prEN 3723

• Abstract:

  This document specifies the characteristics of self-locking hexagonal nuts in FE-PA92HT, MoS2 coated, for aerospace applications.; Classification: 1 100 MPa1/425 °C2.

• Status: Not Published
• Publication Date: 14-Sep-2027
• ICS: 49.030.20 - Bolts, screws, studs
• ICS: 49.030.30 - Nuts
• Technical Committee: ASD-STAN - Aerospace
• Drafting Committee: ASD-STAN/D 3/S 2 - Fasteners
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 16-Jul-2026
• Completion Date: 16-Jul-2026
• Ref Project: oSIST prEN 3723:2026 - Aerospace series - Nuts, hexagonal, self-locking, in heat resisting steel FE-PA92HT (A286), MoS2 coated Aerospace - Classification : 1 100 MPa (at ambient temperature) / 425 °C

• Revises: EN 3723:1996 - Aerospace series - Nuts, hexagonal, self-locking, in heat resisting steel, FE-PA92HT (A286), MoS2 coated - Classification: 1 100 MPa (at ambient temperature)/425°C
• Effective Date: 20-Jan-2026

prEN 3723 is a draft European Standard from CEN for aerospace self-locking hexagonal nuts made of heat resisting steel FE-PA92HT (A286) with an MoS2 coating. It specifies the nuts’ characteristics, dimensions, materials, surface treatment, marking and technical specification for the 1 100 MPa / 425 °C classification. Engineers, buyers and quality teams use it to define and check this specific aerospace nut type.

What does prEN 3723 specify?

prEN 3723 specifies self-locking hexagonal nuts in FE-PA92HT for aerospace applications. The document focuses on the product definition and how the nuts are to be made, identified and qualified.

The standard is organized into:

• Scope
• Normative references
• Terms and definitions
• Required characteristics
• Designation
• Marking
• Technical specification
• Bibliography

Clause 4 carries the main product requirements, with Figure 1 and Tables 1 and 2 giving the detailed form, size and marking information used in practice.

What are the key requirements of prEN 3723?

prEN 3723 ties the nuts to a defined geometry, material set, coating and qualification route. The practical result is that a supplier has to build, mark and qualify the nuts to the same aerospace definition every time.

Clause 4.1 - configuration, dimensions, tolerances and mass

Clause 4.1 requires the configuration, dimensions, tolerances and mass to follow Figure 1 and Table 1. The dimensions and tolerances are given in millimetres and apply before the MoS coating is applied.

In practice, this means the drawing and inspection points are fixed before coating thickness is taken into account. The notes in Figure 1 also state that the finished nuts shall fit a standard socket wrench, so form details must still work with installation tools.

Clause 4.2 - materials

Clause 4.2 allows the material to come from EN 2399, EN 3638, EN 3639 or TR 3791. For MJ3 and MJ4, SAE AMS5525 may be used at the manufacturer’s discretion.

This matters because material choice is part of conformity, not just procurement preference. The manufacturer has to choose from the listed material routes and keep that choice consistent with the nut size.

Clause 4.3 - surface treatment

Clause 4.3 requires the surface treatment to follow EN 2491.

In practice, the coating method is not left open-ended. The MoS2 dry lubricant treatment has to be applied by the referenced aerospace coating method.

Designation, marking and technical specification

Clause 5 gives the designation format, with “NUT EN3723-050” shown as the example and “050” identified as the thread code. Clause 6 requires marking in accordance with EN 2424, with the marking style depending on the diameter code. Clause 7 requires the technical specification to follow EN 3752, with modifications in this document.

Clause 7 also requires the manufacturer to be an approved production organization for aerospace products and to maintain a suitable quality management system, such as EN 9100 or an equivalent accepted system. Product qualification has to use a documented aerospace qualification procedure, such as EN 9133 or an equivalent procedure, unless the customer and supplier agree otherwise.

What terms does prEN 3723 define?

prEN 3723 gives no clause-based definitions, but it uses several key terms and abbreviations that matter for use of the standard.

• FE-PA92HT (A286) - the heat resisting steel named in the title and used for the nuts.
• MoS2 - molybdenum disulphide, the dry lubricant coating required for the nuts.
• MJ threads - the aerospace thread form used for the dimensions and designation.
• Classification 1 100 MPa / 425 °C - the strength and temperature class used to identify the nuts.
• Approved production organization - a manufacturer accepted for aerospace production and able to maintain the required quality system.
• Qualification of products - the documented procedure used to show the nuts meet the aerospace standard product requirements.

Who uses prEN 3723?

prEN 3723 is used by aerospace fastener manufacturers, their subcontractors, and quality and procurement teams that specify or inspect self-locking nuts. It is also used by organizations responsible for approval, product qualification and marking control.

For buyers and engineers, it helps define the exact nut style to request. For manufacturers and test laboratories, it sets the material, coating, identification and qualification framework to follow.

What changed in prEN 3723 from the previous edition?

prEN 3723 supersedes EN 3723:1996. The foreword states three significant changes:

• Clause 3, “Terms and definitions”, was added.
• Clause 4.2 added TR 3791 and SAE AMS5525 as material references.
• Clause 7 was editorially revised.

Which standards are used with prEN 3723?

prEN 3723 refers to several standards that support its requirements:

• EN 2399, EN 3638 and EN 3639 - permitted material sources.
• TR 3791 - material guidance for self-locking nuts and inserts up to 425 °C.
• SAE AMS5525 - alternate material standard for MJ3 and MJ4.
• EN 2491 - MoS2 dry lubricant coating methods.
• EN 2424 - marking of aerospace products.
• EN 3752 - base technical specification for self-locking nuts with MJ threads.
• ISO 5855-2 - limit dimensions for MJ bolts and nuts.
• ISO 7995 - dimensions for hexagonal self-locking nuts with MJ threads.
• EN 9100 - example quality management system for aerospace organizations.
• EN 9133 - example qualification procedure for aerospace standard products.

What does the prEN 3723 document contain?

prEN 3723 contains one main configuration figure, one dimensional and mass table, and one marking table. Figure 1 shows the nut form and identifies the areas for thread, marking, entry form and the self-locking zone.

Table 1 lists the size range from thread code 030 to 120 and gives the related dimensions and mass values. Table 2 links diameter code to the marking style. The document also includes a designation example and a technical specification clause that connects manufacture, approval and product qualification to referenced aerospace standards.

SLOVENSKI STANDARD
01-julij-2026
Aeronavtika - Matice, šestrobe, samozapiralne, iz toplotnoodpornega jekla FE-
PA92HT (A286), prevlečene z MoS2 za letalstvo - Klasifikacija: 1100 MPa (pri
temperaturi okolice)/425 °C
Aerospace series - Nuts, hexagonal, self-locking, in heat resisting steel FE-PA92HT
(A286), MoS2 coated Aerospace - Classification : 1 100 MPa (at ambient temperature) /
425 °C
Luft‑ und Raumfahrt - Sechskantmutter, selbstsichernd, aus hochwarmfesten Stahl
FE‑PA92HT (A286), MoS2‑beschichtet - Klasse: 1 100 MPa (bei Raumtemperatur)/425
°C
Ta slovenski standard je istoveten z: prEN 3723
ICS:
49.025.10 Jekla Steels
49.030.30 Matice Nuts
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2026
ICS 49.030.20 Will supersede EN 3723:1996
English Version
Aerospace series - Nuts, hexagonal, self-locking, in heat
resisting steel FE-PA92HT (A286), MoS2 coated Aerospace
- Classification : 1 100 MPa (at ambient temperature) /
425 °C
Luft- und Raumfahrt ¿ Sechskantmutter,
selbstsichernd, aus hochwarmfesten Stahl FE-PA92HT
(A286), MoS2 beschichtet ¿ Klasse: 1 100 MPa (bei
Raumtemperatur)/425 °C
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee ASD-
STAN.
If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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, 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
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 3723:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 5
4 Required characteristics . 5
4.1 Configuration – Dimensions – Tolerances – Mass . 5
4.2 Materials . 5
4.3 Surface Treatment . 5
5 Designation . 8
6 Marking . 8
7 Technical specification . 8
7.1 General. 8
7.2 Approval of manufacturers . 8
7.3 Qualification of products . 8
Bibliography . 9

European foreword
This document (prEN 3723:2026) has been prepared by ASD-STAN.
After enquiries and votes carried out in accordance with the rules of this Association, this document has
received the approval of the National Associations and the Official Services of the member countries of
ASD-STAN, prior to its presentation to CEN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 3723:1996.
— Clause 3, “Terms and definitions”, added;
— 4.2, “Materials”, standards TR 3791 and SAE AMS5525 added;
— Clause 7, “Technical specification”, editorially revised.
oSIST prEN 3723:202
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