Easy Experimental Cylindricity Tolerance Verifications in Close-Range Bushings of Automotive Hinges

In many areas of engineering, there is a growing need for accuracy and reliability of assembled systems. To ensure this accuracy, and to ensure the correct function of the part within the assembly, both dimensional and geometric tolerances must be correctly set at the design stage. An important tool, now irreplaceable in any CAD software, is the Geometric dimensioning and tolerancing (GD&T) control, which through algorithms can assign geometric and dimensional tolerances. In this manuscript authors present an original procedure for measuring and verifying the cylindricity tolerance of hinge bushings. A millesimal bore gauges was used to measure the internal diameter at different angular positions in each bushings’ sections. Starting from these measurements, the cylindricity of the inner surface of the bushing is evaluated through the least square cylinder (LSC) method. The angular deviation of the bushing axis is then evaluated based on the cylindricity assessment. The procedure allows to easily check, during assembly operations, whether the objects to be assembled are within tolerance without the need to resort to the most expensive and complex procedure through Coordinate Measuring Machines (CMM). Operation could be carried out on an assembly line by an operator using a pre-set spreadsheet. The results of the experimental measurements are compared with the output of a coordinate measuring machine to demonstrate the accuracy of the proposed procedure.