Generally speaking Screws on most hand operated machines use "acme" type screws and nuts. the screws inherently have backlash, the older they get or used, the more backlash. Backlash being the amount a hand wheel is turned in either direction until the nut and screw engage.
a ball screw uses hardend balls in a metal case instead of a nut, these "nuts" travel in a special screw with threads to match the radius of the balls. there is little or no backlash. You will find these types of screws on cnc machines where backlash cannot be tolerated.
for more info on ball screws try "the rockford ball screw company"
Regarding Ball Screews
Re: Regarding Ball Screews
