Finishing method of cylindrical hole and holder selection assisting device

Abstract

To provide a finishing method of a cylindrical hole which can prevent stop of a machine from being caused by swarf tangling the machine and finish multiple cylindrical holes having different hole diameters at low costs without needing human skills.SOLUTION: In a finishing method of a cylindrical hole, a shrink fit holder 1, a carbide arbor 2 formed of cemented carbide, and a replaceable tool 3 are used to move the replaceable tool 3 around a center of a cylindrical hole 20 of a workpiece W in a spiral manner while rotating the replaceable tool 3 with a machining center to finish an inner peripheral surface of the cylindrical hole 20.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for finishing a cylindrical hole and a holder selection support device for use in the method. [Background technology]

[0002] A boring head is generally used when finishing the inner peripheral surface of a cylindrical hole formed in a workpiece (for example, Patent Document 1). An example of a boring head 50 is shown in FIG. 6. The boring head 50 has a tapered shank portion 53 that is inserted and fixed into a tapered hole 52 of a spindle 51 of a machine tool, a rod-shaped shaft portion 54 that extends in the axial direction from the tapered shank portion 53, and a cutting portion 55 provided at the tip of the shaft portion 54. The cutting portion 55 is supported so as to be movable in the radial direction relative to the shaft portion 54, and the radial position of the cutting portion 55 can be adjusted by operating an adjustment screw 56.

[0003] An example of how to use the boring head 50 will be described. First, as shown in Fig. 7, the boring head 50 is set on a tool presetter 57, and the adjustment screw 56 of the boring head 50 is operated to adjust the radial position of the cutting edge 55 at the tip of the boring head 50 to a position slightly offset radially inward from the radial position corresponding to the finishing dimension of the hole diameter of the cylindrical hole 58. Next, as shown in Fig. 6, the boring head 50 is set on the spindle 51 of a machine tool, and the boring head 50 is inserted axially into the cylindrical hole 58 while rotating at a fixed position (the center position of the cylindrical hole 58), thereby cutting the inner peripheral surface of the cylindrical hole 58 over the entire axial length.

[0004] Then, the hole diameter of the cylindrical hole 58 is measured, and the difference between the measured value and the finished dimension of the hole diameter is obtained. As shown in FIG. 7, the boring head 50 is again set on the tool presetter 57, and the position of the blade 55 at the tip of the boring head 50 is manually adjusted so that the radial position of the blade 55 at the tip of the boring head 50 moves radially outward by the amount of the difference between the measured value of the hole diameter and the finished dimension. Then, as shown in FIG. 6, the boring head 50 is again set on the spindle 51 of the machine tool, and the boring head 50 is rotated at a fixed position while being inserted axially into the cylindrical hole 58, thereby cutting the inner peripheral surface of the cylindrical hole 58 over the entire axial length, and the hole diameter of the cylindrical hole 58 is finished to a predetermined finished dimension. As described above, the finishing process of the inner peripheral surface of the cylindrical hole 58 is performed using the boring head 50. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-079517 A Summary of the Invention [Problem to be solved by the invention]

[0006] As shown in FIGS. 6 and 7, when finishing a cylindrical hole 58 using a boring head 50, the following problems arise.

[0007] As shown in FIG. 6, the inner peripheral surface of the cylindrical hole 58 is cut, and then, as shown in FIG. 7, the position of the cutting edge 55 at the tip of the boring head 50 is moved radially outward by the difference between the measured hole diameter and the finished dimension. This requires human skill to manually adjust the position of the cutting edge 55, which is time-consuming and labor-intensive. In addition, as shown in FIG. 8 and FIG. 9, the boring head 50 is rotated at a fixed position while being inserted axially into the cylindrical hole 58, which is prone to generate long chips that are easily entangled with the boring head 50 and cause problems such as machine stoppage. In addition, when finishing a plurality of cylindrical holes 58 with different hole diameters as shown in FIG. 6 and FIG. 8, it is necessary to prepare a plurality of boring heads 50 with different shaft diameters, which is costly. In addition, it takes time and labor to replace the boring head 50.

[0008] The problem that the present invention aims to solve is to provide a method for finishing cylindrical holes that does not require human skill, is less likely to cause machine stoppages due to entanglement of cutting chips, and is capable of finishing a plurality of cylindrical holes of different hole diameters at low cost. [Means for solving the problem]

[0009] The inventors of this invention discovered that by using a shrink fit holder that fixes a tool by shrink fitting, and a carbide arbor formed from a cemented carbide alloy, the shrink fit holder can significantly reduce tool runout compared to a typical collet-type holder, and the carbide arbor has significantly higher rigidity perpendicular to the axis compared to a typical steel arbor. Therefore, by selecting a combination of shrink fit holder and carbide arbor such that the protruding length of the carbide arbor from the shrink fit holder is as short as possible without interfering with the workpiece, it is possible to machine the inner surface of a cylindrical hole in a workpiece with accuracy equal to or greater than that achieved by finish machining with a boring head.

[0010] Based on this finding, in order to solve the above problems, the present invention provides a method for finishing a cylindrical hole having the following configuration. [Configuration 1] A method for finishing an inner peripheral surface of a cylindrical hole of a workpiece, comprising the steps of: A shrink fit holder having a tapered shank portion that is inserted into and fixed to a tapered hole in a spindle of a machining center, and a chuck cylinder portion that extends in an axial direction opposite to the tapered shank portion and has an open tip; a cemented carbide arbor having a base end portion inserted into the chuck cylinder portion and fixed by shrink fitting, a rod-shaped shaft portion extending in the axial direction from the base end portion to the outside of the chuck cylinder portion, and a tool attachment hole opening at a tip end of the shaft portion; an exchangeable tool that is detachably fixed to the tool attachment hole at the tip of the carbide arbor; A method for finishing a cylindrical hole, comprising rotating the exchangeable tool in the machining center while moving it in a spiral shape around the center of the cylindrical hole of the workpiece, thereby finishing the inner surface of the cylindrical hole.

[0011] By adopting this configuration, the shrink fit holder can suppress the vibration of the tool significantly smaller than that of a general collet type holder, and the carbide arbor has a significantly higher rigidity in the axial direction than a general steel arbor. Therefore, by selecting a combination of the shrink fit holder and the carbide arbor so that the protruding length of the carbide arbor from the shrink fit holder is as short as possible within the range where the shrink fit holder does not interfere with the workpiece, the inner surface of the cylindrical hole of the workpiece can be machined to a predetermined hole diameter with an accuracy equal to or higher than that of finishing with a boring head. In addition, the spiral diameter when the replaceable tool moves in a spiral manner can be automatically adjusted by the numerical control of the machining center so that the hole diameter of the cylindrical hole becomes a predetermined finishing dimension. Therefore, manual adjustment of the position of the blade is not required, and no human skill is required. In addition, since the replaceable tool moves in a spiral manner around the center of the cylindrical hole while rotating, the cutting chips when machining the inner surface of the cylindrical hole are finely divided, and long continuous cutting chips are less likely to be generated. Therefore, machine stoppages due to entanglement of cutting chips are unlikely to occur. Also, when finishing multiple cylindrical holes with different hole diameters, the spiral diameter when the replaceable tool moves in a spiral shape can be changed by the numerical control of the machining center, making it possible to finish multiple cylindrical holes with different hole diameters. Therefore, it is low cost and does not require much effort or time.

[0012] [Configuration 2] The method for finishing a cylindrical hole as described in configuration 1, in which the inner surface of the cylindrical hole is finished using a combination of the shrink-fit holder, the carbide arbor, and the replaceable tool such that when the replaceable tool machines the end of the inner surface of the cylindrical hole farther from the spindle, the axial distance from the tip of the chuck barrel portion to the end of the inner surface of the cylindrical hole closer to the spindle is 1 mm or more and less than 25 mm.

[0013] By adopting this configuration, the axial distance from the tip of the chuck tube portion to the end of the inner peripheral surface of the cylindrical hole that is closer to the spindle can be ensured to be 1 mm or more when machining the end of the inner peripheral surface of the cylindrical hole that is farther from the spindle, so that the tip of the chuck tube portion of the shrink fit holder can be reliably prevented from interfering with the workpiece when finishing the inner peripheral surface of the cylindrical hole. Also, since the axial distance from the tip of the chuck tube portion to the end of the inner peripheral surface of the cylindrical hole that is closer to the spindle when machining the end of the inner peripheral surface of the cylindrical hole that is farther from the spindle is less than 25 mm, the protruding length of the carbide arbor from the shrink fit holder is kept short, and the rigidity in the axial direction when the shrink fit holder, carbide arbor, and exchangeable tool are combined is extremely high.

[0014] [Configuration 3] the workpiece has an inner wall surface rising at a predetermined height from a position radially outwardly shifted with respect to an opening edge of the cylindrical hole at an end closer to the spindle, A method for finishing a cylindrical hole as described in configuration 1 or 2, in which the inner surface of the cylindrical hole is finished by a combination of the shrink fit holder, the carbide arbor, and the replaceable tool such that, when the replaceable tool machines the end of the inner surface of the cylindrical hole farther from the spindle, the chuck cylinder portion of the shrink fit holder is positioned opposite the inner wall surface in a direction perpendicular to the axis without interfering with the inner wall surface.

[0015] With this configuration, when machining the end of the inner circumferential surface of the cylindrical hole farther from the spindle, the shrink-fit holder holds the carbide arbor at a position facing the inner wall surface in the axis-perpendicular direction, so the protruding length of the carbide arbor from the shrink-fit holder can be kept short. As a result, the rigidity in the axis-perpendicular direction when the shrink-fit holder, carbide arbor, and replaceable tool are combined is extremely high, and the inner circumferential surface of the cylindrical hole can be finished with high precision.

[0016] The present invention also provides a holder selection support device for use in the cylindrical hole finish machining method, the device having the following configuration. [Configuration 4] A holder selection support device for use in the cylindrical hole finishing method according to configuration 3, comprising: A user inputs input data including a material of the workpiece, a finishing dimension of a hole diameter of the cylindrical hole, an axial length of an inner peripheral surface of the cylindrical hole, a radial distance from an opening edge of an end of the inner peripheral surface of the cylindrical hole closer to the spindle to the inner wall surface, and a height of the inner wall surface; A holder selection support device which, based on the input data, information on multiple types of the shrink fit holders that have been registered in advance, information on multiple types of the carbide arbors that have been registered in advance, and information on multiple types of the replaceable tools that have been registered in advance, selects a combination of the shrink fit holder, the carbide arbor, and the replaceable tool such that when the replaceable tool machines the end of the inner surface of the cylindrical hole that is farther from the spindle, the chuck tube portion of the shrink fit holder is positioned opposite the inner wall surface in a direction perpendicular to the axis without interfering with the inner wall surface, and outputs the selected combination on a screen.

[0017] By using this holder selection support device, when the workpiece has an inner wall surface that rises at a predetermined height from a position shifted radially outward from the opening edge of the end closer to the main axis of the cylindrical hole, it is possible to easily select a combination of shrink fit holder, carbide arbor, and replaceable tool such that the protruding length of the carbide arbor from the shrink fit holder is as short as possible, within the range where the shrink fit holder does not interfere with the inner wall surface of the workpiece.

[0018] [Configuration 5] When there are a plurality of combinations of the shrink fit holder, the carbide arbor, and the replaceable tool such that the chuck tube portion of the shrink fit holder is positioned opposite the inner wall surface in the axis perpendicular direction without interfering with the inner wall surface when the replaceable tool machines the end of the inner surface of the cylindrical hole farther from the spindle, the holder selection support device of configuration 4 outputs on a screen the plurality of combinations of the shrink fit holder, the carbide arbor, and the replaceable tool in order of highest rigidity in the axis perpendicular direction.

[0019] By using this holder selection support device, when there are multiple combinations of shrink fit holder, carbide arbor, and replaceable tool that result in the shortest possible protrusion length of the carbide arbor from the shrink fit holder, it is possible to select the combination with the highest rigidity.Furthermore, if circumstances exist that make it impossible to select the combination with the highest rigidity, it is possible to select the combination with the second highest rigidity, making it possible to make the optimal selection depending on the situation at hand. Effect of the Invention

[0020] In the method for finishing a cylindrical hole of the present invention, the spiral diameter when the replaceable tool moves in a spiral manner can be automatically adjusted by the numerical control of the machining center so that the diameter of the cylindrical hole becomes a predetermined finishing dimension. Therefore, manual adjustment of the position of the blade is not necessary, and no human skill is required. In addition, since the replaceable tool is moved in a spiral manner around the center of the cylindrical hole while rotating, the cutting chips when machining the inner peripheral surface of the cylindrical hole are broken into small pieces, and long continuous cutting chips are unlikely to be generated. Therefore, machine stoppage due to entanglement of cutting chips is unlikely to occur. In addition, when finishing a plurality of cylindrical holes with different hole diameters, the spiral diameter when the replaceable tool moves in a spiral manner can be changed by the numerical control of the machining center, thereby finishing a plurality of cylindrical holes with different hole diameters. Therefore, it is low cost. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a diagram showing an example of a shrink-fit holder, a carbide arbor, and an exchangeable tool used in a cylindrical hole finishing method according to an embodiment of the present invention. [Diagram 2] Close-up of the carbide arbor in Figure 1 [Diagram 3] This figure shows how the diameter of a cylindrical hole is measured with a touch probe after the inner surface of the cylindrical hole is cut using the combination of the shrink fit holder, carbide arbor, and replaceable tool shown in Figure 1. [Figure 4]The figure shows how the inner surface of a cylindrical hole with a larger diameter than that shown in Figure 2 is finished using the combination of the shrink-fit holder, carbide arbor, and replaceable tool shown in Figure 1. [Diagram 5] A diagram showing the state of chips generated in the process shown in Figure 4. [Figure 6] FIG. 10 is a comparative example showing a boring head for finishing the inner peripheral surface of a cylindrical hole. [Figure 7] FIG. 7 shows how the radial position of the cutting edge of the boring head shown in FIG. 6 is adjusted by a tool presetter. [Figure 8] FIG. 7 is a diagram showing a state in which the inner surface of a cylindrical hole having a larger diameter than the cylindrical hole shown in FIG. 6 is finish-machined by a boring head having a larger outer diameter than the boring head shown in FIG. [Figure 9] A diagram showing the state of chips generated in the process shown in Figure 8. [Figure 10] FIG. 2 is a block diagram of a holder selection support device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] FIG. 1 shows an example of a shrink fit holder 1, a carbide arbor 2, and an exchangeable tool 3 used in a cylindrical hole finish machining method according to an embodiment of the present invention.

[0023] The shrink fit holder 1 has a flange portion 4, a tapered shank portion 5 extending in the axial direction (upward in the figure) from the flange portion 4, and a chuck cylinder portion 6 extending in the axial direction (downward in the figure) from the flange portion 4 on the opposite side to the tapered shank portion 5. A circumferential groove 7 is formed on the outer periphery of the flange portion 4 for gripping with a tool changing manipulator (not shown) of a machining center.

[0024] The tapered shank portion 5 is a portion that is inserted into and fixed in the tapered hole 9 of the spindle 8 of the machining center. The machining center used is capable of simultaneously controlling the movement in a total of three axial directions: the Z-axis direction (up and down in the figure), which is the axial direction of the spindle 8; the X-axis direction (left and right in the figure), which is perpendicular to the Z-axis direction; and the Y-axis direction (perpendicular to the paper in the figure). The tapered shank portion 5 is a 7 / 24 tapered shank, the portion that comes into contact with the inner surface of the tapered hole 9 of the spindle 8 being a conical surface with a 7 / 24 gradient (a conical surface with a 7 / 24 ratio of change in diameter to the axial distance). A pull stud 10 is provided at the tip (top end in the figure) of the tapered shank portion 5 to pull and fix the tapered shank portion 5 into the spindle 8. Here, a 7 / 24 taper shank has been used as an example of the taper shank portion 5, but it is also possible to use a 1 / 10 taper shank (a so-called HSK shank) in which the portion that comes into contact with the inner surface of the tapered hole 9 of the spindle 8 is a conical surface with a 1 / 10 gradient.

[0025] The chuck cylinder portion 6 is formed in a cylindrical shape with an open tip. The outer circumferential surface of the chuck cylinder portion 6 is tapered so that the diameter becomes smaller as it gets farther from the flange portion 4. As the chuck cylinder portion 6 having a tapered outer circumferential surface, the figure shows the chuck cylinder portion 6 having a conical outer circumferential surface with a concave curve (preferably a concave quadratic curve) as its generating line, but it is also possible to adopt a chuck cylinder portion 6 having an outer circumferential surface that is a conical surface whose generating line shape is a straight line, and it is also possible to adopt a chuck cylinder portion 6 having an outer circumferential surface that is composed of a cylindrical surface with a constant outer diameter and a conical surface whose diameter gradually becomes smaller from the cylindrical surface toward the tip of the chuck cylinder portion 6.

[0026] The tapered shank portion 5, the flange portion 4, and the chuck cylinder portion 6 are integrally formed of steel. Here, the steel material constituting the chuck cylinder portion 6 is a steel material having a linear expansion coefficient larger than that of the steel material constituting the flange portion 4 and the tapered shank portion 5. Specifically, the flange portion 4 and the tapered shank portion 5 are integrally formed of steel, and the chuck cylinder portion 6 is formed of a steel material (e.g., austenitic steel) having a linear expansion coefficient larger than that of the steel material constituting the flange portion 4 and the tapered shank portion 5, and is integrated by welding or the like. In this way, since the thermal expansion coefficient of the chuck cylinder portion 6 is large, shrink fitting at a relatively low temperature is possible, and the runout of the carbide arbor 2 fixed to the chuck cylinder portion 6 by shrink fitting can be significantly suppressed.

[0027] As shown in FIG. 2, the carbide arbor 2 has a base end 11 that is inserted into the chuck cylinder 6 of the shrink fit holder 1 and fixed by shrink fit, a rod-shaped shaft portion 12 that extends axially from the base end 11 to the outside of the chuck cylinder 6, and a tool attachment hole 13 that opens at the tip of the shaft portion 12. The base end 11 and the shaft portion 12 are cylindrical and elongated in the axial direction, and are integrally formed of cemented carbide. In the figure, the carbide arbor 2 in which the outer diameter of the shaft portion 12 is slightly smaller than the outer diameter of the base end 11 is shown, but it is also possible to adopt a carbide arbor 2 in which the outer diameter of the shaft portion 12 and the outer diameter of the base end 11 are the same size. The tool attachment hole 13 has a threaded hole portion 14 having a female thread on the inner circumference and a fitting hole portion 15 formed on the tip side of the shaft portion 12 with respect to the threaded hole portion 14.

[0028] The replaceable tool 3 is detachably fixed to the tool mounting hole 13 at the tip of the carbide arbor 2. The replaceable tool 3 has a main body 16, an insert tip 17 attached to the main body 16, a fitting shaft 18 extending axially from the rear end of the main body 16, and a threaded shaft 19 extending axially from the fitting shaft 18. The threaded shaft 19 is threadedly engaged with the threaded hole 14 of the tool mounting hole 13, and the fitting shaft 18 is fitted into the fitting hole 15 of the tool mounting hole 13 to position the main body 16 in the radial direction. The insert tip 17 is a double-edged tip for side cutting, with cutting edges spaced 180° apart in the circumferential direction. The cutting edge on the outer periphery of the insert tip 17 has a straight portion of 0.8 mm or more that extends straight in the axial direction.

[0029] An example of a method for finish machining the inner surface of the cylindrical hole 20 of the workpiece W shown in FIG. 1 using the above-mentioned shrink fit holder 1, carbide arbor 2, and exchangeable tool 3 will be described.

[0030] As shown in Fig. 1, workpiece W is attached to a table (not shown) of a machining center so that the axial direction of cylindrical hole 20 is parallel to the axial direction of spindle 8. Workpiece W has an inner wall surface 21 that rises at a predetermined height from a position shifted radially outward from the opening edge of end 22 (upper end in the figure) of cylindrical hole 20 closer to spindle 8. Here, inner wall surface 21 is the inner surface of a hole formed coaxially with cylindrical hole 20.

[0031] Incidentally, there are multiple types of shrink fit holders 1, which differ in the inner diameter dimension of the chuck cylinder portion 6, the axial length from the flange portion 4 to the tip of the chuck cylinder portion 6, the generatrix shape of the outer circumferential surface of the chuck cylinder portion 6, etc. The carbide arbor 2 shown in Fig. 2 also comes in multiple types, which differ in the outer diameter dimension of the base end portion 11, the axial length of the shaft portion 12, etc. Therefore, when finishing the inner circumferential surface of the cylindrical hole 20, there are many combinations of the shrink fit holder 1, the carbide arbor 2, and the replaceable tool 3 that can be used for the processing.

[0032] In this embodiment, a combination of the shrink fit holder 1, the carbide arbor 2, and the replaceable tool 3 is selected and used such that when the end 23 of the inner peripheral surface of the cylindrical hole 20 shown in Fig. 2 on the side farther from the spindle 8 (see Fig. 1) is machined with the replaceable tool 3, the axial distance from the tip of the chuck cylinder portion 6 to the end 22 of the inner peripheral surface of the cylindrical hole 20 on the side closer to the spindle 8 is 1 mm or more and less than 25 mm. Also, when the end 23 of the inner peripheral surface of the cylindrical hole 20 shown in Fig. 1 on the side farther from the spindle 8 is machined with the replaceable tool 3, a combination of the shrink fit holder 1, the carbide arbor 2, and the replaceable tool 3 is selected and used such that the chuck cylinder portion 6 of the shrink fit holder 1 faces the inner wall surface 21 in the axially perpendicular direction without interfering with the inner wall surface 21.

[0033] 2, while rotating the exchangeable tool 3 by rotating the spindle 8, the exchangeable tool 3 is moved in a spiral shape around the center of the cylindrical hole 20 in the workpiece W by simultaneous three-axis control of XYZ of the machining center, thereby cutting the inner surface of the cylindrical hole 20 over the entire axial length. At this time, cutting is performed so that the hole diameter of the cylindrical hole 20 after cutting is slightly smaller than the finishing dimension (target dimension).

[0034] Thereafter, as shown in Fig. 3, the diameter of the cylindrical hole 20 is measured by the touch probe 24 of the machining center. Then, again as shown in Fig. 2, the main spindle 8 is rotated to rotate the replaceable tool 3, while the replaceable tool 3 is moved in a spiral shape around the center of the cylindrical hole 20 of the workpiece W by simultaneous three-axis control of XYZ of the machining center, thereby cutting the inner surface of the cylindrical hole 20 over the entire axial length. At this time, the machining center automatically adjusts the spiral diameter of the replaceable tool 3 shown in Fig. 2 as it moves in a spiral shape by numerical control, based on the measured value of the diameter of the cylindrical hole 20 by the touch probe 24, so that the diameter of the cylindrical hole 20 after cutting becomes the finishing dimension (target dimension).

[0035] When the inner surface of the cylindrical hole 20 is finish-machined using the above method, the shrink fit holder 1 is able to significantly reduce tool runout compared to a typical collet-type holder, and the carbide arbor 2 has significantly higher rigidity perpendicular to the axis compared to a typical steel arbor. Therefore, by selecting a combination of the shrink fit holder 1 and the carbide arbor 2 so that the protruding length of the carbide arbor 2 from the shrink fit holder 1 is as short as possible within the range where the shrink fit holder 1 does not interfere with the workpiece W, as shown in Figure 2, the inner surface of the cylindrical hole 20 in the workpiece W can be machined to a specified hole diameter with accuracy equal to or greater than that achieved by finish machining using a boring head 50 (see Figure 6).

[0036] Furthermore, when the inner peripheral surface of cylindrical hole 20 is finished by the above method, the spiral diameter when replaceable tool 3 shown in Fig. 2 moves in a spiral shape can be automatically adjusted by numerical control of a machining center so that the hole diameter of cylindrical hole 20 has a predetermined finishing dimension. Therefore, there is no need to manually adjust the position of the cutting edge, and no human skill is required.

[0037] 4 and 5, because replaceable tool 3 is moved in a spiral shape around the center of cylindrical hole 20 while rotating, chips produced when machining the inner peripheral surface of cylindrical hole 20 are broken into small pieces and long continuous chips are less likely to be produced. Therefore, machine stoppages due to entanglement of chips are less likely to occur.

[0038] 2 and 4, when finishing multiple cylindrical holes 20 with different hole diameters, the spiral diameter when the replaceable tool 3 moves in a spiral shape can be changed by the numerical control of the machining center, so that multiple cylindrical holes 20 with different hole diameters can be finished. Therefore, it is low cost and does not require much effort and time.

[0039] In addition, a combination of shrink fit holder 1, carbide arbor 2, and replaceable tool 3 is selected and used such that when machining end 23 of the inner surface of cylindrical hole 20 shown in Figure 1 away from spindle 8 with replaceable tool 3, the axial distance from the tip of chuck tube portion 6 to end 22 of the inner surface of cylindrical hole 20 closer to spindle 8 is 1 mm or more, so that it is possible to reliably prevent the tip of chuck tube portion 6 of shrink fit holder 1 from interfering with the workpiece W when finish machining the inner surface of cylindrical hole 20.

[0040] In addition, when machining the end 23 of the inner surface of the cylindrical hole 20 shown in Figure 1 away from the spindle 8 with the replaceable tool 3, a combination of the shrink fit holder 1, carbide arbor 2, and replaceable tool 3 is selected and used such that the axial distance from the tip of the chuck tube portion 6 to the end 22 of the inner surface of the cylindrical hole 20 closer to the spindle 8 is less than 25 mm.Therefore, the protruding length of the carbide arbor 2 from the shrink fit holder 1 is kept short, and the rigidity in the direction perpendicular to the axis when the shrink fit holder 1, carbide arbor 2, and replaceable tool 3 are combined is extremely high, and the inner surface of the cylindrical hole 20 can be finished with high precision.

[0041] In addition, as shown in FIG. 1, a combination of shrink fit holder 1, carbide arbor 2, and replaceable tool 3 is selected and used such that, when the end 23 of the inner surface of cylindrical hole 20 farthest from the spindle 8 is machined with replaceable tool 3, the chuck tube portion 6 of the shrink fit holder 1 does not interfere with the inner wall surface 21 and is positioned opposite the inner wall surface 21 in the direction perpendicular to the axis. Therefore, the protruding length of the carbide arbor 2 from the shrink fit holder 1 is kept short, and the rigidity in the direction perpendicular to the axis when the shrink fit holder 1, carbide arbor 2, and replaceable tool 3 are combined is extremely high, and the inner surface of cylindrical hole 20 can be finished with high precision.

[0042] When performing the above-mentioned finishing process, the user needs to select a combination of the shrink fit holder 1, the carbide arbor 2, and the exchangeable tool 3. An example of a holder selection support device that enables the user to easily select the optimal combination will be described.

[0043] As shown in Fig. 10, the holder selection support device has an input unit 30, an information processing unit 31, and an output unit 32. In the information processing unit 31, information on the dimensions and rigidity of multiple types of shrink-fit holders 1 that differ in the inner diameter dimension of the chuck cylinder portion 6, the axial length from the flange portion 4 to the tip of the chuck cylinder portion 6, the generatrix shape of the outer peripheral surface of the chuck cylinder portion 6, etc. shown in Fig. 1, information on the dimensions and rigidity of multiple types of carbide arbors 2 that differ in the outer diameter dimension of the base end portion 11, the axial length of the shaft portion 12, etc. shown in Fig. 2, and information on the dimensions and cutting conditions of multiple types of replaceable tools 3 that differ in model number, cutting edge diameter, etc. are registered in advance.

[0044] 10, the user inputs input data including the material of the workpiece W shown in FIG. 1, the finishing dimension (target dimension) of the hole diameter of the cylindrical hole 20, the axial length of the inner peripheral surface of the cylindrical hole 20, the radial distance from the opening edge of the end 22 of the inner peripheral surface of the cylindrical hole 20 closer to the spindle 8 to the inner wall surface 21, and the height of the inner wall surface 21. The information processing unit 31 shown in FIG. 10 then processes the input data input by the user, information on multiple types of shrink fit holders 1 registered in advance, and information on the multiple types of shrink fit holders 1 registered in advance. Based on the information of the plurality of types of carbide arbors 2 recorded and the information of the plurality of types of replaceable tools 3 registered in advance, a combination of the shrink fit holder 1, the carbide arbor 2, and the replaceable tool 3 is selected such that the chuck cylinder portion 6 of the shrink fit holder 1 faces the inner wall surface 21 in the axis-perpendicular direction without interfering with the inner wall surface 21 when the replaceable tool 3 shown in Fig. 1 machines the end 23 of the inner peripheral surface of the cylindrical hole 20 farther from the spindle 8, and the combination is output on the screen to the output unit 32 shown in Fig. 10. At this time, when there are a plurality of combinations of the shrink fit holder 1, the carbide arbor 2, and the replaceable tool 3, the plurality of combinations are output on the screen in order of the highest rigidity in the axis-perpendicular direction. Here, the rigidity in the direction perpendicular to the axis can be calculated by calculating the amount of displacement of the blade portion of the replaceable tool 3 in the direction perpendicular to the axis due to the deflection of the chuck tube portion 6 and the carbide arbor 2 when a constant load (e.g., a load of 9.8 N) is applied to the blade portion of the replaceable tool 3 in the direction perpendicular to the axis while the replaceable tool 3 is cantilever-supported by the shrink-fit holder 1 via the carbide arbor 2, and the calculated value can be used.

[0045] By using this holder selection support device, when the workpiece W has a shape having an inner wall surface 21 that rises at a predetermined height from a position shifted radially outward from the opening edge of the end 22 of the cylindrical hole 20 closer to the spindle 8, as shown in Figure 1, it is possible to easily select a combination of shrink fit holder 1, carbide arbor 2, and replaceable tool 3 such that the protruding length of the carbide arbor 2 from the shrink fit holder 1 is as short as possible, within the range where the shrink fit holder 1 does not interfere with the inner wall surface 21 of the workpiece W.

[0046] In addition, when there are multiple combinations of the shrink fit holder 1, the carbide arbor 2, and the replaceable tool 3 that result in the shortest possible protruding length of the carbide arbor 2 from the shrink fit holder 1, it is possible to select the combination with the highest rigidity. Furthermore, when circumstances exist that make it impossible to select the combination with the highest rigidity, it is possible to select the combination with the second highest rigidity, making it possible to make the optimal selection according to the circumstances at hand.

[0047] In order to confirm that the inner surface of a cylindrical hole can be finished using a shrink fit holder 1, carbide arbor 2, and replaceable tool 3 with accuracy equal to or greater than that achieved by using a boring head 50 (see Figure 6), a cylindrical hole was finished using a shrink fit holder 1, carbide arbor 2, and replaceable tool 3 as configured in Figure 1 (Example), and a cylindrical hole was finished using a boring head 50 as configured in Figure 6 (Comparative Example), and a test was conducted to compare the dimensional accuracy of the cylindrical hole after finishing in the Comparative Example with the dimensional accuracy of the cylindrical hole after finishing in the Example.

[0048] The cylindrical hole of the workpiece used in this test had a diameter of 50 mm and an axial length of 30 mm. The cutting conditions are as shown in Table 1 below. [Table 1]

[0049] The test results are shown in Table 2 below. [Table 2]

[0050] As shown in Table 2, when the inner surface of a cylindrical hole is finish-machined using the finishing method of the embodiment, it can be confirmed that the processing can be performed with the same or higher accuracy as when the inner surface of a cylindrical hole is finish-machined using the comparative example (boring head). [Explanation of symbols]

[0051] 1 Shrink fit holder 2 Carbide Arbor 3 Replaceable tools 5 Tapered shank 6 Chuck barrel 8 spindle 9 Tapered hole 11 Proximal end 12 Shaft 13 Tool mounting hole 20 Cylindrical Bore 21 Inner wall surface 22 End closest to the spindle 23 End far from the spindle W work

Claims

1. A method for finishing an inner peripheral surface of a cylindrical hole (20) in a workpiece (W), comprising the steps of: A shrink fit holder (1) having a tapered shank portion (5) that is inserted into and fixed to a tapered hole (9) of a spindle (8) of a machining center, and a chuck cylinder portion (6) that extends in the axial direction opposite to the tapered shank portion (5) and has an open tip; a cemented carbide arbor (2) having a base end (11) inserted into the chuck cylinder portion (6) and fixed by shrink fitting, a rod-shaped shaft portion (12) extending axially from the base end (11) to the outside of the chuck cylinder portion (6), and a tool attachment hole (13) opening at a tip of the shaft portion (12); An exchangeable tool (3) that is detachably fixed to the tool mounting hole (13) at the tip of the carbide arbor (2), A cylindrical hole finishing method in which the replaceable tool (3) is rotated in the machining center while being moved spirally around the center of the cylindrical hole (20) of the workpiece (W), thereby finishing the inner surface of the cylindrical hole (20).

2. 2. The method for finishing a cylindrical hole as claimed in claim 1, wherein the inner surface of the cylindrical hole (20) is finished by a combination of the shrink-fit holder (1), the carbide arbor (2) and the replaceable tool (3) such that, when the replaceable tool (3) machines the end (23) of the inner surface of the cylindrical hole (20) remote from the spindle (8), the axial distance from the tip of the chuck tube portion (6) to the end (22) of the inner surface of the cylindrical hole (20) closer to the spindle (8) is 1 mm or more and less than 25 mm.

3. The workpiece (W) has an inner wall surface (21) that rises at a predetermined height from a position radially outwardly shifted from an opening edge of an end (22) of the cylindrical hole (20) that is closer to the spindle (8), 3. A method for finishing a cylindrical hole as described in claim 1 or 2, in which the inner surface of the cylindrical hole (20) is finished by a combination of the shrink fit holder (1), the carbide arbor (2) and the replaceable tool (3) such that, when the replaceable tool (3) machines the end (23) of the inner surface of the cylindrical hole (20) farther from the spindle (8), the chuck tube portion (6) of the shrink fit holder (1) is positioned opposite the inner wall surface (21) in a direction perpendicular to the axis without interfering with the inner wall surface (21).

4. A holder selection support device for use in the cylindrical hole finishing method according to claim 3, comprising: A user inputs input data including the material of the workpiece (W), the finishing dimension of the hole diameter of the cylindrical hole (20), the axial length of the inner peripheral surface of the cylindrical hole (20), the radial distance from the opening edge of the end (22) of the inner peripheral surface of the cylindrical hole (20) closer to the spindle (8) to the inner wall surface (21), and the height of the inner wall surface (21); A holder selection support device that, based on the input data, information on multiple types of the shrink fit holder (1) that have been registered in advance, information on multiple types of the carbide arbor (2) that have been registered in advance, and information on multiple types of the replaceable tool (3) that have been registered in advance, selects a combination of the shrink fit holder (1), the carbide arbor (2), and the replaceable tool (3) such that, when the replaceable tool (3) machines the end (23) of the inner surface of the cylindrical hole (20) that is farther from the spindle (8), the chuck tube portion (6) of the shrink fit holder (1) is positioned opposite the inner wall surface (21) in a direction perpendicular to the axis without interfering with the inner wall surface (21), and outputs the selected combination on a screen.

5. 5. The holder selection support device according to claim 4, wherein when there are a plurality of combinations of the shrink fit holder (1), the carbide arbor (2), and the replaceable tool (3) such that the chuck tube portion (6) of the shrink fit holder (1) faces the inner wall surface (21) in the axial direction perpendicular to the axis when the replaceable tool (3) machines the end (23) of the inner surface of the cylindrical hole (20) that is farther from the spindle (8), the plurality of combinations of the shrink fit holder (1), the carbide arbor (2), and the replaceable tool (3) are output on a screen in order of increasing rigidity in the axial direction perpendicular to the axis.

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