Abstract
An application of transmitted-type microinterferometry on the form measurement of small spherical parts is investigated.Replicas of the spherical parts to be measured, made of methyl-and ethyl-metaacrylate on a plane mirror, are immersed in oil and observed on an interference microscope with a low magnification. By using proper oil, Newton's rings can be observed over required area on the spherical part irrespective of surface finish.By measuring the radii of curvature of five steel balls and their repricas with microscopic collimation method (Guild's mirror method), it is confirmed that the replicas have satisfactory reproducibility and stability.The equation of a sphere representing the form of each specimen is derived by measuring the positions of interference fringes and by applying Deming's method of least squares and mean radius of curvature and form errors are evaluated.As an example of practical application, the tip forms of the standard hammers for Shore hardness test are measured by this method. The result is compared with the measurement by microscopic collimation and it is revealed that the radius of about 1 mm can be measured with the precision of about 3 μm in standard deviation if the specimen has a good sphericity.
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More From: Journal of the Japan Society of Precision Engineering
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