A motorized precision spindle apparatus (10) including an outer cartridge spindle (12) supported on a motor cartridge spindle (14) and a motor-driven outer cartridge spindle shaft (16) supported for rotation on bearings (22) disposed between the shaft (16) and an outer spindle shaft housing (20). A tool holder (26) releasably holds a tool in position for rotation with the shaft (16). A draw-bar (30) is supported through the shaft (16) and the motor cartridge spindle (14) for reciprocal axial motion, is connected to the tool holder (26), and is biased in an axial direction that causes the tool holder (26) to grip a tool (28). An actuator (32) is connected to the draw-bar (30) and moves the draw-bar (30) in a direction opposite the bias, thereby releasing any tool the holder may be holding. An isolation tube (36) is supported within the motor cartridge spindle (14), is connected to the shaft (16), and supports the shaft (16) against transmitting axial forces to the bearings (22).