High precision roundness

Project Description

A hemispherical glass roundness standard will be circulated among the participants. The laboratories are requested to provide the roundness measurements at the standard 3 mm height in two measuring planes using error separation. Every laboratory in the comparison has a Taylor Hobson Talyrond 73 as roundness measurement instrument, but the error separation is done in different ways in every laboratory.

The measuring instructions for the hemisphere are the same as in a previous BCR high precision roundness comparison, with the exception that no harmonics are required and MZ centering is also not required.

Final Report 2001-04-27

A Hemispherical Glass Roundness Standard was circulated among the participants during 17.9.98-26.7.99.The first draft report was made 14th July 2000 and the final report was made 27th March 2001.
The measured departure from roundness varied from 5.6 nm to 20 nm and the calculated En < 1. The reason for the big variation in values of departure from roundness is believed to be unstability of the artefact.