There is provided an innovative tool mounting device for a turning center in which special manipulation is not required even with a simple configuration, and whereby when a cutting tool is clamped/fixed, the bearing unit is deformed by the retraction force of the drawbar because the cutting tool is supported by the ram, the tapered shank is automatically pressed to the mounting engagement unit in a state in which the cutting tool is supported by the ram, an automatic mechanical lock in a state of dual-surface restraint can be implemented, and the turning tool can be securely clamped/fixed. The tool mounting device for a turning center is configured so that a positioning strike receiving portion (29) is provided to a ram (3) with which the positioning outer surface (28) of a turning tool (1B) makes contact when at least the turning tool (1B) is clamped/fixed, the positioning outer surface (28) strikes the positioning strike receiving portion (29) when a drawbar (7) is retracted, a bearing unit (2) is deformed by the retraction force applied to the drawbar (7) of the clamp mechanism (8) because the retracted position of the drawbar (7) is maintained in the struck state, and the mounting engagement unit 6 exerts elastic pressure/contact on the tapered shank (5).

At least one end portion of a grinding or dressing wheel has a frustoconical projection with a relatively short frustoconical external surface extending into a frustoconical recess which is provided therefor in one end portion of a rotary tool supporting spindle. The wheel is formed with an end face which is located in the region of the maximum-diameter portion of its external surface and abuts against a complementary end face on the spindle to fix the wheel in a preselected axial position wherein the wheel is held by a tension rod which extends into an axial passage of the spindle. The positions of the projection and recess can be reversed.

The cutting tool comprises a cutting head and a holding shank and, for transferring the torque introduced on the cutting head during machining, faces are provided in a recess of the bearing surface of the holding shank on which engage the stop faces of the cutting head. A fixed connection between the cutting head and the holding shank is brought about by a threaded pin screwed into a tapped hole on the holding shank and which projects into a conical blind hole on the cutting head. As the torque is transferred in the vicinity of the bearing surface, the threaded pin is only loaded to the extent that there is a clearance-free connection between the cutting head and the holding shank.

A tool holder apparatus mountable on a machine spindle which apparatus is adjustable and provides a solid stable support for the tool holder to eliminate any gap or spacing between the end of a machine spindle and the support collar of the tool holder.

A coupling (10; 100; 200; 400) for use between the modules of a modular tool holder arm, in particular a machine tool, with a male coupling part (12; 112; 212; 412), forming the end of a first module and containing a central, axially symmetrical journal (14; 114; 214; 414), and a female coupling part (20; 120; 220; 320; 420), forming the end of a second module connected to the first module and containing a central, axially symmetrical seat (18; 118; 218; 318; 418). In the engaged state, the two coupling parts form a shaft-hub seat (14, 18; 114, 118; 214, 218; 414, 418) as a first transmission location and at least one other transmission location. At least under load, a first stress field (26) develops in the first transmission location, and another stress field (27, 28) develops in the at least one other transmission location, wherein separation (24, 25; 124, 125; 224; 324; 424) of the first transmission location from the at least one other transmission location is provided, so that the respective stress field (26, 27, 28) is formed without being impacted by the respective other transmission location(s).