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How to properly secure bearings

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tech talk Learn more at www.igus.com/info/plain-plastic-bearings Part One: Why do bearings move out? If the housing is not to their liking, plastic bearings do not hesitate to move out of their mounting holes. In this three-part series, we'll cover why that happens and how to prevent it, how to secure bearings axially, and why the anti-rotational feature is necessary. How to properly secure bearings Bearings will move out of the housing if the press fit is lost and there is no additional axial securing. Typically, plain bearings are installed with an arbor press. The holes they are fit into are slightly smaller than the outer diameter of the plain bearings. Therefore, the bearing is kept in place and secured by mechanical tension. If this tension is lower than the push out force generated by the load and movement of the pivot point, the bearing moves out of the mounting hole. The result: a metal shaft surface scraping away at a metal housing—and a plastic plain bearing torn to pieces. arbor press used to press-fit a plain bearing during installation Two reasons for loss of press-fit are high temperatures and high loads. If the temperature in the bearing position rises above the material specific threshold, the material begins to loosen, as it cannot maintain the mechanical tension. The other root cause for losing press-fit is an overly high load that stays over prolonged periods. This is also a material-specific value and describes a concept called "creeping," which is a slow process of deformation where the material starts to give in to the load. This deformation can also lead to loss of press fit and bearings moving out. Another more inconsequential (but actually more frequently encountered) issue can be the housing bore being out of tolerance. In that case, if the press fit is too loose due to an oversized housing bore, it can be even more likely that the bearing will move out.

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