Determining roundness from profilograms

Summary

• 1. If the deviation of the points on the actual profile from the inscribing circumference be taken as a criterion of roundness (this criterion has been included in the draft standard), the evaluation from the profilogram of the nature and value of deviations from roundness amount to the following:

• a) finding an inscribing circumference for the profilogram recorded in polar coordinates, or an inscribing cosine wave for a profilogram recorded in rectangular coordinates;

• b) finding the deviations of points on the profilogram from the inscribing circumference or cosine wave. (soL)The rules for obtaining a single-valued determination of an inscribing circumference or cosine wave are given in this article.

• 2. In evaluating roundness from a profilogram recorded in polar coordinates, a graphic elimination of eccentricity entails a systematic error. In order to reduce its value a certain relation must be maintained between the recording radius, magnification of the recording device and the eccentricity determined from (9).