Effect of Measuring Instrument Eccentricity and Tilt Error on Circularity Form Error

From power stations to power tools, from the smallest watch to the largest car, all contain round components. In precision machining of cylindrical parts, the measurement and evaluation of roundness (also called circularity in ASME Geometric Dimensioning & Tolerancing Y14.5) and cylindricity are indispensable components to quantify form tolerance. Of all the methods of measuring these form errors, the most precise is the one with accurate spindle/turntable type measuring instrument. On the instrument, the component is rotated on a highly accurate spindle which provides an imaginary circular datum. The workpiece axis is aligned with the axis of the spindle by means of a centering and tilt adjustment leveling table. In this article, the authors have investigated the dependence of circularity form error on instrument’s centering error (also known as eccentricity) and tilt error. It would be intriguing to map this nonlinear relationship within its effective boundaries and to investigate the limits beyond which the measurement costs and time remain no more efficient. In this study, a test part with different circular and cylindrical features were studied with varying levels of predetermined instrument eccentricity and tilt errors. Additionally, this article explores the significance of incorporating these parameters into undergraduate and graduate engineering curricula, and be taught as an improved toolkit to the aspiring engineers, process engineers and quality control professionals.