roller_screws

most of the pictures on this page were lifted from http://www.hobbycnc.hu/CNC/Otletek/Otletek.htm
if anyone can translate Hungarian it'd be appreciated

Roller Screws  

Roller screws are an alternative to acme and ballscrews - they efficiently convert rotary movement into linear movement by using what is essentially a high helix angle rack and pinion. The thread form of a high quality roller screw is actually an involute curve, but standard 60 degree threads will work just fine for most applications.

> Here is an old SKF roller screw catalog for your perusal. (5.4MB pdf)

There are two types of commercial roller screw rollers - planetary and recirculating (also known as grooved) - the planetary type ensures that the rollers don't touch each other or anything else, and appears to be the most common type. The planetary rollers have helical grooves, like a screw, but the recirculating ones just have multiple angled grooves, or otherwise they would unscrew from their holder.

And this is how it goes together:

Now here is a homebuilt design that looks fairly easy to build, actually: