Publishing and copyright information

The BSI copyright notice displayed in this document indicates when the document was last issued.

The following BSI references relate to the work on this standard:

Committee reference FME/9

Draft for comment 07/30158492 DC

Publication history

First published August 1965
Second edition, December 2007

Foreword

Publishing information

This part of BS 1580 is published by BSI and came into effect on 31 December 2007. It was prepared by Subcommittee SFTSE/1, Screws and fasteners technical specification committee, under the authority of Technical Committee FME/9, Nuts, bolts and accessories. A list of organizations represented on this committee can be obtained on request to its secretary.

Supersession

This part of BS 1580 supersedes BS 1580‑3:1965, which is withdrawn.

Relationship with other publications

BS 1580 is now published in two parts

Part 1: Screw threads with diameters14in and larger – Requirements
Part 3: Screw threads with diameters below14in – Requirements

This part of BS 1580 is intended for use with BS 919‑1 which specifies the corresponding screw gauges.

Information about this document

This part of BS 1580 has been fully revised to bring it up to date.

The range of diameters covered by this part of BS 1580 falls within the range of the B.A. screw thread sizes given in BS 93. The various pitches given for the same diameter in the unified system, however, offer a wider selection of diameter/pitch combinations for specific applications than do those in the B.A. system. The UNF series gives the closest approximation to the B.A. diameter/pitch combinations.

Hazard warnings

WARNING — Attention is drawn to the fact that, with the different screw thread forms available, there is the possibility of a mismatch, which is potentially hazardous. It is the responsibility of the designer of the end product to ensure that this possibility is reduced to a minimum. For further information on mismatches of screw thread systems see PD 6494.

Presentational conventions

The provisions of this standard are presented in roman (i.e. upright) type. Its requirements are expressed in sentences in which the principal auxiliary verb is “shall”.

Commentary, explanation and general informative material is presented in smaller italic type, and does not constitute a normative element.

Contractual and legal considerations

This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

1 Scope

This part of BS 1580 specifies limits of sizes, and tolerances, for single-start, clearance-fit unified screw threads, in inch units with diameters below 14 in.

This part of BS 1580 specifies unified screw threads from Number 0 (0.060 in diameter) to Number 12 (0.216 in diameter), known as the “numbered sizes” in the following standard series:

a coarse thread (UNC) series;
a fine thread (UNF) series;
for Number 12 threads, an extra fine (UNEF) 32 threads per inch diameter/pitch combination.
NOTE Unified screw threads below 14 in diameter for attachment purposes and for general use in the aircraft industry are specified in Annex A.

2 Normative references

3 Terms and definitions and symbols

4 Thread profiles

5 Diameter/pitch combinations

6 Tolerance classes

7 Tolerances, allowances and limits of size for uncoated threads

8 Coated threads

8.1 General

8.2 Class 2A external threads

8.3 Class 2AG external threads

8.4 Class 3A external threads

8.5 Class 2B internal threads

8.6 Class 3B internal threads

9 Designation of threads

9.1 Basic designation

9.2 Additional designations

10 Gauges

Bibliography

BS 1580-3:2007

Unified screw threads - Screw threads with diameters below ¼ in. Requirements

Current

Published:

31 Dec 2007