Abstract: A device for the controlled stabilization of tool holder shanks on the respective ring nut, the tool holder shanks, motorized or non-motorized, being predisposed for ER or other type fixing. The device comprises a ring nut and a tool holder shank of a truncated conical shape provided externally with a groove in which means connecting the ring nut to the tool holder are arranged inside the ring nut. The connecting means consist of an annular body formed of at least two shaped half-rings that define opposite protrusions projecting outwardly and centrally to form a shaped prominence having an arched-convex outer profile; on each of the shaped prominences a recess is made predisposed to house respective elastic pins, by means of which the shaped half-rings are firmly connected inside the ring nut blind holes.

Abstract: Implementations of an adaptive assisted grip apparatus are provided. In some implementations, the adaptive assisted grip apparatus comprises a holder and a wrist strap. In some implementations, a method of using the adaptive assisted grip apparatus comprises inserting a makeup applicator or other suitable item into the holder, placing the wrist strap around a user's wrist, grasping and holding the makeup applicator or other suitable item using the holder, and using the wrist strap to prevent the makeup applicator or other suitable item inserted in the holder from falling to the floor/ground or otherwise being dropped if/when the user loses grip of the holder.

Abstract: The invention relates to a dental tool having a shank region, which is formed for coupling to a dental handpiece, and also having a work region, which is connected to the shank region. In this case, the shank region of the dental tool is formed so that there is the possibility of latchable insertion and removal without actuation. In particular, at least the shank region can consist of plastics material. As a result, facilitated handling of the tool and inexpensive production of the tool are rendered possible.

Abstract: Machine tool, comprising a workpiece carrier assembly (11) including a workpiece carrier (12), said workpiece carrier assembly (11) being supported on a workpiece carrier support (1) for horizontal movement in a first direction in parallel with a horizontal Z axis; a first tool carrier (21), supported on a tool carrier support (2) for horizontal movement in a second direction, said first tool carrier (21) being displaceable in said second direction between an operative position in which said first tool carrier (21) is facing said workpiece carrier assembly (11), and an inoperative position in which said first tool carrier (21) is not facing the workpiece carrier assembly (11). The invention also relates to a method of machining a connecting rod using the machine tool.

Abstract: Machine tool, comprising at least two workpiece carrier assemblies (11), each including a workpiece carrier (12), said workpiece carrier assemblies (11) being supported on respective workpiece carrier support (1) for horizontal movement in a first direction in parallel with a horizontal Z axis; at least a first tool carrier (21), supported on a tool carrier support (2) for horizontal movement in a second direction, said first tool carrier (21) being displaceable in said second direction between at least one operative position (A) in which said first tool carrier (21) is facing one of said workpiece carrier assemblies (11), and at least one inoperative position in which said first tool carrier (21) is not facing any workpiece carrier assembly (11). The invention also relates to a method of machining a connecting rod using the machine tool.

Abstract: When a press-in part 81 is inserted into a press-in hole 93, a vertex of the press-in part 81 deformed to a form along the inner surface of the press-in hole 93 comes into contact with the inner surface of the press-in hole 93 and a press-in force when the press-in part 81 is inserted into the press-in hole 93 or a pull-out force when the press-in part 81 is pulled out from the press-in hole 93 is set in according with the length of an intersecting line that a surface on which the outer surface of the press-in part 81 comes into contact with the inner surface of the press-in hole 93 and a section intersecting orthogonally to the axial direction of the press-in part 81 intersect.

Abstract: A system 5 for securely blocking relative translational movement between a cylindrical shaft and an element 112, includes a blocking element 50 in which an immobilization element 55 is arranged, the immobilization element being associated with a viscoelastic fluid 8 disposed between the blocking element 50 and the immobilization element 55 in such a way that translational movement is blocked when the viscoelastic fluid 8 is pressurized in the blocking cylinder and translational movement is possible when the viscoelastic fluid 8 is no longer pressurized. An actuating cylinder equipped with such a secure blocking system is also described.

Abstract: A drill chuck having a chuck body that has a receptacle on its axially rearward end, having clamping jaws that can be moved relative to the chuck axis, and having a clamping sleeve that serves to move the clamping jaws. An adapter body can be placed in the receptacle and coupled in a torque-transmitting manner, which adapter body has an adapter receptacle for detachable connection to the drilling spindle of a power drill and has, in the wall of the adapter receptacle, at least one detent element that can be moved by a release sleeve.

Abstract: An exhaust gas recirculation valve for a vehicle may include a housing having a flow path through which an exhaust gas flows, a shaft installed in the housing to be rotatable, a flap valve provided to be rotatable about the shaft and configured to open and close the flow path, a bushing provided on the shaft, an anti-wear washer installed on the shaft between the flap valve and the bushing, and a spring means installed on the shaft and configured to elastically support the bushing.

Abstract: The invention relates to an adjusting device for axially supporting a shank tool in a shrink-fit chuck tool holder, comprising a leveling section on the side facing the shank tool to level out or at least reduce any changes in position and/or orientation of the shank tool which are due to shrinkage.

Abstract: A tool holder, in particular for a measuring sensor, with an interface to a spindle of a machine tool is proposed. The tool holder comprises, as seen from the interface for the spindle, a material portion which differs from the customary basic material of a tool holder in a lower coefficient of linear expansion ? and/or in a lower heat conductivity ?. According to the invention, the material portion affords thermal decoupling between the tool-side portion of the tool holder and a tool received therein from the tool spindle for reducing a length change on account of an introduction of heat coming from a comparatively hot tool spindle.

Abstract: A chuck assembly, an assembly for an earth-boring drill assembly, and a method of retaining a drill bit for an earth-boring drill assembly, the drill assembly including a casing. The assembly includes a drill bit having a generally cylindrical head, a chuck connectable to the casing and operable to support the bit, the chuck having an outer surface with a radially-outwardly extending chuck ridge, an axially-extending first slot being defined in the ridge, a sleeve having an inner surface with a radially-inwardly extending sleeve ridge engageable with the chuck ridge to limit axial movement of the sleeve relative to the chuck, the sleeve having a first lug supported on the inner surface, the first lug being positionable in the first slot to limit relative rotational movement between the sleeve and the chuck. The assembly may also include a retainer assembly provided between the sleeve and the bit.

Abstract: It is already common in many devices like spanners or pipe wrenches for the pressure between the gripping faces and gripped faces to be related to the torsional load that is applied to turn the gripped object. In these apparatus the grip can be made to relax automatically as the load is removed. The invention relates to improvements in such devices, and to novel designs of mechanical coupling devices that utilise this basic idea. More specifically, the invention firstly proposes a method of improving the performance of an object-gripping tool of the cam-operated gripper-element type, in which method there is applied to the gripper surface a friction-enhancing chemical.

Abstract: A system for use in securing an attachment to a driver having an attachment mounting area includes an attachment mount configured for releasable engagement with an attachment as well as a driver mount interconnected with the attachment mount. The driver mount includes a removable mounting member configured for engagement with the attachment mounting area of the driver.

Abstract: A system, in certain embodiments, includes a cutting tool, a drive, and a chuck rotatable by the drive. The chuck includes a body having a core disposed in a shell, wherein the shell is made of a metal and the core is made of a composite material. The chuck also includes a set of jaws coupled to the body, wherein the jaws are configured to hold a work piece adjacent the cutting tool.

Abstract: A chuck is described. The chuck may include: a plurality of chuck jaws. Each chuck jaw is radially movable toward and way from a chuck axis, and each chuck jaw including: two substantially coplanar surfaces perpendicular to a chuck jaw axis and substantially parallel to the chuck axis; a ridge located between the two substantially coplanar surfaces; and two troughs, one trough located between the ridge and one of the substantially coplanar surface and the other trough located between the ridge and the other coplanar surface. A chuck jaw and method of configuring a chuck are also described.

Abstract: There is disclosed chuck configurations for internally engaging the hollow core element of a roll of packaging or printing sheet or other web material in which a generally cylindrical chuck body insertable in a web core has at least one hole through the chuck body at an acute angle with the tangent to the chuck body at the outer entrance point of the hole and at an acute angle with the plane perpendicular to the chuck cylindrical axis. At least one elongated element is configured to engage rotatably in each of the holes and having on a distal end thereof one or more pointed or toothed extensions for engagement with the interior of a hollow web whereby chuck engagement with a hollow core may be made by manipulating such elongated elements to extend outside the periphery of said chuck body. The chuck may also be provided with means for securing it on a spindle or shaft for rotation therewith which is separate and independent of the holes and elongated elements for engaging the hollow core.

Abstract: A device (10) for thermally clamping and releasing tools (11) in shrink-fit chucks (12), having a socket (15) for a shrink-fit chuck (12), a heating unit (16) that can be moved toward and away from the mounted shrink-fit chuck (12), and a cooling unit (20) for cooling the heated shrink-fit chuck (12). The cooling unit (20) has at least one coolant distributor (21, 22) that is capable of moving in relation to the socket (15) with the mountable shrink-fit chuck (12), conveys a preferably fluid coolant, e.g. cooling water, and has outlets (23) for the coolant, which are oriented toward the socket (15) with the mountable shrink-fit chuck (12) and out of which the coolant travels under pressure to act on the outside of the socket (15) with the mountable shrink-fit chuck (12) for cooling purposes (FIG. 1).

Abstract: A tool employs a connect-disconnect coupling for a power drill to hold a multi-functional bit having at its one end a drill element adapted to form a hole and a countersink and at its other end a driver element to drive a screw or other type of fastener.

Abstract: The invention relates to a clamping system as a point of separation inside a tool or workpiece support system, or as an interface between a tool or workpiece support system and a machine tool for the detachable, non-positive connection of two clamping system parts. According to the present invention, it is proposed to coat at least one joining surface of a joining surface pairing between components of the clamping system parts that are to be connected in non-positive fashion with a layer of solid lubricant applied in an abrasion-resistant manner. On the one hand, this coating with solid lubricant enables significant improvement in the sliding characteristics of the joining surfaces, subjected to friction, of the components of the clamping system to be connected with one another. On the other hand, the joining surfaces, which are in addition subjected to a high surface pressure, exhibit improved corrosion characteristics.

Abstract: A chuck assembly comprises a housing defining a longitudinal axis and having a first end. A plurality of pins extend substantially parallel with the axis from the first end. The plurality of pins is located at a first radius relative to the axis. At least one of the pins is operable to move from the first radius to a second radius, relative to the axis. The chuck assembly also includes a means for moving at least one pin between the first radius and the second radius. A prime mover provides the necessary drive to the means for moving. The chuck assembly may be used in combination with various other components to form combinations or systems.

Abstract: A coupling device for engaging an exchangeable tool support (7) for corotation with a shaft (2) of a motor (1), with the shaft (2) mounting at is driven end a hollow shaft projection (3) for receiving the tool support (7). Alternatively, the tool support (7) can mount the hollow shaft projection for receiving the driven end of the shaft. The shaft (2) and/or the tool support mounts a locking device for securing the tool support (7), and which is actuated by centrifugal force. The coupling device is designed and constructed so as to permit a simple mounting of even heavy tools to the output shaft of the motor, and a reliable connection of the tool and drive.

Abstract: A shrinkage device for rapidly shrinking and outshrinking tools, especially hard metal tools, in so-called shrinkage tension chucks using an induction heating coil, wherein a plurality of shrinkage chucks of paramagnetic or ferromagnetic materials can be positioned on a turntable and brought from a position below the induction coil, which can be lowered, into a cooling position.

Abstract: Apparatus and methods for a wafer handling system that manipulates semiconductor wafers. The present invention includes an end effector having a vacuum chuck, an internal vacuum plenum, and a plurality of flow diverters positioned within the vacuum plenum to define vacuum distribution channels in fluid communication with respective vacuum ports of the vacuum chuck. The present invention also includes a vacuum chuck having flow diverters positioned in one or more internal vacuum plenums which are in fluid communication with the vacuum ports of the vacuum chuck. The flow diverters of the vacuum chucks adjust the vacuum pressure supplied to the vacuum ports such that, as vacuum ports are occluded by the wafer, the vacuum pressure is preferentially applied to unblocked vacuum ports for increasing the attractive force applied to unengaged portions of the wafer.

Abstract: A drill chuck has a chuck body centered on an axis and formed with a forwardly open seat and with a plurality of angled guides spaced angularly about the axis and open forward into the seat. Respective jaws slidable in the guides each have a toothed outer edge meshing with a screwthread of a tightening ring rotatable about the axis to axially and radially displace the jaws in the body. An adjustment sleeve rotationally coupled to the ring is rotatable about the axis on the body. It has an outer grip surface of a predetermined outer diameter and an indicia band axially offset from the grip surface and of an outer diameter smaller than the outer grip surface.

Abstract: A low-pressure processor for processing substrates includes a chuck that engages the substrates' peripheries for purposes of clamping, sealing, and centering the substrates on chuck bodies. For accomplishing all three purposes, a mechanical clamp can be arranged with two sealing regions. One of the sealing regions seals the clamp to a chuck body or an extension of the chuck body, and another of the sealing regions engages a peripheral edge surface of a substrate for sealing the clamp to the substrate. The second sealing region includes an inclined seating surface that engages a front edge of the substrate's peripheral edge surface and divides a clamping force into a first component that presses the substrate against the chuck body and a second component that centers the substrate on the chuck body.

Abstract: A hydraulic chuck includes a center bore for receiving a tool shank. At least one closed cavity is disposed in the chuck body adjacent the bore and extend circumferentially by a distance less than 360 degrees. The cavity containing device communicates with the medium for pressurizing the medium to radially deform and expand the bore wall from a normal diameter to a larger diameter to enable the tool shank to be moved into or from the bore. A depressurizing of the medium causes the bore wall to radially retract to the normal diameter for clamping the member in the bore.

Abstract: A mounting tool for a hydromechanical chuck or mandrel of the type which is clamp connected using a pressure medium in order to clamp connecting a shaft or a shaft tool or a working piece, and in which said shaft or working piece is dismantled from the chuck, and which chuck using a pressure medium in the opposite direction, and which chuck is formed with two separate pressure chambers, a first chamber acting as a clamp connection chamber, and a second chamber acting as a dismantling chamber, which chambers are formed with inlets/outlets provided on opposite sides of the chuck and opening at the periphery thereof.

Abstract: A chuck for securing a working tool in a machine tool and including a one-piece, ring-shaped carrier member arranged outside of the end surface of the receiving end region of the chuck and parallel thereto and provided with cutting regions having additional cutting elements distributed circumferentially around the receiving bore of the receiving end region and extending transverse to a plane defined by the ring-shaped carrier member and projecting away from the carrier member which secured by crews to the receiving end region of the chuck.

Abstract: A vibration dampened spindle and tool holder assembly for a rotary cutting machine. The assembly includes a spindle and a tool holder retained therewith. The tool holder has an interfacing ledge with a top surface for abutment with a distal spindle surface, and a continuous channel disposed in a proximal portion of the top surface. A resilient dampening member, having a rectangular or a circular cross sectional configuration, resides in the channel for compressed abutment with the spindle surface. Because the dampening member is situated within the channel, the interfacing placement of the spindle surface and tool holder top surface meet as the dampening member is enshrouded in the channel by these abutting surfaces and thereby protected from contaminant entry during dampening action.

Abstract: A mechanism for engaging a chuck to a chuck body includes a bore within the chuck body having first and second opposed channels in communication therewith. A shaft extending from the chuck is configured for seating in the bore and includes two opposed vanes for seating in the channels. The vanes are depressible allowing for initial bore penetration and seating of the chuck shaft into the bore. Upon seating the vanes are biased into the channels locking the chuck shaft in the bore. A tool provides for depression of the vanes allowing for removal of the seated chuck shaft from the bore. Alternative mechanisms for locking a chuck, chuck body and a driven shaft are disclosed.

Abstract: A cutting tool including a tool holding portion and a tool. The tool is configured to be inserted into a hole of the tool holding portion. The tool includes a tool main body, a guide portion, and a shoulder portion. The tool maim body has a tool outer diameter larger than the hole inner diameter of the hole when the tool holding portion is not heated. The guide portion is coaxially connected to the tool main body and configured to position the tool substantially coaxially with respect to the tool holding portion. The guide portion has a guide outer diameter smaller than the hole inner diameter of the hole so that the guide portion is inserted into the hole. The shoulder portion is formed between the tool main body and the guide portion so as to sit on a surface around the hole to support the tool when the guide portion is inserted into the hole.

Abstract: A shrinkage device for rapidly shrinking and outshrinking tools, especially hard metal tools, in so-called shrinkage tension chucks using an induction heating coil, wherein a plurality of shrinkage chucks of paramagnetic or ferromagnetic materials can be positioned on a turntable and brought from a position below the induction coil, which can be lowered, into a cooling position.

Abstract: A drill chuck has a body element formed of fiber-reinforced plastic, centered on and rotatable about an axis, and formed centered on the axis with a rearwardly open spindle hole and a forwardly open tool hole. A ring element is axially fixed but rotatable about the axis on the body element and one of the elements is formed with a plurality of angled guide passages opening axially forward into the tool hole and the other of the elements is formed centered on the axis with a screwthread exposed in the passages. Respective jaws axially and radially displaceable in the passages are each formed with a row of teeth meshing with the screwthread so that rotation of the ring element in one direction displaces the jaws toward one another and opposite rotation displaces them away from one another.

Abstract: A tool holder that uses a dampening drive member to reduce slippage between the tool holder and the spindle and while further eliminating harmonic resonance. The tool holder is used in a rotating spindle that has at least one cam recess formed on a lower face thereof. The tool holder includes a conically tapered shank portion which is insertable into the spindle. Disposed adjacent to the shank portion is a flange portion. Extending about the flange portion is a compressible dampening drive member that has at least one cam portion sized and configured to engage a respective one of the cam recesses of the spindle. When the tool holder is secured to the spindle, the dampening drive member is compressed therebetween. The dampening drive member is adapted to eliminate harmonic resonance attributable to the use of the tool holder and prevent slippage between the tool holder and the spindle.

Abstract: A drill chuck has a body centered on and rotatable about an axis and formed centered on the axis with a rearwardly open spindle hole, a forwardly open tool hole, and a plurality of angled guide passages opening axially forward into the tool hole. Respective jaws axially and radially displaceable in the guide passages are each formed with a row of teeth in mesh with an internal thread of a metallic tightening ring axially fixed but rotatable about the axis on the body. Thus rotation of the tightening ring displaces the jaws in their guide passages. The body is formed of plastic and includes an imbedded metallic reinforcement element which has a frustoconical portion forming outside walls of the guide passages and the jaws ride directly on the metallic element.

Abstract: A rotary power tool, such as a router, includes an actuating device engaged with a chuck device to move the chuck device between its gripping and release positions. The actuating device includes a lever member that extends axially relative to a casing of the power tool within an inner circumference of a base member. This lever member is movable relative to the casing and is engaged with the chuck so that movement of the lever is imparted to the chuck device causing the chuck device to move axially between its gripping and release positions.

Abstract: A chucking device for mounting a tool on a machine tool is provided, having a mounting section for mounting the chucking device on the machine tool and a thermally expandable shrink section which comprises a holding section intended to receive the tool in shrink-fit relationship. A lead-in section is provided at the outer end of the shrink section, whose inner diameter is selected to ensure that the shank of the tool can be placed in the lead-in section and can be centered therein in a cold condition of the shrink section. A suitable rotatably driven mounting intended to receive the chucking device during clamping of the tool is provided, preferably in vertical arrangement, in order to ensure that the shank of the tool will slide into the holding section from above under the action of gravity.

Abstract: A tool holder for use in a rotating spindle of a milling machine. The tool holder comprises a conically tapered shank portion for insertion into the spindle and a cutting tool mounting portion. Disposed between the shank and mounting portions is a flange portion. Additionally, extending about the shank portion is a dampening member. The dampening member is compressible between the flange portion and the spindle when the tool holder is inserted into the spindle, and is adapted to eliminate harmonic resonance attributable to the use of the tool holder with an extended shank cutting tool.

Abstract: A chuck device for use with a manual or powered driver has a body member with a plurality of angularly disposed passageways formed therethrough. A jaw is slidably positioned in each passageway. Each jaw has a tool engaging face formed on one side and threads formed on the opposite side. The jaws are threadedly engaged with a rotatable nut mounted on the body member. A sleeve member is in rotational engagement with a nut whereby rotation of the sleeve causes the nut to rotate and the jaws to advance or retract within their respective passageways. Each jaw and its respective passageway has a unique matching profile different from the other jaws and respective passageways so that the jaws cannot be interchanged with different passageways in the chuck.

Abstract: A chuck assembly for use with a rotary tool includes a chuck mechanism having a plurality of spaced apart jaws. The jaw spacing is adjusted by rotation of an adjustment ring. A sleeve encircles and is affixed to the adjustment ring. A plurality of spaced apart ribs radially extend from the sleeve. An elastomeric grip extends generally circumferentially about the sleeve. The ribs radially protrude from the grip at a plurality of openings defined by the grip. The ribs lie in outboard shielding relationship to the grip to protect the grip from excessive wear and damage due to contact with other objects during operation of the rotary tool.

Abstract: A system for securing a blood separator bowl in an autotransfusion machine includes a split ring or collar adapted to grip an enlarged cap on the base of the bowl and a clamp assembly for moving the collar between retracted and expanded positions. In the retracted position, the clamp assembly includes both an overcenter lock system for securing the collar in the retracted position and a backup auxiliary lock in the event of failure. The system further provides for centering the separator bowl on its axis of rotation to prevent undue vibration.

Abstract: The chuck includes a slitted body with an axial bore that holds the tool shank during rotation of the chuck. A gripping sleeve applies compressive pressure via cam elements to reduce the diameter of the axial bore. A spring biased locking sleeve can activate locking elements to lock the gripping sleeve to the body member in the locked position.An engagement mechanism connects the chuck to a drive spindle and also has a mounting mechanism for facilitating automated mounting of the chuck to a drive spindle.

Abstract: An improved tool holding device has at least one tool engaging member for selectively engaging a tool during operation, such as the jaw blades of a chuck device and gripping jaw blades of a collet device. The tool holding device includes an actuating mechanism for causing the tool engaging members to selectively engage upon a tool. The actuating mechanism includes at least two components in frictional engagement. At least a portion of the frictional engaging components is coated with a solid film lubricant.

Abstract: An improved tool holder system and method of using the same is disclosed, characterized by use of a plural extension member assemblies which permit the rapid adaptation of conventional machine tool holders for use in both automated machine tool changers as well as manual machine tool changer systems. In addition, the present invention discloses an improved method of mounting a cutting tool within a tool holder to accurately position the cutting tool height within the tool holder and subsequently prevent any backing out of the cutting tool from the tool holder during the cutting operation. Further, an improved apparatus and method of ensuring concentric mounting cutting tool within a tool holder is disclosed.

Abstract: A hand power tool has a tool holder, and a blocking device for the tool holder, the blocking device being connectable with the tool holder and provided with a key unlockable blocking body which secured the blocking device from undesired withdrawal. When the blocking body is connected with the tool holder it blocks the tool holder from insertion of a tool.

Abstract: An improved collet lock arrangement for a hand-held power tool having a housing is provided. The collet lock arrangement includes a powered rotatable shaft including a base portion and distal end portion defining a collet for adaptably connecting a driver tool attachment thereto and a locking structure for securely locking the shaft to the housing to selectively prevent the shaft from rotating when in a locked position while allowing the shaft to freely rotate in an unlocked position. The locking structure has a locking sleeve coaxially coupled around the shaft for axial movement relative thereto between the locked and unlocked positions, a clamp nut fixedly connected to the housing, and a sleeve guide non-rotatably coupling the locking sleeve to the clamp nut. The clamp nut and sleeve guide are coaxially arranged for coaxially receiving therethrough the shaft and the locking sleeve.

Abstract: The present invention relates to a method and process for manufacturing an improved machine tool collet. The invention further relates to an improved machine tool collet having design parameters optimized to maximize the gripping strength of the collet. The collet according to the invention is of the type having a plurality of gripping jaws spaced around a common longitudinal axis with resilient material between the gripping jaws. The method includes calculating the total torque generated on a bar passing through the collet for a given collet configuration having predetermined design parameters. The total torque includes the torque generated just prior to a toggle condition occurring between the gripping jaws and the bar and the maximum moment force generated between the gripping jaws and the bar at a toggle condition.

Abstract: This invention relates to a method and apparatus for retaining disk-like structures, such as magnetic memory substrate plates, or disks, during machining, cutting, or grinding operations. A fluid is applied to one surface of the disk to retain the other surface of the disk against a chuck at a force which is sufficient to maintain the disk against the chuck during the operations.

Abstract: The present invention relates to an apparatus for and method of picking-up a center hub used with a flexible disk at a step of fixing the center hub and flexible disk to each other or at a similar step in the flexible disk cartridge manufacturing process. The spindle is lowered toward the center hub until the centering pin provided at the end thereof is projected into the central hole in the central portion of the center hub for centering. Next, the collet chuck is lowered until the end claws thereof are projected into the concavity in the central portion of the center hub. At this time, the flange portion of the center hub is raised due to as attraction exerted thereon by the magnets buried in the outer end face portion of the collet chuck other than at the end claws.