Product Description:

The 1MR240H-A087 is a rotor element supplied by Bosch Rexroth Indramat for the 1MB High-Speed Asynchronous Motors series. The component serves as the rotating core of a frameless spindle motor, converting electromagnetic torque from the stator into the high surface velocities required in metal-cutting and grinding spindles. By integrating directly into the machine shaft instead of using a complete housed motor, it allows compact layouts and reduced thermal mass in industrial automation. This arrangement is common in machine-tool spindles that require high stiffness and direct integration with the shaft assembly.

The rotor dimensions determine its compatibility with associated stators and toolholders. The frame classification of 240 establishes the overall cross-section, while the internal step measures 107 mm, providing a shoulder that aligns the part in the spindle cartridge. The outside diameter of 163.9 mm maximizes magnetic area without exceeding the housing bore. Axially, the active stack is 320 mm, and the central bore of 87 mm uses an H6 fit to maintain concentricity with the drawbar. This bore uses a step interference fit to improve torque transfer without keys. The runout tolerance of 0.04 mm limits radial error at high speed, while the spindle relief diameter is limited to 86.8 mm and the spindle seat diameter of 87 mm mates with the front bearing set. Mounting threads of M4×0.5 are provided for transport fixtures.

Balancing and overall spindle geometry are set by assembly features rather than by the magnetic core alone. A balance ring secured to the M8 thread allows residual vibration to be trimmed after the rotor is inserted to the minimum spindle length of 335 mm within the machine. The motor length code H marks this version as the longest build in the family, providing a longer magnetic path while keeping the unit inside the available installation envelope. A 30° taper on the nose supports coupling to the tool interface and provides self-centering during drawbar engagement.