in the circumferential direction. A blade 3 is formed. Between the cutting edges 3 adjacent to each other in the circumferential direction in the cutting edge portion 6 of the tool body 2, among these cutting edges 3, the cutting edge 3 located on the rear side in the tool rotation direction T is on the front side in the tool rotation direction T. A chip discharge groove 8 that is continuous and recessed radially inward of the cutting edge 3 and extends along the direction of the axis O is formed.

  In the cross-sectional view shown in FIG. 2 (sectional view perpendicular to the axis O), the wall surface 8a facing the front side in the tool rotation direction T in the chip discharge groove 8 extends radially inward from the cutting edge 3. This wall surface 8 a is the rake face of the cutting edge 3. Further, the wall surface 8b facing the tool rotation direction T rear side in the chip discharge groove 8 gradually extends toward the tool rotation direction T rear side as it goes radially inward.

  The round land portions 4 are formed adjacent to the rear side in the tool rotation direction T of all the cutting edges 3, and in this embodiment, the length (circumferential length) along the circumferential direction between the round land portions 4 is set. They are almost identical to each other. When the diameter of the cutting edge portion 6 of the tool body 2 is, for example, φ4 to 20 mm, the circumferential length of each round land portion 4 is in the range of 0.05 to 0.5 mm, for example. In the cross-sectional view shown in FIG. 2, the round land portion 4 is formed in an arc shape so as to be positioned on the rotation locus around the axis O of the cutting edge 3 indicated by a two-dot chain line in the drawing, A ridge line portion formed at the edge of the round land portion 4 on the front side in the tool rotation direction T is a cutting edge 3.

  The flank surfaces 5 are formed adjacent to the rear side of the tool rotation direction T of all the round lands 4, and the wall surfaces 8 b of the chip discharge grooves 8 are respectively formed on the rear side of the flank surfaces 5 in the tool rotation direction T. It is lined up. In the cross-sectional view shown in FIG. 2, the flank portion 5 extends linearly toward the inner side in the radial direction gradually toward the rear side in the tool rotation direction T. 2, the amount of radial displacement per unit length along the circumferential direction of the flank portion 5 is smaller than the amount of displacement of the wall surface 8b of the chip discharge groove 8. That is, in the cross-sectional view of the tool main body 2, the inclination of the flank portion 5 is gentler than the inclination of the wall surface 8b of the chip discharge groove 8, and the flank portion 5 is formed. Compared to the configuration in which the wall surface 8b is directly connected to the rear side of the tool rotation direction T of the portion 4, the thickness of the rear side of the cutting edge 3 of the tool body 2 is ensured.

  Further, in the present embodiment, the length along the circumferential direction of the round land portion 4 is shorter than the length along the circumferential direction of the flank surface portion 5. The total length along the circumferential direction of the round land portion 4 is set so that the inner wall surface of the processed hole formed in the workpiece is within a desired surface roughness range.

  Further, in the cross-sectional view shown in FIG. 2, the pair of cutting blades 3 that are arranged in a back-to-back direction (facing each other back to back) with respect to the axis O are 180 ° rotationally symmetric with respect to each other (two-fold symmetric). ) Position is not set. In the present embodiment, six cutting blades 3 are formed, and three pairs of cutting blades 3 arranged in the back direction are provided, and each of the cutting blades 3 in these three pairs of pairs, All are set so as not to be in a position of 180 ° rotational symmetry.

  Specifically, out of a pair of cutting edges 3 that are arranged backward with the axis O in between, the other cutting edge 3 is rotated around the axis O from the position where the other cutting edge 3 is 180 ° rotationally symmetrical (tool) The angle α shifted to the front side or the rear side in the rotation direction T is in the range of 1 to 10 °. Here, the direction of the circumferential direction in which the other cutting edge 3 is shifted around the axis O from the position where the other cutting edge 3 is 180 ° rotationally symmetric with respect to one cutting edge 3 is determined by which one of the reference cutting edges 3 is Therefore, the angle α may be directed from the 180 ° rotationally symmetric position toward the front side of the tool rotation direction T or toward the rear side of the tool rotation direction T. Specifically, in FIG. 2, among a pair of cutting blades 3 arranged back and forth in FIG. 2 across the axis O, a one-dot chain line passing through one cutting blade 3 positioned below and the axis O. The crossing angle (center angle) α formed between the straight line shown and the straight line passing through the other cutting edge 3 positioned above and the axis O (corresponding to the wall surface 8a) is 1 ° ≦ α ≦ 10. Within the range of °.

  Further, in the cross-sectional view shown in FIG. 2, the angles θ1 to θ6 formed around the axis O between the cutting edges 3 adjacent in the circumferential direction are all set to be different from each other. In the case where six cutting edges 3 are formed as in the present embodiment, for example, the angles θ1 to θ6 are all set to different values within a range of 50 to 70 °.

  In the drilling tool 1 of the present embodiment described above, the number (total number) of cutting edges 3 formed on the outer peripheral surface of the tool body 2 is an even number, and the axis O of the tool body 2 is sandwiched in the center. A pair of cutting blades 3 are arranged backward (arranged back to back). And in the cross-sectional view perpendicular | vertical to the axis O of the tool main body 2, since all the said pair of cutting blades 3 are the arrangement | positioning which is not in a mutually 180 degree rotational symmetry position, there exists the following remarkable effect. .

  That is, in the cross-sectional view of the tool body 2 shown in FIG. 2, the distance between the pair of cutting edges 3 arranged in the back direction is the diameter of the circular rotation locus drawn by the cutting edges 3 about the axis O. When one of the pair of cutting blades 3 cuts into the inner wall surface (inner peripheral surface) of the lower hole of the workpiece, the one of the pair of cutting blades 3 The external force (reaction force) that the cutting edge 3 receives by cutting is less likely to affect the cutting of the other cutting edge 3 through the tool body 2. That is, in this cross-sectional view, since the other cutting edge 3 is not on the straight line connecting the one cutting edge 3 and the axis O of the tool body 2, the cutting load generated on one cutting edge 3 is It is difficult to be transmitted to the cutting edge 3. Further, since the straight line connecting the pair of cutting edges 3 does not pass on the tool axis O, the axial runout of the tool body 2 is less likely to occur.

  In this way, since the back-facing cutting edges 3 are less likely to affect each other and the shaft runout is suppressed, the roundness and cylindricity of the machining hole formed in the workpiece are reliably increased. It is done. Therefore, according to the drilling tool 1 of this embodiment, the dimensional accuracy of the drilled hole can be sufficiently increased.

  In addition, since the angles θ1 to θ6 formed around the axis O between the cutting edges 3 adjacent to each other in the circumferential direction in the cross section perpendicular to the axis O are set to be different from each other, this embodiment The above-described configuration (a configuration in which all the back-facing cutting blades 3 are not positioned at 180 ° rotational symmetry) is easily realized. In addition, the effect of preventing vibration and resonance of the tool body 2 is remarkably enhanced, and high-precision cutting can be performed.

In addition, the tool body 2 is disposed on the outer peripheral surface adjacent to the rear side in the tool rotation direction T of the cutting edge 3, and overlaps the rotation locus of the cutting edge 3 in a cross-sectional view of the tool body 2. Since the round land portions 4 are respectively formed, the following effects are obtained.
That is, in a cross-sectional view shown in FIG. 2, a pair of cutting blades 3 arranged in the back direction (for example, a pair of cutting blades 3 arranged in the back direction from upper left to lower right across the axis O in FIG. 2) Round land adjacent to the other cutting edge 3 (upper left cutting edge 3 in FIG. 2) on a straight line passing through at least one cutting edge 3 (lower right cutting edge 3 in FIG. 2) and the axis O. The part 4 can be arranged. Therefore, when one of the cutting edges 3 receives an external force by cutting, the round land portion 4 positioned on the opposite side across the axis O comes into contact with the inner wall surface of the machining hole, whereby the one cutting edge 3 Is supported from the inner side in the radial direction, and the cutting edge 3 is suppressed from being retracted from the rotation locus (that is, the machining surface). As a result, the dimensional accuracy of the processed hole is significantly increased. Such an action is difficult to obtain when the number of cutting edges 3 is an odd number.

  Further, in the hole drilling tool 1 of the present embodiment, the round land portion 4 and the flank portion 5 are provided on the plurality of cutting edges 3 arranged on the outer peripheral surface of the tool body 2 at intervals in the circumferential direction. Are formed in this order from the tool rotation direction T toward the rear side. That is, by forming the round lands 4 adjacent to the cutting edge 3, a vanish effect is obtained by the round lands 4, that is, the round lands 4 are smooth by rubbing the inner peripheral surface of the processing hole. A finished surface is obtained and the surface roughness of the machined hole is ensured. Further, by forming the flank portions 5 adjacent to the round lands 4, the length along the circumferential direction of the round lands 4 can be suppressed to be small, and the round lands 4 are inside the machining holes. It is suppressed that the cutting resistance increases due to excessive rubbing of the wall surface.

  Therefore, according to the drilling tool 1 of the present embodiment, it is possible to prevent vibration and resonance of the tool body 2 by suppressing the cutting resistance while ensuring the surface roughness of the drilled hole. Accurate cutting can be performed stably. In addition, the machined hole thus cut has higher dimensional accuracy and is excellent in roundness and cylindricity.

  In particular, as described in the present embodiment, when the hole machining tool 1 is used for machining a stem guide hole through which a valve stem is inserted in a cylinder head of an automobile engine or the like, for example, as described above, a round land is used. Since the vanish effect by the part 4 is obtained as appropriate, it does not become excessive, and the following effects are produced.

That is, in the stem guide hole, it is preferable that a certain amount of porous (pores) is exposed on the inner peripheral surface of the processed hole, and the lubricating oil is held in the porous, so that the inside of the stem guide hole The valve stem slides smoothly.
According to the drilling tool 1 of the present embodiment, the burnish effect by the round land portion 4 can be obtained as appropriate, but it is not excessive (that is, the surface roughness of the processed surface easily falls within the target value (predetermined range)). ), Seizure of the inner peripheral surface of the processed hole is prevented at the time of drilling, cutting resistance is reduced, and it is also possible to prevent the porous material from being crushed too much. That is, while ensuring the surface roughness, the porous is appropriately left on the inner peripheral surface of the processed hole, and the valve stem slides smoothly in the processed stem guide hole.

Moreover, since the length along the circumferential direction of the round land portion 4 is shorter than the length along the circumferential direction of the flank surface portion 5, the above-described effect is more easily obtained.
In the present embodiment, the number of cutting edges 3 is described as six. However, the number of cutting edges 3 may be four or eight other than that, and in this case, each of the round land portions 4 It is preferable to appropriately set the length along the circumferential direction so that the sum of the lengths of all the round land portions 4 falls within a predetermined range. Specifically, when the number of cutting edges 3 is four as compared with the case where the number of cutting edges 3 is six as in the present embodiment, the length of each round land portion 4 is increased and the cutting edges 3 are increased. When the number of is eight, it is preferable to set the length of each round land portion 4 so that the inner wall surface of the processed hole is within a desired surface roughness range.

Here, the present embodiment will be described in more detail using the reference examples of FIGS. 3 and 4.
In the example of FIG. 3, six cutting edges 3 are formed on the outer peripheral surface of the tool body 2 at unequal intervals in the circumferential direction. The points where the flank portions 5 are connected to each other in this order are the same as those in the above-described embodiment. On the other hand, in the cross-sectional view shown in FIG. The cutting edges 3 are set so as to be 180 ° rotationally symmetrical with each other.

Specifically, in FIG. 3, the angles θ1 to θ3 formed around the axis O between the cutting edges 3 adjacent in the circumferential direction are set to be different from each other, while these angles θ1 to θ3 are Two sets are provided in this order along the tool rotation direction T. Then, the angles θ1, facing each other across the axis O, the angles θ2, and the angles θ3 are set to have the same value.
In this reference example, the angles θ1 to θ3 are set to different values, so that an effect of preventing vibration and resonance of the tool body 2 can be obtained. The blades 3 tend to affect each other's cutting, and the tool body 2 tends to run out, and the dimensional accuracy of the processed hole cannot be ensured with high quality.

5 and 6 show a drilling hole in the prepared hole of the workpiece using the drilling tool 1 according to the embodiment of the present invention and the drilling tool described in the reference example of FIG. It was formed and its roundness was measured.
Among the two hole drilling tools used in this test, in the hole drilling tool 1 of this embodiment, the angles θ1 to θ6 are 63 °, 57 °, 62 °, 58 °, 61 °, 59 ° (in no particular order). The six cutting edges 3 are arranged so as to be completely unequal intervals in the circumferential direction. On the other hand, in the drilling tool of the reference example, the angles θ1 to θ3 were 59 °, 58 °, and 63 ° (in no particular order).
The cutting conditions are: hole machining tool: φ5.5 mm 6-blade reamer, workpiece: sintered material (stem guide), cutting speed (vc): 30 m / min, feed per rotation (fr): 0.3 mm / Rev, drilling length (ld): 25 mm, cutting fluid (pressure): chlorine-free emulsion (5 MPa). Moreover, each cutting process was performed 3 times.

  As is apparent from the measurement results of FIGS. 5 and 6, the machining holes cut by the drilling tool 1 of the present embodiment shown in FIGS. 5A to 5C are shown in FIGS. The roundness was all excellent as compared with the drilled holes cut by the drilling tool of the reference example shown in FIG.

  In the example of FIG. 4, six cutting edges 3 are formed on the outer peripheral surface of the tool body 2 at equal intervals in the circumferential direction (that is, the angle θ is 60 °, and all are the same). Among them, the round land portion 4 and the flank face portion 5 are connected in this order to the rear side of the tool rotation direction T of some of the cutting edges 3, Only the round land portions 9 that are longer in the circumferential direction than the land portions 4 are connected.

  Specifically, the round land portion 9 is located on the rotation locus of the cutting edge 3 indicated by a two-dot chain line in the drawing, and the circumferential length of the round land portion 9 connected to one cutting edge 3 is It is set to be substantially the same as the sum of the circumferential lengths of the round land portion 4 and the flank portion 5 connected to another cutting blade 3 different from the other cutting blade 3.

Also in this reference example, the pair of cutting blades 3 arranged in the back direction with the axis O interposed therebetween are likely to affect each other's cutting, and the shaft runout of the tool body 2 is liable to occur, resulting in a machining hole. The dimensional accuracy cannot be ensured. Further, the tool body 2 may easily vibrate and resonate during processing. Moreover, since the thing with which the round circumference part 9 with a long circumference is formed in the tool rotation direction T back side of the cutting edge 3 is included, the vanish effect by this round land part 9 and the round land part 4 becomes excessive. The cutting resistance increases, the roundness or cylindricity of the processed hole may not be ensured, and the porous surface of the inner peripheral surface of the processed hole is likely to be crushed. As described above, the hole drilling tool of the reference example shown in FIG. 4 is unsuitable for use in machining a stem guide hole through which a valve stem is inserted in a cylinder head of an automobile engine, for example.
That is, like the hole drilling tool 1 of the above-described embodiment, the pair of cutting blades 3 that are arranged backward with respect to the axis O are all arranged at positions that are not rotationally symmetrical with each other by 180 °. Preferably, a round land portion 4 having a short circumferential length and a flank face portion 5 retracted radially inward from the round land portion 4 are connected in this order to the rear side in the tool rotation direction T of all the cutting edges 3. Thus, the vanishing effect is obtained but not excessive, and both the surface roughness and the finished dimensional accuracy are improved. For example, when used for the processing of the stem guide hole, a particularly remarkable effect is obtained. It is obtained.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the above-described embodiment, six cutting edges 3 are formed on the outer peripheral surface of the tool body 2, but if the number of cutting edges 3 is an even number, the effect of the present invention can be obtained. There may be other two, four, eight, etc.

  Moreover, the front-end | tip part 3a in at least one part cutting edge 3 among the some cutting edges 3 may be made into the honing cutting edge to which the honing process was performed.

DESCRIPTION OF SYMBOLS 1 Hole machining tool 2 Tool main body 3 Cutting edge 4 Round land part O Axis line T Tool rotation direction (theta) 1- (theta) 6 The angle formed centering on an axis line between the cutting edges adjacent to the circumferential direction

Claims (3)

A hole machining tool that is inserted into a prepared hole formed in a work material in advance and forms a processed hole by cutting the inner wall surface of the prepared hole,
A tool body that has an axial shape and is rotated around the axis,
A plurality of cutting blades formed on the outer peripheral surface of the tool body at intervals in the circumferential direction and extending along the axial direction,
The number of cutting edges is an even number,
A drilling tool characterized in that a pair of cutting blades arranged in a back direction across the axis in a cross section perpendicular to the axis are not in a rotationally symmetric position with respect to each other by 180 °. The drilling tool according to claim 1,
A drilling tool characterized in that angles formed around the axis line between the cutting edges adjacent in the circumferential direction in the cross section perpendicular to the axis line are all different from each other. The drilling tool according to claim 1 or 2,
On the outer peripheral surface of the tool main body, a round land which is arranged adjacent to the rear side in the tool rotation direction of the cutting edge and has an arc shape so that a cross section perpendicular to the axis overlaps the rotation locus of the cutting edge. A drilling tool characterized by comprising a part.

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