A plain bearing slide system has a carriage mounted on a slide by use of bearing pads. Each bearing pad is coated with a layer of polymeric material having a convex surface, and is arranged to ride on a counterface. The combined thickness of the layer and a layer providing the counterface is such that the difference between the static and dynamic coefficients of friction is substantially less than the difference associated with the material when used in bulk bearings. A slide system using PTFE, and with a combined thickness of the layers of 2 to 3 micrometers, operated as a measuring instrument under ambient conditions such that the PTFE is substantially non-eroding, has proved capable of providing measurements to an accuracy of 0.05 nanometers.
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