National foreword

This British Standard reproduces verbatim ISO 3161:1999 and implements it as the UK national standard. It supersedes BS 4084:1996 which is withdrawn.

The UK participation in its preparation was entrusted by Technical Committee ACE/12, Aerospace fasteners and fastening systems, to Subcommittee ACE/12/1, Aerospace fasteners and fastening systems (International), which has the responsibility to:

aid enquirers to understand the text;
present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed;
monitor related international and European developments and promulgate them in the UK.

A list of organizations represented on this subcommittee can be obtained on request to its secretary.

Cross-references

The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue.

A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application.

Compliance with a British Standard does not of itself confer immunity from legal obligations.

This British Standard, having been prepared under the direction of the Engineering Sector Committee, was published under the authority of the Standards Committee and comes into effect on 15 January 2000

Summary of pages

This document comprises a front cover, an inside front cover, the ISO title page, pages ii and iii, a blank page, pages 1 to 40, an inside back cover and a back cover.

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

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.

Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.

International Standard ISO 3161 was prepared by Technical Committee ISO/TC 20, Aircraftandspacevehicles, Subcommittee SC 4, Aerospacefastenersystems.

This third edition cancels and replaces the second edition (ISO 3161:1996), which has been technically revised.

1 Scope

This International Standard specifies the general requirements and limit dimensions of inch series UNJ threads with controlled root radius for aerospace construction.

It determines the basic triangular profile for this type of thread and gives a system for designating the diameter and number of threads per inch combinations. For all diameters 0,060 in (1,524 mm) to 6,000 in (152,4 mm), it offers in the form of tables the basic dimensions and tolerances for a selection of diameter and number of threads per inch combinations. It also provides the method of calculation for the dimensions and tolerances for any diameter and number of threads per inch combination not given in the tables, including threads with a diameter in excess of 6.000 in.

2 Normative reference

3 Term and definition

4 Basic profile

4.1 Symbols

4.2 Basic profile dimensions

4.3 Basic dimensions of thread

5 Series of threads

5.1 General

5.2 Diameters

5.3 Number of threads per inch (n)

5.4 Threads outside selection

6 Tolerances

6.1 Length of thread engagement used for calculating the pitch diameter tolerances

6.2 Position of tolerances

6.3 Values of tolerances for profile dimensions and tolerances of the profile form

6.4 Provisions for coated threads

7 Gauging

8 Designation of threads

8.1 General

8.2 Thread symbols with increasing (progressive) pitches

8.3 Thread symbols with constant (uniform) pitches

8.4 Special threads

8.5 Designation of threads having modified crests

9 Tables

BS A 346:2000

UNJ threads. General requirements and limit dimensions

Current, Under Review

Published:

15 Jan 2000