The preload of Spindle Bearings determines the running characteristic of a Working Spindle and the Work Piece quality thereof. Heavy preload raises stiffness, lower preload enables to work with higher speed of the bearing.
Advanced design of Machine Tools often meets a wider range of speeds. At one hand a sufficient stiffness of the bearings for higher working forces is necessary, at the other hand higher speed for efficient cutting operations.
Only a bearing design qualified to adapt the preload whilst operating will achieve best possible results.
The UKF System VARIORING makes it possible by oil pressure to vary the preload of a bearing from „light" via „middle" to „heavy" in order to adapt the bearing to given operation with highest possible speed and stiffness. This begins as „light" preload. The Outer Ring of a Double Row Spindle Bearing (design USO) gets a circumferential groove with O-Ring seals at both sides. Under oil pressure into the groove the Outer Ring will be compressed centrically by a few micron which rise the inner preload of the bearing.