JP7483524B2 - Cutting tools and cutting methods - Google Patents

Description

The present invention relates to a cutting tool for cutting a workpiece having multiple holes, and a cutting method thereof.

Patent Document 1 describes a cutting tool for cutting a workpiece having a plurality of holes, and a cutting method thereof.
The cutting tool described in Patent Document 1 is a boring bar, which is used to cut holes located in the middle of a plurality of holes in a workpiece, excluding support holes located at both ends. The boring bar extends in the longitudinal direction and has one or more cutting blades provided in the middle and a support device provided at the base end. Paragraph [0017] of Patent Document 1 states that the cross section of the base 3 of the boring bar 1 is substantially circular.
In the cutting method described in Patent Document 1, after a boring bar is inserted into a plurality of holes in a workpiece, a counter tool, which is an example of a jig, is connected to the tip of the boring bar by a connecting device. The tip of the boring bar is held in one of the support holes in the workpiece via the counter tool, and the base end is held in the other of the support holes via a support device. In this state, the boring bar is rotated and moved relatively in the axial direction, thereby cutting the processed holes in the workpiece.

Patent No. 4750253

The objective of the present invention is to provide a cutting tool and a cutting method that can perform cutting processing on a workpiece having multiple holes without using a jig or the like.

The workpiece to be cut has a plurality of preformed holes, and the holes located at both ends of the plurality of holes are reference holes, and one or more of the intermediate holes among the plurality of holes excluding the reference holes located at both ends are the processed holes to be cut.
The cutting tool according to the present invention extends in the longitudinal direction and has one or more cutting edges provided in the middle portion and guide portions provided at both end portions.
In the cutting method according to the present invention, the cutting tool is inserted into a plurality of holes in the workpiece and moved in a direction perpendicular to the axis by relative movement between the cutting tool and the workpiece in the axial direction. As a result, each of the guide parts provided at both ends is brought close to the inner peripheral surface of the reference hole, and the cutting edge is brought close to the inner peripheral surface of the machined hole. Next, the cutting tool is moved relative to the workpiece in the axial direction while being rotated. As a result, the machined hole in the workpiece is machined. As the cutting tool rotates, centrifugal force acts, and the guide parts are pressed against the inner peripheral surface of the reference hole. The cutting is performed with the guide parts in contact with the inner peripheral surface of the reference hole, and the machined hole can be machined with high precision.
As described above, the cutting tool according to the present invention has guide portions provided at both ends, and therefore the cutting method according to the present invention does not require jigs such as counter tools that were necessary in the cutting method described in Patent Document 1.

1 is a conceptual diagram showing an entire working device in which a cutting tool according to an embodiment of the present invention is used, and a cutting method according to an embodiment of the present invention is carried out in this working device. FIG. 2 is a perspective view of the cutting tool. FIG. 2 is another perspective view of the cutting tool. FIG. 2 is a side view (partially sectional view) of the cutting tool. FIG. 2 is a cross-sectional view of the cutting tool taken along line AA. FIG. 5 is a cross-sectional view of the cutting tool shown in FIG. FIG. 3 is a CC cross-sectional view of the cutting tool. FIG. 5 is a cross-sectional view of the cutting tool shown in FIG. FIG. 5 is an E-E cross-sectional view of the cutting tool. FIG. 5 is an operational diagram conceptually showing a case where cutting is performed using the cutting tool. FIG. 5 is an operational diagram (sectional view taken along the line B-B) when cutting is performed using the cutting tool. FIG. 1A and 1B are diagrams illustrating the operation of a holder for holding the cutting tool, and FIG. 1C is a diagram illustrating a method for evaluating a workpiece.

The cutting tool according to one embodiment of the present invention will be described in detail below with reference to the drawings. This cutting tool can be used, for example, to machine a crank hole in a cylinder block as a workpiece W, and can be used in a machining center, an NC machine tool, a machine tool, or other work device.

An example of a working device in which a cutting tool 10 is used is shown in Fig. 1. The working device includes a device base 12, a turntable 14 as a workpiece holding table, a column 18 that holds a spindle 16, and a control device 20 mainly composed of a computer. A workpiece W is placed and held on the turntable 14. In this working device, the turntable 14 is provided rotatably and swingably relative to the device base 12, the column 18 is provided on the device base 12 so as to be movable in the horizontal direction, and the spindle 16 is held by the column 18 so as to be movable in the vertical direction.
The structure of the working device is not limited. For example, the turntable 14 can be provided so as to be movable horizontally and vertically relative to the device base 12. The main shaft 16 may extend generally horizontally or vertically.

In this work device, one of a number of tools (e.g., cutting tool 10) stored in a tool magazine (not shown) is selectively attached to the spindle 16 and operated. This allows various operations such as cutting to be performed. The control device 20 controls the drive device that drives the column 18, the drive device that drives the spindle 16, the drive device that drives the turntable 14, etc. according to a predetermined operation program. Work on the workpiece W is performed by the rotation of the spindle 16 and the relative movement of the turntable 14 and the spindle 14.

The workpiece W has a number of holes (five holes in this embodiment) J (J1, J2, J3, J4, J5) that have been formed in advance in a row. Of the multiple holes J, the holes J1 and J5 located at both ends are reference holes, and the holes J2, J3, J4 located in the middle are machined holes to be cut by the cutting tool 10. In general, the radius Ra of the machined holes J2, J3, J4 before cutting by the cutting tool 10 is smaller than the radius Rb of the reference holes J1, J5 (Rb>Ra), and the inner surfaces of the machined holes J2, J3, J4 are cut by the cutting tool 10 to approach the radius Rb.

As shown in Figures 2 to 4, the cutting tool 10 is a line bar used as a boring bar, and includes a main body 30 extending in the longitudinal direction, a plurality of cutting blade cartridges 32 provided in the middle of the main body 30 and spaced apart in the longitudinal direction, and guide portions 34, 36 provided at both ends of the main body 30. The line bar 10 is held by a floating holder 40 at the base end of the main body 30, and is held by the main shaft 16 via the floating holder 40, for example.

As shown in Figures 2 to 4, the main body 30 has a sector-shaped portion 30h having a generally sector-shaped cross section perpendicular to the axis Lr (the axis extending in the longitudinal direction) of the line bar 10, and a held portion 30v having a generally circular cross section that is held by the floating holder 40. As shown in Figures 5 to 7 and 9, the sector-shaped portion 30h has a wide portion 42 including an outer circumferential surface extending in an arc shape, and a mountain-shaped portion 44 having an outer shape of a mountain shape and including its apex. As shown in Figure 5, the outer circumferential surface of the wide portion 42 forms an arc shape with a radius Rc (Rc<Rb) smaller than the radius Rb with the center T located on the axis Lr, and the central angle φ is smaller than 180 degrees.
The central angle φ is designed based on the radius Rc of the main body 30, the radius Rb of the reference holes J1, J5, etc. For example, it can be designed so that the guide portions 34, 36 provided on the main body 30 can be spaced from the inner circumferential surfaces of the reference holes J1, J5, and can be set to, for example, about 150 degrees.

The center of gravity G of the sector portion 30h is located closer to the wide portion than the center T, and the distance between the center T and the center of gravity G in the direction perpendicular to the axis Lr is Dg. On the other hand, the sector portion 30h can be considered to have a shape obtained by removing the removed portion 54, which is the portion facing the wide portion 42, from a cylindrical member of radius Rc at the center T, as shown in FIG. 9.

For example, if the distance Dm from the center T to the end on the mountain-shaped portion side is the same, and the central angle φ of the wide width portion 42 is the same, the distance Dg between the center of gravity G and the center T will be greater when the volume of the removed portion 54 is large than when it is small. If the volume of the removed portion 54 is the same, and the central angle φ of the wide width portion 42 is the same, the distance Dg between the center T and the center of gravity G will be greater when the distance Dm from the center T to the end on the mountain-shaped portion side is small than when it is large. Also, if the weight of the fan-shaped portion 30h is the same, the amount of imbalance will be greater when the distance Dg is large than when it is small, and if the rotation speed is the same, the centrifugal force acting on the fan-shaped portion 30h when the line bar 10 rotates will be greater.

Taking the above into consideration, the shape of the sector-shaped portion 30h is designed, and for example, the distance Dm can be set to 70% or less of the radius Rc, and the volume of the removed portion 54 can be set to 30% or more of the volume of the cylindrical member of radius Rc. In this case, the distance Dg between the center of gravity G and the center T can be set to 15% or more of the radius Rc. This makes it possible to increase the amount of imbalance (for example, 0.059 kgmm), and to apply a large centrifugal force to the sector-shaped portion 30h.

The distance Dg between the center of gravity G and the center T of the sector portion 30h is a value calculated on the assumption that the density of the main body 30 is uniform. However, in reality, the main body 30 may be provided with a coolant supply hole, a gap for weight reduction, or the like, or a cutting blade cartridge 32 or the like may be attached, so the distance Dg may differ from the calculated value.
Furthermore, the sectorial portion 30h of the line bar 10 is not necessarily manufactured by cutting the removed portion 54 from a cylindrical member. The above description merely expresses the shape of the sectorial portion 30h, and does not limit the manufacturing method of the sectorial portion 30h.

The ratio (VA/VB) of the volume VA on the mountain-shaped portion side from the line H perpendicular to the center T of the sector portion 30h to the volume VB on the wide portion side is 0.6 or less (0.5 or less in this embodiment). When the ratio is small, the distance Dg between the center of gravity G and the center T is greater than when the ratio is large.
In addition, since the sector-shaped portion 30h often has coolant supply holes or gaps, the volume ratio and the weight ratio do not necessarily correspond one-to-one.

As shown in FIG. 4 etc., a plurality of cutting blade cartridges 32 (six in this embodiment) are provided in the middle of the main body 30 in the direction in which the axis Lr of the line bar 10 extends (hereinafter, sometimes referred to as the axial direction of the line bar 10). Of these six cutting blade cartridges 32, three are for rough cutting, and the remaining three are for finishing. The rough cutting and finishing blade cartridges are adjacent to each other, and in this embodiment, the rough cutting blade cartridge 32 is located at the tip side of the finishing cutting blade cartridge 32. It is not essential to provide a rough cutting blade cartridge and a finishing cutting blade cartridge in the line bar 10.

As shown in FIG. 6, the cutting blade cartridges 32 are each provided in the middle of the main body 30, near the end face of the sector-shaped portion 30h. Each cutting blade cartridge 32 has a cartridge body and a tip 46 provided on the cartridge body, and the cartridge body is attached to the main body 30 of the line bar 10 by a bolt 48. The tip 46 has a cutting blade 32c, and the cutting blade 32c is located on a circumference of a circle with a radius Rb and a center T.

One of the guide parts 34, 36 is the tip side guide part 34 shown in FIG. 5 provided on the tip side of the main body 30, and the other is the base side guide part 36 shown in FIG. 7 provided on the base side. These tip side guide part 34 and base side guide part 36 each include a plurality of guide pads 50 (three in this embodiment) provided on the outer peripheral surface of the wide part 42 of the main body 30. The guide pads 50 each extend generally in the axial direction of the line bar 10, and are attached to the outer peripheral surface of the wide part 42 of the main body 30 at intervals in the circumferential direction by a plurality of bolts. The length of the guide pads 50 is determined based on the length of the reference holes J1, J5 and the relative axial movement amount between the line bar 10 and the workpiece W during cutting processing. In addition, the outer peripheral surface of each guide pad 50 is located in an arc shape with a radius Rb of the center T. In this embodiment, the guide surface is formed by the outer peripheral surfaces of the three guide pads 30.

As shown in FIG. 6, these three guide pads 50 and cutting edge 32c are arranged within a range of a central angle θ around the center T of the sector portion 30h when viewed from the front of the line bar 10. The central angle θ is smaller than 180 degrees. During cutting, cutting resistance (principal force, thrust force, feed force) acts on the cutting edge 32c, but the guide pad 50 is arranged in a portion of the main body 30 that receives most of the cutting resistance (principal force, thrust force).

In this embodiment, the floating holder 40 transmits the rotation of the main shaft 16, and holds the line bar 10 so that it can move in a direction perpendicular to the axis Lf of the floating holder 40 and tilt with respect to the axis Lf. As shown in Figs. 4 and 8, the floating holder 40 includes a first member 40a that is held rotatably integrally with the main shaft 16, a second member 40b that is attached rotatably integrally to the held portion 30v of the line bar 10, and an Oldham coupling 60 provided between the first member 40a and the second member 40b. The first member 40a has an axis Lf, and is held on the main shaft 16 in a state in which the axis Lf extends in the same line as the rotation axis of the main shaft 16. The second axis 40b is attached to the line bar 10 in a state in which it is positioned in the same axis as the axis Lr of the line bar 10.

The Oldham coupling 60 connects the first member 40a and the second member 40b, transmitting the rotation of the first member 40a to the second member 40b, and allowing the second member 40b to move relative to the first member 40a in a direction perpendicular to the axis Lf. An intermediate body (not shown) of the Oldham coupling 60 is held by a key and a key groove to the first member 40a (see FIG. 8) so as to be movable relative to the first member 40a in a first direction perpendicular to the axis Lf, and the second member 40b is held by a key and a key groove to be movable relative to the intermediate body in a second direction perpendicular to the axis Lf and the first direction.

As shown in FIG. 4, the second member 40b has a flange portion 62 protruding in the radial direction, and a bearing having a pair of balls 64, 66 is provided on both sides of the flange portion 62 in the direction of the axis Lf. A radial gap is provided between the outer circumferential surface of the flange portion 62 and the first member 40a. This radial gap allows the second member 40b to move relative to the first member 40a in a direction perpendicular to the axis Lf. A gap is provided in the direction of the axis Lf between the end face of the bearing having the balls 64, 66 and the first member 40a, or between the flange portion 62 and the bearing. This gap in the direction of the axis Lf allows the second member 40b to tilt relative to the axis Lf of the first member 40a.
Thus, in this embodiment, as shown in Figures 13(a) and (b), the line bar 10 is held by the floating holder 40 on the main shaft 16 so as to be movable and tiltable in a direction perpendicular to the axis of the main shaft 16 (axis Lf of the first member 40a).

A case where cutting is performed on a workpiece W in the working device configured as above will be described.
Before the machining holes J2 to J4 of the workpiece W are cut by the line bar 10, the reference holes J1 and J5 are cut.
A workpiece W is held on the turntable 14, and a cutting tool 80, which is different from the line bar 10, is attached to the spindle 16 via a holder. As shown in Fig. 10(a), cutting processing is performed for the reference hole J5 using the cutting tool 80, and then, as shown in Fig. 10(b), the turntable 14 is rotated 180 degrees, and cutting processing is performed similarly for the reference hole J1. The radii of the reference holes J1 and J5 are set to approximately the radius Rb.

Next, cutting is performed with the line bar 10 to form the holes J2 to J4.
The line bar 10 is attached to the main shaft 16 via a floating holder 40 .
11(a) and 12(a), the line bar 10 is located at a position where the axis Lr of the line bar 10 is separated by a distance Dr from the axis Lw of the workpiece W (which is a line passing through the centers A of the reference holes J1 and J5) in the direction of a straight line α, in other words, where the cutting blade 32c and the guide surface are spaced apart from the inner peripheral surfaces of the holes J1 to J5 of the workpiece W, and a clearance exists between the cutting blade 32c and the guide surface and the inner peripheral surfaces of the holes J1 to J5. The straight line α is a line passing through 1/2 of the central angle θ of the region of the sector portion 30h where the three guide pads 50 and the cutting blade 32c are located. In this embodiment, when viewed from the front of the line bar 10, the guide pad 50 and the cutting blade cartridge 32 are arranged within a region where the central angle is less than 180 degrees (in this embodiment, within a region of approximately 150 degrees). Therefore, by separating the axis Lr of the line bar 10 from the axis Lw of the workpiece W along the straight line α, the outer peripheral surface of the guide pad 50 and the cutting blade 32c can be separated favorably from the inner peripheral surfaces of the holes J1 to J5.

Next, as shown in FIG. 11(b), the line bar 10 is moved relative to the workpiece W in the axial direction, and is inserted into the multiple holes J in the workpiece W. The line bar 10 is inserted until the tip guide portion 34 reaches the reference hole J1. This process is called the insertion process.

Next, as shown in Figures 11(c) and 12(b), the line bar 10 is moved Dr in the direction indicated by the arrow p (a direction perpendicular to the axis Lr) to align the axis Lr of the line bar 10 with the axis Lw of the workpiece W. In this state, theoretically, in each of the tip guide portion 34 and the base guide portion 36, the outer peripheral surface of the guide pad 50 contacts the inner peripheral surface of the holes J1 and J5, and the cutting edge 32c contacts the inner peripheral surface of the machined holes J2, J3, and J4. This process is called the shift process.

As shown in FIG. 11(d), the main shaft 16 is rotated, and the turntable 14 and column 18 are moved relative to each other. The line bar 10 is moved forward relatively while being rotated about the axis (axis of rotation) Lr. With the guide parts 34, 36 pressed against the reference holes J1, J5 by centrifugal force, i.e., with the guides in effect, cutting is performed on the machining holes J2, J3, and J4. This process is called the cutting process.

After cutting the machining holes J2 to J4, as shown in Figures 11(e) and 12(c), the line bar 10 is moved a distance Dr in the direction indicated by the arrow q (a direction perpendicular to the axis Lr), and the guide pad 50 and the cutting edge 32c are separated from the inner surface of the workpiece W.
Next, as shown in FIG. 11( f ), the line bar 10 is retracted and pulled out from the workpiece W.

As described above, the cutting tool according to this embodiment includes guide portions 34, 36 provided at both the tip and base ends, so that the cutting method according to this embodiment does not require a jig such as a counter tool that was necessary in the cutting method described in Patent Document 1. Also, a cutting method is known in which a support is placed near the workpiece W and cutting is performed with the tip of the line bar held by the support, but the cutting method according to this embodiment does not require any additional equipment such as a support. In other words, cutting of the workpiece W can be performed in the working device without using any jig or additional equipment.

In the line bar 10 according to the present embodiment, the rough cutting blade 32c and the finish cutting blade 32c are adjacent to each other, and the rough cutting blade 32c is located on the tip side of the finish cutting blade 32c. Therefore, both rough cutting and finish cutting can be performed by advancing the line bar 10 in the axial direction once.
When the rough cutting blade 32c is provided at a position on the base end side of the finishing cutting blade 32c, both rough cutting and finishing can be performed by retracting the line bar 10 in the axial direction. In this embodiment, since both the tip guide portion 34 and the base guide portion 36 are provided in a portion of the main body 30 with a central angle of 180 degrees or less, it is possible to move the line bar 10 in a direction perpendicular to the axis to a position in good contact with the inner circumferential surface and a position spaced apart from the inner circumferential surface, and cutting can be performed both when advancing and when retracting.

On the other hand, the workpiece W after cutting is evaluated based on the deviation Δ of each center line of the machined holes J2 to J4 from the axis Lw (a line passing through the centers A of the reference holes J1 and J5) of the workpiece W, as shown in Figure 13(c). When Δ is small, the workpiece W is evaluated higher than when Δ is large.
In contrast, in this embodiment, the cutting process is performed on the machining holes J2 to J4 in a state where the guide portions 34, 36 of the line bar 10 are in contact with the reference holes J1, J5 of the workpiece W by centrifugal force. In other words, the cutting process is performed using the holes J1, J5 as the reference holes J1, J5 for the cutting process, but the reference holes J1, J5 are also the reference holes for evaluating the workpiece W. In this way, the cutting process is performed using the reference holes J1, J5 for evaluation as the reference holes J1, J5 for the cutting process, so that the workpiece after the cutting process can be highly evaluated.

While the cross-sectional shape of the base body 3 of the boring bar described in Patent Document 1 is substantially circular, the cross-sectional shape of the sector portion 30h of the line bar 10 in this embodiment is generally sector-shaped. Therefore, the distance between the center of gravity G of the line bar 10 and the axis of rotation Lr (=Lw) can be increased, and the centrifugal force acting on the line bar 10 can be increased compared to a cross-sectional shape that is substantially circular.

In this embodiment, a guide pad 50 is provided in a portion of the body 30 that receives the cutting resistance applied to the cutting edge 32c. In addition, because the body 30 is fan-shaped, a large centrifugal force acts on the body 30 in a direction that presses the guide surface against the reference holes J1, J5 and presses the cutting edge 32c against the processing holes J2, J3, J4. Therefore, the guide pad 50 can be effectively pressed against the inner peripheral surfaces of the reference holes J1, J5, and the cutting edge 32c can be effectively prevented from floating up. As a result, cutting can be performed with high precision on the processing holes J2 to J4.

Depending on the design of the sector portion 30h, the rotational speed of the main shaft 16, etc., the centrifugal force can be made greater than the cutting resistance, in which case the cutting edge 32c can be prevented from floating up even more effectively.
Furthermore, the centrifugal force can be made larger than the sum of the cutting resistance and the weight of the line bar 10. For example, when the axis of the main shaft 16 extends generally horizontally, the pressing force pressing the guide parts 34, 36 and the cutting blade 32c against the holes J1 to J5 due to the weight of the line bar 10 may be reduced depending on the rotation phase. On the other hand, when a centrifugal force larger than the sum of the cutting resistance acting on the cutting blade 32c and the gravity acting on the line bar 10 acts on the line bar 10, it is possible to effectively suppress the lifting of the cutting blade 32c caused by the change in the rotation phase of the line bar 10, and the machining accuracy of the machined holes J1 to J4 can be further improved.

For example, in the driver 10, if the distance Dm between the center T and the end on the mountain-shaped portion side is set to 65% or less of the radius Rc, and the removal portion 54 is set to 30% or more of the cylindrical member, the distance between the center of gravity G and the center T can be set to 20% or more of the radius Rc, and by setting the rotational speed to 52.3 rad/s or more, the centrifugal force can be made to be more than twice the weight, and can be made larger than the combined value of the cutting resistance and the weight.

In addition, the spindle 16 and the axis Lw of the workpiece W may not be aligned in a straight line. For example, as shown in Figures 10(a) and (b), when machining the reference holes J1 and J5, the relative positions of the reference hole J1 and the cutting tool 80 and the relative positions of the reference hole J5 and the cutting tool 80 may be misaligned due to the accuracy of the turntable 14, etc., resulting in misalignment between the reference holes J1 and J5.

On the other hand, in this embodiment, the line bar 10 is attached to the spindle 16 via the floating holder 40, and is held by the floating holder 40 so that it can move relative to the axis Lf (which is on the same line as the axis of the spindle 16) in a direction perpendicular to the axis Lf, and can tilt with respect to the axis Lf. Therefore, even if the axis Lw of the workpiece W is horizontally or vertically shifted with respect to the axis of the spindle 16 (axis Lf of the floating holder 40), or even if the axis Lw of the workpiece W is tilted with respect to the axis Lf, as shown in Figures 13(a) and (b), the line bar 10 can be inserted into the multiple holes J1 to J5 along the axis Lw of the workpiece W, that is, the axis Lw passing through the centers of the reference holes J1 and J5. In other words, although the line bar 10 extends in a straight line, the curvature of the line bar 10 when inserted into the multiple holes J1 to J5 can be reduced. Therefore, by rotating the line bar 10 around the axis Lw (= Lr) and moving it forward with the guide parts 34, 36 in contact with the reference holes J1, J5, the distance Δ between the center line of each of the machining holes J2 to J4 and the axis Lw can be reduced, and a highly rated workpiece W can be obtained.

On the other hand, there are cases where the guide portion is provided only at the tip of the line bar. In such a case, cutting is performed on the machining hole while being guided by the guide portion provided at the tip and one reference hole.
In contrast, the line bar 10 according to this embodiment includes guide portions 34, 36 provided at both the tip and base ends, and the machining holes J2 to J4 are cut with the guide portions 34, 36 in contact with the reference holes J1, J5 of the workpiece W. Therefore, compared to the above-mentioned case, the machining holes J2 to J4 can be cut with high accuracy.

When the main shaft 16 of the working device extends generally vertically, the reduction in the pressing force of the guide parts 34, 36 against the reference holes J1, J5 caused by the weight of the line bar 10 can be effectively suppressed, and cutting can be performed with high precision.

In addition, the number of cutting blade cartridges 32, the number of guide pads 50, etc., for the line bar 10 are not limited to those in the above embodiment. In addition, the shape and type of the workpiece W are not important, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

10: Line bar 14: Turntable 16: Main shaft 30: Main body 30h: Fan-shaped section 32: Cutting blade cartridge 32c: Cutting blade 36: Base end guide section 34: Tip end guide section 40: Floating holder 42: Wide section 50: Guide pad 60: Oldham coupling 62: Flange section

Patentable inventions

(1) A cutting tool for cutting a workpiece having a plurality of holes formed in advance in a line, comprising:
The workpiece includes reference holes that are holes located at both ends of the plurality of holes, and processed holes that are one or more holes located in the middle of the plurality of holes excluding the reference holes,
The cutting tool,
A body extending in a longitudinal direction;
one or more cutting edges provided in an intermediate portion of the body;
a guide portion provided at each end of the body and capable of contacting each inner circumferential surface of the reference hole.
The cutting tool performs cutting on the machining hole while being positioned by the guide parts provided at both ends and the reference hole.

(2) The cutting tool according to (1), wherein the main body includes a sector portion having a generally sector-shaped cross-sectional shape, and the central angle of the sector portion is smaller than 180 degrees.
The central angle can be, for example, 90 degrees or more, 100 degrees or more, 110 degrees or more, or 120 degrees or more, and can be 170 degrees or less, 160 degrees or less, 150 degrees or less, 140 degrees or less, etc.
The outer periphery of the cross section of the main body that is curved in an arc shape is not limited to being composed of an arc of one circle, and may include arcs of a plurality of circles.

(3) the center of gravity of the sector is located closer to the generally arc-shaped outer circumferential surface of the sector than the rotation axis of the cutting tool;
The cutting tool according to claim 2, wherein the distance between the center of gravity and the axis of rotation is 15% or more of the distance from the axis of rotation to the generally arcuately curved outer circumferential surface.
When the ratio of the distance between the rotation axis and the center of gravity to the distance from the rotation axis to the outer circumferential surface is large, the amount of imbalance becomes relatively larger than when the ratio is small, and the centrifugal force acting on the fan-shaped portion can be made larger. Also, it is desirable for the ratio to be 20% or more, or 25% or more.

(4) A cutting tool according to (2) or (3), wherein the fan-shaped portion has a shape obtained by removing from a cylindrical member centered on the rotation axis of the cutting tool a portion that faces the generally arc-shaped curved outer peripheral surface of the cylindrical member, the portion accounting for 25% or more of the volume of the cylindrical member.
The volume of the portion excluded from the cylindrical member is desirably 60% or less, 50% or less, or 45% or less of the volume of the cylindrical member, and desirably 30% or more, 35% or more, 40% or more, etc.

(5) A cutting tool according to any one of (2) to (4), wherein the ratio of the distance from the axis of rotation of the cutting tool to the end of the sector opposite the generally arcuately curved outer circumferential surface to the distance from the axis of rotation to the generally arcuately curved outer circumferential surface is 0.7 or less.
A small ratio tends to result in a larger distance Dg between the center of gravity and the axis of rotation than a large ratio. The ratio may be 0.65 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, etc. The ratio may even be 0.

(6) A cutting tool according to any one of (2) to (5), wherein the ratio of the area of the cross section of the sector portion on the side where the outer peripheral edge is generally curved in a circular arc shape relative to a line perpendicular to the rotation axis of the cutting tool to the area of the portion on the opposite side to the side where the outer peripheral edge is generally curved in a circular arc shape relative to a line perpendicular to the rotation axis of the cutting tool is 0.6 or less.
Since the cross section of the main body is sector-shaped, the cross-sectional area SA of portion A on the generally arcuate side of line H (see FIG. 9) perpendicular to the axis of rotation is larger than the cross-sectional area SB of portion B on the opposite side of line H to portion A. It is desirable for this ratio (SB/SA) to be greater than 0 and equal to or less than 0.55, equal to or less than 0.5, equal to or less than 0.45, equal to or less than 0.4, etc.
In addition, since cutting tools are provided with coolant supply holes, hollow portions for reducing weight, etc., the cross-sectional area ratio and the weight ratio do not necessarily correspond one-to-one. However, it can be considered that, relatively speaking, when the cross-sectional area ratio is large, the weight ratio also becomes large.

The features described in paragraphs (3) to (6) above are not limited to cases where the cross-sectional shape of the main body is generally fan-shaped. They can also be applied to cases where the cross-sectional shape of the main body is generally circular with a portion cut out.

(7) The cutting tool according to any one of (1) to (6), wherein the guide portion includes a plurality of guide pads provided on the outer circumferential surface of each of the two end portions of the main body.
The guide pads may be provided on the outer circumferential surface of the sector portion of the main body.
The guide pad extends in the longitudinal direction and has a length that allows it to contact the reference hole even when the cutting tool is moved in the axial direction.
Additionally, the guide pads may be made of an ultra-hard material.

(8) The cutting tool according to (7), wherein the plurality of guide pads and the cutting edge are provided in a portion of the sector portion where the central angle is smaller than 180 degrees when viewed from the front of the cutting tool.
By moving the cutting tool in a direction perpendicular to the axis, the guide pad and cutting edge can be moved between a position in which they contact the inner surface of the reference hole and the machining hole and a position away from the inner surface.

(9) A cutting tool according to any one of items (1) to (8), in which the cutting tool is attached to a spindle via a holder and is held in the holder so as to be movable relative to the holder in a direction perpendicular to the axis of the holder and tiltable with respect to the axis of the holder.

(10) a spindle that holds a cutting tool via a holder;
A cutting method for a workpiece having a plurality of holes formed in a line and a workpiece holder that holds the workpiece, the method comprising the steps of: rotating the spindle and moving the spindle and the workpiece holder relative to each other, and using the cutting tool to perform cutting on one or more holes that are located at intermediate positions among the plurality of holes in the workpiece, the method comprising the steps of:
The cutting tool includes a body extending in a longitudinal direction, one or more cutting blades provided in a middle portion of the body, and guide portions provided at both ends of the body,
The cutting method comprises:
an insertion process of inserting the cutting tool into the holes in the workpiece by bringing the cutting tool and the workpiece close to each other in a state in which the one or more cutting blades and the guide portions provided at each of the two end portions are spaced from inner circumferential surfaces of the holes;
a shift process in which the cutting tool and the workpiece are moved relative to each other in a direction perpendicular to the axis of the cutting tool to bring guide portions provided at both ends of the cutting tool closer to inner peripheral surfaces of reference holes, which are holes located at both ends of the plurality of holes in the workpiece, and bring the cutting blade closer to an inner peripheral surface of the machined hole;
The cutting method includes a cutting process in which the cutting tool is guided by the guide portion and the reference hole, and the cutting tool is rotated and the cutting tool and the workpiece are moved relative to each other to perform cutting on a machined hole in the workpiece.
The main shaft may extend generally horizontally or generally vertically. The cutting tool used in carrying out the cutting method described in this section may be any of the cutting tools described in sections (1) to (9).

(11) The cutting method described in (10) in which, in the cutting step, the cutting tool is rotated, and centrifugal force acting on the main body presses the guide portion against the inner surface of the reference hole and presses the cutting edge against the machined hole.

(12) A cutting method according to paragraph (10) or (11), in which the centrifugal force acting on the main body in the cutting step is greater than the cutting resistance acting on the cutting blade.

(13) A cutting method according to any one of items (10) to (12), in which the centrifugal force acting on the cutting tool is greater than the gravity acting on the cutting tool and is applied to the main body during the cutting process.

(14) The main body includes a sector portion having a generally sector-shaped cross-sectional shape in a direction perpendicular to the axis,
The cutting method according to any one of items (10) to (13), wherein in the cutting step, the centrifugal force is applied to the fan-shaped portion.
The cross-sectional shape of the main body is not limited to a sector shape, and may be, for example, a circular shape with a part cut out.

(15) The cutting method according to any one of (10) to (14), wherein the cutting process is performed on the workpiece with the spindle extending in a generally vertical direction.

Claims (6)

A cutting tool for cutting a workpiece having a plurality of holes formed in advance in a line,
The workpiece includes reference holes that are holes located at both ends of the plurality of holes, and processed holes that are one or more holes located in the middle of the plurality of holes excluding the reference holes,
The cutting tool,
A body extending in a longitudinal direction;
one or more cutting edges provided in an intermediate portion of the body;
a guide portion provided at each end of the body and capable of contacting an inner circumferential surface of each of the reference holes,
A cutting tool, wherein the main body includes a sector having a generally sector-shaped cross-sectional shape, and the central angle of the sector is smaller than 180 degrees. a center of gravity of the sector portion is located closer to the generally arcuate curved outer circumferential surface of the sector portion than a rotation axis of the cutting tool;
2. The cutting tool according to claim 1, wherein a distance between the center of gravity and the axis of rotation is 15% or more of a length from the axis of rotation to the generally arcuately curved outer periphery. the sector-shaped portion has a shape obtained by removing a removed portion that is a part of a portion of a cylindrical member that is centered on a rotation axis of the cutting tool and that faces an outer peripheral surface of the cylindrical member that is curved in a generally arc shape,
3. The cutting tool according to claim 1 or 2, wherein a ratio of a distance from the rotation axis to an end opposite to the arc-shaped curved outer peripheral surface to a radius of the cylindrical member is 0.7 or less, and a ratio of a volume of the removed portion to a volume of the cylindrical member is 25% or more. A cutting tool according to any one of claims 1 to 3, wherein the guide portion includes a plurality of guide pads provided on the outer peripheral surface of each of both ends of the main body. The cutting tool according to any one of claims 1 to 4, wherein the cutting tool is attached to the spindle via a holder and is held by the holder so as to be movable relative to the holder in a direction perpendicular to the axis of the holder and tiltable with respect to the axis of the holder. a spindle that holds a cutting tool via a holder;
A cutting method for a workpiece having a plurality of holes formed in a line and a workpiece holder that holds the workpiece, the method comprising the steps of: rotating the spindle and moving the spindle and the workpiece holder relative to each other, and using the cutting tool to perform cutting on one or more holes that are located at intermediate positions among the plurality of holes in the workpiece, the method comprising the steps of:
The cutting tool includes a body extending in a longitudinal direction, one or more cutting blades provided in a middle portion of the body, and guide portions provided at both ends of the body,
The cutting method comprises:
an insertion process of inserting the cutting tool into the holes in the workpiece by bringing the cutting tool and the workpiece close to each other in a state in which the one or more cutting blades and the guide portions provided at each of the two end portions are spaced from inner circumferential surfaces of the holes;
a shift process in which the cutting tool and the workpiece are moved relative to each other in a direction perpendicular to the axis of the cutting tool to bring guide portions provided at both ends of the cutting tool closer to inner peripheral surfaces of reference holes, which are holes located at both ends of the plurality of holes in the workpiece, and bring the cutting blade closer to an inner peripheral surface of the machined hole;
a cutting step of cutting a hole in the workpiece by rotating the cutting tool and moving the cutting tool relative to the workpiece while the cutting tool is positioned by the guide portion and the reference hole,
The main body includes a sector portion having a generally sector-shaped cross-sectional shape in a direction perpendicular to the axis,
In the cutting step, the cutting tool is rotated to press the guide portion against the inner surface of the reference hole by centrifugal force acting on the fan-shaped portion, and the cutting blade is pressed against the machined hole.

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