MICROFORM CALIBRATIONS IN SURFACE METROLOGY

Microform calibrations include the measurement of complex profile form s and position errors of micrometer scale in combination with the meas urement of deviations from a specified profile and surface texture of profile segments. Tolerances on the profile form are specified and may correspond geometrically to surface texture parameters. One example o f micrform calibration is the calibration of Rockwell diamond indenter s used for hardness testing of materials. Previously reported measurem ent techniques do not meet the stringent microform calibration require ments for Rockwell diamond indenters. Inadequate microform calibration of hardness indenters may be one factor resulting in significant inte rlaboratory differences in results from Rockwell hardness tests. By us ing a stylus instrument, in combination with a series of calibration a nd check standards and calibration and measurement uncertainty calcula tion procedures, we have calibrated Rockwell diamond indenters in acco rdance with the definitions specified in ISO and ASTM standards. Our p rocedures for conducting microform calibration yield total measurement uncertainties less than ten percent of the tolerance values specified in ISO and ASTM standards. In this paper, the general calibration req uirements, calibration and check standards, and calibration and uncert ainty procedures that we use in performing microform calibrations are introduced. Some general considerations on stylus radius correction, d ata fitting, calibration traceability, uncertainty and reproductibilit y are also discussed.