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Power Transmission


to those of the bearings, because they must be capable of spacing the bearings to accuracies of 1-2 micrometres or better. Bearing ring faces must be well aligned and solidly seated and there must be extreme cleanliness during assembly. Axial adjustment does not increase bearing friction and is therefore preferred for very low torque applications.


Ready-to-mount bearings


With Duplex bearings, the means of achieving preload is built-in. This method can be the simplest for the customer, who receives the bearings ready-to-mount and with the confidence that those bearings are preloaded to the precise requirement of the application. Duplex bearings are matched pairs of bearings that have


bearing are offset axially. Threaded members, shims and spacers are typical methods of providing rigid preloads via axial adjustment. Great care and accuracy are required in order to avoid


excessive take up of internal clearance, which may occur during setup by overloading the bearings, or during operation due to thermal expansion. Precision lapped shims are normally preferred to threaded


members, as helical threads can lead to misalignment. The shims should be manufactured to parallelism tolerances equal


their inner or outer ring faces selectively relieved by a precise amount known as the preload offset. When the bearings are clamped together during installation, the offset faces align, establishing a permanent preload in the bearing set. Duplex bearings are normally speed-limited due to heat generated by this rigid preload. Duplexing is used mainly where the requirement is for


predictable radial and axial rigidity. Duplex bearings can withstand bi-directional thrust loads or heavy uni-directional thrust loads. Other advantages include their ease of assembly and minimum runout. l


Enter 50 or ✔ at www.engineerlive.com/ede


Gary Hughes is Product Engineering Manager, Barden Corporation UK Ltd., Estover, Plymouth, Devon, UK. www.bardenbearings.co.uk


Circle 50A or ✔ at www.engineerlive.com/ede


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