R gauge, also called R model, radius gauge.
The R gauge is a tool that measures the arc radius using the light gap method. During measurement, the measurement surface of the R gauge must be in complete and close contact with the arc of the workpiece. When there is no gap between the measurement surface and the arc of the workpiece, the degree of circularity of the workpiece is indicated by the R gauge for this purpose. digital. Due to visual inspection, the accuracy is not very high and qualitative measurements can only be made.