The Series 1510 miniature precision ball screw from (Steinmeyer Inc., Burlington, Mass., comes with a double nut preloaded by a spring between the two nuts.
This compensates for torque variations due to inaccurately ground threads. It also compensates for wear over time, so the ball screw continuously delivers smooth motion with near-constant idling torque. The standard nut has a cylindrical body with an attaching thread. It is available in diameters from 3 to 16 mm with pitches down to 0.5 mm.