A ball spline is a linear motion component consisting of a spline shaft with ground raceway grooves and a nut containing recirculating steel balls. Unlike a linear bushing, the balls sit in grooves, so the nut can transmit torque while still moving freely along the shaft.
Typical specifications include shaft diameter, basic dynamic load rating, permissible torque, accuracy grade and preload. For miniature splines (Φ3–Φ12 mm), shaft straightness and groove grinding quality determine positioning repeatability.
Ball splines are used where a single axis must both move linearly and rotate or resist rotation: SMT nozzle heads, SCARA Z-axes, die bonders, and indexing machines.