from web site
A precision linear shaft is a cylindrical rod with high accuracy that directs motion in linear bushings or bearings. In order to provide smooth, reliable, and regulated linear motion in applications requiring strict control, these shafts are engineered to exact tolerances. In contrast to conventional shafts, these are produced under precise specifications and put through a thorough testing process to guarantee their load-bearing capacity, surface quality, and dimensional precision. Their main purpose? to act as the rail or track that allows machine parts to glide, rotate, or slide with the least amount of friction and the highest precision.