Linear Slides

Page 5 Specifications subject to change without notice or incurring obligations – Engineering Considerations for Product Selection 1-4-99 Steel shell linear ball bearings – Yes! Inexpensive linear ball bearings – No! Fabco-Air linear ball bearing slides use high qual ity, high precision “steel shell” bearings that provide superior load support. Here's why. . With steel shell bearings, the bearing load is dis- tributed back to the housing bore via the entire bearing O.D. The ball bearing's I.D. is unaffected by the housing bore size, therefore providing a very precise “fit” to the guide shaft. Bearing-to- shaft pre-load can be accurately established and maintained. Competitor's slides, equipped with bearings with plastic housings and load-plate type ball circuit construction can be problematic. This self aligning bearing concept is useful in applications where misalignment is likely. But it is unnecessary and often detrimental when used with packaged linear slides in which bearing housings are machined to such a high degree of accuracy. Problem: bearing load is distributed back to the housing bore through small, crown shaped “bumps” on the load plates. High loads and/ or sudden impacts cannot be supported by such a small area, causing the crowns to deform the housing bore. Furthermore the ball bearing's I.D. is DIRECTLY affected by the housing bore size. Enlarged housing bores, whether caused by deformation or by improperly finished I.D.s will cause bearing “slop” and toolbar “play”. Conversely, bores that are too small, such as when closed up by over anodizing, will increase the pre-load to the shaft. Excessive pre-load causes bearing overload and premature bearing and/or shaft failure. Some recently developed plastic housing linear ball bearings have a ring or band in the center to help support the load. This feature still does not have support equal to the steel shell bearings used on Fabco-Air slides, and because the ring is “split”, the bearing's I.D. is still directly affected by the final housing bore diameter. Steel shell Housing Steel shell Ball circuit Ball circuit Plastic shell Load-plate type ball circuit Plastic and load-plate type bearing construction Plastic shell Crown shaped “Bump” Housing Load-plate type ball circuit Clearance spaces