JP6579182B2 - Threading method - Google Patents

Description

  The present invention belongs to a technical field related to a screw machining method in which a screw hole is formed in a workpiece by a machine tool that is mounted on a tip end of a main shaft via a tapping holder and includes a tap for cutting a female screw on the workpiece.

  2. Description of the Related Art Conventionally, a technique for forming a screw hole in a workpiece by a tap attached to the tip of a main shaft that rotates around an axis is known.

  For example, Patent Document 1 discloses an elevating mechanism provided at the tip of a robot arm, a rotating mechanism provided at the tip of the elevating mechanism, and a rotating mechanism provided at the tip of the elevating mechanism, and cutting a screw on the workpiece. A threading method is disclosed in which a thread is cut using a threading device that is provided between a tap and the tap and the lifting machine and includes a support part that is movable in the processing direction. .

  And the screw processing method of patent document 1 is a tap cutting process which forms a screw hole in a workpiece | work by making this tap enter into a workpiece | work, rotating a tap with a rotation mechanism, and the tap entered into a workpiece | work. Consists of a supporting part raising step for raising the supporting part by a predetermined distance without rotating and raising and lowering, and a tap removing step for removing the tap from the work while rotating the tap in reverse by the rotation mechanism.

JP 2009-248279 A

  By the way, when a component having a threaded portion (male screw) is attached to the formed screw hole (female screw), the component is screwed in until a predetermined torque is generated. At this time, there is a demand for the desired orientation of the component when screwed until a predetermined torque is generated. In particular, when a plurality of screw holes are formed in one workpiece, and a component is mounted in each of the plurality of screw holes, a predetermined torque is generated for each component, and each component is mounted in the screw hole. At this stage, there is a demand to align the orientation of all the parts in a desired direction.

  As described above, when the components are mounted in the screw holes, in order to set the orientations of all the components to a desired direction, it is necessary to set the angular position of the screw thread start position of the screw holes to a desired angular position. For this purpose, it is necessary to set the angular position of the screw thread start position in the threaded portion of the tap to the desired angular position when the tip of the threaded portion of the tap comes into contact with the work surface of the workpiece during threading. There is.

  The present invention has been made in view of such a point, and an object of the present invention is to make it possible to set the angular position of the screw thread start position of the screw hole to a desired angular position in threading with a tap. It is an object of the present invention to provide a threading method that can change the orientation of a component to a desired orientation when the component is mounted in a hole.

In order to solve the above-mentioned problems, in the present invention, a machine comprising a main shaft that rotates around an axis and a tap that is fixed to a tapping holder attached to the tip of the main shaft and has a threaded portion for cutting a female screw on a workpiece. machine by forming a female thread on the workpiece, as an object the thread cutting method, the tapping holder, and the distal end surface abutting contact surface of the main shaft when mounted on the spindle, mounted on the spindle Sometimes, a holder side mark portion provided at an angular position corresponding to the reference angular position in the circumferential direction of the main shaft is provided, and a relative position between the tap and the workpiece at the start of machining is set. With the machining start position setting step and the tapping holder attached to the main shaft, the relative position between the tap and the workpiece is the machining start position. A positioning step for positioning the workpiece and the tap so as to be the relative position set in a fixing step, and the machining start position setting step includes the tip of the tap at the start of machining and the tap The processing start distance, which is the distance between the work surface of the workpiece, is the desired thread start position of the thread portion of the tap when the thread portion of the tap and the work surface of the work contact each other. In addition to the step of setting the above relative position so that the distance is an angular position, the gauge side mark portion formed in advance at the angular position of the bottomed screw hole and the starting position of the complete thread of the screw hole The machining start position setting step further includes a step of setting the threaded portion of the tap in the screw hole of the setting gauge, and the tip of the tap being raised. The tap screwing step of screwing in until it contacts the bottom surface of the screw hole of the setting gauge, and the angular position of the gauge side mark portion of the setting gauge as viewed from the axial direction of the tap after the tap screwing step, An angle adjusting step of loosening the setting gauge until the angular position of the holder side mark portion of the tapping holder viewed from the axial direction of the tap matches, and after the angle adjusting step, the screw of the setting gauge A virtual tool length setting step for setting a distance between the bottom surface of the hole and the contact surface of the tapping holder as a virtual tool length, and based on the virtual tool length set in the virtual tool length setting step Thus, the process is a step of setting the relative position .

  In threading to make the orientation of the parts to be mounted in the screw holes the desired direction, the relative position between the tap and the workpiece at the start of machining is the integral distance of the pitch of the threaded part of the tap. Set to be a distance. Then, at least one of the tap and the workpiece is moved so that the relative distance between the tip of the tap and the work surface of the workpiece changes by one pitch of the tap screw portion while the screw portion of the tap rotates once. . For this reason, for example, if the machining start distance is set to a distance obtained by adding a distance corresponding to 1/4 pitch to a distance that is an integral multiple of the pitch of the thread portion of the tap, the tip of the tap and the machining surface of the workpiece will be in contact. The angle position of the thread start position (hereinafter referred to as the tap thread start position) of the thread portion of the tap at the time of contact is 90 ° with respect to the angle position of the thread start position of the thread portion of the tap at the start of machining. You can advance by minutes. That is, if the machining start distance is set appropriately, the tap screw thread starting position when the tap thread portion and the workpiece machining surface abut can be set to a desired angular position. Therefore, at the time of threading by tapping, the angular position of the screw thread start position of the screw hole can be set to a desired angle position, and when the part is mounted in the screw hole, the direction of the part is set to the desired direction. be able to.

In addition, when the tool is attached to the spindle, there is a phase shift between the spindle and the tap thread start position (that is, a position shift between the reference angle position of the spindle and the angle position of the tap thread start position). In order to make the tap screw thread start position a desired angular position when the threaded portion of the tap and the work surface of the workpiece come into contact with each other, it is necessary to consider the phase shift. Therefore, in the present invention , the relative position between the tip of the tap and the work surface of the workpiece can be set in consideration of the above phase shift.

  In the above configuration, the tap is fixed to the tapping holder, and when the tapping holder is attached to the main shaft, the holder side mark provided at a position corresponding to the reference angle position in the circumferential direction of the main shaft. Therefore, when the tap is attached to the main shaft via the tapping holder, the phase shift between the main shaft and the tap screw thread start position is determined by the holder side mark portion of the tapping holder and the tap screw thread start position. This corresponds to a phase shift of.

  The gauge side mark part of the setting gauge is formed at an angular position corresponding to the starting position of the complete thread of the screw hole of the setting gauge, so the tap is screwed into the screw hole of the setting gauge, and the tip of the tap is the screw. When contacting the bottom surface of the hole, the gauge side mark portion is located at an angular position corresponding to the tap thread start position. Therefore, in the state where the tip of the tap is in contact with the bottom surface of the screw hole of the setting gauge, the positional deviation between the angle position of the gauge side mark portion of the setting gauge and the angle position of the holder side mark portion of the tapping holder is the tapping holder. This corresponds to the phase shift between the holder side mark portion and the tap screw thread start position.

  In the angle adjustment process, loosen the setting gauge until the angle position of the gauge side mark on the setting gauge matches the angle position on the holder side mark on the tapping holder. A gap having a length corresponding to a phase shift from the start position (hereinafter referred to as an offset length) is generated between the tip of the tap and the bottom surface of the screw hole of the setting gauge. If the distance between the bottom surface of the screw hole of the setting gauge and the contact surface of the tapping holder is set as the virtual tool length, this virtual tool length will be the actual tool length (the tip of the tap and the contact surface of the tapping holder). The above-mentioned offset length is added to the distance).

  After setting the virtual tool length, the relative position is set based on the virtual tool length. For example, when it is desired to set the machining start distance to a distance obtained by adding the offset length to a distance that is an integral multiple of the pitch of the thread portion of the tap, first, from the tip surface of the main shaft, The virtual tip position of the tap is set by regarding the position separated by the virtual tool length on the workpiece side in the axial direction of the spindle as the tip position of the tap. Next, the position of the work surface of the work is set so that the work is located at a position separated from the virtual tip position of the tap by an integer multiple of the pitch of the thread portion of the tap in the axial direction. Thereby, the relative position between the tap and the workpiece at the start of machining is set. Then, the tap is attached to the main shaft via the tapping holder, and the tap and the work are aligned so that the relative position between the tap and the work becomes the set position, and the screw portion of the tap rotates once. In the meantime, at least one of the tap and the workpiece is moved so that the relative distance between the tip of the tap and the work surface of the workpiece is reduced by one pitch of the thread portion of the tap.

  When the relative distance between the tip of the tap and the work surface of the workpiece becomes the offset length, the angular position of the tap thread starting position is the angular position when the tap is mounted on the main shaft. When the relative distance between the tip of the tap and the work surface of the workpiece is further reduced at the same pace as described above, the relative distance between the tip of the tap and the work surface of the work is reduced by the offset length (in this example, Until the threaded part of the tap and the work surface of the workpiece come into contact), the tap has a phase shift between the holder side mark of the tapping holder and the tap thread start position, that is, the spindle and the tap thread start position. Rotate by the amount of phase shift. As a result, when the threaded portion of the tap and the work surface of the workpiece come into contact with each other, the tap thread start position is located at the angular position of the reference angular position of the main shaft.

  Therefore, for example, when the desired angular position of the screw thread start position of the screw hole formed in the workpiece is the same angular position as the reference angular position of the spindle, the workpiece side in the axial direction from the tip surface of the spindle The work surface of the workpiece is positioned at a position separated from the virtual tip position by an integer multiple of the pitch of the threaded portion of the tap, with the position separated by the virtual tool length as the virtual tip position. If the position of is set, the angle position of the tap screw thread starting position when the thread portion of the tap comes into contact with the work surface of the workpiece can be positioned at the desired angle position during screw processing. .

  On the other hand, for example, when the desired angular position of the screw thread starting position of the screw hole formed in the workpiece is an angular position shifted by 90 ° with respect to the angular position of the reference angular position of the spindle, the machining start distance The relative position between the tap and the workpiece is set so that the distance is an integral multiple of the pitch of the tap thread and the offset length plus a quarter pitch of the tap thread. To do. Specifically, after setting the virtual tip position of the tap as described above, a distance corresponding to a quarter pitch of the screw portion from the virtual tip position to a distance that is an integral multiple of the pitch of the screw portion of the tap. The position of the processed surface of the workpiece is set so that the workpiece is positioned at a position separated by the distance added. Thereby, after the relative distance between the tip of the tap and the work surface of the work is reduced by an integral multiple of the pitch of the threaded portion of the tap and the offset length, a further 1/4 pitch, that is, Since it rotates by 90 °, when the screw part of the tap comes into contact with the work surface of the workpiece, the tap screw thread start position is located at an angular position shifted by 90 ° with respect to the angular position of the reference angular position of the spindle. Will do.

  Therefore, the angle position of the screw thread start position of the screw hole can be set to a desired angle position at the time of threading with the tap. And if a component is mounted | worn with the formed screw hole, direction of components can be made into a desired direction.

  The screw machining method further includes a machining surface position measuring step of measuring a position of the machining surface of the workpiece with a touch sensor attached to the spindle, and the alignment step is set in the machining start position setting step. It is preferable that the workpiece and the tap are aligned based on the relative position and the position of the processed surface of the workpiece measured in the processed surface position measuring step.

  According to this configuration, since the relative position between the tap and the workpiece can be set accurately at the start of machining, the angular position of the screw thread start position of the screw hole can be more accurately set when threading with the tap. A desired angular position can be obtained.

In the threading method, the gauge-side mark portion is formed by a notch obtained by notching the outer peripheral portion of the setting gauge in the circumferential direction, while the holder-side mark portion has the outer peripheral portion of the tapping holder in the circumferential direction. The angle adjusting step is performed by projecting the shadow of the setting gauge toward the holder side in the axial direction of the tap by the projector. It is preferable that this is a step of matching the angular position between the holder side mark portion and the holder side mark portion.

  According to this configuration, the angular positions of the gauge-side mark portion and the holder-side mark portion can be accurately matched in the angle adjustment step. As a result, the virtual tool length including the offset length can be obtained more accurately, so that the angular position of the screw thread start position of the screw hole can be more accurately set to a desired angular position at the time of threading with a tap. Can do.

In the screw machining method , the workpiece is a cylinder head of a multi-cylinder engine having a plurality of cylinders, and a screw hole formed in the workpiece is a screw for setting a spark plug in each cylinder in the cylinder head. It is a hole, and the positioning step is performed for each cylinder.

  In other words, since the spark plugs are involved in controlling the combustion of fuel in the cylinder, the orientation of all the spark plugs is desired when they are mounted on the cylinder head so that there is no combustion variation between the cylinders. It is desirable that they are aligned in the direction. Therefore, the effect that the direction of the component can be set to a desired direction at the stage where the component is mounted in the formed screw hole can be more appropriately exhibited.

  Since the alignment process is performed for each cylinder, it is possible to suppress the occurrence of deviation in the direction of the spark plug in each cylinder and to align all the spark plugs in a desired direction.

As described above, according to the thread cutting process of the present invention, the machining start distance is the distance between the working surface of the tap of the tip and the workpiece at the start processing, the processing surface of the threaded portion of the tap and the workpiece To set the relative position between the tap and the workpiece at the start of machining so that the screw thread starting position of the threaded part of the tap is at the desired angular position when a At times, the screw thread start position of the screw hole can be positioned at a desired angle, and when the component is mounted in the screw hole, the direction of the component can be set to a desired direction.

It is an engine provided with the cylinder head which is an example of the workpiece | work which has the screw hole processed by the processing method which concerns on embodiment of this invention, Comprising: It is a figure which shows a combustion chamber periphery. It is a perspective view which shows the machine tool used for the screw processing method. It is sectional drawing which shows the state in which the tapping holder was attached to the main axis | shaft. It is the front view which looked at the main axis | shaft in the state where the tapping holder is not mounted | worn from the front end side of the axial direction of this main axis | shaft. It is the schematic which shows the process of forming a screw hole, Comprising: The state which is performing the seat surface process is shown. The state which is measuring the position of a seat surface after the process shown in FIG. The state which is performing the pilot hole process which forms the pilot hole for screw holes after the process shown in FIG. After the process shown in FIG. 7, a state where the female thread is cut by the tap is shown. It is a perspective view which shows a setting gauge. It is sectional drawing which shows the state which screwed the tap until the front-end | tip of the tap contact | abutted to the bottom face of the screw hole of a setting gauge. It is sectional drawing which shows the state which loosened the setting gauge so that the angular position of a gauge side mark part and a holder side mark part may correspond from the state of FIG. It is a figure which shows roughly the positional relationship of the front-end | tip of a tap, and the processing surface of a workpiece | work at the time of a process start, and the positional relationship of the thread start position of a tap, and the reference | standard angle position of a main axis | shaft. FIG. 13 is a view corresponding to FIG. 12 when the relative distance between the tip of the tap and the work surface of the workpiece becomes an offset length. FIG. 13 is a view corresponding to FIG. 12 when the tip of the tap comes into contact with the work surface of the workpiece.

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

  FIG. 1 shows the periphery of a combustion chamber 5 in an engine 1 including a cylinder head 2 which is an example of a workpiece having a screw hole machined by a machining method according to an embodiment of the present invention.

  The engine 1 is a multi-cylinder engine having four cylinders 3 a and includes a cylinder block 3 and a cylinder head 2 mounted on the cylinder block 3. In the cylinder block 3, four cylinders 3a are arranged side by side in a direction perpendicular to the paper surface.

  A piston 4 is fitted in each cylinder 3a so as to reciprocate within the cylinder 3a. A combustion chamber 5 is defined for each cylinder 3a by the top surface 4a of the piston 4, the side surface of the cylinder 3a, and the bottom surface 2a of the cylinder head 2.

  In the cylinder head 2, two intake ports 6 and two exhaust ports 7 are formed for each cylinder 3a. Each intake port 6 and each exhaust port 7 communicate with the combustion chamber 5. Although not shown, each intake port 6 is provided with an intake valve capable of blocking the communication between the combustion chamber 5 and the intake port 6, while each exhaust port 7 has the combustion chamber 5 and the exhaust port 7. An exhaust valve that can cut off communication with is provided.

  An injector 8 is attached to the cylinder head 2 for each cylinder 3a. As shown in FIG. 1, the injector 8 is attached to the cylinder head 2 so as to be positioned on the axial center of the cylinder 3a. The injector 8 is configured to directly inject fuel (gasoline or fuel containing gasoline) into the combustion chamber 5.

  The cylinder head 2 is provided with a spark plug 9 for each cylinder 3a. In the engine 1, one spark plug 9 is provided for each cylinder 3a. The spark plug 9 is located between the two intake ports 6 as shown in FIG. The spark plug 9 is attached to the cylinder head 2 so as to be inclined from the upper side to the lower side so as to approach the axial center of the cylinder 3a.

  The spark plug 9 includes a rod-shaped plug body 91, a center electrode 93 provided at the tip of the plug body 91, a tip of the plug body 91 that extends from the side of the center electrode 93, and a part of the center electrode 93. And an L-shaped ground electrode 94 extending so as to face each other. In the engine 1, the spark plug 9 has an L-shaped ground electrode 94 in a direction (a direction in which the portion of the ground electrode 94 facing the center electrode 91 extends) from the radially inner side of the cylinder 3a to the radially outer side. It is attached to the cylinder head 2 so as to face the direction.

  The spark plug 9 is attached to the cylinder head 2 by screwing a screw portion 92 formed at a portion near the tip of the plug body 91 into a screw hole 2 b formed in the cylinder head 2. The screw portion 92 is configured such that the screw thread start position and the screw thread end position are located at the same angular position in the circumferential direction of the screw portion 92. In addition, the spark plug 9 is attached to each cylinder 3a, and the thread portion 92 of each spark plug 9 is formed so that the thread start position of the thread portion 92 of each spark plug 9 is substantially the same angular position. Yes. In addition, the screw thread starting position of the threaded portion 92 of each spark plug 9 is located at substantially the same angular position as the connecting portion between the plug body 91 and the ground electrode 94 in the circumferential direction of the threaded portion 92.

  In the present embodiment, a screw hole 2b for attaching the ignition plug 9 to the cylinder head 2 is formed. In the following description, the cylinder head 2 may be simply referred to as a workpiece W.

  In the present embodiment, the screw hole 2b to which the spark plug 9 is attached is formed by screw machining by the machine tool 10 shown in FIG. The machine tool 10 is a machining center that is automatically controlled (NC controlled) by a control device (not shown), and is configured to execute various types of processing according to processing program data created in advance corresponding to the workpiece W. ing.

  As shown in FIG. 2, the machine tool 10 has an XYZ coordinate system composed of X, Y, and Z axes as machine coordinates. The X axis and the Z axis are horizontal directions, and the Y axis direction is a vertical direction.

  The machine tool 10 includes a main shaft 11 that rotates about an axis (Z axis), a tool 12 such as a drill or a tap that is attached to the tip of the main shaft 11 via a holder 160, and the tool 12 together with the main shaft 11. And a column 16 that moves in the axial direction and the Y-axis direction. Further, the machine tool 10 includes a processing table 20 for placing a jig 18 for positioning the workpiece W, a rotating mechanism 22 for rotating the processing table 20 around a rotation axis extending in the Y-axis direction, and a rotating mechanism 22. And a feed mechanism 24 that moves in the Z-axis direction. That is, the machine tool 10 is configured to adjust the relative distance between the workpiece W and the tool 12 by moving the workpiece W in the Z-axis direction by the feed mechanism 24.

  Further, although not shown, the machine tool 10 includes an automatic tool changer (hereinafter referred to as ATC). This ATC is for automatically exchanging the tool 12 attached to the spindle 11, and according to the machining program data, the tool 12 attached to the spindle 11 and various machining tools waiting in a tool magazine, for example. Is configured to replace one of the two. A measuring instrument such as a touch sensor 122, which will be described later, is also set in the tool magazine, and the ATC may attach the touch sensor 122 or the like to the spindle 11 according to the machining program data.

  The tool 12 is mounted on the tool mounting portion 13 of the spindle 11 via a holder. As an example showing a state in which the tool 12 is mounted on the main shaft 11, FIG. 3 shows a state in which a tap 50 (see FIG. 10 or the like) as the tool 12 is mounted on the main shaft 11 via a tapping holder 60 that is a holder. Is shown. Hereinafter, the configuration of the tapping holder 60 and the attachment of the tapping holder 60 to the main shaft 11 will be described. However, the holders of other tools are basically the same in configuration as the tapping holder 60, and the main shaft 11 of the tapping holder 60 is also described. It is attached to the main shaft 11 in the same manner as the attachment to the main shaft 11.

  The tapping holder 60 includes a columnar base 61 and a shank portion 62 which is provided on the side opposite to the tap 50 of the base 61 and has a cylindrical shape with a smaller diameter than the base 61. The base portion 61 and the shank portion 62 are arranged coaxially. As shown in FIG. 3, the surface of the base 61 on the side opposite to the tap 50 is a contact surface 61 a that contacts the tip end surface 11 a of the main shaft 11 when the tapping holder 60 is attached to the main shaft 11. As shown in FIG. 3, the shank portion 62 has a concave portion 62 a that is recessed from the axially opposite tap 50 side toward the tap 50 side, and an inclined surface into which a tool holding ball 13 b described later is fitted. A through hole 62b is formed. A drive key 13c, which will be described later, is fitted in the recess 62a. Further, as will be described in detail later, the tapping holder 60 has an angular position corresponding to the reference angular position in the circumferential direction of the main shaft 11 when the tapping holder 60 is attached to the tool mounting portion 13 of the main shaft 11. The provided holder side mark part 63 (refer FIG. 10) is provided.

  As shown in FIG. 3, the tool mounting portion 13 of the main shaft 11 is provided around the axial rod 14 of the main shaft 11. The tool mounting portion 13 is formed with a fitting hole 13 a into which the shank portion 62 of the tapping holder 60 is fitted. Moreover, as shown in FIG. 4, it has the two drive keys 13c extended toward the outer side of radial direction from the axial center rod 14. As shown in FIG. The two drive keys 13 c are respectively arranged so as to be symmetric around the axis of the main shaft 11.

  As shown in FIG. 3, a circular recessed hole 14a and a cam surface 14b are continuously formed in a portion of the shaft rod 14 where the tool mounting portion 13 is provided. Further, a through hole 13d through which the tool holding ball 13b is inserted is formed in a portion of the tool mounting portion 13 corresponding to the recessed hole 14a and the cam surface 14b.

  In order to attach the tapping holder 60 to the tool mounting portion 13 of the main spindle 11, first, the shank portion 62 is inserted into the fitting hole 13a so that the drive key 13c is fitted into the concave portion 62a. Thereafter, when the axial rod 14 is retracted, the tool holding ball 13b rides on the cam surface 14b, protrudes radially outward of the main shaft 11 from the recessed hole 14a, and the protruding tool holding ball 13b is shown in FIG. As shown in FIG. 3, it fits into the through-hole 62b of the shank part 62. As a result, the tapping holder 60 is pulled into the fitting hole 13a, and the contact surface 61a of the tapping holder 60 and the tip surface 11a of the main shaft 11 contact each other as shown in FIG. Thus, the tap 50 is attached to the main shaft 11.

  Next, a process of forming a screw hole in the workpiece W by the machine tool 10 will be described. Here, the workpiece W is the cylinder head 2, and the formed screw hole is a screw hole 2 b for attaching the spark plug 9 to the cylinder head 2.

  First, as shown in FIG. 5, a seat surface for attaching the spark plug 9 to the workpiece W is formed by the first drill 121 having a relatively large diameter. The screw hole is formed from the seat surface 2c. That is, the seating surface 2c corresponds to the machining surface 100 of the workpiece W.

  Next, the first drill 121 is replaced with the touch sensor 122 by the ATC, and as shown in FIG. 6, the workpiece W is moved in the Z-axis direction until the tip of the touch sensor 122 contacts the seat surface. The control device measures the Z coordinate of the seating surface when the tip of the touch sensor 122 comes into contact with the seating surface 2c.

  Next, the touch sensor 122 is replaced with the second drill 123 having a diameter smaller than that of the first drill 121 by the ATC, and a pilot hole for forming a screw hole is formed as shown in FIG. Here, the pilot hole is drilled until it penetrates the bottom surface of the workpiece W (cylinder head 2).

  After forming the pilot hole, the second drill 123 is replaced with the tap 50 which is a tool for cutting the female thread on the workpiece W by the ATC, and the thread is cut with respect to the peripheral surface of the pilot hole as shown in FIG. I do. At this time, the control device of the machine tool 10 operates the feed mechanism 24 so that the workpiece W moves by one pitch of the screw portion 51 of the tap 50 while the screw portion 51 of the tap 50 makes one rotation. . Although details will be described later, at the start of machining, the tip 50a of the tap 50 and the seat surface 2c (the workpiece W machining surface 100) are separated by a predetermined distance based on the Z coordinate of the seating surface measured by the touch sensor 122. The tap 50 is controlled so as to approach at the above rate from a state separated from the seating surface 2c.

  Thus, the screw hole 2b for attaching the spark plug 9 is formed in the cylinder head 2 as the workpiece W.

  Here, for example, in a multi-cylinder engine such as the engine 1, there is a demand to prevent the combustion variation between the cylinders 3 a. One of the causes of the combustion variation between the cylinders 3a is the variation in the direction of the spark plug 9 between the cylinders 3a. That is, in order to generate combustion by the spark discharge of the spark plug 9, it is necessary to generate a spark discharge in a state where a mixture of fuel and intake air flows between the center electrode 93 and the ground electrode 94. Since the air-fuel mixture in the combustion chamber 5 has a flow such as a tumble flow or a swirl flow, the air-fuel mixture hardly flows between the center electrode 93 and the ground electrode 94 depending on the orientation of the spark plug 9. Combustion is less likely to occur. For this reason, if there is variation in the direction of the ignition plug 9 between the cylinders 3a, combustion variation may occur.

  From the above viewpoint, in a multi-cylinder engine such as the engine 1, it is desired that all the spark plugs 9 are aligned in a desired direction. For this purpose, in each spark plug 9, it is necessary to make the screw thread start positions of the screw portions 92 substantially the same, and to set the angular positions of the screw thread start positions of the screw holes 2b of the cylinder head 2 to desired angular positions. is there. As described above, in the present embodiment, since the thread portion 92 of each spark plug 9 is formed so that the thread plug 92 of each spark plug 9 is located at the screw thread start position, each screw in each spark plug 9 is formed. The angular position of the thread of the part 92 is substantially the same. Therefore, it is necessary to set the angular position of the screw thread start position of the screw hole 2b of the cylinder head 2 to a desired angular position.

  In order to set the angle position of the screw thread start position of the screw hole formed by threading with the tap 50 to a desired angle position, the phase of the main shaft 11 of the machine tool 10 and the mounting of the tap 50 on the main shaft 11 It is necessary to consider the phase of the tapping holder 60 attached to the main shaft 11 and the phase of the screw part 51 of the tap 50 fixed to the tapping holder 60 (that is, the angular position of the thread start position of the screw part 51). . As shown in FIG. 4, the phase of the main shaft 11 is set such that the positions of the two drive keys 13c of the tool mounting portion 13 are 90 ° and 270 °, and clockwise from the position of the phase 90 ° around the axis. The position returned by 90 ° is set to phase 0 °, and the position advanced 90 ° counterclockwise around the axis from the position of phase 90 ° is set to 180 °. Further, the machine tool 10 is controlled by the control device so that the position of the phase 0 ° is on the upper side when the tool is changed, and the angle position of the phase 0 ° is set as a reference angular position in the circumferential direction of the spindle 11. Has been.

  In the present embodiment, the phase of the spindle 11 and the phase of the tapping holder 60 are made uniform by devising the configuration of the tool mounting portion 13 of the spindle 11 and the shape of the tapping holder 60.

  As described above, the two tool keys 13c are formed on the tool mounting portion 13 of the spindle 11, and the tapping holder 60 is formed with the recess 62a that fits with the drive key 13c. That is, when the recess 62a of the tapping holder 60 is inserted into the fitting hole 13a of the tool mounting portion 13 so that the recess 62a is fitted to the drive key 13c, the phase of the spindle 11 and the phase of the tapping holder 60 are aligned. Or be shifted 180 °.

  In order to prevent the phase of the main shaft 11 and the phase of the tapping holder 60 from being shifted by 180 °, in this embodiment, the base portion 61 of the tapping holder 60 has a holder side mark portion at a position of the phase of 0 ° of the tapping holder 60. 63 is provided. The holder side mark portion 63 is formed by cutting out a part of the base portion 61 in the circumferential direction. As described above, when the tool is changed, the phase is set so that the position of 0 ° is on the upper side. Therefore, the tapping holder 60 is attached to the tool mounting portion of the main shaft 11 so that the holder-side mark portion 63 is on the upper side. If it is attached to 13, the phase of the main shaft 11 and the phase of the tapping holder 60 are aligned. Therefore, the holder-side mark portion 63 is provided at a position corresponding to the reference angle position in the circumferential direction of the main shaft 11 (phase 0 ° position) when the tapping holder 60 is attached to the main shaft 11. Will be.

As described above, the phase of the main shaft 11 and the phase of the tapping holder 60 can be aligned. However, since the tap 50 is fixed to the tapping holder 60, the phase of the screw portion 51 of the tap 50 and the phase of the tapping holder 60 are Even if there is a deviation in the phase, it is difficult to rotate the tap 50 itself around the axis and align the phase of the threaded portion 51 of the tap 50 with the phase of the main shaft 11 and the tapping holder 60. Therefore, in this embodiment, the machining start distance L is a distance between the processing surface 100 of the tip 50a and the workpiece W of the tap 50 at the start of processing, the screw portion 51 (the embodiment of the tap 50, in particular the tap When the tip 50a of the workpiece 50 comes into contact with the machining surface 100 of the workpiece W, that is, when the tap 50 actually starts machining the workpiece W, the thread start position SP of the screw portion 51 of the tap 50 (FIG. 12). The relative position between the tap 50 and the workpiece W at the start of machining, more specifically, at the start of machining, in order to obtain a distance such that the tap screw thread starting position SP is a desired angular position. The relative position between the tip 50a of the tap 50 and the machining surface 100 of the workpiece W is appropriately set. Details will be described below.

  In the present embodiment, the relative position between the tap 50 and the workpiece W at the start of machining is set using the setting gauge 70 before the tapping holder 60 is attached to the main shaft 11. As shown in FIG. 9, the setting gauge 70 includes a cylindrical portion 71 having a relatively large outer diameter, and a cylindrical portion having a diameter smaller than the outer diameter of the cylindrical portion 71 and disposed coaxially with the cylindrical portion 71. 72.

  As shown in FIG. 9, a screw hole 73 is formed in the cylindrical portion 71 at the center in the radial direction so as to penetrate in the cylindrical axis direction. The opening on the one side in the cylinder axis direction of the screw hole 73 is closed by the surface on the other side in the axial direction of the cylindrical portion 72. Thereby, in the entire setting gauge 70, the screw hole 73 is a bottomed screw hole.

  Further, the screw hole 73 of the setting gauge 70 is formed with a diameter corresponding to the diameter of the screw portion 51 of the tap 50.

  The cylindrical portion 71 of the setting gauge 70 is provided with a gauge side mark portion 74 at an angular position corresponding to the start position of the complete thread of the screw hole 73. As shown in FIG. 9, the gauge side mark portion 74 is configured by cutting out the outer peripheral portion of the cylindrical portion 71 in the circumferential direction.

  Next, a method for setting the relative position between the tap 50 and the workpiece W at the start of machining using the setting gauge 70 will be described.

  First, as shown in FIG. 10, after the tapping holder 60 is set on a predetermined setting table T, the screw portion 51 of the tap 50 is inserted into the screw hole 73 of the setting gauge 70, and the tip 50 a of the tap 50 is set to the setting gauge 70. The screw hole 73 is screwed in until it comes into contact with the bottom surface 73a (the surface on the other side in the axial direction of the cylindrical portion 72) (tap screwing step). At this time, as shown in FIG. 10, when viewed from the axial center direction of the tap 50, the angular position of the gauge side mark portion 74 and the angular position of the holder side mark portion 63 are located at different angular positions.

  As described above, the gauge side mark portion 74 of the setting gauge 70 is formed at an angular position corresponding to the start position of the complete thread of the setting gauge 70, so that the tap 50 is screwed into the screw hole 73 of the setting gauge 70. Thus, when the tip 50a of the tap 50 comes into contact with the bottom surface 73a of the screw hole 73, the gauge side mark portion 74 is located at an angular position corresponding to the tap screw thread start position SP. Therefore, when the tip 50 a of the tap 50 is in contact with the bottom surface 73 a of the screw hole 73 of the setting gauge 70, the angular position of the gauge side mark portion 74 and the angle of the holder side mark portion 63 around the axis of the tap 50. The positional deviation between the positions corresponds to the positional deviation between the angular position of the holder side mark portion 63 and the angular position of the tap screw thread start position SP (see FIG. 12 and the like).

  Next, as shown in FIG. 11, the setting gauge 70 is loosened until the angular position of the gauge side mark portion 74 and the angular position of the holder side mark portion 63 coincide (angle adjustment step). In this step, the shadow of the setting gauge 70 is projected by the projector toward the holder side in the axial direction of the tap 50, and the shadow of the gauge side mark portion 74 of the setting gauge 70 and the holder side mark of the tapping holder 60. The angular position with the part 63 is made to coincide.

  When the setting gauge 70 is loosened until the angular position of the gauge side mark portion 74 and the angular position of the holder side mark portion 63 coincide, the angular position of the holder side mark portion 63 of the tapping holder 60 and the tap thread start position SP ( A gap having a length corresponding to a positional deviation from the angular position (refer to FIG. 12 etc.) (hereinafter referred to as offset length OL) is formed between the tip 50a of the tap 50 and the bottom surface 73a of the screw hole 73 of the setting gauge 70. Occurs during. In FIG. 11, the offset length OL is shown as a relatively large length so that the offset length OL can be easily seen. However, in actuality, the offset length OL is shorter than one pitch of the screw portion 51 of the tap 50. .

  Next, the distance between the bottom surface 73a of the screw hole 73 of the setting gauge 70 and the contact surface 61a of the tapping holder 60 is set as a virtual tool length H '(virtual tool length setting step). The virtual tool length H ′ is obtained by adding the offset length OL to the actual tool length H (the distance between the tip 50 a of the tap 50 and the contact surface 61 a of the tapping holder 60).

  Thereafter, the relative position between the tap 50 and the workpiece W at the start of machining is set based on the virtual tool length H ′. Specifically, in the threading by the tap 50 for setting the direction of the parts (such as the spark plug 9) to be mounted in the screw hole to a desired direction, the tip surface 11a is based on the tip surface 11a of the main shaft 11. A tap 50 separated by the actual tool length H from the workpiece W side in the axial direction of the spindle 11 (which coincides with the Z-axis direction of the machine tool 10; hereinafter simply referred to as the Z-axis direction) In the XYZ coordinate system, as a Z coordinate of the tip 50a of the tap 50 when the tap 50 is mounted on the main shaft 11, a distance that is an integral multiple of the pitch of the threaded portion 51 of the tap 50 from the Z coordinate of the tip 50a (hereinafter referred to as a reference). A position separated in the Z-axis direction by a distance BL) is set as the Z coordinate of the machining surface 100 of the workpiece W. That is, the relative distance between the tap 50 and the workpiece W so that the distance between the tip 50a of the tap 50 and the machining surface 100 of the workpiece W at the start of machining (hereinafter referred to as the machining start distance L) becomes the reference distance BL. The position is set. In contrast, in this embodiment, the virtual tool length H ′ is used instead of the actual tool length H. That is, as shown in FIG. 12, from the front end surface 11a of the main shaft 11 to the workpiece W side in the axial direction of the main shaft 11, a position separated by the virtual tool length H ′, that is, from the front end 50a of the actual tap 50. The position on the workpiece W side by the offset length OL is set as the virtual tip position of the tap 50 when the tap 50 is mounted on the spindle 11, and the Z coordinate at a position separated from the Z coordinate of the virtual tip position by the reference distance BL. Is set to the Z coordinate of the machining surface 100 of the workpiece W.

  And after setting the relative position of the tap 50 and the workpiece | work W at the time of a process start as mentioned above, the tap 50 and the workpiece | work W in the state which the tapping holder 60 was attached to the main axis | shaft 11, as shown in FIG. The workpiece W and the tap 50 are aligned so that the relative position between the workpiece W and the tap 50 becomes the set relative position. Thereby, the processing start distance L can be set to a distance obtained by adding the offset length OL to a distance that is an integral multiple of the pitch of the thread portion 51 of the tap 50.

  At this time, when the screw holes 2b are formed at a plurality of locations, the Z coordinate (that is, the position of the machining surface 100) of each machining surface 100 that forms each screw hole 2b is set for each machining surface 100. The position of the workpiece W and the tap 50 is aligned each time. For example, in the case of machining for forming the screw hole 2b for attaching the spark plug 9 to the cylinder head 2 as the workpiece W as in the present embodiment, the machining surface 100 (seat surface) is provided for each cylinder 3a. ) And the cylinder head 2 and the tap 50 are aligned. Specifically, first, the touch sensor 122 is attached to the spindle 11, and the Z coordinate of the processing surface 100 when the tip of the touch sensor 122 and the processing surface 100 of the workpiece W come into contact is measured. Thereby, the relative position of the front end surface 11a of the spindle 11 and the processing surface 100 of the workpiece W can be set accurately. As shown in FIG. 3, when the tap 50 is attached to the main shaft 11 via the tapping holder 60, the Z coordinate of the contact surface 61 a of the tapping holder 60 and the Z coordinate of the front end surface 11 a of the main shaft 11 coincide. For this reason, if the relative position of the front end surface 11a of the spindle 11 and the processing surface 100 of the workpiece W can be set accurately, the relative position of the contact surface 61a of the tapping holder 60 and the processing surface 100 of the workpiece W is determined. It becomes possible to set accurately, and the relative position between the tap 50 and the workpiece W can be set accurately. Thereby, even if the initial position of each processing surface 100 of the workpiece W is different, at the time of processing, the relative position between the tap 50 and the workpiece W is such that the processing start distance L is equal to the reference distance BL and the offset length OL is set. The workpiece W and the tap 50 can be aligned so that the relative position becomes the added distance.

  Next, the relationship between the relative distance between the tip 50a of the tap 50 and the machining surface 100 of the workpiece W and the angular position of the tap thread start position SP during actual machining will be described. In the following description, with the tap 50 attached to the main shaft 11, the angular position of the tap screw thread start position is retarded by about 300 ° with respect to the reference angular position of the main shaft 11 (that is, the position at phase 0 °). Assuming that In the following description, a case will be described in which the threading is performed so that the angle position of the screw thread start position of the screw hole 2b becomes the reference angle position (0 ° angle position) of the main shaft 11. 12 and 13 referred to in the following description, the offset length OL is shown as a relatively large length so that the offset length OL can be easily seen. In practice, however, the offset length OL is one of the screw portions 51 of the tap 50. The length is shorter than the pitch.

  As shown in FIG. 12, at the start of machining, the relative distance between the tip 50a of the tap 50 and the machining surface 100 of the workpiece W is a distance obtained by adding the offset length OL to the reference distance BL. Since the angle position of the tap thread start position SP is delayed by about 300 ° with respect to the reference angle position of the main shaft 11, as shown in FIG. 12, the thread start position of the thread portion 51 of the tap 50 is It is located at an angular position shifted by about 300 ° clockwise relative to the reference angular position of the main shaft 11.

  Next, from the state of FIG. 12, the relative distance between the tip 50 a of the tap 50 and the machining surface 100 of the workpiece W is equal to one pitch of the thread 51 of the tap 50 while the screw 51 of the tap 50 makes one rotation. It is assumed that the workpiece W is moved so as to shrink and the relative distance between the tip 50a of the tap 50 and the machining surface 100 of the workpiece W becomes the offset length OL as shown in FIG. At this time, since the main shaft 11 has returned to the initial position around the axis, the tap screw thread start position SP is also positioned at the initial position as shown in FIG.

  The offset length OL is a phase shift between the holder-side mark portion 63 of the tapping holder 60 and the screw portion 51 of the tap 50 (a position shift between the angular position of the holder-side mark portion 63 and the angle position of the tap screw thread start position SP). Because of the corresponding length, the tip 50a of the tap 50 and the workpiece W are further moved at the same pace as described above from the state in which the relative distance between the tip 50a of the tap 50 and the processing surface 100 of the workpiece W is the offset length OL. When the relative distance from the machining surface 100 is reduced, the tap 50 is positioned on the holder side of the tapping holder 60 until the tip 50a of the tap 50 comes into contact with the machining surface 100 of the workpiece W as shown in FIG. The mark portion 63 rotates by an amount corresponding to a positional deviation between the angular position of the mark portion 63 and the angular position of the tap screw thread start position SP.

  As described above, the holder-side mark portion 63 of the tapping holder 60 is located at a position corresponding to the reference angle position of the main shaft 11 when attached to the main shaft 11. The positional deviation between the angular position of the mark portion 63 and the angular position of the tap screw thread starting position SP corresponds to the positional deviation between the reference angular position of the main shaft 11 and the angular position of the tap screw thread starting position SP. Therefore, when the relative distance between the tip 50a of the tap 50 and the machining surface 100 of the workpiece W is reduced by the offset length OL, that is, when the tip 50a of the tap 50 and the machining surface 100 of the workpiece W come into contact with each other, the tap 50 The angular position of the screw thread start position SP in the thread portion 51 of the main shaft 11 is located at the reference angular position of the main shaft 11.

  Therefore, for example, when the desired angular position of the screw thread start position of the screw hole formed in the workpiece W is the same as the reference angle position of the spindle 11, the machining start distance L is offset to the reference distance BL. If the relative position between the tap 50 and the workpiece W at the start of machining is set so that the distance to which the length OL is added, the tip 50a of the tap 50 will contact the machining surface 100 of the workpiece W during screw machining. The angle position of the tap thread start position SP when touching can be positioned at the desired angle position.

  On the other hand, for example, when the desired angular position of the screw thread starting position of the screw hole formed in the workpiece W is an angular position advanced by 90 ° with respect to the reference angular position of the spindle 11, the machining starts. The distance L is set to a distance obtained by adding the offset length OL and the 1/4 pitch length of the threaded portion 51 of the tap 50 to the reference distance BL. Specifically, after setting the Z coordinate of the virtual tip position of the tap 50 as described above, the length corresponding to the 1/4 pitch of the screw portion 51 is set from the virtual tip position to the reference distance BL. The Z coordinate of the machining surface 100 of the workpiece W is set so that the workpiece W is located at a position separated by the added distance. As a result, the tap 50 further advances by 1/4 pitch after the relative distance between the tip 50a of the tap 50 and the processing surface 100 of the workpiece W is reduced by the reference distance BL and the offset length OL, that is, 90 °. Rotate by minutes. As a result, when the tip 50a of the tap 50 comes into contact with the machining surface 100 of the workpiece W, the angular position of the tap thread start position SP is an angular position advanced by 90 ° with respect to the reference angular position of the spindle 11. Become.

  Therefore, at the time of threading by the tap 50, the angular position of the thread start position of the screw hole can be set to a desired angular position. Then, if a component (for example, a spark plug 9) is mounted in the formed screw hole, the orientation of the component can be set to a desired direction.

  In the present embodiment, since the position of the machining surface 100 of the workpiece W is measured by the touch sensor 122 attached to the spindle 11, the tip 50a of the tap 50 and the machining surface of the workpiece W at the start of machining. The relative position with respect to 100 can be accurately set, and the angular position of the screw thread start position of the screw hole can be more accurately set to a desired angular position when threading with the tap 50.

  Furthermore, in the present embodiment, the angle position of the gauge side mark portion 74 and the angle position of the holder side mark portion 63 coincide with each other in setting the relative position between the processing surface 100 of the workpiece W and the tip 50a of the tap 50 at the start of processing. When projecting, the shadow of the setting gauge 70 is projected by the projector toward the holder side in the axial direction of the tap 50, and the shadow of the gauge side mark portion 74 of the setting gauge 70 and the holder side mark of the tapping holder 60 are projected. Since the angular position with the part 63 is made to coincide, the angular position between the gauge side mark part 74 and the holder side mark part 63 can be accurately matched. Thereby, since the virtual tool length H ′ including the offset length OL can be obtained more accurately, the angle position of the screw thread start position of the screw hole can be more accurately determined at the desired angular position when threading with the tap 50. Can be.

  Therefore, in the present embodiment, the machining start distance that is the distance between the tip 50a of the tap 50 and the machining surface 100 of the workpiece W at the beginning of machining is determined by the screw portion 51 of the tap 50 and the machining surface 100 of the workpiece W. In order to set the relative position between the tap 50 and the workpiece W at the start of machining so that the screw thread starting position SP of the threaded portion 51 of the tap 50 becomes a desired angular position when in contact, the tap is set. At the time of threading by 50, the screw thread start position of the screw hole can be set to a desired angular position, and when the part is mounted in the formed screw hole, the direction of the part can be set to a desired direction. .

  The present invention is not limited to the embodiment described above, and can be substituted without departing from the spirit of the claims.

  For example, in the above-described embodiment, the projector is used to match the angular position of the gauge-side mark portion 74 and the angular position of the holder-side mark portion 63, but the angular position of the gauge-side mark portion 74 and the holder As long as the angle position of the side mark portion 63 can be matched, it is not always necessary to use a projector.

  In the above-described embodiment, for example, the desired angular position of the screw thread start position of the screw hole formed in the workpiece W is advanced by 90 ° with respect to the angular position of the reference angular position of the spindle 11. In this case, the tap 50 and the workpiece W are set such that the machining start distance L is a distance obtained by adding the offset length OL and a length corresponding to ¼ pitch of the threaded portion 51 of the tap 50 to the reference distance BL. However, the present invention is not limited to this, and the machining start distance L is set to a distance obtained by adding the offset length OL to the reference distance BL, and the spindle 11 is moved to 90 while the position of the workpiece W is fixed. Then, the relative distance between the tip 50a of the tap 50 and the processing surface 100 of the workpiece W may be shortened while the main shaft 11 is rotated.

  Furthermore, in the above-described embodiment, the machine tool 10 is one in which the position of the tool 12 (including the tap 50) is fixed and the workpiece W moves in the Z-axis direction. May be such that the position of the workpiece W is fixed and the tool 12 advances in the Z-axis direction, or both the tool 12 and the workpiece W can be fed in the Z-axis direction.

  In the above-described embodiment, the cylinder head 2 is shown as an example of the workpiece W, and the spark plug 9 is shown as an example of a component. However, the workpiece W may be other than the cylinder head 2 as long as a screw hole is formed. The components may be other than the spark plug 9 as long as the orientation at the time of attachment is important.

  The above-described embodiments are merely examples, and the scope of the present invention should not be interpreted in a limited manner. The scope of the present invention is defined by the scope of the claims, and all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention is useful as a screw machining method in which a screw hole is formed in a workpiece by a machine tool that is fixed to a tapping holder attached to the tip of a main shaft and includes a tap having a thread portion for cutting a female screw on the workpiece.

1 Engine 2 Cylinder head (work)
2b Screw hole (Female thread for setting spark plug in cylinder)
2c Bearing surface (machined surface)
3a Cylinder 9 Spark plug 10 Machine tool 11 Spindle 11a Spindle tip surface 50 Tap 50a Tap tip 51 Threaded portion 60 Tapping holder 61a Abutting surface 63 Holder-side mark portion 70 Setting gauge 73 Screw hole 74 Gauge-side mark portion 100 Work surface H 'Virtual tool length W Work SP Thread start position of tap thread

Claims (4)

Screw machining, wherein a female screw is formed on the workpiece by a machine tool including a main shaft that rotates around an axis, and a tap that is fixed to a tapping holder attached to the tip of the main shaft and has a thread portion for cutting a female screw on the workpiece. A method,
The tapping holder corresponds to a contact surface that contacts the tip surface of the main shaft when attached to the main shaft, and a reference angle position in a circumferential direction of the main shaft when attached to the main shaft. A holder-side mark provided at an angular position,
A machining start position setting step for setting a relative position between the tap and the workpiece at the start of machining;
Position of the workpiece and the tap so that the relative position between the tap and the workpiece is the relative position set in the machining start position setting step in a state where the tapping holder is attached to the main shaft. An alignment process for performing the alignment,
The machining start position setting step, a machining start distance is the distance between the tip and the processing surface of the work of the tap at the start processing, and the threaded portion and the processing surface of the work of the tap contact The step of setting the relative position so that the screw thread starting position of the thread portion of the tap becomes a desired angular position , and the bottomed screw hole and the screw hole A step of performing using a setting gauge having a gauge side mark portion formed in advance at the angular position of the start position of the complete thread,
Furthermore, the processing start position setting step
A tap screwing step of screwing the screw portion of the tap into the screw hole of the setting gauge until the tip end of the tap contacts the bottom surface of the screw hole of the setting gauge;
After the tap screwing step, the angular position of the gauge side mark portion of the setting gauge as viewed from the axial direction of the tap, and the holder side mark portion of the tapping holder as viewed from the axial direction of the tap. An angle adjustment step of loosening the setting gauge until the angle position matches,
A virtual tool length setting step of setting a distance between the bottom surface of the screw hole of the setting gauge and the contact surface of the tapping holder as a virtual tool length after the angle adjustment step;
A thread machining method, wherein the relative position is set based on the virtual tool length set in the virtual tool length setting step . The threading method according to claim 1 ,
A machining surface position measuring step of measuring the position of the machining surface of the workpiece by a touch sensor attached to the spindle;
In the positioning step, the workpiece and the tap are set based on the relative position set in the machining start position setting step and the position of the machining surface of the workpiece measured in the machining surface position measurement step. Threading method characterized by aligning. In the screw processing method according to claim 1 or 2 ,
The gauge side mark portion is configured by a notch obtained by cutting out the outer peripheral portion of the setting gauge in the circumferential direction, while the holder side mark portion is configured by a notch obtained by cutting out the outer peripheral portion of the tapping holder in the circumferential direction. Has been
In the angle adjustment step, the shadow of the setting gauge is projected by the projector toward the holder side in the axial direction of the tap, and the angular position between the shadow of the gauge side mark portion and the holder side mark portion A screw machining method characterized by being a step of matching. In the screw processing method according to any one of claims 1 to 3 ,
The workpiece is a cylinder head of a multi-cylinder engine having a plurality of cylinders,
The female screw formed on the workpiece is a female screw for setting a spark plug in each cylinder in the cylinder head,
The screw machining method, wherein the positioning step is performed for each cylinder.

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