High-speed spindle with forced mechanical vibration assistance

Abstract

A spindle (1) for a machine tool is disclosed, the spindle (1) comprising a housing (10), a shaft (20) for driving a cutting tool, rotatably mounted inside the housing with the possibility of axial movement relative to the housing, and a single ball (200) axially interposed between a bearing ring (202) fixed relative to the housing and a bearing ring (201) movable with the shaft, one of the rolling rings defining an inclined bearing surface (231) that is not perpendicular to the axis of rotation of the shaft, so that rotation of the ball generates axial oscillation of the shaft.

Description

Technical Field

[0001] The present invention relates to a high-speed spindle with forced mechanical vibration assistance.

Background Art

[0002] The applicant has developed many solutions for vibration drilling in which the cutting tool undergoes axial oscillation while rotating.

[0003] These oscillations make it possible to break up the chips and improve the drilling performance.

[0004] To provide the axial movement of the tool, many existing solutions are based on the use of rolling bearings, and one or more of the raceways of the rolling bearings have undulating surfaces.

[0005] Patent Document 1 and Patent Document 2 describe examples of vibration machining apparatuses.

[0006] Rolling bearings typically consist of balls that are held in a predetermined angular position relative to each other by a rotating cage during rotation.

[0007] In known solutions, the frequency of the axial oscillation depends on the rotational speed and the number of undulations that the rolling bearing undergoes while rotating.

[0008] The rotational speed of the tool depends on its cutting speed and its diameter. Therefore, the smaller the diameter of the hole to be drilled, the more necessary it is to increase the rotational speed to maintain the same cutting speed. However, the frequency of the axial oscillation cannot exceed a threshold of about 300 Hz without generating excessive mechanical load, especially due to the inertia of the moving parts. Therefore, the rotational speed of known vibration drilling spindles is generally limited to 10000 rpm based on the mechanical conversion of the rotational movement into the axial vibration movement.

[0009] In some applications, for productivity reasons, it is necessary to manufacture a large number of small-diameter holes very quickly. Therefore, in conventional non-vibratory drilling, it is common to drive small-diameter drill bits at rotational speeds far exceeding 10,000 rpm, for example about 20,000 rpm, in order to conform to their cutting speeds. In some materials, in conventional drilling, the chips generated during cutting at these rotational speeds are short in length and are easily discharged.

[0010] However, other materials generate longer chips during conventional drilling, and these cannot be easily discharged without chip removal cycles. Therefore, the selection of materials that can be machined by conventional drilling remains limited without sacrificing productivity, which has proven to be a drawback in certain applications.

[0011] There are purely mechanical vibratory drilling solutions where the selection of the oscillation frequency is decoupled from the rotational speed of the shaft, but these are based on the use of electromechanical or piezoelectric elements, and these solutions are much more expensive and complex than purely mechanical solutions, and their implementation remains economically infeasible in many applications, especially when it is desired to minimize the changes added to the existing pool of machine tools during the implementation of the vibratory drilling solution if mechanically possible.

[0012] Patent Document 3 presents a drilling tool comprising a rocking unit incorporating a rolling bearing of the "thrust ball bearing" type having a single ball rolling between a first ring and a second ring. Such a rolling bearing is not designed to operate at high rotational speeds due to centrifugal separation of the balls. A calibration spring generates a forward movement that keeps the rolling bearing under compression.

[0013] Patent Document 4 describes a rocking drilling tool having a rolling bearing of the "thrust ball bearing" type. The rocking motion is achieved by a split ring that results in a rocking motion with significant discontinuities, considering its arrangement and the steps imposed on the balls. Therefore, such a device cannot operate at high rotational speeds due to mechanical wear and the resulting vibrations.

Prior Art Documents

Patent Documents

[0014]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0015] Therefore, as far as the applicant is aware, there is still an unmet need to benefit from a compact spindle that can rotate at high rotational speeds while axially rocking the cutting tool at a frequency suitable for reducing the length of the chips formed.

Means for Solving the Problems

[0016] The present invention aims to meet this need and achieves this object with a spindle for a machine tool, which spindle comprises a housing, a shaft for driving a cutting tool rotatably mounted inside the housing so as to be axially movable relative to the housing, A single ball axially interposed between a rolling bearing ring fixed to the housing and a rolling bearing ring movable with the shaft, one of these rings defining an inclined rolling bearing surface that is not perpendicular to the axis of rotation of the shaft such that rotation of the ball results in axial oscillation of the shaft, the single ball having.

[0017] The use of the single ball in the present invention for causing axial oscillatory movement of the shaft makes it possible to maintain the axial oscillation frequency at a value that matches the inertia of the moving parts, including rotational speeds exceeding 10,000 rpm. Further, since there is no cage rotating with the ball, heating at high rotational speeds of the rolling bearing is reduced. The present invention makes it possible to create a compact vibration drilling spindle that can replace a conventional spindle without modifying the machine tool, if desired.

[0018] Preferably, the ball is partially fitted into an annular groove formed in the shaft. This makes it possible to reduce the distance of its center of gravity from the axis, and thus the imbalance associated with its rotation, and the bending moment exerted on the shaft by the ball.

[0019] Preferably, the fixed rolling bearing ring is the one that defines the inclined rolling bearing surface. The inclined rolling bearing surface is advantageously planar, allowing it to be created very easily with high precision and good surface condition, which is advantageous for minimizing the friction between the ball and the rolling bearing ring.

[0020] Such an inclined rolling bearing surface has no steps. The absence of steps limits the occurrence of vibration and mechanical wear.

[0021] Advantageously, the axial cutting load is at least partially reacted by the rolling bearing ring fixed to the housing.

[0022] Preferably, the ball is made of ceramic, making it possible to optimize the strength / density ratio.

[0023] The ball is preferably located at the rear part of the spindle. This limits the influence of the bending moment on the quality of the guidance of the shaft in the tool.

[0024] The spindle preferably has two sets of ball bearings at the front and rear parts of the spindle respectively. These rolling bearings are preferably angular contact and flanged rolling bearings. The ball is preferably arranged behind the rear set.

[0025] The rolling bearings are preferably centered so that they can move axially by means of an elastic strip having a directed deformation and an annular overall shape. The strip preferably has fixed tabs on its outer periphery that are fixed to the housing, and between these fixed tabs, tabs for holding the rolling bearings. The flexibility of the part of the strip extending between the fixed tabs and the tabs for holding the rolling bearings allows the rolling bearings to move axially during axial rocking of the shaft. The use of the strip provides an elegant solution to the problem of ensuring radial rigidity while allowing the axial movement necessary for the shaft to be able to rock axially. The strips have high radial rigidity, but their thin thickness allows them to bend in order to follow the axial movement of the rolling bearings. The strips may be superimposed to increase the radial rigidity while maintaining the axial flexibility.

[0026] The rolling bearing may preferably be attached to a bearing indexed in the rotational direction with respect to the strip by a pin passing through the strip. The bearing has a sector forming a protrusion at its edge, against which the strip abuts, and the strip contacts the outer ring of the rolling bearing via a retaining tab. These sectors allow the axial movement of the rolling bearing with respect to the housing during axial oscillation of the shaft, and allow the portion of the strip extending between the immobilization regions to bend in order to maintain an axial clearance between the immobilization regions, while enabling the retaining tab of the strip to be fixed to the bearing.

[0027] Leaf springs may be present to press the strip against the outer ring of the rolling bearing. These leaf springs may be omitted, except for those that function as elastic members for applying an axial preload to the shaft as required, as described below.

[0028] The spindle has an elastic return member that returns the shaft rearward during rotation of the ball. This axial preload of the shaft toward the rear is advantageously provided by at least one leaf spring. Thus, the spindle may have at least one leaf spring, or a single leaf spring, that exerts a return force toward the rear. This leaf spring may be located at the front or rear of the spindle. By arranging the leaf spring at the rear, it is possible to avoid introducing compressive forces along a relatively long rotor length. The return force of such an elastic member toward the rear is advantageously maximum during non-zero cutting forces and is relaxed when the cutting force is greater than zero.

[0029] The axial immobilization of the strip with respect to the housing may be performed in various ways, but very preferably, the strip is held to the fixing tab using a series of spacers. Thus, the spindle preferably has a main tubular spacer fixed to the housing and fixing positioning rings arranged on both sides of the main spacer, and the strip preferably has a fixing tab gripped between the main spacer and the positioning ring.

[0030] The spindle preferably has bearing end rings on both sides of the bearing, with the pins described above fitted into these end rings, and one or more leaf springs press on one end of these end rings, while the other end supports a surface fixed to the housing.

[0031] The housing is preferably closed at the rear by an end piece against which a rolling bearing ring defining an inclined rolling bearing surface abuts.

[0032] Preferably, the spindle has a peripheral rolling bearing ring coaxial with the shaft in order to react to the centrifugal force of the balls. Reacting to the centrifugal force is particularly advantageous for drilling holes at rotational speeds exceeding 10,000 rpm.

[0033] Ratio d ball / d path is preferably between 1 / 4 and 1 / 2, where d ball represents the diameter of the ball and d path represents the diameter of the contact point between the ball and the inclined rolling bearing surface.

[0034] A further subject of the invention is a machining method, in particular a drilling method, in which the shaft of the spindle according to the invention is driven at a rotational speed of at least 10,000 rpm, for example between 15,000 and 30,000 rpm, particularly about 15,000 to 20,000 rpm.

[0035] A further subject of the invention is a machining method, in particular a drilling method, in which the shaft of the spindle according to the invention oscillates axially at an oscillation frequency of 0.4 to 0.6 axial oscillations per revolution, particularly about 0.5 axial oscillations per revolution.

[0036] The spindle may be subjected to a forward movement during rotation of the shaft in a conventional manner.

[0037] The invention can be better understood by reading the following description of its non-limiting embodiments and by considering the accompanying drawings.

Brief Description of the Drawings

[0038]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0039] In particular, the spindle 1 according to the present invention shown in FIGS. 1 to 4 has a housing 10 having an overall cylindrical shape of rotation about the longitudinal axis X, preferably made of metal.

[0040] The casing 10 is attached to a guiding and advancing mechanism (not shown) of a machine tool known per se. The support 11 fixed to the housing enables the mechanism to move the spindle 1 axially by the distance necessary to generate a perforation.

[0041] The spindle 1 is intended to support a tool such as a drill bit (not shown) at the front, and has a shaft 20 coupled at the rear to a pulley 21 for rotationally driving it. The drill bit has a diameter of, for example, 2.5 mm or less.

[0042] The rotational speed of the shaft 20 is, for example, 10,000 to 20,000 revolutions per minute.

[0043] The present invention is not limited to a specific tool or the formation of a perforation. In particular, it may be found useful to perform machining operations such as milling operations and boring operations.

[0044] The shaft 20 is guided to rotate about the axis X with respect to the housing 10 by a set 30 of front rolling bearings and a set 40 of rear rolling bearings.

[0045] The set 30 of front rolling bearings has two angular contact ball bearings 31 with a contact angle of, for example, 15°, each having an inner ring 32 in contact with the shaft 20, balls 33, an outer ring 34, and a flange 35. The rolling bearings 31 support each other and are fitted into the front bearing 50.

[0046] The set 40 of rear rolling bearings is embodied in a similar manner using two angular contact rolling bearings 41 with a contact angle of, for example, 15°, each having an inner ring 42 in contact with the shaft 20, balls 43, an outer ring 44, and a flange 45. The rolling bearings 41 support each other and are fitted into the rear bearing 51.

[0047] The inner ring 42 of the rearmost rolling bearing comes into axial contact with the shoulder 23 of the shaft 20, particularly as seen in FIG. 3.

[0048] The tubular inner spacer 24 is attached to the shaft 20 between the set 30 of front rolling bearings and the set 40 of rear rolling bearings and comes into contact with the corresponding inner rings 32 and 42 of the rolling bearings at its ends.

[0049] A blocking ring 70 is fixed to the front shaft 20 to fix the inner ring 32 of the rolling bearing 31, the inner spacer 24, and the inner ring 42 of the rolling bearing 41, thereby applying an axial preload to the shaft.

[0050] The ring 70 is fixed to the shaft in the illustrated example using three conical point-stop screws 71 that enable correction of circularity deviation as required.

[0051] The O-ring seal 72 is housed within the groove 73 of the shaft 20 and presses against the blocking ring 70.

[0052] As shown in FIG. 2, the housing 10 can be held in various ways on the housing 10, for example using a nut 96. The front part is closed by a front nut 90, screwed therein, and the rear part is closed by a rear closure 95.

[0053] The front nut 90 has a forward-facing collar 190, which forms a labyrinth 192 together with the rearward-facing collar 191 of the blocking ring 70.

[0054] The inner ring 195 is attached to the shaft 20 at the rear and has a forward-facing collar 196, which forms a labyrinth 198 together with the collar 197 of the closure 95.

[0055] The labyrinths 192 and 198 form a non-contact sealing system at the front and rear of the spindle 1, providing a clearance that allows rotational and translational movement without friction between opposing rotating and stationary components.

[0056] The O-ring seal 199 is housed within the groove 27 of the shaft 20 and presses against the opposing surface of the inner ring 195.

[0057] A series of spacers are arranged in contact with the inner surface within the housing 10 and are fixed to the ring forming the front spacer 91, the ring forming the front bearing spacer 92, the main tubular spacer 93, and the ring forming the rear bearing spacer 94, between the front nut 90 and the rear closure 95, i.e., from the front to the rear.

[0058] The four stacks 100, 101, 102 and 103 of the elastic strip 110 are axially interposed between spacers 91 and 92, between spacers 92 and 93, between spacers 93 and 94, and between spacers 94 and 95, respectively.

[0059] Each stack 100, 101, 102 or 103 has, in the example in question, at least two strips 110, for example five, one of which is shown alone in FIG. 5.

[0060] Each strip 110 has an annular overall shape and has fixing tabs 111 regularly distributed around it, three of which are, in the example in question, directed radially outwards and bear their radially outer edges against the inner face of the housing 10. The height of the fixing tabs 111 is slightly greater than the thickness of the bearing spacers 92 and 94.

[0061] The arc portion 112 connecting the fixing tabs 111 supports, in the middle of its length, other tabs 113 directed radially inwards. Each of these tabs 113 has, at one end, a radial slot 114 opening onto the radially inner free edge of the tab 113 and, at the opposite end, into a circular hole 115 formed in the arc portion 112.

[0062] The front bearing 50 is arranged between two bearing end rings 121, 122. The pins 130 are fitted into the corresponding perforations 140 and 141 of these end rings 121 and 122 and of the front bearing 50 in order to keep the rings 121 and 122 at a predetermined angular orientation with respect to the front bearing 50.

[0063] These pins 130 pass through the strip 110 by means of the holes 115. The slots 114 facilitate the fitting of the pins 130. Thus, the stacks 100 and 101 are held angularly in a predetermined position with respect to the bearing 50 and the end rings 121 and 122.

[0064] The bearing 50 and the rings 121 and 122 have projecting sectors 143 on their opposing faces, as seen in FIGS. 6 and 7, the angular range of which substantially corresponds to the angular range of the tabs 113 and which surround the tabs 113 with respect to each other.

[0065] The rear bearing 51 is similarly arranged between the bearing end rings 120, 121, and the pin 130 angularly fixes the strip 110 arranged therebetween, as in the case of the front bearing 50.

[0066] The tabs 113 of the strip 110 are in axial contact with the outer rings 32 and 42 of the rolling bearings 31 and 41.

[0067] This assembly allows a certain degree of freedom of axial movement of the sets 30 and 40 of rolling bearings while keeping the sets 30 and 40 of rolling bearings centered as a result of the radial rigidity of the strip 110, as will be explained in detail below.

[0068] At both ends of the main spacer 93, shoulders 171 are formed which are set back from the end portions 172 surrounding the corresponding end rings 121 or 122.

[0069] Leaf springs 170 are attached inside each end portion 172 and are axially interposed between the shoulder 171 and this end ring 121 or 122.

[0070] At the front, two overlapping leaf springs 170 are attached around the blocking ring 70 and are axially interposed between the front nut 90 and the end ring 121, as seen in FIG. 2.

[0071] The closure 95 has a shoulder 176 and a front end portion 177 of the shoulder 176 extending around the adjacent end ring 122.

[0072] Leaf springs 170 are attached inside the end portion 177 and are axially interposed between the closure 95 and the adjacent end ring 122.

[0073] The leaf spring 170 grips the elastic strip around the front and rear rolling bearings via the end rings 121 and 122 by means of tabs 113 that abut against the outer ring of the rolling bearing.

[0074] The presence of an additional leaf spring 170 at the front between the end ring 121 adjacent to the nut 90 creates a permanent elastic load on the rear part of the shaft 20 in order to press the balls 200 against the rings 201 and 202.

[0075] According to the present invention, the spindle 1 has a mechanism for generating an axial oscillation of the shaft 20 during rotation.

[0076] This mechanism has a single ball 200 that rolls between a rotating rolling bearing ring 201 attached to the shaft 20 and rotating with the shaft and a fixed rolling bearing ring 202 supported by the closing part 95.

[0077] The peripheral rolling bearing ring 203 is inserted into the closing part 95 behind the shoulder 176 and extends around the path followed by the ball 200 while the ball 200 rotates. This peripheral ring 203 enables it to react to the centrifugal force during the rotation of the ball 200.

[0078] The rotating ring 201 is held against the shoulder 28 of the shaft 20 adjacent to the annular groove 29, and its concave surface substantially coincides with the path followed by the ball 200.

[0079] The rolling bearing ring 202 has a rear face 230 that is planar and perpendicular to its axis, and a front face 231 that is planar and extends obliquely, and the normal to this face forms an angle g of a few degrees, for example about 0.3° in the example in question, with respect to the axis of the rolling bearing ring 202. The formula for g is g = Arctan(amplitude / d path ) where "amplitude" corresponds to the total peak / trough variation of the oscillatory oscillation and d path is the diameter of the path of the contact point.

[0080] As can be seen, there is no step on the rolling bearing surface 231.

[0081] Therefore, during its rotation about the axis X, the ball 200 performs a periodic and sinusoidal axial movement caused by the inclination of the front surface 231. The ball 200 is in contact only with the fixed rolling bearing ring 202, the rotating rolling bearing ring 201, and the peripheral rolling bearing ring 203 during its high-speed rotation. Since a single ball is used, the rolling of the ball induces bending stress on the shaft, but this is controlled because the distance between the ball 200 and the spindle shaft 20 is relatively small and remains within an acceptable amplitude.

[0082] The fact that the rolling bearing surface 231 has no undulations and is rather a flat surface makes it possible to manufacture the rolling bearing surface very easily with a very good surface condition.

[0083] Preferably, the ball 200 is made of ceramic. Its diameter is preferably 5 mm or more, which makes it possible to reduce the Hertz pressure at the contact point. Its diameter is, for example, 6 mm.

[0084] To attach the spindle 1, all internal components can be arranged on the shaft 20, the assembly can be inserted through the front end of the housing 10, the closing part 95 is already in place, and then the front screw 90 can be fixed.

[0085] The spindle 1 operates as follows.

[0086] The shaft 20 is rotationally driven, for example, by a pulley 21 via a belt.

[0087] The ball 200 rolls between the rolling bearing rings 201 and 202, and in so doing, moves the shaft 20 forward against the preload associated with the presence of an additional leaf spring 170 at the front.

[0088] The movement of the shaft 20 is made possible by the presence of the strip 110, and its arcuate portion 112 can bend due to the clearance provided adjacent to them by the presence of the sectors 143. This bending enables the front bearing 50 and the rear bearing 51 to move axially so as to follow the rocking brought about by the movement of the balls 200.

[0089] Accordingly, an axial rocking of the shaft 20 is obtained, the frequency of which is given by both the rotational speed of the shaft 20 and the Willis formula applied to this rolling bearing having three contact points.

[0090] The axial movement of the shaft 20 during the rocking motion is, for example, between 0.02 mm and 0.15 mm. The spindle shaft rocks at an oscillation frequency of 0.4 to 0.6, for example about 0.5, per revolution.

[0091] When the groove 29 in which the balls 200 are partially inscribed is present in the shaft 20, the distance 200 from the axis X, and thus the phenomenon of imbalance associated with the use of a single ball 200, is reduced. Furthermore, the distance the balls 200 travel and the resulting wear are reduced. Finally, the bending moment caused by the asymmetric load by a single ball is reduced.

[0092] Of course, the present invention is not limited to the examples described herein.

[0093] For example, as shown in FIG. 9, it is possible to close the housing 10 differently at the rear. In this figure, the rear closure 95 is held within the housing by an elastic ring 300 attached to a corresponding groove in the housing 10, whereby it is clear that the axial and radial space requirements of the housing are reduced.

[0094] Separate from what is used to provide an axial preload to the shaft, it is possible to dispense with the leaf spring. The leaf spring used to provide an axial preload to the shaft may be arranged at the rear, that is, at a position arranged between the rear shoulder 171 and the ring 121 where the leaf spring 170 rolls radially inside the bearing 51 and is adjacent to the rolling bearing 41 in FIG. 2.

Explanation of Signs

[0095] 1 Spindle, 10 Housing, 11 Support, 20 Shaft, Spindle Shaft, 21 Pulley, 23 Shoulder, 24 Inner Spacer, 28 Shoulder, 29 Groove, 30 Set of Front Rolling Bearings, 31 Rolling Bearing, Ball Bearing, 32 Inner Ring, 33 Ball, 34 Outer Ring, 35 Flange, 40 Set of Rear Rolling Bearings, 41 Rolling Bearing, 42 Inner Ring, 43 Ball, 44 Outer Ring, 45 Flange, 50 Front Bearing, 51 Rear Bearing, 70 Blocking Ring, 71 Set Screw, 72 O-Ring Seal, 73 Groove, 90 Nut, 91 Spacer, 92 Spacer, Positioning Ring, 93 Main Spacer, 94 Spacer, Positioning Ring, 95 Closing Part, 96 Nut, 100 Stack, 101 Stack, 102 Stack, 103 Stack, 110 Strip, 111 Fixed Tab, 112 Arc Portion, 113 Tab, 114 Slot, 115 Hole, 121 End Ring, 122 End Ring, 130 Pin, 140 Perforation, 141 Perforation, 143 Sector, 170 Leaf Spring, 171 Shoulder, 172 End, 176 Shoulder, 177 End, 190 Collar, 191 Collar, 192 Shank, 195 Inner Ring, 196 Collar, 197 Collar, 198 Shank, 199 O-Ring Seal, 200 Ball, 201 Rolling Bearing Ring, 202 Rolling Bearing Ring, 203 Rolling Bearing Ring, 230 Rear Surface, 231 Front Surface, 300 Elastic Ring

Claims

1. A high-speed spindle (1) for a machine tool, comprising: a housing (10); a shaft (20) rotatably mounted inside the housing for driving a cutting tool that can move axially relative to the housing; a single ball (200) axially interposed between a rolling bearing ring (202) fixed to the housing and a rolling bearing ring (201) movable with the shaft, wherein one of the rolling bearing rings defines an inclined rolling bearing surface (231) that is not perpendicular to the axis of rotation of the shaft such that rotation of the ball causes axial oscillation of the shaft, and the spindle can operate at a rotational speed of the shaft exceeding 10,000 rpm; and the ball (200) is partially fitted into an annular groove (29) formed in the shaft (20). Spindle (1).

2. The spindle according to claim 1, wherein the fixed rolling bearing ring (202) defines the inclined rolling bearing surface (231).

3. The spindle according to claim 1, wherein the inclined rolling bearing surface (231) is a flat surface.

4. The spindle according to claim 1, wherein the ball (200) is made of ceramic.

5. The spindle according to claim 1, wherein the ball (200) is located at the rear of the spindle (1).

6. The spindle according to claim 1, having two sets (30, 40) of two ball bearings respectively at the front and rear of the spindle.

7. The spindle according to claim 1, wherein the axial preload on the rear of the shaft is ensured by at least one leaf spring (170).

8. The rolling bearing is held by an annular strip (110) having an overall shape, and the strip (110) has a fixed tab (111) fixed to the housing on the outer periphery of the strip and a tab (113) for holding the rolling bearing between the fixed tabs. The flexibility of the portion (112) extending between the fixed tab (111) and the tab (113) of the strip for holding the rolling bearing allows the rolling bearing to move axially during the axial oscillation of the shaft. The rolling bearing is attached to a bearing (50; 51) that is prevented from rotating relative to the strip by a pin (130) passing through the strip. The bearing has a sector (143) that forms a protrusion at an edge of the bearing. With respect to the sector, the strip is placed in the region of the tab (113) to hold the rolling bearing. The strip (110) contacts the outer rings (34, 44) of the rolling bearing via the holding tab (113). The spindle has a leaf spring (170) for pressing the strip against the outer ring of the rolling bearing. The spindle has a main tubular spacer (93) fixed to the housing and fixing positioning rings (92, 94) arranged on both sides of the main spacer (93). The strip (110) has the fixed tab (111) gripped between the main spacer (93) and the positioning rings (92, 94). The spindle according to claim 1.

9. The spindle according to claim 8, wherein the spindle has end rings (121, 122) on both sides of the bearing (50, 51), the pin (130) is fitted into the end rings, one end of the leaf spring (170) presses an end of the end ring, and the other end abuts against the tab (113) for holding the strip.

10. The spindle according to claim 8, wherein the rolling bearings (31) and (41) are angular contact rolling bearings.

11. The spindle according to claim 1, wherein the spindle has a peripheral rolling bearing ring (203) coaxial with the shaft to react to the centrifugal force of the ball (200).

12. Ratio d ｂａｌｌ / d ｐａｔｈ is from 1 / 4 to 1 / 2, and d ｂａｌｌ represents the diameter of the ball, and d ｐａｔｈ represents the diameter of the contact point between the ball and the inclined rolling bearing surface. The spindle according to claim 1.

13. A machining method, wherein the shaft of the spindle according to claim 1 is driven at a rotational speed of at least 10,000 rpm.

14. A machining method, wherein the vibration frequency of the shaft of the spindle according to claim 1 is an axial rocking of 0.4 to 0.6 per rotation.

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