BS 3580:1964

This guide relates to applications of triangular (V-form) screw threads where strength considerations have to be borne in mind. It is intended to draw the attention of designers to the principal strength factors to be considered in following out details of a design, with some mention of measures which may be adopted to improve strengths. The guide has been largely based on results obtained with steel components and while many of the considerations will apply to other materials, care should be exercised in the interpretation of certain data. For quantitative data, it will often be necessary to refer to an appropriate source of information, such as a component or material manufacturer or a Government laboratory, though it is emphasized that information on many aspects of the subject is still inadequate.

The guide also relates to behaviour at temperatures where creep and metallurgical changes are unimportant and is concerned with screwed connections, i.e., with “bolt” and “nut” combinations; the strength of a threaded bar, not assembled with a nut, is not considered. For the latter, reference should be made to appropriate theoretical and experimental work on notched and threaded bars (¹) (²)¹⁾.

NOTE “Nut” and “bolt” are used throughout in the general sense to mean internally and externally threaded members respectively, except where it is obvious that ordinary nuts and bolts are meant.

The effect of the various strength factors are considered under the following headings:

Materials

Method of production

General form of threaded members and type of loading

Diameter, pitch, D/p ratio and length of engagement

Thread form

Depth of engagement, degree of fit and truncation of threads

Friction conditions.

Gives guidance on the design of load-bearing connections and discusses the various factors which influence the strength of such connections with the aim of giving some indication of the effect of these factors. Only screw threads of triangular (V) form are considered and the data presented have been collected from tests conducted mainly on steel components.