STR ball transfer units are composed of a large precision ball rolling on a bed of small precision balls seated in a hardened hemispheric cup.

All balls are ground and heat treated; they start moving when the main big ball (which is made of hardened steel, stainless steel or plastic) rolls, to let it move with the lowest possible friction and guarantee a regular movement. This kind of construction allows moving with small effort any kind of heavy material, whose surface is plain, smooth and rigid enough.

Friction is extremely reduced and a smooth movement is provided at a speed of 2m/sec. In this way, very heavy loads can be easily moved.

One production range includes different kinds of ball transfer units, starting from a main supporting ball's dimension of 8mm up to a maximum of 90 mm in steel, stainless steel or polyacetal plastic material, and loading capacities from 15 kg to 2000 kg. Basically there are tow kinds of products: Machined Heavy Duty units (studied for heavy shock loads and long life applications), and Pressed Light Duty units (suitable for light loads). The housings of the units are bright metal zinc plated or completely stainless steel made and they incorporate self cleaning bottom holes and oiled felt sealing system (except SP8-12-15-25). This is available on request on SP 15 and 25 series only. We can also provide ball transfer units with main balls made of AISI 440C, AISI 304, AISI 316, teflon, glass, with various coupling between big and small balls.


The ball transfer units can be assembled horizontally, vertically or ball down, they do not need hard maintenance and are provided with felt sealing (or a plastic on if they have to be exposed to high temperature). Under particular conditions (high humidity, dyes, soaking baths, sea water) the usual correct activity can be damaged; in order to repair these inconveniences, some kinds of ball transfer units have a dirt exit hole in the bottom.


STR ball transfer units are widely used in all industries to allow freely conveying in any direction of heavy loads with low stress. Most popular applications include: