Design Application

Sealing at an angle

PROBLEM Angular-contact ball bearings form the mainstay of many machine tool spindle applications.

In most designs one outer ring land is relieved but a drawback of this approach is that the profile of the ring no longer leaves enough material in which a seal recess can be machined. It is for this reason that many angular-contact bearings in machine tool applications are not greased for life as many of their peers are in other applications.

This lack of 'in-built' lubrication of necessitates the need for ancillary lubrication systems, adding cost and complexity to machine tool systems.

SOLUTION FAG/Barden says it has come up with a solution to this dilemma. The "revolutionary new design" of its 2RSD bearings will allow spindle builders (and other users of angular contact bearings) to enjoy the benefits of cost, life and maintenance-free operation offered by a sealed bearing architecture.

The advance has been made possible with the introduction of a new seal and recess that specifically target angular-contact bearings. The depth of the recess is not as great as that machined into standard bearings and it can be accommodated into the narrow cross section left by the relief machined into the outer rings.

The introduction of the seal will allow grease retention and the exclusion of contamination from both sides of the bearing. The retention characteristics are equal to standard seal designs and, as there is no contact with the inner ring, friction is minimised and bearing temperature does not rise.

APPLICATIONS The B7 (standard sealed) and HCB7 (sealed with ceramic balls) variants of the 2RSD bearings are supplied ready to fit and are fully interchangeable with standard open type bearings.

The bearings are provided, lubricated for life, under controlled conditions by the manufacturer, which removes many of the preparation steps required by other non-sealed bearings.

Operational tests have shown that after many hours of operation, the sealed bearings were much cleaner than their non-sealed counterparts. Because the grease life is prolonged and the bearings use Cronidur 30 material the bearing life can be up to five times more than open-type designs. MF

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