Unification of Screw Threads

Abstract

An attempt was made after the 1914–18 war to follow up the need which had then arisen for common British and American standard threads, and Sir Richard Glazebrook, on behalf of British industry, went to America in order to put forward a proposal for the unification of screw threads. This unfortunately was not adopted, and the diversity of practice between the United States and Canada and Great Britain on the form and dimensions of the screw thread has been a source of trouble in the recent war even more than in the 1914–18 war. A number of conferences, under the auspices of the Combined Production and Resources Board of the United States, United Kingdom, and Canada, have therefore taken place at the instigation of the respective Governments in an endeavour to establish common systems for the main types of screw thread used in the three countries.

The Combined Production and Resources Board's Conferences in 1943 and 1944 reached agreement on a truncated Whitworth thread series, primarily for application in the war effort. Preliminary discussions were also opened on the major subjects of unifying the American National and British Whitworth series, and on pipe threads, instrument threads, and buttress and Acme threads. To pursue these discussions, a further series of conferences were arranged to take place in the autumn of 1945 at Ottawa, and as it was desirable to obtain the views of British engineers and industrialists on these projects for the guidance of the British delegates attending the Ottawa Conference, the Institution subcommittee arranged for the papers and discussions that are printed on the following pages. The British views were also sought by the British Standards Institution in order to assist them to fulfil the request of the Government to implement the technical aspects of any recommendations adopted.