SIST EN 3750:2026

Aerospace series - Nut, anchor, self-locking, fixed, 90° corner, reduced series, with counterbore, in heat resisting steel, MoS2 lubricated - Classification: 1 100 MPa (at ambient temperature) / 315 °C

This document specifies the characteristics of 90° corner, reduced series, counterbored fixed anchor nuts, with a self-locking feature achieved by forming the upper portion out-of-round, in heat resisting steel, MoS2 lubricated.
Classification: 1 100 MPa  / 315 °C .

Luft- und Raumfahrt - Annietmutter, selbstsichernd, einseitiger verkürzter 90° Eckflansch, mit zylindrischer Aussenkung, aus hochwarmfestem Stahl, MoS2-geschmiert - Klasse: 1 100 MPa (bei Raumtemperatur) / 315 °C

Série aérospatiale - Écrous à river, à freinage interne, fixes, d'angle 90°, série réduite, avec chambrage, en acier résistant à chaud, lubrifiés MoS2 - Classification : 1 100 MPa (à température ambiante) / 315 °C

Le présent document spécifie les caractéristiques des écrous à river fixes, d’angle 90°, série réduite, avec chambrage, à freinage interne obtenu par déformation de la partie supérieure, en acier résistant à chaud, lubrifiés au MoS2.
Classification : 1 100 MPa /315 °C.

Aeronavtika - Matica, sidrna, samozaporna, fiksna, rob 90°, zmanjšana serija, z izvrtino za vijake, iz toplotnoodpornega jekla, namazana z MoS2 - Klasifikacija: 1100 MPa (pri temperaturi okolice)/315 °C

Ta dokument določa značilnosti 90° kotnih, zmanjšane serije, vgrezno izvrtanih fiksnih sidrnih matic s samovarovalno funkcijo, doseženo z oblikovanjem zgornjega dela v neokroglo obliko, iz jekla, odpornega na visoke temperature, mazano z MoS2 (molibdenov disulfid).
Razvrstitev: 1 100 MPa / 315 °C.

General Information

• Status: Published
• Public Enquiry End Date: 22-Oct-2024
• Publication Date: 30-Mar-2026
• ICS: 49.030.30 - Nuts
• Technical Committee: I13 - Imaginarni 13
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 18-Mar-2026
• Due Date: 23-May-2026
• Completion Date: 31-Mar-2026
• Ref Project: EN 3750:2026 - Aerospace series - Nut, anchor, self-locking, fixed, 90° corner, reduced series, with counterbore, in heat resisting steel, MoS2 lubricated - Classification: 1 100 MPa (at ambient temperature) / 315 °C

Relations

• Revises: SIST EN 3750:2010 - Aerospace series - Nuts, anchor, self-locking, fixed, 90° corner, reduced series, with counterbore, in heat resisting steel, MoS2 lubricated - Classification: 1100 MPa (at ambient temperature)/315 °C
• Effective Date: 06-Dec-2023

Overview

SIST EN 3750:2026 is an internationally recognized European standard developed by CEN, within the Aerospace series, that specifies the characteristics for a specialized type of self-locking, fixed anchor nut. These nuts are designed for use at a 90° corner in the reduced series, equipped with a counterbore, and manufactured from heat resisting steel. They are further treated with molybdenum disulfide (MoS₂) lubrication to enhance performance, particularly for high-strength and elevated-temperature applications. The standard classifies these nuts for use at a tensile strength of 1 100 MPa (at ambient temperature) and up to operating temperatures of 315 °C, making them suitable for demanding aerospace environments.

Key Topics

• Scope & Characteristics:
  • Covers nuts with a self-locking feature, achieved by forming the upper portion out-of-round.
  • Applicable to nuts with a counterbore, intended for fixed installation at 90° corners.
  • Specifies reduced series designs for optimized weight and fit.
• Material & Surface Treatment:
  • Uses heat resisting steel according to referenced standards.
  • MoS₂ lubrication on the thread area for reduced friction and improved durability.
  • Requires passivation to enhance corrosion resistance.
• Dimensions & Tolerances:
  • Compliance with ISO 9156 for configuration, dimensions, and tolerances.
  • Form and position tolerances must follow ISO 8788.
• Quality Assurance:
  • Manufacturers must operate within approved aerospace quality management systems (e.g., EN 9100).
  • Product qualification must align with standardized aerospace procedures (e.g., EN 9133).

Applications

Anchor nuts compliant with SIST EN 3750:2026 are primarily used in the following contexts:

• Aerospace Structures:
  • Installation in primary and secondary aircraft structures where reliable, high-temperature fastener retention is critical.
  • Common for attaching panels, access doors, hatches, and removable components around corners and confined areas.
• High-Temperature Environments:
  • Suitable for applications requiring performance at elevated temperatures up to 315 °C, such as engine compartments and exhaust assemblies.
• Maintenance & Assembly:
  • Self-locking feature reduces risk of loosening under vibration, enhancing safety and maintenance intervals.
  • Counterbore and fixed mounting design aids quick and secure installation during assembly or retrofit.

With these capabilities, SIST EN 3750:2026 nuts deliver enhanced safety, reliability, and performance in challenging aerospace conditions.

Related Standards

Several referenced and related standards enhance the application and compliance of SIST EN 3750:2026, including:

• EN 2398 / EN 2399 / EN 3638 / EN 3639: Specify suitable heat resisting steel materials for aerospace fasteners.
• EN 2424: Defines marking requirements for aerospace products.
• EN 2491: Details coating methods for molybdenum disulphide (MoS₂) dry lubricants.
• EN 2516: Covers passivation of corrosion-resisting steels.
• ISO 5855-2: Prescribes limit dimensions for MJ threads on bolts and nuts.
• ISO 8788: Establishes form and position tolerances for metric aerospace nuts.
• ISO 9156: Provides further specification on aerospace anchor nuts, including dimensions and temperature classes.
• EN 9100: Sets out requirements for aerospace quality management systems.
• EN 9133: Standardizes qualification procedures for aerospace standard products.

Practical Value

Adherence to SIST EN 3750:2026 ensures:

• Interchangeability and compliance within the aerospace supply chain
• Traceability and consistent quality in manufacturing and maintenance
• Enhanced safety and reliability for mission-critical fastened assemblies

By referencing SIST EN 3750:2026 in procurement and design, aerospace manufacturers and suppliers can ensure nuts meet stringent international requirements for performance, safety, and durability in high-stress environments.

Standards Content (Sample)

SLOVENSKI STANDARD
01-maj-2026
Aeronavtika - Matica, sidrna, samozaporna, fiksna, rob 90°, zmanjšana serija, z
izvrtino za vijake, iz toplotnoodpornega jekla, namazana z MoS2 - Klasifikacija:
1100 MPa (pri temperaturi okolice)/315 °C
Aerospace series - Nut, anchor, self-locking, fixed, 90° corner, reduced series, with
counterbore, in heat resisting steel, MoS2 lubricated - Classification: 1 100 MPa (at
ambient temperature) / 315 °C
Luft- und Raumfahrt - Annietmutter, selbstsichernd, einseitiger verkürzter 90°
Eckflansch, mit zylindrischer Aussenkung, aus hochwarmfestem Stahl, MoS2-geschmiert
- Klasse: 1 100 MPa (bei Raumtemperatur) / 315 °C
Série aérospatiale - Écrous à river, à freinage interne, fixes, d'angle 90°, série réduite,
avec chambrage, en acier résistant à chaud, lubrifiés MoS2 - Classification : 1 100 MPa
(à température ambiante) / 315 °C
Ta slovenski standard je istoveten z: EN 3750:2026
ICS:
49.030.30 Matice Nuts
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 3750
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2026
EUROPÄISCHE NORM
ICS 49.030.30 Supersedes EN 3750:2010
English Version
Aerospace series - Nut, anchor, self-locking, fixed, 90°
corner, reduced series, with counterbore, in heat resisting
steel, MoS lubricated - Classification: 1 100 MPa (at
ambient temperature) / 315 °C
Série aérospatiale - Écrou à river, à freinage interne, Luft- und Raumfahrt - Annietmutter, selbstsichernd,
fixe, d'angle 90°, série réduite, avec chambrage, en einseitiger verkürzter 90°-Eckflansch, mit
acier résistant à chaud, lubrifié au MoS - Classification zylindrischer Aussenkung, aus hochwarmfestem Stahl,
: 1 100 MPa (à température ambiante)/315 °C MoS2-geschmiert - Klasse: 1 100 MPa (bei
Raumtemperatur)/315 °C
This European Standard was approved by CEN on 2 February 2026.

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, 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.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATIO N

EUROPÄISCHES KOMITEE FÜR NORMUN G

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. EN 3750:2026 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 — Masses . 5
4.2 Materials . 5
4.3 Surface treatment . 5
5 Designation . 6
6 Marking . 7
7 Technical specification . 7
7.1 General. 7
7.2 Approval of manufacturers . 7
7.3 Qualification of products . 7
Bibliography . 8

European foreword
This document (EN 3750:2026) 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 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 September 2026, and conflicting national standards
shall be withdrawn at the latest by September 2026.
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 3750:2010.
— normative references updated;
— Clause 3 “Terms and definitions” added;
— Figure 1 corrected (hole diameter);
— Bibliography added.
Any feedback and questions on this document should be directed to the users’ national standards body.
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