NPL Notes on Screw Gauges
Now available for free download: NPL Notes on Screw Gauges (
PDF, 7.8 MB).
Background and history
As a result of experience gained in testing large numbers of screw gauges during the first World War, the Metrology Division of the National Physical Laboratory published a pamphlet "Notes on Screw Gauges", to assist firms who were unfamiliar with the accuracy required in the manufacture and testing of gauges. This pamphlet has been in continuous demand since it was first published, and was reprinted and revised several times. In 1951 the pamphlet was extensively rewritten and was renamed "Gauging and Measuring Screw Threads", forming the first of the series of handbooks prepared at the National Physical Laboratory under the general title of "Notes on Applied Science". Further editions followed, the latest in 1961.
The latest edition
Interchangeability and quality of fit of nuts, bolts, and other screwed fasteners e.g. threaded pipe joints, require precision in manufacture as monitored by screw gauges. Methods of measurement have been developed continuously at NPL over 70 years and are described in NPL Notes on Screw Gauges. Plugs and rings, parallel or taper, over a range from the BA series to 20 inch casing for oil wells are considered. This report deals with the principles and practice of measuring screw threads and includes technical data and references which will be useful to a wide range of industry users, including designers and inspectors, as well as to machine operators and students.