Form Errors of a Spherical Part of a Rockwell Diamond Indenter

Abstract

The form errors of a spherical part of a Rockwell diamond indenter are analysed by applying micro-interferometry and microscopic collimation which have been developed by Kentaro Yamamoto. The conclusions are as follows ;
1) The apex form of the indenter is in many cases made up of eight spherical parts owing to ununiform machinability of diamond considering fringe patterns of a micro interferometer.
2) In the view field of a microscopic collimator several images of a pin hole of the collimator can be observed corresponding to the spherical parts mentioned above. And the images are converged or diverged as the indenter is displaced along the optical axis of the collimator.
3) The position of the indenter where the images are converged indicates the position of the center of the indenter within the angular aperture of the objective lens.
4) The convergency of the images depends on the amount of the form error, and so the accuracy of determining the position of the center of curvature depends on its form error. When an indenter is finished in high grade the accuracy of the positioning is ±3 microns with con fidence coefficient of 95%.