National foreword

This British Standard is the UK implementation of EN ISO 7040:2025. It is identical to ISO 7040:2025. It supersedes BS EN ISO 7040:2012, which is withdrawn.

The UK participation in its preparation was entrusted to Technical Committee FME/9, Fasteners.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

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

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 June 2025.

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.

The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of ISO document should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see https://www.iso.org/directives-and-policies.html).

ISO draws attention to the possibility that the implementation of this document may involve the use of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s) which may be required to implement this document. However, implementers are cautioned that this may not represent the latest information, which may be obtained from the patent database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.

Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISO's adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 2, Fasteners, Subcommittee SC 12, Fasteners with metric internal thread, in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 185, Fasteners, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).

This fourth edition cancels and replaces the third edition (ISO 7040:2012) which has been technically revised.

The main changes are as follows:

the design principles of these nuts have been clarified in scope (see Note);
for nuts with D < M5, appropriate nut design in accordance with ISO/TR 16224, style 1, has been added in Annex A (historical nuts not conforming to ISO 898‑2 because of their heigth m_min less than 0,8D have been deleted);
style, relevant property classes and related quenching and tempering conditions for steel nuts have been specified in Clause 5 in accordance with ISO 898‑2 (see Table 3);
stainless steel nuts have been added in accordance with ISO 3506‑2;
M7, M18, M22, M27, M33 and M39 have been added;
d_a,max has been specified with two decimal places;
d_w,min for sizes D ≤ M5 has been changed from s_min – IT16 to s_min – IT15 in order to have a larger bearing surface area and thus less contact pressure;
h_max for M5 and M20 has been increased so that regular, high and thin nuts have an identical room for the prevailing torque feature (h_max – m_min) to accommodate the non-metallic insert; h_min has therefore been increased in accordance with the specified tolerance (see Tables 1 and 2);
specifications for marking and labelling have been added as Clause 6.

Any feedback or questions on this document should be directed to the user's national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

This European Standard was approved by CEN on 20 June 2025.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czechia, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and United Kingdom.

European foreword

This document (EN ISO 7040:2025) has been prepared by Technical Committee ISO/TC 2 " Fasteners " in collaboration with Technical Committee CEN/TC 185 “Fasteners” the secretariat of which is held by BSI.

This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by December 2025, and conflicting national standards shall be withdrawn at the latest by December 2025.

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

This document supersedes EN ISO 7040:2012.

Any feedback and questions on this document should be directed to the users’ national standards body/national committee. A complete listing of these bodies can be found on the CEN website.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the United Kingdom.

Endorsement notice

The text of ISO 7040:2025 has been approved by CEN as EN ISO 7040:2025 without any modification.

1 Scope

This document specifies the characteristics of prevailing torque hexagon regular nuts (with non‑metallic insert), in steel and stainless steel, with metric coarse pitch thread M3 to M39, and with product grades A and B.

NOTE These nuts are designed with an overall height equal to m_min (as specified in ISO 898‑2 and ISO 4032 for style 1) plus the prevailing torque feature. The height of the prevailing torque feature (h_max – m_min) for the non-metallic insert is identical for regular, high and thin nuts for a given diameter.

Nuts with sizes D < M5 and design principles in accordance with style 1 are specified in Annex A.

If in certain cases other specifications are requested, property classes and stainless steel grades can be selected from ISO 898‑2 or ISO 3506‑2.

2 Normative references

3 Terms and definitions

4 Dimensions

5 Requirements and reference International Standards

6 Marking and labelling

6.1 Marking on product

6.2 Labelling on package

7 Designation

Bibliography

BS EN ISO 7040:2025

Fasteners. Prevailing torque hexagon nuts. Regular nuts (with non-metallic insert)

Current

Published:

30 Jun 2025