Roller screw ( effective roller diameter)


A roller screw, also known as a planetary roller screw or satellite roller screw, is a low-friction precision screw-type actuator, a mechanical device for converting rotational motion to linear motion, or vice versa. A roller screw is a mechanical actuator similar to a ball screw that uses rollers as the load transfer elements between nut and screw instead of balls. The rollers are typically threaded but may also be grooved depending on roller screw type. The three main elements of a typical planetary roller screw are the screw shaft, nut and planetary roller. Standard roller screws are typically identified by screw diameter (typically ranging from 3.5mm – 200mm) and lead (1mm – 42mm). The threading of the screw (3 – 6 starts) is either rolled (lower capacity) or ground (higher capacity). The diameters of the nut and rollers (7 – 14 in quantity) are simple functions of the screw diameter and lead.

Related formulas


rdThe effective roller diameter (mm)
sdThe effective screw diameter, or pitch diameter (mm)
tThe thread starts on nut and screw (dimensionless)