JP2013094899A - Lathe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lathe in which a rotational position of a characteristic shape part such as a reference hole of a workpiece can be detected by using sensors commonly used for machining control without any special sensors, and a wiring system can be simplified.SOLUTION: A detection contactor 24 in a shape of a bar or the like is attached to a tool rest 3. A rotational position detection means 27 for the characteristic shape part is provided to a control device 2. In response to a signal showing that the contactor 24 comes to a prescribed position, the means 27 monitors torque detected by a main spindle torque detection means 19 while rotating a main spindle motor 11. When the torque is a set value or more, the means 27 stores a rotational position detected by a rotational position detection means 16 as a rotational position of the characteristic shape part H. When the characteristic shape part H is a hole, a main spindle 6 is rotated forward and backward to measure respective positions of two parts on a hole inside surface, and a center of the hole is derived from an average thereof.

Description

  The present invention relates to a lathe such as a turret lathe having a function of performing machining at a predetermined rotational position of a workpiece.

  Some lathes that can be equipped with a large number of tools such as a turret lathe can perform drilling and tapping of workpieces. When such drilling or tapping is performed, a feature shape portion serving as a reference position such as a hole or a notch may be used for the workpiece. In order to know the rotational position of such a characteristic shape portion, conventionally, a touch switch or the like is mounted on a tool post such as a turret, and the rotational position (coordinates in the rotational direction) is detected by rotating the spindle ( For example, Patent Documents 1 and 2).

JP-A-10-309651 JP 05-061511 A

  In the configuration in which the conventional touch switch is mounted on the tool post, a touch switch which is a dedicated detector is required and wiring is required. Since this wiring is provided between the touch switch mounted on the moving or rotating tool post and the position fixing control device, it becomes a complicated wiring system and there is a risk of disconnection. Although it is possible to use wireless communication means using light or the like as a medium between the fixed part and the movable part, there is a risk that communication failure may occur due to oil stains in the machine tool.

An object of the present invention is to detect the rotational position of a characteristic shape portion such as a reference position of a workpiece by using sensors normally used for machining control without using special sensors. It is also to provide a lathe that can be simple.
Another object of the present invention is to detect that the characteristic shape portion is at a specific rotational position by using sensors that are usually used for processing control without using special sensors. The wiring system should be simple.
Still another object of the present invention is to make it possible to detect the rotational position of the center of the feature shape portion with a simple configuration when the feature shape portion is a hole.

The lathe of the present invention has a spindle (6) for supporting and rotating a workpiece (W), and a relative feed in the direction of the spindle axis and the direction perpendicular to the spindle axis (O) with respect to the spindle (6). A tool post (3) on which a tool (22) is mounted so as to be movable, a spindle motor (11) for rotating the spindle (6), and the feed of the spindle (6) or the tool post (3) In a lathe equipped with a control device (2) for controlling a feed motor (12, 14) for moving,
The tool post (3) is provided with a contact (24) for detection to be brought into contact with the work (W) supported by the spindle (6),
A rotational position detecting means (16) for detecting the rotational position of the spindle (6) is provided;
A spindle torque detecting means (19) for detecting the torque of the spindle motor (11) is provided;
A feature shape portion rotation position detecting means (27) for detecting a rotation position of the feature shape portion (H) of the workpiece (W);
The feature shape portion rotation position detecting means (27) is configured such that the contact (24) rotates the feature shape portion (H) of the work (W) by the relative movement of the spindle (6) or the tool post (3). When at the feed position where the phase can be detected, the torque of the spindle torque detecting means (19) is monitored while rotating the spindle motor (11), and the contact (24) and the workpiece ( The contact of the characteristic shape portion (H) of W) is detected, and the rotational position of the characteristic shape portion (H) is stored based on the rotational position detected by the rotational position detecting means (16) at this time.

According to this configuration, when the contact (24) is determined by relative movement of the tool post (3) and comes to a position, for example, when the characteristic shape portion (H) is a hole, the contact (24) is placed in the hole. When it comes, the characteristic shape portion rotation position detection means (27) monitors the torque detected by the spindle torque detection means (19) while rotating the spindle motor (11). When it is detected that a change defined in the detected torque, for example, the torque is equal to or greater than a set value, the rotational position detected by the rotational position detecting means (16) at this time is detected as the characteristic shape portion (H ) Is stored as the rotation position.
Thus, it can detect by the rotational position detection means (16) of a spindle motor (11), or a spindle torque detection means (19), without using special sensors, such as a touch sensor. These rotational position detecting means (16) and spindle torque detecting means (19) are usually provided for highly accurate machining control by position feedback and current feedback in numerically controlled lathes. The rotational position of the characteristic shape portion (H) can be detected using each detection means. Further, since the rotational position detecting means (16) and the spindle torque detecting means (19) are installed in the fixed part of the lathe, the wiring system can be simplified. As described above, the rotation position of the characteristic shape portion (H) such as the reference position of the workpiece (W) can be determined by using sensors that are normally used for processing control without using special sensors. It can be detected and the wiring system can be simplified.
The rotational position detecting means (16) can be a pulse coder, an encoder or the like equipped on the spindle motor (11).

In the present invention, feed motor torque detecting means (20, 21) for detecting the torque of the feed motor (12, 14) is provided, and the characteristic shape portion (H) of the workpiece (W) is present at a specific position. You may provide the feature shape part presence detection means (26) to detect.
The characteristic shape portion presence detecting means (26) is configured to detect the contact () in a locus formed by the rotation of the main shaft (6) of the characteristic shape portion (H) of the work (W) supported by the main shaft (6). 24) After driving the feed motor (12, 14) so as to be positioned, the spindle shaft of the feed motor torque detecting means (20, 21) while rotating the workpiece (W) by the spindle motor (11) The torque in the central direction is monitored, and it is detected that the characteristic shape portion exists at a specific rotational position of the workpiece (W) by the change in the torque.

In the case of this configuration, after the tool post (3) is relatively moved so that the contact (24) comes to the specific position, the tool post moving torque detecting means (20, 21) is rotated while the workpiece (W) is rotated. ) Monitor the detected torque. It is detected that the characteristic shape portion (H) is present at a specific rotational position of the main shaft (6) by detecting that the change defined in the detected torque has occurred. For example, when the characteristic shape portion (H) is a hole, when the work (W) is rotated in a state where the contact (24) is pressed against the work (W), the contact (24) becomes the characteristic shape portion (H ), The torque of the feed motors (12, 14) that are fitted in the holes and drive the turret (3) against the work (W) is rapidly reduced. Due to this sudden decrease in torque, it can be detected that the contact (24) is fitted in the hole, that is, that the characteristic shape portion (H) is at a specific rotational position.
In this way, the fact that the characteristic shape portion (H) is at a specific rotational position can also be detected using sensors normally used for machining control without using special sensors. Is easy.

In the present invention, the characteristic shape portion (H) of the workpiece (W) is a hole formed in the axial direction, and the characteristic shape portion rotation position detecting means (27) rotates the spindle motor (11) in the normal direction. And the rotation position of the inner side surface of the hole is rotated and the rotation position on both sides in the rotation direction is stored, and the rotation position of the center of the hole which is the characteristic shape portion (H) is obtained from these two stored rotation positions. Also good.
In the case of this configuration, when the characteristic shape portion (H) is a hole, the rotational position of the center can be detected with a simple configuration by measuring two points.

  The lathe according to the present invention is provided with a main shaft for supporting and rotating a work, and a relative feed movement with respect to the main shaft and a direction perpendicular to the main shaft axis so that the tool is mounted. A lathe provided with a tool post, a spindle motor for rotating the spindle, and a control device for controlling a feed motor for performing the feed movement of the spindle or the tool rest. A contact for detection to be brought into contact, a rotational position detecting means for detecting a rotational position of the spindle, a spindle torque detecting means for detecting torque of the spindle motor, and a rotational position of the characteristic shape portion of the workpiece The characteristic shape portion rotational position detecting means is provided for detecting the characteristic shape portion rotational position detecting means. The characteristic shape portion rotational position detecting means detects the characteristic shape of the workpiece by the feed relative movement of the spindle or the tool post. When the spindle motor is in a feed position where the rotation phase of the part can be detected, the torque of the spindle torque detecting means is monitored while rotating the spindle motor, and the contact between the contactor and the characteristic shape part of the workpiece is detected by a change in this torque. In order to store the rotation position of the feature shape portion based on the rotation position detected by the rotation position detection means at this time, the rotation position of the feature shape portion such as the reference position of the workpiece is stored using special sensors. Without being used, it can be detected by using sensors normally used for controlling the machining, and the wiring system can be simplified.

  A feed motor torque detecting means for detecting the torque of the feed motor is provided, a feature shape portion presence detecting means for detecting that the feature shape portion of the workpiece is present at a specific position is provided, and the feature shape portion presence detecting means is The feed motor is driven so that the contactor is positioned in a locus formed by the rotation of the main shaft of the characteristic shape portion of the work supported by the main shaft, and then the work is rotated while the work is rotated by the main shaft motor. When monitoring the torque in the direction of the spindle axis of the motor torque detecting means and detecting that the characteristic shape portion exists at a specific rotational position of the workpiece by the change in the torque, the characteristic shape portion is at the specific rotational position. Can be detected using sensors normally used for machining control without using special sensors, and the wiring system is simple. It can be a.

  The feature shape portion of the workpiece is a hole formed in the axial direction, and the feature shape portion rotation position detecting means rotates the main shaft motor forward and backward to rotate the rotation positions on both sides in the rotation direction of the inner surface of the hole. When the rotational position of the center of the hole which is the characteristic shape portion is obtained from these two stored rotational positions, the rotational position of the center can be simply calculated when the characteristic shape portion is a hole. Can be detected by configuration.

It is a block diagram which shows the conceptual structure of the lathe main body of the lathe which concerns on one Embodiment of this invention, and its control system. It is a top view of the lathe main body of the same lathe. It is a front view of the lathe main body of the same lathe. (A) (B) is a front view of each operation state showing an example of a workpiece processed by the same lathe and a detection operation. It is a perspective view which shows the other example of the workpiece | work processed with the same lathe. It is a front view which shows the further another example of the workpiece | work processed with the same lathe.

  An embodiment of the present invention will be described with reference to FIGS. This lathe is composed of a lathe body 1 that is a machine part and a control device 2 that controls the lathe body 1. As shown in FIGS. 2 and 3, the lathe body 1 includes a bed 4, a headstock 5 mounted on the bed 4 and rotatably supporting a main shaft 6, and a turret-type tool rest 3. The tool post 3 has a polygonal front shape, and a tool 22 is attached to a tool station formed of each plane portion of the outer peripheral surface. As the tool 22, in addition to the bite, a rotary tool (not shown) such as a drill, a tap tool, or a milling head is attached. The spindle 6 has a chuck 6 a that grips the workpiece W attached to the tip, and is driven to rotate by the spindle motor 11. The chuck 6a has a chuck claw 6aa.

  On the side of the headstock 5 on the bed 4, a feed base 8 is installed via a guide rail 7, and the tool post 3 is mounted on the feed base 8. The feed base 8 includes a feed base portion 8a that can move on the guide rail 7 in a direction orthogonal to the axis O of the main shaft 6 (X-axis direction), and an axis O of the main shaft 6 on the feed base portion 8a. The turret-type tool post 3 pivots on the feed base upper part 8b via the turret shaft 10 and is movably mounted in the front-rear direction (Z-axis direction). It is installed freely. The feed base 8a is advanced and retracted in the X-axis direction via the ball screw mechanism 13 by the X-axis feed motor 12. The feed base upper part 8b is moved back and forth in the Z-axis direction via the ball screw mechanism 15 by the motor 14 in the Z-axis direction. The tool post 3 is driven to move back and forth in two orthogonal directions with respect to the main shaft 6 by the movement of the feed base portion 8a and the feed base upper portion 8b. The turning drive of the tool post 3 is performed by a motor (not shown) mounted on the feed base upper part 8b.

  The spindle motor 11 that rotationally drives the spindle 6 and the feed motors 12 and 14 for each axis for moving the tool post 3 are provided with rotational position detecting means 16, 17, and 18, respectively. In addition, a main shaft torque detection means 19 and a feed motor torque detection means 20 and 21 each comprising an ammeter are provided on the power supply wiring of the feed motors 12 and 14, respectively. The rotational position detecting means 16, 17, 18 may be an incremental pulse coder or an absolute encoder.

  In the lathe of this embodiment, in the above configuration, a contact 24 is provided in one tool station of the tool post 3, and the characteristic shape portion presence detecting means 26 and the characteristic shape portion rotational position detecting means are added to the control device 2 of FIG. 27 is provided.

  The workpiece W to be machined has, for example, a characteristic shape portion H that serves as a reference for the circumferential position for machining. The characteristic shape portion H may be a concave portion or a convex portion, but is a portion having a shape that serves as a reference for positioning the workpiece W in the circumferential direction and can be distinguished from other portions. As a specific example of the workpiece W, as shown in FIG. 4 (A), a circular feature shape portion H serving as a reference hole is formed on the end surface, and the reference hole that is the feature shape portion H The processing scheduled portion B (FIG. 4B) is tapped at the workpiece peripheral surface position that is separated from the center of the circle by a predetermined angle α in the circumferential direction around the center of the workpiece. A pilot hole for processing) exists.

  1 and 2, the contact 24 is a rod-like part made of steel or the like extending in a direction parallel to the spindle axis O in this example, and is attached to the tool post 3 via the contact holder 28. Yes. The tip 24a of the contactor 24 is a spherical ball portion. This contactor 24 is for detecting the characteristic shape portion H that becomes a reference hole provided on the end face of the workpiece W. In addition, in order to detect the characteristic shape portion H (FIG. 5) serving as a reference hole provided on the peripheral surface of the workpiece W, the contactor 24 has a shape extending in a direction orthogonal to the main shaft axis O.

  The control system will be described with reference to FIG. The control device 2 is a computer-type numerical control device, and includes computer hardware (including an operation program) and a machining program (not shown) including NC codes executed on the computer hardware. Processing control means 25, feature shape portion presence detection means 26, and feature shape portion rotation position detection means 27 are configured. The machining program includes a program part that causes the lathe body 1 to perform machining and a program part that performs a detection operation, and the machining control unit 25 is a program part that causes the machining operation to be performed. Each detection means 26 and 27 is comprised, respectively. The control device 2 performs position feedback control with respect to the movement command of each axis for moving the tool post 3 (movement command for the X-axis and Z-axis feed motors 12 and 14) and the rotation command for the spindle motor 11. Means for performing (not shown).

  The machining control means 25 is a means for controlling the machining of the workpiece W by each tool by controlling the movement of the tool rest 3 in each axial direction, the rotation of the spindle 6 and the rotary tool provided on the tool rest 3. . In the case of the workpiece W in FIG. 4A, the machining control means 25 moves the tool post 3 in each axial direction so as to perform tapping on the prepared hole which is the machining scheduled portion B located on the outer peripheral surface of the workpiece W. The spindle 6 is rotated, and a tap tool (not shown) attached to the tool post 3 is controlled.

The feature shape portion presence detection means 26 is a means for detecting that the feature shape portion H of the workpiece W exists at a specific position. In the example shown in the drawing, the characteristic shape portion H is a circular hole serving as a reference hole provided on the end surface of the work W so as to be off the center of the work. The specific position is an angular position that is horizontal on the tool post 3 side with respect to the axis of the main shaft 6.
The characteristic shape portion presence detecting means 26 is a tool post so that the contact 24 is positioned in a locus R (FIG. 4) formed by the rotation of the main shaft 6 of the characteristic shape portion H of the workpiece W supported by the main shaft 6. 3, the feed motors 12 and 14 of the respective axes for performing the relative movement are driven. In the example of FIG. 4, the locus R is an annular region around the center of the workpiece, as indicated by the dashed line hatching. In this example, the contact 24 is positioned on the end face of the workpiece W within the locus R by driving the axis feed motors 12 and 14 that move the tool post 3, and the pressing state is maintained. This pressing is performed, for example, by giving a command value to the Z-axis motor 14 to be positioned at a target position on the back side of the end face position of the workpiece W.

  After the pressing, the characteristic shape portion presence detecting means 26 in FIG. 1 monitors the detected torque of the Z-axis feed motor torque detecting means 21 while rotating the workpiece W by driving the spindle motor 11 that rotates the spindle 6. . By detecting that the change defined in the detected torque has occurred, it is detected that the characteristic shape portion H exists at a specific rotational position of the main shaft 6. The rotation of the workpiece W is performed at a very low speed by limiting the torque so that it can be stopped immediately in response to the detection signal. When the change is detected by the feed motor torque detecting means 21, the rotation of the workpiece W is rotated. Stop. In the example, the “determined change” is a decrease in the detected torque to a set value or less, or a sudden decrease in the detected torque. When the characteristic shape portion H is a hole, when the contact 24 is fitted into the hole due to the rotation of the workpiece W, the torque of the Z-axis motor 14 rapidly decreases. This sudden drop is detected by the feed motor torque detecting means 21.

  The characteristic shape portion rotation position detecting means 27 is a signal indicating that the contact 24 has come to a predetermined position by relative movement of the tool post 3, specifically, the characteristic shape portion H detected by the characteristic shape portion presence detecting means 26. In response to a signal indicating that the existence of the Z-axis motor 14 has been completed, that is, a detection signal indicating a decrease in torque of the Z-axis motor 14, the detected torque of the spindle torque detecting means 19 is monitored while the spindle motor 11 is rotated. The rotation of the spindle motor 11 is performed at a very low speed with a torque limit so that it can be stopped immediately in response to the detection signal. During this monitoring, if a change determined in the detected torque, for example, when the detected torque exceeds a set value or a sudden increase in the detected torque is detected, the rotational position detected by the rotational position detecting means 16 at this time is characterized. It is stored as the rotational position of the shape portion H.

  When the characteristic shape portion H of the workpiece W is a hole, the characteristic shape portion rotation position detecting means 27 detects that the predetermined change has occurred in the detected torque as described above. After storing the rotational position detected by the rotational position detecting means 16, the detected torque of the main spindle torque detecting means 19 is monitored while rotating the main spindle motor 11 in the reverse direction. Also at this time, the rotation of the spindle motor 11 is performed at a very low speed by applying a torque limit so that it can be stopped immediately in response to the detection signal. When it is detected that a change defined in the detected torque has occurred, the rotational position detected by the rotational position detection means 16 at this time is stored, and the characteristic shape portion is determined from these two stored rotational positions. The rotational position of the center of the hole which is H is obtained.

  Note that more specific functions of the feature shape portion presence detection means 26 and the feature shape portion rotation position detection means 27 will be described together with the following operation description.

The operation of the above configuration will be described. The workpiece W is assumed to have been described above with reference to FIG. When the workpiece W is supported by the spindle 6, the feature shape portion detection mode, which is a detection mode under the control of the feature shape presence detection means 26, is set prior to the start of machining. At this time, the rotational position of the characteristic shape portion H is unknown.
In the characteristic shape portion detection mode, the tool post 3 is moved in the X-axis direction so that the contact 24 is positioned in the locus R of the characteristic shape portion H on the end surface of the workpiece W supported by the main shaft 6. At this time, the X coordinate (from the workpiece center to the hole center) of the center position of the hole which is the characteristic shape portion H when the rotation position of the characteristic shape portion H is at the specific position (a horizontal position facing the tool post 3). The radius of the tool post 3 is known, and the tool post 3 is moved to the known X coordinate in the X-axis direction. Thereafter, the tool post 3 is moved in the Z-axis direction. This movement in the Z-axis direction is continuously moved to the target position with torque limitation. When the target position is not reached by the set time, the contact 24 is out of phase with the hole that is the characteristic shape portion H, stops at the workpiece end surface, and presses the workpiece end surface. At this time, the main shaft 6 is rotated by continuing to push in the Z-axis direction.

  When the feature-shaped portion H pivots to the position of the contact 24 by the rotation of the work W, the Z-axis movement of the tool post 3 starts so that the contact 24 fits in the hole that is the feature-shaped portion H. Immediately stop the rotation of the spindle motor 11 and wait for the completion of the Z-axis movement. Thereby, it is confirmed that the characteristic shape part H exists in a specific position.

  When the contact 24 is moved in the Z-axis direction in the trajectory R at the beginning and reaches the target position by the set time, the contact 24 is positioned in the hole which is the characteristic shape portion H. It is a case. In this case, the main shaft 6 is not rotated, and it is confirmed that the characteristic shape portion H exists at the specific position by detecting that the target position in the Z-axis direction has been reached.

When the feature shape portion H is confirmed to be present at a specific position in this way, a rotation position detection mode controlled by the feature shape portion rotation position detection means 27, that is, a reference coordinate calculation mode is set.
In the rotational position detection mode, from the state where the contactor 24 enters the hole which is the characteristic shape portion H, the spindle 6 is sequentially rotated forward and backward while applying torque restriction to the spindle motor 11, and the spindle torque during each rotation. The detection position of the rotational position detection means 16 when the detection means 19 reaches the set torque is read.

  That is, when the main shaft 6 is rotated forward and the contact 24 hits the inner surface of the hole which is the characteristic shape portion H, the main shaft torque detecting means 19 increases because it cannot rotate any more, and the torque has reached the set value. , And the detected position of the rotational position detecting means 16 at that time is read and stored, and the rotation is stopped and reversely rotated. When the contact 24 comes into contact with the inner surface on the opposite side of the hole which is the characteristic shape portion H by reverse rotation, it can no longer be rotated and the spindle torque detecting means 19 increases, so that it detects that the torque has reached the set value. Then, the detected position of the rotational position detecting means 16 at that time is read and stored.

  Next, from the two stored rotational positions, the rotational position of the center of the hole, which is the crest-shaped portion H, is calculated and stored as an average value of both rotational positions. The rotational position of the center of the characteristic shape portion H thus obtained is the reference position in the circumferential direction of the workpiece W.

  The processing control means 25 controls the lathe body 1 so as to perform processing of the planned processing portion B, for example, tap processing on the prepared hole, using the reference position obtained as described above.

  According to the lathe of this configuration, as described above, the feature shape portion H such as the reference position of the workpiece W is at a specific rotation position, and the rotation position (coordinates in the rotation direction) of the feature shape portion H is touched. Detected by using a contactor 24 made of a simple iron rod, etc., and a rotational position detecting means 16 and a spindle torque detecting means 19 that are usually used for machining control without using special sensors such as switches. can do. In addition, since the tool post 3 does not require sensors, the wiring system can be simplified.

In the above example, the case where the characteristic shape portion H is a hole on the end surface of the workpiece W has been described. However, the present invention can also be applied to the case where the characteristic shape portion H is a hole on the peripheral surface of the workpiece W as shown in FIG. In this case, the X-axis direction feed motor torque detecting means 26 is used instead of the Z-axis direction feed motor torque detecting means 21, but the characteristic shape portion H is at a specific rotational position in the same manner as described above. And the position of the characteristic shape portion H can be detected.
Furthermore, not only when the characteristic shape portion H is a hole, but also when the inner end portion of the spiral groove G in the workpiece W shown in FIG. Rotation can be detected. The present invention can also be applied when the characteristic shape portion H is a protruding portion.
The present invention can also be applied to a lathe that performs relative movement in one direction or both directions of the tool rest 3 with respect to the spindle 6 by movement of the spindle base 5.

DESCRIPTION OF SYMBOLS 1 ... Lathe body 2 ... Control apparatus 3 ... Tool post 4 ... Bed 5 ... Spindle base 6 ... Spindle 8 ... Feed base 8a ... Feed base base part 8b ... Feed base upper part 11 ... Spindle motors 12, 14 ... Feed motor 16, 17, 18 ... Rotational position detection means 19 ... Spindle torque detection means 20, 21 ... Feed motor torque detection means 22 ... Tool 24 ... Contact 25 ... Machining control means 26 ... Feature shape portion presence detection means 27 ... Feature shape portion rotation position Detecting means B ... Processing scheduled portion H ... Feature shape portion O ... Spindle axis W ... Work

Claims (3)

A spindle for supporting and rotating the workpiece, a turret on which a tool is mounted so as to be able to move relative to the spindle in a direction of the spindle axis and a direction perpendicular to the spindle axis; and the spindle A lathe equipped with a spindle motor that rotates the spindle and a control device that controls the feed motor that performs the feed movement of the spindle or the tool post,
The tool post is provided with a contact for detection to be brought into contact with the work supported by the spindle.
Providing a rotational position detecting means for detecting the rotational position of the spindle;
A spindle torque detection means for detecting the torque of the spindle motor;
Providing a feature shape portion rotation position detection means for detecting the rotation position of the feature shape portion of the workpiece;
The feature shape portion rotation position detecting means rotates the spindle motor when the contactor is at a feed position where the rotation phase of the feature shape portion of the workpiece can be detected by the feed relative movement of the spindle or the tool post. While monitoring the torque of the spindle torque detection means, the contact between the contact and the feature shape part of the workpiece is detected by a change in the torque, and the feature is based on the rotational position detected by the rotational position detection means at this time. A lathe that stores the rotational position of the shape part. A feed motor torque detecting means for detecting the torque of the feed motor is provided;
Providing a feature shape portion presence detecting means for detecting that the feature shape portion of the workpiece is present at a specific position;
The feature shape portion presence detecting means drives the feed motor so that the contactor is positioned in a trajectory formed by rotation of the main shaft of the feature shape portion of the work supported by the main shaft, and then the main shaft. 2. The torque in the main shaft axis direction of the feed motor torque detecting means is monitored while rotating the workpiece by a motor, and the presence of the characteristic shape portion at a specific rotation position of the workpiece is detected by a change in the torque. The lathe described. The characteristic shape portion of the workpiece is a hole formed in an axial direction;
The feature shape portion rotation position detecting means stores the rotation position of both sides of the rotation direction of the inner surface of the hole by rotating the main shaft motor forward and backward, and from the two stored rotation positions, the feature shape portion The lathe according to claim 1 or 2, wherein the rotational position of the center of the hole is obtained.

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