A Thomson Precision ball spline consists of mating inner and outer races containing concave axial races and a complement of bearing balls. The balls provide the only physical contact between the inner and outer races. Unlimited rolling travel is achieved by diverting the path of the balls at the extremes of the outer race into the end cap return circuit. This provides a closed loop through which the balls recirculate when the races are displaced axially relative to each other. The bearing balls resist radial displacement resulting from torque loads.

• Efficiency - coefficient of friction .007 maximum
• Hardness - minimum of RC 56 in ball race
• Lash - .005 inch maximum standard play perpendicular to rotational axis