What is wringing of slip gauges?

Answer 1

Wringing is the property of measuring faces of a gauge block of adhering, by sliding or pressing the gauge against the measuring faces of the another gauge blocks without the use of any extraneous means. While wringing the gauges, it is assumed that the surfaces have been cleaned thoroughly and exhibit a good standard of flatness and smoothness. The wrung gauge can be handled as a unit without the need for clamping all the pieces together. It is believed that the phenomenon of wringing is due to molecular adhesion between the liquid film and mating surfaces of the flat surfaces. It has been found that the gap between two wrung flat pieces is of the order of 0.00635 microns from which it would be very clear that the film thickness in two wrung flat pieces contributes no effect in measurement process. It should be remembered that slip gauges are wrung together by hand through a combined blinding and twisting motion. First the gauge is oscillated slightly with very light pressure over other gauge so as to detect presence of any foreign particles between the sur- faces. One gauge is then placed perpendicular to other using standard gauging pressure and rotary motion is then applied until the blocks are lined up. In this way air is expelled from between the gauge faces causing the two blocks to adhere. This adherence is caused partly by molecular attraction and partly by atmospheric pressure. The overall thickness of the wrung gauges, for most practical purposes, is the sum of the individual sizes in combination.