Calculation of the accuracy of a snap-gauge to control the diameter of the bearing journals of the camshaft

Control of linear dimensions in mechanical engineering can have carried out for two purposes. The first goal is to determine the size of the quantity in absolute units with the required precision. The second goal is to determine the suitability of the part, that is, the fact that its size is in the range of limiting dimensions, characterized by the tolerance. The second goal is easiest to accomplish with gauges, which increase accuracy and reduce the labor intensity of inspection. It had revealed that the standard gauge for monitoring the diameter $054−0.105−0.065$ of the bearing journals of the camshaft of YaMZ engines cannot be used, since the tolerance is between the standard values IT7=30 µm and IT8=46 µm, and the deviations are so they are not-standard from the standpoint of the system of tolerances and fits according to ISO 286-1: 2010. The calculation of the executive dimensions of the snap-gauge for diameter control $054−0.105−0.065$ of the bearing journals of the camshaft of YaMZ engines during the overhaul of engines. The tolerance for the production of the go and not-go sides has determined, which is 7 microns. The magnitude of the inward shift in the middle of the tolerance fit of the passage side was - 6 µm. The wear limit had assumed to be 3 µm, as it is normalized for gauges that control IT7 tolerances. The tolerance for the manufacture of the dimensions of the control gauge was taken equal to 3 microns, the calculation of the limiting dimensions of the control gauge had performed. A diagram of the location of the tolerance fits of the snap-gauge for controlling the diameter $054−0.105−0.065$ of the bearing journals of the camshaft of YaMZ engines has been built.