Dimensional MeasurementsDiameter MeasurementsTechnical Contacts: Please contact the technical staff before shipping instruments or standards to the address listed below. Mailing Address:
back to top | back to index of dimensional measurements Special Tests of Cylindrical Diameter Standards (i.e., Plug and Pin Gages) (11010S-11014S)Plain plug gages (not threaded) are calibrated using a laser-interferometer-based micrometer. The uncertainty of the diameter is dependent on the geometry of the artifact, particularly the roundness. Unless instructed otherwise either a specific diameter (if marked on the cylinder) or the average diameter (if unmarked) at the center of the gage is measured. Please consult the technical contacts listed above for alternative measurement points or auxiliary measurements needed to assure a satisfactory level of accuracy. back to top | back to index of dimensional measurements Measuring Wires for Threads and Gears (11020C-11021C)This service provides for measurement of the diameter of thread and gear measuring wires by either comparison to NIST master wires or absolute calibration with a laser-interferometer-based micrometer. Both types of calibrations are carried out under a measurement assurance program based on the measurement of control wires. Thread measuring wires for 60° and 29° threads are tested for compliance with the latest specifications in commercial use. These wires are calibrated, and the deformed diameter under standard conditions (as specified out in the Federal Standard H-28 Screw Thread Standards) are reported. The primary elements of uncertainty are based on the reproducibility of the check standards and estimates of the uncertainty in the deformation corrections. For wires in good condition the expanded uncertainty is 0.10 µm (4 µ in). All measuring wires submitted for test should be in substantially new condition. Each wire should be appropriately bottled, and the bottle should be labeled with an identification number. In shipping wires, extreme care should be taken to prevent corrosion; all wires should be properly greased and their bottles rigidly contained inside an appropriate packing case. back to top | back to index of dimensional measurements Roundness Calibration Specimens and Measurements (13020S)NIST provides special tests on the roundness of optical roundness standards. The deviation from roundness at eight or more positions around nominally round standards is determined, as well as the size of the calibration step or deviation from roundness is determined. The departure from roundness of components and gages is measured, and the results are reported in graphical form. NIST will provide special tests of roundness calibration specimens by request. Please consult with the technical contacts listed. back to top | back to index of dimensional measurements Special Tests of Roundness (13030S)NIST provides special tests on the roundness of optical roundness standards. The deviation from roundness at eight or more positions around nominally round standards is determined, as well as the size of the calibration step or deviation from roundness is determined. The departure from roundness of components and gages is measured, and the results are reported in graphical form. NIST will provide special tests of roundness calibration specimens by request. Please consult with the technical contacts listed. back to top | back to index of dimensional measurements Special Tests of Spherical Diameter Standards: Balls (11030S-11034S)NIST provides special tests to determine the spericity of a ball. Ball diameters are determined from multiple comparisons in random orientations with either NIST master balls or calibrated gage block stacks. The ball diameter reported is the undeformed size as calculated using the Hertz relations. For calibrations at a specific orientation or with roundness traces to reduce the geometric components of uncertainty, the technical contact listed should be contacted before the calibration is submitted. back to top | back to index of dimensional measurements Special Tests of Internal Diameter Standards: Ring Gages (11040S)NIST provides special tests to determine the internal diameter of ring gages. Ring gages are normally calibrated using a high-accuracy CMM. Alternately, NIST provides special tests that can calibrate certain gages by mechanical comparison to a calibrated gage block stack. The gage block stack is calibrated by multicolor interferometry to minimize the uncertainty due to wringing and geometry variations in the stack. The diameter is measured at one marked orientation. The technical contact listed should be consulted about calibrations needed in different orientations or roundness traces needed for a fuller determination of the ring geometry, if needed. back to top | back to index of dimensional measurements Special Tests of Diameter (11050S)NIST has a wide variety of state-of-the-art metrology equipment and provides services associated with dimensional quality control as special tests in addition to the regular and special tests described above. A three-dimensional measuring machine is available for calibration of two- and three-dimensional ball plates, two-dimensional grid plates, and other artifacts of complex shape. Please consult with the technical contacts listed. back to top | back to index of dimensional measurements References-Diameter MeasurementsFederal Standard H-28, Screw Thread Standards for Federal Services, English and metric versions. These handbooks are available from the General Services Administration (GSA). American National Standard B1.2, ANSI, New York. On the Measurement of Thread Measuring Wires, B. N. Norden, Natl. Bur. Stand. (U.S.) Report 10 987 (Jan.1973). Measurements of Cylindrical Standards, R. C. Veale, Natl. Bur. Stand. (U.S.), NBSIR 73-136 (1973). On the Compression of Cylinders in Contact with a Plane Surface, B. Norden, Natl. Bur. Stand. (U.S.), NBSIR 73-243 (1973). back to top | back to index of dimensional measurements Program questions: Calibrations Phone: 301-975-2200, Fax: 301-869-3548 NIST, 100 Bureau Drive, Stop 2300, Gaithersburg, MD 20899-2300 |
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