A self-balancing line shaft of a machine tool includes a spindle device, a cutter tool holder and at least one balancing assembly. The spindle device includes a spindle extending along and rotatable about an axis, and at least one precision lock nut threadedly engaged with and rotated with the spindle. The cutter tool holder is coaxially connected and rotated with the spindle. The balancing assembly includes an annular groove formed in one of the precision lock nut and the cutter tool holder and extending along a circle path surrounding the axis, and a plurality of weight members disposed in the annular groove to be moved in a direction opposite to a rotation unbalance during rotation of the spindle such that the center of mass of the whole rotating system is close to the axis.

A self-balancing line shaft of a machine tool includes a spindle device, a cutter tool holder and at least one balancing assembly. The spindle device includes a spindle extending along and rotatable about an axis, and at least one precision lock nut threadedly engaged with and rotated with the spindle. The cutter tool holder is coaxially connected and rotated with the spindle. The balancing assembly includes an annular groove formed in one of the precision lock nut and the cutter tool holder and extending along a circle path surrounding the axis, and a plurality of weight members disposed in the annular groove to be moved in a direction opposite to a rotation unbalance during rotation of the spindle such that the center of mass of the whole rotating system is close to the axis.

A self-balancing line shaft of a machine tool includes a spindle device, a cutter tool holder and at least one balancing assembly. The spindle device includes a spindle extending along and rotatable about an axis, and at least one precision lock nut threadedly engaged with and rotated with the spindle. The cutter tool holder is coaxially connected and rotated with the spindle. The balancing assembly includes an annular groove formed in one of the precision lock nut and the cutter tool holder and extending along a circle path surrounding the axis, and a plurality of weight members disposed in the annular groove to be moved in a direction opposite to a rotation unbalance during rotation of the spindle such that the center of mass of the whole rotating system is close to the axis.

A tool-changing device which is used on machine tools (18). Here, provision is made to carry out positioning of a tool holder (2) in the working position (6) of the tool holder with the aid of the locking element (7) of the drive device (4) of the tool-changing device (1). An adjusting movement (22) of the locking element (7) into the locking position (9) of the locking element on the tool holder (2) that is required for the use of the tool (3) is used to position the tool holder (2) in the working position (6) thereof, by the adjusting movement (2) of the locking element (7) being converted into a positioning movement (21) of the tool holders (2).

A tool-changing device which is used on machine tools (18). Here, provision is made to carry out positioning of a tool holder (2) in the working position (6) of the tool holder with the aid of the locking element (7) of the drive device (4) of the tool-changing device (1). An adjusting movement (22) of the locking element (7) into the locking position (9) of the locking element on the tool holder (2) that is required for the use of the tool (3) is used to position the tool holder (2) in the working position (6) thereof, by the adjusting movement (2) of the locking element (7) being converted into a positioning movement (21) of the tool holders (2).

A screwdriver allows a screwing operation and an unscrewing operation to be performed smoothly. A screwdriver includes a housing, a motor including a stator and a rotor, a spindle, a clutch assembly, and a spindle locking assembly. The spindle includes a rod to which a tip tool is attachable, and is supported by the housing in a manner movable between an advanced position and a retracted position in a front-rear direction. The spindle has a reception hole extending frontward from a rear end face of the spindle. The clutch assembly transmits a rotational force from the rotor to the spindle in response to the spindle moving to the retracted position during forward rotation of the rotor. The spindle locking assembly transmits a rotational force from the rotor to the spindle during reverse rotation of the rotor, and includes the reception hole, and a countershaft placed in the reception hole.

A screwdriver allows a screwing operation and an unscrewing operation to be performed smoothly. A screwdriver includes a housing, a motor including a stator and a rotor, a spindle, a clutch assembly, and a spindle locking assembly. The spindle includes a rod to which a tip tool is attachable, and is supported by the housing in a manner movable between an advanced position and a retracted position in a front-rear direction. The spindle has a reception hole extending frontward from a rear end face of the spindle. The clutch assembly transmits a rotational force from the rotor to the spindle in response to the spindle moving to the retracted position during forward rotation of the rotor. The spindle locking assembly transmits a rotational force from the rotor to the spindle during reverse rotation of the rotor, and includes the reception hole, and a countershaft placed in the reception hole.

The inventive working spindle comprises a spindle housing and a spindle shaft with axial positioning surface and axial contact surface by which the correct axial position of each fitting provided spindle shaft in the spindle housing is obtained. For torque-proof holding of the spindle shaft in the spindle housing, preferably with stationary motor, a braking unit is provided that comprises a radial outer part that is coupled with the spindle housing in a torque-proof manner and a radial inner part that is coupled with the spindle shaft in a torque-proof manner. The largest outer diameter of the peripheral surface of the inner part is smaller than the narrowest location of the through-opening of the spindle housing between the braking unit and the tool side end of the spindle housing. For this reason the spindle shaft can be readily removed from the spindle housing without disassembly measures of the braking unit, if required, and can be reinserted in reverse route. The inventive working spindle is simply constructed and can be versatilely used. Concurrently it is remarkably easy to maintain.

A control method for the use of a core drilling system including a core drill and a feed device for driving the core drill along a machine holding device. The method includes the steps of determining the end of a core drilling operation on the basis of reaching a predetermined threshold value for at least one corresponding predefined drilling parameter; and of selecting a reversing mode for retracting a drilling tool out of a borehole at a reversing rotational speed which corresponds to a multiple of a predetermined tapping rotational speed of the drilling tool at the beginning of the core drilling operation.

A control method for the use of a core drilling system including a core drill and a feed device for driving the core drill along a machine holding device. The method includes the steps of determining the end of a core drilling operation on the basis of reaching a predetermined threshold value for at least one corresponding predefined drilling parameter; and of selecting a reversing mode for retracting a drilling tool out of a borehole at a reversing rotational speed which corresponds to a multiple of a predetermined tapping rotational speed of the drilling tool at the beginning of the core drilling operation.