What Is a Crossed Roller Bearing?

A crossed roller bearing is a precision bearing whose cylindrical rollers alternate orientation at 90° to each other inside a V-shaped raceway. Because adjacent rollers face opposite directions, one bearing simultaneously carries radial loads, bidirectional axial loads, and overturning (moment) loads.

Why Robot Joints Prefer It

Standard deep-groove ball bearings mainly take radial load; covering combined loads usually requires paired bearings and a bigger structure. Robot joint loads are inherently combined — a humanoid hip joint simultaneously supports body weight (axial), leg-swing centrifugal force (radial), and the bending moment of a cantilevered leg (overturning). A crossed roller bearing handles all three load types in a single bearing position:

• High stiffness: roller line contact resists deformation better than ball point contact.
• High rotational precision: a stable reference for output-side measurement by dual absolute encoders.
• Space savings: the single-bearing design keeps joint motors thinner and lighter.

The BXI 85/70/50-series joint motors fit crossed roller bearings at the output across the whole lineup, from load-bearing legs to dexterous arms.