The Precision Screw in Scientific Instruments of the 17th - 19th Centuries: With Particular Reference to Astronomical, Nautical and Surveying Instruments

The application and perfecting of the screw for scientific purposes has been studied for the period ca. 1600-1900. An historical review of the means of producing screws, with special attention to precision screws, provides the basis for historical studies of the application of the screw to various types of micrometers and dividing engines. Developmental histories of micrometers, mainly astronomical, and dividing engines are also provided. Means of studying the profiles and accuracy of screws have been developed; the methods adopted employ techniques of period searching which are used for variable star studies. The Jurkevich-Swingler period searching technique (a modified Fourier transform method) has been used to study precision screws which may be fundamentally characterized as a periodic phenonena. Using the primary period of the screw thread (the pitch) an 'atlas' of screw profiles has been produced to determine the characteristics of the screws and to search for patterns in the profiles as a function of maker, period and use. The profiles and direct measurements of the micrometer screws have also provided estimates of the errors of the Instruments. Summaries and graphical analysis of these data have permitted a search for relationships between some of the fundamental characteristics of various classes of screws. These studies have identified the most serious types of errors encountered in precision-screws. Estimates of the accuracy of the best machining capabilities and the accuracy of astronomical observations and scale dividing, etc. as a function of time are provided. These estimates are compared with contemporary estimates and modern estimates for other types of related mechanism.