JP2002160133A - Multitasking machine - Google Patents

Abstract

(57) [Problem] To provide a machining machine capable of performing cutting and grinding in the same machine, the machine configuration becomes large, the manufacturing cost is high, and many cutting tools cannot be prepared. A turret for a cutting tool which has a rotation center in the same direction as a grinding wheel axis and can be indexed, which can be given a rotation speed for grinding or cutting to a workpiece gripped by a headstock and a tailstock. A composite tool rest is provided adjacent to the grindstone, and the tool rest is provided with the grindstone shaft drive unit and the turret drive unit to constitute a complex processing machine capable of cutting and grinding in the same machine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-tasking machine capable of performing turning and grinding with one machine. More specifically, the present invention relates to a multi-tasking machine provided with a grindstone shaft rotatable around a turning center in the same direction as a turret capable of turning indexing so that turning and grinding can be performed by the same machine.

[0002]

2. Description of the Related Art Conventionally, a multi-tasking machine for performing turning and grinding in the same machine includes a type in which a grindstone base and a tool post are separately provided and guided on respective guide surfaces, and a turret including a grindstone unit and a tool unit. There is a type provided on the tool post.

The prior art related to the present invention is the latter, and is disclosed in Japanese Utility Model Laid-Open No. 1-114240 and Japanese Patent Laid-Open No. 3-2.
No. 28571 is known. JP-A-3-2285
No. 71 discloses a rectangular turret tool rest provided with a cutting unit, a grindstone unit, and a measuring unit at four corners. Accordingly, the work is machined by rotating the turret wheel head and selecting a unit suitable for the machining. The cutting unit and the grindstone unit are provided in common for the grindstone base capable of turning indexing, and a description will be given below of Japanese Utility Model Laid-Open No. 1-114240.

The technique disclosed in Japanese Utility Model Laid-Open Publication No. 1-114240 is shown in FIGS. In the present invention, a grinding wheel and a cutting tool for turning are mounted on a grindstone table, and the turning position of the workpiece with the grindstone and the turning table are turned by turning the grindstone table so that the grindstone does not interfere with the workpiece during turning. By turning and positioning the grindstone table at two positions, ie, a position where a workpiece is machined, rough turning and finish grinding are performed.

In FIG. 5, reference numeral 110 denotes a machine tool bed, on which a table 111 is mounted on a table 110 so as to be slidable in a horizontal direction, and is controlled by a servomotor M1. It has become.
A headstock 112 and a tailstock 113 are provided on the table 111 at a predetermined interval in the sliding direction of the table 111, and the workpiece W rotates between the centers of the headstock 112 and the tailstock 113. And is rotatably driven by a spindle drive motor (not shown). A swivel table 116 is mounted on the bed 110 so as to be rotatable and indexable in a horizontal plane.
Is slidably mounted in a direction intersecting with the sliding direction of the table 111, and is controlled to be fed by the servomotor M2. A grindstone wheel 117 for grinding is rotatably mounted on the grindstone stand 115, and a turning blade 118 is attached to a front portion of the grindstone stand 115. Thus, the whetstone 115 is the swivel 1
The rotation indexing of 16 causes the grinding wheel 117 to be indexed into two positions, an angular position shown in FIG. 5 corresponding to the workpiece W and the cutting tool 118 shown in FIG. It has become.

When the workpiece W supported between the centers of the headstock 112 and the tailstock 113 is to be roughly machined by turning, the grindstone 115 is rotated at a predetermined angle as shown in FIG. At the same time as the grinding wheel 117 is retracted from the workpiece W, the turning tool 118 is moved closer to the workpiece W. In a proper state, the table 111 and the grindstone stand 115 are
The workpiece is turned into a predetermined shape by the cutting tool 118 while simultaneously controlling two axes by 1 and M2.

Subsequently, when finishing the workpiece W by grinding, the grindstone stand 115 is rotated and indexed to the angular position shown in FIG. The table 111 and the grindstone 115 are moved to the servomotor M
The workpiece is ground by the grinding wheel 117 under two-axis control by 1 and M2. FIG. 7 shows another embodiment of the present invention, in which a grinding wheel 117 and a cutting tool 118 are arranged at a point symmetrical position about the center of rotation of the grinding wheel stand 115, and the grinding wheel stand 115 is moved to the carriage 11.
6, and the turning and grinding can be performed by 180-degree rotation indexing.

[0008]

In the multi-tasking machine described in the prior art, a cutting tool for rough machining and a grindstone for finish machining are provided on the same grindstone base. Since interference occurs between the workpiece and a tool that does not need to be involved in the machining, there has been a problem that the grindstone table must be turned each time during rough machining and finish machining in order to avoid this. In general, cutting is a method suitable for processing a soft material with large chips in a short time, and grinding is generally performed by heat-treating the material after cutting and turning the hardened material into fine chips. It was a processing method suitable for precision processing.

[0009] Accordingly, the processing machines have been developed with the characteristics of tools and mechanical structures, as represented by a lathe and a grinding machine, respectively. However, the conventional multi-tasking machines do not exceed the technical idea in the machine configuration described above, and the conventional tool post and grindstone stand are introduced as separate units into one machine to configure the multi-tasking machine. It is just doing. Therefore, the tool rest and the grindstone stand are provided on separate guide surfaces, or the tool unit and the grindstone unit are provided on the revolving tool stand, which increases the machine configuration, which is disadvantageous in terms of the manufacturing cost of the multi-tasking machine. There's a problem. In addition, when using a turning tool stand, it is necessary to make the turning tool post polygonal in order to increase the number of turning tools to be attached, and the machine configuration becomes large, so the number of cutting tools to be prepared cannot be increased. Had the problem that

On the other hand, recently, with the advent of diamond and CBN, machining of a hard material after heat treatment, which could only be performed by grinding, has become possible by cutting. Also, with the emergence of new tools, the cutting and grinding fields have expanded, and tools that can be used in common in each processing area have been developed, and the area of parts that can be put to practical use has been developed. Multitasking machines that take advantage of the features of these new tools have become necessary.

In particular, in the mass production processing part, there is an increasing number of cases where the outer shape is made as close as possible to the final shape by the near-net shape forming method and only the finishing processing is performed by the multi-tasking machine. In order to be able to cope with such a new processing method, there is a problem in that a compact multi-tasking machine in which any one of the cutting and grinding processes can be appropriately selected on the final machine has not been supplied.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a cutting rotary tool which has a center of rotation in the same direction as a grinding wheel axis of a grinding wheel stand and is indexable. A turret that can be installed is provided, and the rotation of the spindle that grips the workpiece is controlled by the rotation for turning and the rotation for grinding, enabling turning and grinding on the same machine.
There is no need to swivel the wheel head when switching between cutting operations. Furthermore, the number of cutting tools can be increased by using a turret, and the wheel axis and turret can be provided on the same wheel head or tool post to quickly respond to various types of processing that can be achieved. Provide a multi-tasking machine.

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the first aspect of the present invention, a headstock for rotatably supporting a spindle having a work holding means at a tip thereof is provided, and a cutting tool is provided on a surface thereof. A turret capable of turning and indexing, and a tool rest having a grindstone rotatable at a turning center substantially concentric with the turning center of the turret, wherein the headstock and the tool rest include the turning center of the turret and the main spindle. A moving means capable of relatively moving within a plane is provided to enable cutting and grinding.

According to the first aspect of the present invention, a compound tool rest is formed by providing a grindstone and a turret on the same tool rest, and
The shaft center of the grinding wheel shaft and the rotation center of the turret table are provided so as to be substantially concentric. The feed of the workpiece and the tool is configured so that the workpiece and the tool can move relative to each other within a plane including the turret or grindstone axis and the spindle. Further, at a predetermined index position of the turret, only the front surface of the grindstone is protruded, so that grinding by the grindstone can be performed. In the case of turning, machining is performed by projecting only the cutting tool, and adopting a turret method that uses many types of cutting tools enables diversification and automation of machining.

According to a second aspect of the present invention, the tool rest is provided so as to be pivotable about an axis orthogonal to the plane. According to the second aspect of the present invention, by adding the function of positioning the rotation about the B axis to the composite tool rest, plunger grinding can be performed in addition to the effect described in the first aspect, and the application field in the grinding process is expanded. Here, the B axis refers to the turning axis of the grinding wheel head orthogonal to the XZ axis plane of the cylindrical grinding machine.

According to a third aspect of the present invention, the outer peripheral surface of the turret is formed to have a smaller diameter than the outer diameter of the grindstone, and the turning trajectory of the cutting tool at the time of indexing the turret is set to be larger than the outer diameter of the grindstone. The cutting tool is held by a turret, and a surface that does not hold the cutting tool is provided on a part of the outer periphery of the turret, so that the surface that does not hold the cutting tool during grinding is determined. .

According to the third aspect of the present invention, the tool of the turret tool rest for working the workpiece is adjacent to the outer diameter portion of the grinding wheel, and the processing surface during turning and the processing surface during grinding are substantially the same. It is necessary to avoid mutual interference when performing each processing. For this reason, the cutting tool is projected with a turret that projects the cutting tool edge to a position larger than the grinding wheel outer diameter, and cutting is performed.When performing grinding, the turret is turned and the turning tool edge is smaller than the grinding wheel outer diameter. In this method, a tool is determined or the position of a turret to which a tool holder is not attached is determined so as not to hinder grinding.

According to a fourth aspect of the present invention, there is provided a first cover for covering an outer periphery of a grindstone except for a contact portion of the grindstone with the work and its vicinity, and a work for the grindstone provided on the first cover so as to be pivotable. And a second cover that covers the contact area with the turret and the vicinity thereof, so that the grinding wheel is covered by the second cover during machining by the cutting tool on the turret.

According to the fourth aspect of the present invention, when performing the turning, the front surface of the grindstone is close to the cutting edge of the cutting tool though it is located at a smaller diameter. As a result, chips may be scattered and adhere to the grindstone, possibly damaging the grindstone. In order to prevent this, a second cover capable of covering a part of the first cover of the grindstone, that is, the front surface of the grindstone is provided.
By providing the second cover, it is possible to prevent damage to the grindstone due to flying chips during cutting.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. [Embodiment 1] FIG. 1 is a plan view of a multi-tasking machine according to the present invention, which is based on a grinder. FIG. 2 (a) shows a state of grinding by a grindstone of a composite tool rest, which is provided integrally with a grindstone stand, which is provided integrally with the grindstone base and has a center of rotation in the same direction as the grindstone axis. (B) is a front view of the composite tool rest, with the second cover opened. FIG. 3A is a diagram showing a state of turning by a cutting tool mounted on the turret of the composite tool post, and FIG. 3B is a front view of the composite tool post with the second cover closed.

In FIG. 1, a moving means for relatively moving the headstock and the tool rest within a plane including the center of rotation of the turret and the spindle is provided on a table 11 placed on a longitudinal Z-axis guide surface 10a of the bed 10. It is a member including the provided headstock 12 and tailstock 13, the combined machining tool rest movably provided in the X-axis direction, and their driving devices. Table 11 is Z
The feed is controlled in the axial direction by the motor 22 of the moving table driving device. A workpiece W is rotatably supported between the chuck 12 b of the headstock 12 and the tailstock 13, and the spindle 12 a rotatably mounted on the headstock 12 controls the spindle motor 29 by a spindle drive device provided on the headstock 12. The rotation can be controlled between low-speed rotation during grinding and high-speed rotation during cutting. On the bed 10, a composite tool rest 15 is slidably mounted on a second moving stand 28 on an X-axis direction guide surface 10b intersecting the moving direction of the table 11, and is driven by a motor 23 of a moving stand driving device. Feed control is performed.

The composite tool rest 15 is provided with a grinding wheel 17 for grinding.
And a tool portion including a turret 19 to which a plurality of cutting tools 18 for cutting are attached, a grinding wheel shaft driving portion 25 of a grinding wheel shaft 23 supporting the grinding wheel 17, and a turret driving portion 26 for rotating and positioning the turret 19. It is configured. A compound tool rest having a turning center in the same direction as the axis of the grindstone shaft 24 near the grindstone 17 between the grindstone 17 and the combined tool rest 15 provided at the shaft end of the grindstone shaft 24 and bearing the grindstone shaft. A turret 19 is rotatably supported on the main body 15. The outer peripheral surface of the turret 1a is formed to have a smaller diameter than the front surface 17a of the grindstone. The tool holder 14 is attached to the turret 19.
When the cutting tool 18 is set, the turning trajectory of the cutting edge of the cutting tool 18 is held so as to have a larger diameter than the front face 17a of the grindstone when the cutting tool 18 is turned for indexing. The configuration is such that a case where the tool holder 14 is not attached to the portion or a case where the cutting tool 18 is not held is provided.

The grindstone shaft 24 is provided with a grindstone 17 having a large outer diameter and rotating at high speed at the shaft end, and an extremely good rotation accuracy is required. The type of shaft diameter is selected. High precision is achieved by using Mackensen-type metal in combination with high-precision rolling bearings. The grindstone shaft 24 may be integrated with the bearing into a sleeve to form a unit and assembled to the composite tool rest 15. A grindstone shaft drive unit 25 for driving the grindstone shaft is provided on the main body of the composite tool rest 15 at the other end of the grindstone shaft 24 having the grindstone 17 attached to one end. A controlled rotation speed is transmitted to the grinding wheel shaft 24 directly or via a belt.

The turret 19 is composed of a grindstone 17 and a composite tool rest 15.
Can be provided in the middle of or with the main body inside. In any case, the turret 19 is pivotally supported by the main body, and the indexing position is defined by a carbic coupling provided opposite to each of the turret and the main body. In the case of the composite tool rest 15, the axial movement and the turning drive of the turret 19 are applied from the outer periphery of the turret 19.

For example, the turret 19 is always urged by a spring provided around the body in the direction of the main body, and is indexed and positioned by a Carbic coupling. Prior to turning, the turret 19 is moved in the direction of the grindstone 17 to release the engagement with the carbic coupling. For this purpose, a power cylinder function may be provided at a plurality of locations on the outer peripheral portion of the composite tool rest, and the turret and the carbic gear may be made to protrude in the direction of the grindstone to separate them. After disengagement,
The turret 19 is rotated by a predetermined angle by engaging a gear tooth formed on a part of the outer circumference of the turret 17 over a whole circumference with a pinion provided on an output shaft of a turret driving unit 26 provided on the main body. It can be indexed to the position of the tool holder 14.

The grindstone 17 is provided with a first cover 20 having an open front surface of the grindstone as a grindstone protection cover. At the front of the grindstone, the chips 17 enter through the opening during the cutting process,
A second cover 21 is provided on the front surface of the first cover 20 so as to be openable and closable with a hinge 27 so as not to be damaged. Although the opening and closing and fixing of the second cover 21 are not shown, the opening and closing and fixing can be performed manually or automatically using power of a power cylinder or the like. It has been described that the rotation center direction of the grindstone and the turret is the same direction and provided in close proximity.However, the rotation center of the grindstone and the turret are shared, and the grindstone and the turret are separately provided on both side ends of the composite tool rest. Is also possible.

As an attached device, a direct sizing device 31 for the workpiece W can be provided on the front surface of the bed 10, and a dresser 32 for correcting a grinding wheel can be provided on the headstock 12. The multi-tasking machine of the present invention can be implemented with a grinder-based configuration as shown in FIG. 1, but the grindstone table is replaced with a saddle and a middle table, and the headstock and tailstock are provided on a bed. A lathe-based configuration can also be used. Also, the headstock is X axis,
It is also possible to appropriately change the axis configuration such as moving to both Z-axis or moving the tool post to both X-axis and Z-axis. In addition, when the workpiece is short, the tailstock is used. It can be changed as appropriate, for example, or a tailstock center may be provided instead of the chuck to support both centers.

Next, the operation of the composite tool rest will be described with reference to FIGS. FIG. 2A shows a positional relationship between the composite tool rest 15 and the workpiece W during grinding, and FIG. 2B is a front view of the composite tool rest. 2 (a) and 2 (b), the whetstone 1
When machining the workpiece W on the front surface 17a of the
1 is opened manually or automatically, and is fixed with a screw or a piston cylinder member or the like. The turret 19 is indexed and positioned so that the surface 19a to which the tool holder 14 is not attached faces the workpiece W side. The composite tool rest 15 (second moving stand) guided on the bed 10 is feed-controlled by a motor 23, and the grinding wheel shaft 24 and the workpiece W are given a predetermined number of revolutions at the time of grinding, respectively, to carry out grinding. The outer diameter of the grindstone 17 can be corrected by the dresser 32 every time the grinding process at the predetermined number of revolutions is completed.

FIG. 3A shows a composite tool post 1 during turning.
5A and 5B show a positional relationship between a workpiece 5 and a workpiece W, and FIG. Before turning is started in FIGS. 3A and 3B, a second protection for the front surface 17 a of the grindstone 17 is performed.
The cover 21 is closed manually or automatically, and is fixed with a screw or a piston cylinder member. Turret 19
A predetermined cutting tool is indexed and positioned at a processing position of the workpiece W, and the workpiece W is given a predetermined number of rotations to perform turning. In turning, it is possible to increase the number of cutting tools that can be prepared in the turret 19. Further, by attaching a processing unit such as an inner lab unit or a drill unit, diversification of the processing and multifunctionalization can be achieved. At the time of the grinding described in FIG. 2 and the turning described in FIG. 3, the workpiece W can be appropriately measured by using the sizing device 31 directly to obtain a product of a predetermined size.

During the grinding process, it is necessary that the indexed surface 19a of the turret 19 is retracted from the front surface 17a of the grindstone 17 toward the center of the grindstone 17. for that purpose,
The tool holder 14 is not attached to the turret 19 indexed to a position near the front surface 17a of the grindstone 17 so as to avoid interference with the workpiece W. The turning of the turret 19 is completely prohibited during the grinding. When the outer diameter of the grindstone 17 is large, the number of indexable turrets 19 can be increased, so that the number of attachable tools also increases. In such a case, a plurality of continuous tool mounting surfaces on the turret are set as no tool mounting,
By determining the intermediate position of the non-attached surface during the grinding process, interference can be avoided. Further, the multi-tasking machine provided with the compound tool rest 15 of the first embodiment is characterized in that the machining efficiency can be changed without turning the grindstone surface 23 each time when switching between grinding and cutting. . In the first embodiment, the multi-tasking machine is configured based on the grinding machine, but the machine serving as the base is not limited to the grinding machine.

[Embodiment 2] FIG. 4 shows a turning composite tool post 16 in which a turning function is added to the compound tool post 15 of the first embodiment.
In this embodiment, a compound turning tool post is provided instead of the compound tool post 15. The turning composite tool rest 16 can be turned around the center of the B axis perpendicular to the XZ axis by using a compound processing machine based on an angle grinding machine by forming the axis of the grinding wheel shaft 24 and the main shaft 12a at θ degrees. The basic configurations at the time of grinding and turning are common to the first embodiment and the second embodiment, and the description is omitted. Also in this embodiment, a first cover 20 which is a grindstone cover for preventing danger when a grindstone is missing, and a second cover 21 which can be freely opened and closed and can be fixed as a countermeasure against chip scattering at the time of cutting are provided.

Next, the operation of the multi-tasking machine according to the second embodiment provided with the swivel tool post will be described. Since the grindstone 17 and the turret 19 are inclined with respect to the axis of the workpiece W by a predetermined angle θ with respect to the first embodiment, plunge grinding can be performed by mounting an angle grindstone on the grindstone shaft 23. Also in this embodiment, when switching between grinding and cutting, the grinding wheel shaft 2 is used each time.
The feature is that there is no need to turn the 3.

[0033]

The multi-tasking machine according to the present invention is constructed as described above, and has the following effects. In the multi-tasking machine according to the first aspect, the grindstone and the indexable cutting tool turret having a center of rotation in the same direction as the grindstone axis are compactly provided, and each drive unit is compactly configured in the multi-tool post. Have been. In addition, since the spindle speed control is performed so that the workpiece can be gripped and used for grinding and turning, it has both functions of grinding and turning, and it is easy to switch between both processes. The overall size of the machine can be reduced.

According to the second aspect of the present invention, the angle grinder is used as a base machine, and instead of a compound tool rest in which feed control is performed only in the X-axis direction, turning control can be performed by X-axis feed control and B-axis feed. Since the multi-tasking machine has a simple turning composite tool post, the multi-tasking that allows plunger grinding and turret cutting by attaching an angle whetstone has become possible.

According to a third aspect of the present invention, there is provided the multi-tasking machine, wherein the number and kinds of cutting tools which can be prepared in the indexable turret having a center of rotation in the same direction as the sleeve of the grindstone shaft or increase the number of drills on the turret The function of combined machining has been expanded by the attachment of the unit and the inner laboratory unit. In addition, when switching between grinding and cutting, the turning of the composite tool rest centering on the B axis becomes unnecessary.

According to a fourth aspect of the present invention, in the multi-tasking machine according to any of the first to third aspects, the multi-tasking machine can be added to the first cover as a grindstone safety cover and can be freely opened and closed as a grindstone protection cover due to scattering of chips during cutting. In addition, since the second cover that can be fixed is provided, a safe operation can be continuously performed during the grinding and the turning.

[Brief description of the drawings]

FIG. 1 is a plan view of a multi-tasking machine according to a first embodiment of the present invention. This is a multi-tasking machine in which a turret having a grinder as a base, a turret having the axis of a grindstone shaft and a rotation center in the same direction instead of a grindstone table is provided on a bed.

FIG. 2A is a diagram illustrating a state of a grinding process performed by a grindstone with a cutting tool of a turret tool post in a retracted position according to the first embodiment of the present invention, and FIG. 2B is a front view of a composite tool post with a second cover. It is a figure showing the case where it opened.

FIG. 3 (a) is a diagram showing a state of turning with a cutting tool in which a cutting edge of the cutting tool of the compound tool post according to the first embodiment of the present invention is located at a position protruding from the outer diameter of the grindstone, and FIG. It is a figure showing the case where the 2nd cover is closed in the front view.

FIG. 4 is an explanatory view of a position of an angle grindstone and a workpiece of a turning composite tool rest according to a second embodiment of the present invention.

FIG. 5 is an explanatory view of an indexing position in which finishing processing is performed with a grindstone in the conventional multi-tasking machine.

FIG. 6 is an explanatory diagram of an indexing position at which rough machining in a previous process is performed by cutting in the multi-tasking machine of FIG. 5; The position where the tool post is turned so that the grindstone and the workpiece do not interfere with each other is defined as the cutting position.

FIG. 7 is an explanatory view of a tool arrangement in which the grindstone and the cutting tool are arranged point-symmetrically with respect to the center of rotation in the grindstone table of FIG.

[Explanation of symbols]

 Reference Signs List 10 bed 11 table 12 headstock 13 tailstock 14 tool holder 15 compound turret 16 turning compound turret 17 grindstone 18 cutting tool 19 turret 20 first cover 21 second cover 22, 23 motor 24 grindstone shaft 25 grindstone shaft control unit 26 Turret drive unit 27 Hinge 28 Moving table 31 Direct sizing device 32 Dresser

Continuation of front page (72) Inventor Kojiro Furukawa 1 Okuma Co., Ltd., 5-25-5 Shimo-Koguchi, Oguchi-machi, Niwa-gun, Aichi Prefecture

Claims (4)

[Claims] A turret capable of rotatably supporting a spindle having a workpiece holding means at a tip thereof and rotatably indexing by holding a cutting tool on a surface thereof, and a turret substantially concentric with the center of rotation of the turret. A tool rest having a grindstone rotatable at the center of rotation is provided, and a moving means capable of relatively moving the headstock and the tool rest on a plane including the center of rotation of the turret and the spindle is provided; A multi-tasking machine characterized by enabling machining. 2. The multi-tasking machine according to claim 1, wherein the tool rest is pivotably provided around an axis orthogonal to the plane. 3. The method according to claim 1, wherein the outer peripheral surface of the turret is formed to have a diameter smaller than an outer diameter of a grindstone, and a turning trajectory of the cutting tool at the time of turret turning index is larger than the outer diameter of the grindstone. The cutting tool is held in a turret, and a surface that does not hold the cutting tool is provided on a part of the outer periphery of the turret, and a surface that does not hold the cutting tool is determined during grinding. The multi-tasking machine according to claim 1 or 2, wherein 4. A first cover for covering an outer periphery of a grindstone except for a contact portion of the grindstone with the work and its vicinity, and a contact portion of the grindstone provided on the first cover so as to be rotatable with the work and its vicinity. The multi-tasking machine according to any one of claims 1 to 3, further comprising a second cover that covers the grindstone, wherein the grindstone is covered by the second cover during processing by the cutting tool on the turret.