Publishing and copyright information

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

© BSI 2009

ISBN 978 0 580 68654 2

The following BSI references relate to the work on this standard:
Committee reference FME/9
Draft for comment 07/30158490 DC

Publication history

First published June 1949
Second edition, November 1953
Third edition, as Parts 1 and 2, September 1962
Fourth edition, as Part 1, 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This part of BS 1580 supersedes BS 1580: Parts 1 & 2:1962, which is withdrawn.

Relationship with other publications

BS 1580 is now published in two parts:

Part 1: Screw threads with diameters 14 in and larger – Requirements
Part 3: Screw threads with diameters below 14 in – Requirements

This part of BS 1580 is intended for use with BS 919‑1 and BS 919‑4 which specify the corresponding screw gauges.

Information about this document

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

The diameter/pitch combinations which are recognized as standard threads in the ISO inch system include the American numbered sizes. A copy of the ISO table of these standard threads (but with the omission of the numbered sizes), is reproduced in Table 1 of this part of BS 1580.

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.

Section 1 General

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 nominal diameters 14 in and above, having the ISO basic profile as specified in BS ISO 68‑2:1998.

The part of BS 1580 specifies the following unified thread series as follows:

standard variable pitch series:
- a coarse thread series (UNC) from 14 in to 4 in nominal diameter;
- a fine thread series (UNF) from 14 in to 112 in nominal diameter;
- an extra fine thread series (UNEF) from 14 in to 11116 in nominal diameter;
standard constant pitch series:
- a 4-threads per inch series (4 UN) from 258 in to 6 in nominal diameter;
- a 6-threads per inch series (6 UN) from 1716 in to 6 in nominal diameter;
- an 8-threads per inch series (8 UN) from 1116 in to 6 in nominal diameter;
- a 12-threads per inch series (12 UN) from 58 in to 6 in nominal diameter;
- a 16-threads per inch series (16 UN) from 716 in to 6 in nominal diameter;
- a 20-threads per inch series (20 UN) from 516 in to 3 in nominal diameter;
- a 28-threads per inch series (28 UN) from 516 in to 112 in nominal diameter;
- a 32-threads per inch series (32 UN) from 716 in to 1 in nominal diameter;
a special thread series (UNS) with diameter/pitch combinations other than those specified for the standard series.

NOTE 1 A transition fit series and an interference fit series of UNC and UNF threads for application to screwed studs are given in BS 2693‑1 and -2, respectively.

NOTE 2 Bases of tolerances and allowances are given in Annex A, guidance for calculating limits of size is given in Annex B, information on crest forms of external threads is given in Annex C, some general symbols are given in Annex D (see 3.2), information on tolerances is given in Annex E, guidance on selection and use of the standard unified thread series is given in Annex F and information and guidance on tolerance classes is given in Annex G.

2 Normative references

3 Terms and definitions and symbols

4 Profile of unified screw threads

Section 2 Standard series

5 Diameter/pitch combinations

6 Tolerance classes of external and internal threads

7 Limits of size, and tolerances, for uncoated threads

8 Allowances for uncoated threads

9 Coated threads

10 Gauges

11 Designation of unified screw threads

Section 3 Special series (UNS)

12 Diameter/pitch combinations, fractional sizes

13 Diameter/pitch combinations, decimal sizes

14 Tolerance classes of external and internal UNS threads

15 Tolerances and allowances

16 Coated UNS threads

17 Designation of UNS threads

Bibliography

BS 1580-1:2007

Unified screw threads - Screw threads with diameters ¼ in and larger. Requirements

Current

Published:

31 Dec 2007