In a collaborative effort with Mitutoyo America Corp, The National Institute of Standards and Technology (NIST) has recently begun calibrating roundness of precision spheres and hemispheres more accurately than any other laboratory in the world. Using a standard Mitutoyo RA-H5000 roundness tester, NIST has developed calibration procedures that achieve a measuring uncertainty of less than 3 nanometers, or close to 1/10 of a millionth of an inch.
A federal agency within the U.S. Commerce Dept, NIST has a mission that includes providing advanced measurement services in support of U.S. industry. Within its 578-acre campus in Gaithersburg, MD lies the Engineering Metrology Group, whose laboratories and equipment provide industry with standards directly traceable to national and international standards through use of state-of-the-art calibration services.
In the past, NIST''s ability to provide roundness calibrations had not kept up with the accuracy needs of industry. But by adopting techniques recently developed for use in conjunction with the Mitutoyo RA-H5000, NIST has become the international leader in roundness calibration. (Pictured, the Mitutoyo RA-H5000 in NIST''s Advanced Measurement Laboratory; the machine control room, in background, is separated from the machine in order to maintain the best possible environmental conditions.)
In a presentation at the 2005 NCSLI International Workshop and Symposium, Dr. Theodore Doiron, acting group leader for NIST''s Engineering Metrology Group, explained that the keys to achieving remarkably low uncertainty are a special error separation measuring method, a tight temperature-controlled environment, and the stability of the RA-H5000.
Some of the labs within the Advanced Measurement Laboratory control temperature to an incredible 0.01°C, and the RA-H5000 is located in one of these. NIST researchers have found that the RA-H5000, used in this environment, has a long-term repeatability of around 1 nanometer, which is key to their world class uncertainty.
Dr. James Salsbury, corporate metrologist at Mitutoyo America Corp, worked with NIST researchers to develop this measurement process.
"The new roundness capability at NIST will quietly impact many U.S. industries where roundness is controlled to tighter and tighter tolerances," says Dr. Salsbury. "This is quite significant, and I''m very excited for NIST."