A spindle arrangement such as a machine tool spindle which rotates at high rotational speeds includes separate elements, which may be in the form of a counter-weight and a driving and positioning shoulder, that are mounted on the spindle nose. The separate elements are secured to the spindle nose by locking pins that arranged at an angle to the rotational axis of the spindle nose. During rotation of the spindle nose, centrifugal force gives the locking pins a component force in a direction causing the elements to be wedged and the locking pins to be pressed into the bores.

A numerically controlled automatic tool changing machining center is provided with a rotary driven spindle concentric within which is a spindle bar that may be reciprocated out from or into the spindle by a hydraulic cylinder. Located at the forward end of the spindle bar is a tool receiving socket which is operative to releasably engage the shank of a single toolholder or multiple spindle toolhead transferred to the spindle bar from the machine tool storage magazine by a tool transfer arm. When a large, single toolholder is engaged by the spindle bar, the spindle bar is retracted into the spindle to urge the large single toolholder against the nose of the spindle. In the case of a multiple spindle toolhead being engaged by the spindle bar, the spindle bar is retracted into the spindle to urge the multiple spindle toolhead against the spindlehead so that locating pins extending rearwardly from the multiple spindle toolhead body seat in complementary locating cones spaced about the spindle on spindlehead to secure the multiple spindle toolhead body against rotation.

A high speed motorized spindle is provided with a hollow tool-driving shaft having tool clamping means slidably disposed therein. A piston rod actuates the tool clamping means to slide in one direction to release a tool shank and spring means actuates the tool clamping means to slide in the other direction for gripping the tool shank when the piston rod is withdrawn. The piston rod actuates a collect clamp to clamp the tool-driving shaft against movement from tool unclamping forces when the tool clamping means is slid in the direction to release the tool shank. The tool-driving shaft is releasably oriented in a tool exchange position by a cam plate rotatable therewith being engaged by solenoid actuated cam lock member movably mounted in the housing.

A device for clamping a rod to stop axial and/or rotative movement between the rod and the device. The device includes pressure and clamp units, the clamp unit having a bushing fixed therein and provided with a radially resilient center section normally sized to permit movement of the rod therein. The pressure unit has an actuating piston normally held under fluid pressure in one position but movable under spring pressure toward a second position should the fluid pressure be lost or released. Such movement results in the application of pressure to the bushing to radially deflect its center section inwardly into clamping engagement with the rod to stop its movement. The center section remains clamped on the rod until sufficient fluid pressure is applied to the actuating piston to move it back to its first position thus permitting radial expansion of the center section to release the rod for movement.