ABSTRACT
This chapter summarizes the efforts at National Bureau of Standards (NBS) in the early 1920s to improve the calibration of precision gage blocks. Gage blocks have been the major source of length standardization for industry, and their calibration is one of the most important high precision calibrations made in dimensional metrology. By the end of the nineteenth century, the idea of interchangeable parts begun by Eli Whitney had been accepted by industrial nations as the model for industrial manufacturing. One of the drawbacks to this new system was that, in order to control the size of parts, numerous gages were needed to check the parts and set the calibrations of measuring instruments. In the United States, Henry Ford enthusiastically adopted the idea, and the use of gage blocks was eventually adopted as the primary transfer standard for length in industry.
