THK RA7008 C UUCC0 Kreuzrollenlager (70x86x8)

As a crossed roller bearing, this bearing carries loads from all directions as well as tilting moments. The mounting dimensions are 70x86x8 mm and the weight is 0.1 kg; technical details beyond these are shown in the specification table. A non-contact seal on both sides screens the rolling chamber of this rotary-table and joint arrangement without noticeably raising the frictional torque.

In the crossed roller bearing, adjacent cylindrical rollers are offset by ninety degrees against one another and run on a common, cross-divided raceway. Every second roller therefore carries one direction and the one between it the other, so that a single row simultaneously takes radial forces, axial forces in both directions and tilting moments — duties that would otherwise call for an adjusted pair or a bearing set.

High tilting stiffness and low axial play in a small section follow from this compact, usually preloaded arrangement, which is why the design is used on rotary tables, swivel axes and joints. The non-contact seal on both sides forms a narrow gap to the counterface, holds back coarse dirt and barely adds to the power loss, which is dominated by the preload anyway; against fine dust and moisture it protects less than a contact version.

After hardening, standard bearing steel provides raceway hardness and dimensional stability; for the design, tilting moment, preload, speed and contamination level should be assessed together.