Machine tool and friction joining method

Abstract

This machine tool (1) comprises: a front main shaft (11) capable of gripping a first member (W1); a rear main shaft (12) capable of gripping a second member (W2); and a guide bush device (13) disposed between the front main shaft (11) and the rear main shaft (12). The first member (W1) gripped by the front main shaft (11) and the second member (W2) gripped by the rear main shaft (12) are rotated relative to each other and brought into contact with each other to generate frictional heat at joining surfaces (CS) of the first member (W1) and the second member (W2) and the members are frictionally joined. The guide bush device (13) guides an outer peripheral surface (OS1) of the first member (W1) without guiding an outer peripheral surface (OS2) of the second member (W2) when the contact between the first member (W1) and the second member (W2) during relative rotation starts, and guides the outer peripheral surface (OS2) of the second member (W2) when pressing the first member (W1) and the second member (W2).

Description

Machine tool and friction joining method

[0001] The present disclosure relates to a machine tool and a friction joining method.

[0002] An apparatus is known that can perform friction joining by bringing a first member and a second member into contact while rotating them relative to one another to generate frictional heat, and then pressing the first member and the second member against each other to join the first member and the second member (see Patent Document 1).

[0003] Japanese Unexamined Patent Publication No. 51-140855

[0004] However, when the friction joining is performed using a machine tool, it is not easy to prevent misalignment between the first member and the second member.

[0005] Therefore, it is desirable to provide a machine tool that can suppress misalignment between two members to be friction-welded.

[0006] A machine tool according to an embodiment of the present disclosure is a machine tool in which two main shafts, which are rotated and grip a first member and a second member, respectively, are arranged opposite each other so as to be movable in the axial direction, a guide member is provided between the two main shafts, and the first member and the second member, which are in contact in a rotational state due to the relative rotation of the two main shafts, are pressed together by the movement of the main shafts while being guided by the guide member, thereby frictionally joining them, and is configured to be provided with a movement control means for controlling the movement of the main shafts so that the guide member guides one of the first member and the second member when the pressing starts, and the guide member guides the other of the first member and the second member when the pressing ends.

[0007] The above-described machine tool can suppress misalignment between the two members to be friction-welded.

[0008] FIG. 1 is a perspective view of a machine tool according to an embodiment of the present disclosure; FIG. 2 is a cross-sectional view of a guide bush device; FIG. 3 is a flowchart of remnant material processing; FIG. 4 is a diagram showing steps of remnant material processing; FIG. 5 is a flowchart of friction welding processing; FIG. 6 is a diagram showing steps of friction welding processing; FIG. 7 is a cross-sectional view of a first member, a second member, a back spindle, and a guide bush device; FIG. 8 is a diagram showing an example of a configuration of a joint between a remnant material and a new material to be friction welded; FIG. 9 is a diagram showing another example of a configuration of a joint between a remnant material and a new material to be friction welded; FIG. 10 is a diagram showing yet another example of a configuration of a joint between a remnant material and a new material to be friction welded.

[0009] FIG. 1 is a perspective view of a machine tool 1 according to this embodiment. In the machine tool 1, a front spindle 11, a back spindle 12, a guide bush device 13, and a tool rest 14 are mounted on a bed 10. The front spindle 11 is one of the spindles mounted on the machine tool 1 and is rotatably mounted on a front headstock that moves along rails 15 extending in the Z1 direction, which is the axial direction. The front spindle 11 is provided so as to be movable in the Z1 direction via the front headstock. The back spindle 12 is another of the spindles mounted on the machine tool 1 and is rotatably mounted on a back headstock that moves along rails 16 and 17 that are perpendicular to each other. The rails 16 extend in the Z2 direction, which is the axial direction of the back spindle 12. The back spindle 12 is provided so as to be movable in both the Z2 direction and the X2 direction, which is perpendicular to the Z2 direction, via the back headstock.

[0010] The front spindle 11 and the back spindle 12 are provided with collet chucks as in the conventional case, and can freely open and close to grip a long bar material.

[0011] Tools serving as processing means for processing the material are mounted on the tool rest 14. The tool rest 14 is installed on a slide that moves along rails extending in the X1 and Y1 directions, which are perpendicular to each other and perpendicular to the Z1 direction, and is provided so as to be movable in the X1 and Y1 directions.

[0012] The rotation and movement of the front spindle 11 and the back spindle 12, as well as the movement of the tool rest 14, are controlled by an NC unit 18, which is a numerical control device mounted on the machine tool 1, as movement control means.

[0013] 2 is a cross-sectional view of the guide bush device 13. The guide bush device 13 includes a guide bush 21, a guide bush sleeve 22, a bearing 23, a guide bush holder 24, and a draw bar 25.

[0014] The guide bush 21 is an example of a guide member that guides the material, and is housed in a guide bush sleeve 22. The guide bush sleeve 22 is rotatably supported by a guide bush holder 24 via a bearing 23. The guide bush holder 24 is fixed to the bed 10 of the machine tool 1. A draw bar 25 is screwed onto the rear end (right end) of the guide bush 21.

[0015] When the guide bush 21 is screwed into the draw bar 25, the tapered surface 26 formed at the tip of the guide bush 21 engages with the tapered surface 27 formed at the tip of the guide bush sleeve 22, thereby adjusting the opening degree.

[0016] In the machine tool 1, material is supplied from the material feeder 19 to the front spindle 11, the tip of the material (first member W1) held by the front spindle 11 protrudes from the guide bush 21, and the material is guided by the guide bush 21 so that it can rotate freely and move freely in the axial direction, while a tool mounted on the tool post 14 is selected and processing is performed.

[0017] After the tip of the material is machined, it is cut off, and the cut-off portion on the front spindle 11 side is gripped by the back spindle 12 for back machining, completing the machining. The back machining can be performed using a cutting tool as a machining means attached to a tool rest for the back spindle 12, which is provided separately from the tool rest 14. After the cut-off, the front spindle 11 releases its grip on the material, retreats by the amount of machining on the front spindle 11 side, and grips the material again, and the machining is repeated. When the front spindle 11 retreats by the amount of machining and can no longer grip the material, the material runs out, and the material remains as scrap. The material out state is detected by a sensor or the like. When the machine tool 1 runs out of material, it is configured to perform scrap disposal so that part of the scrap can be reused.

[0018] Figure 3 is a flowchart showing an example of the flow of waste material disposal executed by machine tool 1. Figure 4 is a cross-sectional view of front spindle 11, back spindle 12, and guide bush device 13, with parts hatched for clarity. The waste material disposal shown in Figures 3 and 4 is realized by the operation of each element of machine tool 1 in response to commands from NC device 18.

[0019] The NC device 18 of the machine tool 1 determines whether or not a shortage of material has been detected (step ST1).

[0020] If the NC device 18 has not detected that the material is out of stock (NO in step ST1), the NC device 18 ends the remaining material disposal and continues machining. When the NC device 18 detects that the material is out of stock, as shown in Fig. 4(a), by controlling the movement and gripping of the front spindle 11, the material (second member W2) gripped by the front spindle 11 is protruded from the guide bush 21 by a length that can be gripped by the back spindle 12, the machined tip portion of the second member W2 is cut off and transferred to the back spindle 12, and after being machined on the back spindle 12 side, as shown in Fig. 4(b), the back spindle 12 is moved toward the front spindle 11, facing the front spindle 11 on the same axis, and the tip of the second member W2 is gripped by the back spindle 12.

[0021] Thereafter, as shown in FIG. 4(c), the NC device 18 pulls out the second member W2, which has been released from the grip of the front spindle 11, from the front spindle 11 and the guide bush device 13 as a remaining material by moving the back spindle 12 (step ST2).

[0022] Thereafter, as shown in FIG. 4(d), the NC device 18 abuts the tip of the remaining material (the end on the front spindle 11 side) against a roughly L-shaped stopper SP provided on the tool post 14, and changes the gripping position of the remaining material by the back spindle 12 to the vicinity of the tip of the remaining material, as shown in FIG. 4(e).

[0023] Thereafter, the NC device 18 performs back surface machining so that a protrusion PT is formed on the tip end surface of the remaining material as shown in FIG. 4(f) (step ST3).

[0024] As shown in FIG. 4(g), the NC device 18 uses the material feeder 19 to insert new material (first member W1) into the guide bush 21 so that the tip protrudes a predetermined length from the guide bush 21 (step ST4), and then has the new material gripped by the front spindle 11.

[0025] Thereafter, the NC device 18 processes the tip of the new material so as to form a recess RS that fits with the protrusion PT, as shown in FIG. 4(h) (step ST5).

[0026] Thereafter, the NC device 18 positions the first member W1 and the second member W2 facing each other so that the distance between the inner bottom surface of the recess RS of the first member W1 and the tip surface (right end surface) of the protrusion PT of the second member W2 is a predetermined distance DS, with the front spindle 11 and the back spindle 12 still holding the new material and the remnant material as the first member W1 and the second member W2, respectively, and completes the remnant material processing. After completing the remnant material processing, the machine tool 1 is configured to perform a friction joining process to frictionally join the remnant material and the new material.

[0027] 5 and 6 is realized by the operation of each element of the machine tool 1 in response to commands from the NC device 18. In Fig. 6, some parts are hatched with oblique lines for clarity.

[0028] As a result of the residual material processing, the NC device 18 moves from a state in which the first member W1 and the second member W2 are arranged opposite each other as shown in Figure 6(a) (step ST11) to a state in which the first member W1 starts to rotate by rotating the front spindle 11 as shown in Figure 6(b) (step ST12).

[0029] 6(c), the NC device 18 starts contact between the first member W1 and the second member W2 (step ST3). The NC device 18 moves the front spindle 11 away from the back spindle 12 so that the first member W1 moves to the opposite side of the back spindle 12 (the right side in the figure) at a predetermined moving speed M1, and moves the back spindle 12 toward the front spindle 11 so that the second member W2 moves toward the front spindle 11 (the right side in the figure) at a predetermined moving speed M2 that is faster than the moving speed M1. Then, at a predetermined timing, the second member W2 comes into contact with the first member W1, generating frictional heat at the contact surface (joint surface CS) between the first member W1 and the second member W2.

[0030] Thereafter, the NC device 18 stops the rotation of the first member W1 (step ST14), as shown in Figure 6(d), and moves the first member W1 to the right at a first moving speed V1, as shown in Figure 6(e), and moves the second member W2 to the right at a second moving speed V2 that is higher than the first moving speed V1 (step ST15), thereby performing an "upsetting process" in which the first member W1 and the second member W2 are pressed against each other, thereby frictionally joining the first member W1 and the second member W2.

[0031] 6(f) shows the state when the movement of the first member W1 and the second member W2 is stopped (step ST16) and the "upsetting process" is completed. The NC device 18 sets the first movement speed V1 and the second movement speed V2 and controls the movement of the front spindle 11 and the back spindle 12 so that the guide bush 21 guides the first member W1 when the "upsetting process" starts and the guide bush 21 guides the second member W2 when the "upsetting process" is completed.

[0032] Thereafter, as shown in FIG. 6( g), the NC device 18 releases the grip of the back spindle 12 on the joined member WC formed by friction welding between the first member W1 and the second member W2, and causes the front spindle 11 to retreat in a direction away from the back spindle 12, thereby removing the joined member WC from the back spindle 12 and pulling back the joined member WC (step ST17).

[0033] By pulling back the joining workpiece WC, the guide bush 21 guides the second workpiece W2. In this way, the NC device 18 joins the second workpiece W2, which is a remnant material, to the first workpiece W1 by friction welding, thereby enabling the remnant material to be processed.

[0034] The "upsetting process" is performed by moving the first member W1 rightward at a first moving speed V1 and moving the second member W2 rightward at a second moving speed V2, so that the first member W1 and the second member W2 are pressed against each other as they move integrally to the right. When the upsetting process is started, the first member W1 and the second member W2 move in a pressed state, and as shown in Fig. 7(a) , the outer peripheral surface OS1 of the first member W1 is guided by the inner peripheral surface 28 of the guide bush 21, and then as shown in Fig. 7(b) , both the outer peripheral surface OS1 of the first member W1 and the outer peripheral surface OS2 of the second member W2 are guided by the guide bush 21, and the "upsetting process" is completed as shown in Fig. 6(f) . In this way, when the upsetting process is being performed, the guide bush 21 continuously guides the outer surfaces OS1 and OS2 using the inner surface 28, thereby suppressing misalignment between the axis AX1 of the first member W1 and the axis AX2 of the second member W2.

[0035] Next, referring to FIG. 8 , an example of the structure of a joint between a new material (first member W1) and a remaining material (second member W2) will be described. FIG. 8 is a schematic diagram of the first member W1 and the second member W2. FIG. 8( a) is a diagram showing the state before the first member W1 and the second member W2 are joined, including a cross-sectional view and a front view of the first member W1 along the axis AX1 (viewing the joining surface CS of the first member W1 from the axial direction), and a cross-sectional view and a front view of the second member W2 along the axis AX2 (viewing the joining surface CS of the second member W2 from the axial direction). FIG. 8( b) is a diagram showing the state after the first member W1 and the second member W2 have been joined, including a cross-sectional view of the joining member WC along the axial direction.

[0036] The first member W1 is a cylindrical, elongated member with a diameter D1, and has a cylindrical recess RS at its tip (left end) with a diameter D1a (< diameter D1) and a depth D1b. The second member W2 is a cylindrical, elongated member with a diameter D2, and has a cylindrical protrusion PT2 at its tip (right end) with a diameter D2a (< diameter D2) and a protrusion amount D2b. In the illustrated example, the diameter D1 of the first member W1 and the diameter D2 of the second member W2 are the same, the diameter D1a of the recess RS is larger than the diameter D2a of the protrusion PT2, and the protrusion amount D2b of the protrusion PT2 is larger than the depth D1b of the recess RS.

[0037] 6(c), when the first member W1 is rotating at the rotational speed RF and the protrusion PT2 of the second member W2 is pressed against the inner bottom surface of the recess RS of the first member W1, the joint surface CS1 of the first member W1 and the joint surface CS2 of the second member W2 come into contact with each other, generating frictional heat. Note that in FIG. 8, for clarity, a cross pattern is applied to the joint surfaces CS (joint surfaces CS1 and CS2).

[0038] The edges ED of the joint surfaces CS (the edges ED1 of the joint surfaces CS1 and the edges ED2 of the joint surfaces CS2) are located inside the inner wall of the recess RS, i.e., near the axis AX (the axis AX1 of the first member W1 and the axis AX2 of the second member W2). Also, the edges ED of the joint surfaces CS (the edges ED1 of the joint surfaces CS1 and the edges ED2 of the joint surfaces CS2) are located inside the outer peripheral surfaces OS (the outer peripheral surfaces OS1 of the first member W1 and the outer peripheral surfaces OS2 of the second member W2), i.e., near the axis AX.

[0039] In this way, the machine tool 1 forms the recess RS at the tip (left end) of the first member W1 and the protrusion PT at the tip (right end) of the second member W2, and then performs the friction welding process. Therefore, as shown in Figure 8(b), the machine tool 1 can confine burrs FS generated during the friction welding process within the space formed by the recess RS and the protrusion PT, preventing them from protruding outward from the outer peripheral surface OS of the joined workpieces WC. Therefore, the machine tool 1 has the effect of eliminating the need for deburring to remove burrs FS that protrude outward from the outer peripheral surface OS1 or OS2.

[0040] In the illustrated example, the machine tool 1 is configured to form a chamfered portion CF at the tip (right end) of the outer peripheral surface OS2 of the second member W2. Therefore, the machine tool 1 has the effect of preventing the second member W2 from being unable to enter the inside of the guide bush device 13 due to contact between the tip surface (right end surface EF) of the second member W2 and the tip (left end) of the guide bush 21 (see FIG. 6 ) in the guide bush device 13 during the upsetting process.

[0041] Next, another example of the configuration of the joint between the first member W1 and the second member W2 will be described with reference to Fig. 9. Fig. 9 is a schematic diagram of the first member W1 and the second member W2. In Fig. 9, the chamfered portion CF is omitted for simplicity of explanation. Fig. 9(a) is a cross-sectional view showing the state before the first member W1 and the second member W2 are joined. Fig. 9(b) is a cross-sectional view showing the state after the first member W1 and the second member W2 are joined.

[0042] The first member W1 in Figure 9 differs from the first member W1 in Figure 8, which has a recess RS formed at its tip (left end), in that it has a protrusion PT1 formed at its tip (left end), but is otherwise the same as the first member W1 in Figure 8.

[0043] The second member W2 in Fig. 9 differs from the second member W2 in Fig. 8 in that the protrusion PT2 is formed at the tip end (right end) in that the protrusion PT is not formed at the tip end (right end). However, the second member W2 in Fig. 9 is otherwise the same as the second member W2 in Fig. 8.

[0044] 9, the machine tool 1 performs the friction welding process after forming the protrusion PT1 at the tip (left end) of the first member W1. Therefore, the machine tool 1 can prevent the burrs FS generated during the friction welding process from protruding outward from the outer peripheral surface OS of the joined workpiece WC. This is because the burrs FS are formed around the protrusion PT1, as shown in FIG. 9(b). Therefore, the machine tool 1 has the advantage of being able to omit the process for removing the burrs FS, similar to the example shown in FIG. 8.

[0045] Next, referring to Fig. 10, another example of the configuration of the joint between the first member W1 and the second member W2 will be described. Fig. 10 is a schematic diagram of the first member W1 and the second member W2. As with Fig. 9, the chamfered portion CF is omitted for simplicity of explanation. Fig. 10(a) is a cross-sectional view showing the state before the first member W1 and the second member W2 are joined. Fig. 10(b) is a cross-sectional view showing the state after the first member W1 and the second member W2 are joined.

[0046] The first member W1 in Figure 10 differs from the first member W1 in Figure 8, which has a recess RS formed at its tip (left end), in that it has a protrusion PT1 formed at its tip (left end), but is otherwise the same as the first member W1 in Figure 8.

[0047] The second member W2 in Fig. 10 differs from the second member W2 in Fig. 8 in that the outer peripheral surface OS2 does not have a chamfered portion at its distal end (left end) but has a chamfered portion CF at its distal end (right end). However, the second member W2 in Fig. 10 is otherwise the same as the second member W2 in Fig. 8.

[0048] 10, the machine tool 1 performs the friction welding process after forming the protrusion PT1 at the tip (left end) of the first member W1 and the protrusion PT2 at the tip (right end) of the second member W2. Therefore, the machine tool 1 can prevent burrs FS generated during the friction welding process from protruding outward from the outer peripheral surface OS of the joined workpiece WC. This is because the burrs FS are formed around the protrusions PT1 and PT2, respectively, as shown in FIG. 10(b). Therefore, the machine tool 1, similar to the example shown in FIG. 8, has the effect of eliminating the process for removing the burrs FS.

[0049] The machine tool 1 is a movable-spindle lathe, also known as a Swiss-type lathe, in which the front spindle 11 and the back spindle 12 are movable. As shown in FIG. 6( c), the machine tool 1 is configured to relatively rotate and bring into contact a first member W1 held by the front spindle 11 and a second member W2 held by the back spindle 12, thereby generating frictional heat at the contact surfaces (joint surfaces CS) of the first member W1 and the second member W2, thereby frictionally joining them. In the illustrated example, the machine tool 1 rotates the first member W1 at a rotational speed RF while not rotating the second member W2. However, the second member W2 may be rotated without rotating the first member W1, or both the first member W1 and the second member W2 may be rotated. When both the first member W1 and the second member W2 are rotated, the rotation directions may be the same or opposite to each other.

[0050] In the machine tool 1 according to this embodiment, when the "upsetting process" is started, the guide bush 21 guides the first member W1, and when the "upsetting process" is completed, the guide bush 21 guides the second member W2, thereby suppressing radial displacement of the second member W2 and suppressing misalignment between the first member W1 and the second member W2 during friction joining.

[0051] Furthermore, as shown in Figure 8, the machine tool 1 may be configured to have a chamfered portion CF at the outer diameter corner (outer diameter tip) of the second member W2 on the side facing the first member W1.

[0052] With this configuration, when the machine tool 1 pulls a portion of the second member W2 into the guide bush device 13, it is possible to prevent the outer diameter tip of the second member W2 from coming into contact with the guide bush device 13, thereby preventing the second member W2 from being pressed against the first member W1.

[0053] In addition, as shown in Figure 8, the machine tool 1 may process the end face of the second member W2 so that the edge ED2 of the joint surface CS2 of the second member W2 is positioned closer to the axis AX2 than the outer peripheral surface OS2 of the second member W2 guided by the guide bush device 13.

[0054] 8(b), the machine tool 1 has the advantage of being able to prevent burrs FS generated during friction welding from rising beyond the outer peripheral surfaces OS (outer peripheral surfaces OS1 and OS2) of the two members (first member W1 and second member W2) to be friction welded. As a result, the machine tool 1 has the advantage of being able to omit the cutting process for removing burrs FS.

[0055] Furthermore, as shown in FIGS. 8 to 10 , the machine tool 1 may machine at least one end surface of the first member W1 and the second member W2 facing each other so that the end surface of at least one of the first member W1 and the second member W2 has a protrusion PT protruding in the axial direction. In this case, the tip surface of the protrusion PT becomes the joining surface CS. In the example shown in FIG. 8 , the end surface of the second member W2 has a protrusion PT2 protruding in the axial direction. In the example shown in FIG. 9 , the end surface of the first member W1 has a protrusion PT1 protruding in the axial direction. In the example shown in FIG. 10 , the end surface of the first member W1 has a protrusion PT1 protruding in the axial direction, and the end surface of the second member W2 has a protrusion PT2 protruding in the axial direction.

[0056] With this configuration, the machine tool 1 has the effect of being able to prevent burrs FS from rising beyond the outer peripheral surfaces OS (outer peripheral surfaces OS1 and OS2) of the two members to be friction-joined (first member W1 and second member W2) simply by processing at least one end surface of the two members to be friction-joined (first member W1 and second member W2), as shown in Figures 8 to 10.

[0057] 8(a), the machine tool 1 may machine the end faces of the first member W1 and the second member W2 so that the end face of the first member W1 has a recess RS recessed in the axial direction, and the end face of the second member W2 has a protrusion PT protruding in the axial direction. In this case, the tip surface of the protrusion PT and the inner bottom surface of the recess RS form the joining surface CS.

[0058] With this configuration, the machine tool 1 can confine the burr FS within the recess RS, as shown in Figure 8 (b), which has the effect of more reliably preventing the burr FS from rising beyond the outer peripheral surfaces OS (outer peripheral surfaces OS1 and OS2) of the two members (first member W1 and second member W2) to be frictionally joined.

[0059] Furthermore, the friction joining method using the machine tool 1 according to an embodiment of the present disclosure includes a friction process (step ST13 in FIG. 5) in which the first member W1 and the second member W2, which are rotating relative to each other, are brought into contact with each other while the guide bush device 13 guides the outer peripheral surface OS1 of the first member W1 without guiding the outer peripheral surface OS2 of the second member W2, as shown in FIG. 6(c), and an upsetting process (step ST15 in FIG. 5) in which the first member W1 and the second member W2 are pressed together while the guide bush device 13 guides a portion (tip) of the outer peripheral surface OS2 of the second member W2, as shown in FIG. 6(e).

[0060] This friction welding method has the effect of suppressing misalignment between the two members to be frictionally joined. This friction welding method has the effect of suppressing radial displacement of the second member W2 by guiding a part (tip) of the outer peripheral surface OS2 of the second member W2 with the guide bush device 13 during the upsetting process, thereby suppressing misalignment between the two members to be frictionally joined.

[0061] The preferred embodiments of the present disclosure have been described above in detail. However, the present invention is not limited to the above-described embodiments. Various modifications or substitutions may be applied to the above-described embodiments without departing from the scope of the present invention. Furthermore, the features described with reference to the above-described embodiments may be combined as appropriate unless technically inconsistent.

[0062] This application claims priority based on Japanese Patent Application No. 2023-173481, filed on October 5, 2023, the entire contents of which are incorporated herein by reference.

[0063] DESCRIPTION OF SYMBOLS 1...Machine tool 10...Bed 11...Front spindle 12...Back spindle 13...Guide bush device 14...Tool rest 15, 16, 17...Rail 18...NC device 19...Material feeder 21...Guide bush 22...Guide bush sleeve 23...Bearing 24...Guide bush holder 25...Draw bar 26, 27...Tapered surface AX, AX1, AX2...Axis CF...Chamfered portion CS, CS1, CS2...Joint surface ED, ED1, ED2...Edge EF...Right end surface FS...Burner OS, OS1, OS2...Outer peripheral surface PT, PT1, PT2...Convex portion RS...Concave portion W1...First member W2...Second member WC...Joint member

Claims

1. A machine tool comprising two main shafts which are rotated while gripping a first member and a second member, respectively, and which are arranged opposite each other so as to be movable in the axial direction, a guide member provided between the two main shafts, and which presses and frictionally joins the first member and the second member, which are in contact in a rotating state due to the relative rotation of the two main shafts, by moving the main shafts while being guided by the guide member, wherein the machine tool further comprises a movement control means for controlling the movement of the main shafts so that the guide member guides one of the first member and the second member when the pressing starts, and the guide member guides the other of the first member and the second member when the pressing ends.

2. The machine tool according to claim 1, wherein, when the relative rotation is stopped, the spindle gripping the first member is controlled at a first moving speed, and the spindle gripping the second member is controlled at a second moving speed, a direction of the first moving speed and a direction of the second moving speed are the same, and one of the first moving speed and the second moving speed is set to be greater than the other of the first moving speed and the second moving speed.

3. A machine tool as claimed in claim 1 or 2, wherein one end face of the first member and the second member has a convex portion protruding in the axial direction, and a tip face of the convex portion forms a joining surface.

4. A machine tool as claimed in claim 1 or 2, wherein one end face of the first member and the second member has a convex portion protruding in the axial direction, and the other end face of the first member and the second member has a concave portion recessed in the axial direction, and the tip face of the convex portion and the inner bottom surface of the concave portion form a joint surface.

5. The machine tool according to claim 1, wherein a chamfer is formed on the end face of the first member or the second member held by the spindle having a high moving speed, the end face facing the other member.

6. A machine tool as claimed in claim 1, comprising a processing means for processing the first member and the second member, and the guide member is a guide bush for guiding the first member or the second member during processing.

7. A friction joining method using a machine tool, comprising: disposing two main shafts which are rotated while gripping a first member and a second member, respectively, facing each other and movable in the axial direction; providing a guide member between the two main shafts; and friction joining the first member and the second member, which are in contact in a rotating state due to the relative rotation of the two main shafts, by moving the main shaft while being guided by the guide member, the friction joining method comprising the steps of: guiding one of the first member and the second member with the guide member when the pressing starts; and guiding the other of the first member and the second member with the guide member when the pressing ends.

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