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Angular contact bearings for machine tool spindles

22 April 2013

NSK’s RobustShot series high precision angular contact bearings are designed to satisfy the exacting demands of motorised machine tool spindles for smooth, reliable operation, rapid acceleration/deceleration, higher speeds – over 3million dmn - and longer life.

The RobustShot series meets the requirements of the global machine tool industry for ever increasing spindle speeds to enable a wider range of machining operations to be performed on a single machine tool.

For machines to provide this flexibility it is essential that their spindles are able to supply high speed performance and short start-stop times (i.e. high acceleration and deceleration).

These requirements place increasing demands upon spindle bearings. A reliable, continuous supply of lubrication to the working surfaces of the bearings is a particular challenge; without this lubrication, bearing operation would be impossible.

The NSK developed RobustShot series of angular-contact ball bearings meets this requirement. Solving the technical problems experienced with conventional oil-air lubrication methods that attempt to inject the lubricant into bearings from the side using nozzles, the RobustShot series employs a system where lubricating oil is routed straight to the working surfaces on the bearing outer ring, via a circular groove and a through-hole in the outer ring. This guarantees a reliable, even supply of lubricant, enabling rotational speeds of over 3 million dmn.

The fact that there are no injection nozzles between the bearings with RobustShot system enables extremely compact spindles to be designed. In addition, because the RobustShot angular-contact ball bearings have the same dimensions as grease lubricated bearings, it is easier to use spindle components as modules across various spindle series.

This is one major factor in increasing cost competitiveness for spindle manufacturers. A second is the RobustShot series compliance with DIN ISO standards. This means that the bearings fit the same size envelope as conventional angular contact bearings, making them easy to retrofit to existing spindle designs.

The RobustShot series is available in nominal bore sizes from 30mm to 110mm, and can be supplied in a wide range of configurations: SU universal design (single row), DU universal design (double row), DB back-to-back (O-arrangement), DF face-to-face (X-arrangement), DT tandem arrangement, and Triplex and Quadruplex sets.

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