Roundness measurement using limacons – D.G. Chetwynd

Most roundness measuring systems which find automatically the “reference circles” to a profile have used, for convenience,
a limacon figure as an approximation to a circle. However this figure has important geometrical properties relevant to
normal roundness measurement and can be regarded as the basis of an analytical system rather than an instrumental
convenience. This paper examines some of the implications of the limacon method under practical conditions by
comparison with circular references. It includes a comparison of roundness measurements taken using
limacon references according to minimum zone, minimum circumscribing, maximu’m inscribing an d least squares
criteria