FprEN 3004

Aerospace series - Nuts, self-locking, MJ threads, in heat resisting steel FE-PA2601 (A286), classification: 1 100 MPa (at ambient temperature)/650 °C - Technical specification

This document specifies the characteristics, qualification and acceptance requirements for self-locking nuts with MJ threads in FE-PA2601.
Classification: 1 100 MPa /650 °C .
It is applicable whenever referenced.

Luft- und Raumfahrt - Muttern, selbstsichernd, MJ-Gewinde, aus hocharmfestem Stahl FE-PA2601 (A286), klasse: 1 100 MPa (bei Raumtemperatur)/650 °C - Technische Lieferbedingungen

Série aérospatiale - Écrous, à freinage interne, filetages MJ, en acier résistant à chaud FE-PA2601 (A286) - Classification : 1 100 MPa (à température ambiante)/650 °C - Spécification technique

Le présent document spécifie les caractéristiques, et les exigences de qualification et de réception des écrous à freinage interne, à filetage MJ, en FE-PA2601.
Classification : 1 100 MPa /650 °C.
Elle est applicable chaque fois qu'elle est citée en référence.

Aeronavtika - Matice, samozapiralne, navoj MJ, iz toplotnoodpornega jekla FE-PA2601 (A286), klasifikacija: 1 100 MPa (pri temperaturi okolice)/650 °C - Tehnična specifikacija

General Information

• Status: Not Published
• Publication Date: 04-Oct-2026
• ICS: 49.030.30 - Nuts
• Technical Committee: ASD-STAN - Aerospace
• Drafting Committee: ASD-STAN/D 3/S 2 - Fasteners
• Current Stage: 4599 - Dispatch of FV draft to CMC - Finalization for Vote
• Start Date: 11-Mar-2026
• Completion Date: 11-Mar-2026
• Ref Project: oSIST prEN 3004:2025 - Aerospace series - Nuts, self-locking, MJ threads, in heat resisting steel FE-PA2601 (A286), classification: 1 100 MPa (at ambient temperature)/650 °C - Technical specification

Relations

• Revises: EN 3004:1997 - Aerospace series - Nuts, self-locking, MJ threads, in heat resisting steel FE-PA2601 (A286) - Classification: 1 100 MPa (at ambient temperature)/650°C - Technical specification
• Effective Date: 08-Apr-2024

Overview

FprEN 3004 is a European standard formulated by CEN that specifies the characteristics, qualification, and acceptance requirements for self-locking nuts with MJ threads made of heat resisting steel FE-PA2601 (A286). These nuts are classified for use at 1,100 MPa tensile stress at ambient temperature and for operational durability at temperatures up to 650 °C. The standard is part of the aerospace series and is applicable wherever it is referenced in the aerospace and aeronautics industry.

By establishing rigorous technical specification criteria, FprEN 3004 ensures reliability and consistency in the performance of self-locking nuts used in demanding aerospace environments.

Key Topics

• Scope: Focuses on self-locking nuts with MJ threads, using FE-PA2601 (A286) heat resisting steel.
• Classification: Suitable for applications up to 1,100 MPa tensile strength at room temperature and 650 °C operating temperature.
• Material Requirements: Specifies the use of FE-PA2601 and necessary heat treatments for material integrity.
• Technical Requirements: Covers dimensions, tolerances, surface quality, mechanical properties, and surface coatings.
• Qualification and Acceptance: Outlines procedures for qualification testing and batch acceptance, including sampling plans and defect classification.
• Testing Methods: Details non-destructive and destructive tests for characteristics such as axial load, self-locking torque, vibration resistance, surface discontinuities, and reusability.
• Surface and Metallurgical Properties: Includes specifications for microstructure, grain size, and permissible surface discontinuities.
• Packaging and Labelling: Sets guidelines for packaging integrity and accurate product identification to ensure traceability.

Applications

FprEN 3004 is vital for:

• Aerospace Fastener Systems: Ensures that self-locking nuts withstand extreme mechanical and thermal stresses encountered in aircraft structures, engines, and propulsion systems.
• High-Temperature Environments: Critical for components exposed to sustained high temperatures, such as turbine assemblies or exhaust structures, where FE-PA2601/A286’s resistance to oxidation and high strength is required.
• Quality Assurance in Manufacturing: Provides manufacturers, suppliers, and quality control engineers with clear requirements and test methods for certifying production batches of aerospace fasteners.
• Standardization in the Supply Chain: Enables consistency across different suppliers and ensures end-users receive interchangeable, compliant products whenever the standard is referenced in procurement or design documentation.
• Critical Safety Applications: Used wherever reliable self-locking features are required to prevent loosening under vibration, thermal cycling, or load fluctuations - an essential property in aerospace safety-critical assemblies.

Related Standards

The implementation and use of FprEN 3004 is often complemented by other international and European standards, including:

• EN 2516: Passivation of corrosion resisting steels-a process for improving corrosion resistance in aerospace fasteners.
• EN 2786: Electrolytic silver plating of fasteners for electrical conductivity and corrosion resistance.
• ISO 8642: Test methods for self-locking nuts with maximum operating temperature greater than 425 °C.
• ISO 2859-1: Sampling procedures for inspection by attributes; defines batch acceptance conditions based on AQL.
• ASTM E 112: Standard Test Methods for Determining Average Grain Size.
• EN 9133: Quality Management Systems-Qualification Procedures for Aerospace Standard Products.

These references ensure a harmonized approach to manufacturing, testing, and inspection of aerospace-grade fasteners, thereby safeguarding product quality and performance.

Practical Value

Using FprEN 3004 as a reference in contracts, product specifications, and quality assurance plans helps organizations:

• Achieve compliance with stringent aerospace regulatory requirements.
• Streamline supply chains and reduce the risk of non-conformities.
• Enhance product reliability and safety in high-stress, high-temperature aerospace applications.

In summary, FprEN 3004 is a cornerstone standard for ensuring the integrity and reliability of self-locking nuts in the aerospace industry, supporting critical safety and performance needs in modern aircraft and spacecraft assemblies.

Standards Content (Sample)

SLOVENSKI STANDARD
01-januar-2025
Aeronavtika - Matice, samozapiralne, navoj MJ, iz toplotnoodpornega jekla FE-
PA2601 (A286), klasifikacija: 1 100 MPa (pri temperaturi okolice)/650 °C - Tehnična
specifikacija
Aerospace series - Nuts, self-locking, MJ threads, in heat resisting steel FE-PA2601
(A286), classification: 1 100 MPa (at ambient temperature)/650 °C - Technical
specification
Luft- und Raumfahrt - Muttern, selbstsichernd, MJ-Gewinde, aus hocharmfestem Stahl
FE-PA2601 (A286), klasse: 1 100 MPa (bei Raumtemperatur)/650 °C - Technische
Lieferbedingungen
Série aérospatiale - Écrous à freinage interne, à filetage MJ, en acier résistant à chaud
FE-PA2601 (A286), classification : 1 100 MPa (à température ambiante)/650 °C -
Spécification technique
Ta slovenski standard je istoveten z: prEN 3004
ICS:
49.030.30 Matice Nuts
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
prEN 3004
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2024
ICS 49.030.30 Will supersede EN 3004:1997
English Version
Aerospace series - Nuts, self-locking, MJ threads, in heat
resisting steel FE-PA2601 (A286), classification: 1 100
MPa (at ambient temperature)/650 °C - Technical
specification
Série aérospatiale - Écrous à freinage interne, à filetage Luft- und Raumfahrt - Muttern, selbstsichernd, MJ-
MJ, en acier résistant à chaud FE-PA2601 (A286), Gewinde, aus hocharmfestem Stahl FE-PA2601 (A286),
classification : 1 100 MPa (à température klasse: 1 100 MPa (bei Raumtemperatur)/650 °C -
ambiante)/650 °C - Spécification technique Technische Lieferbedingungen
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
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 3004:2024 E
worldwide for CEN national Members.

prEN 3004:2024 (E)
Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
3.2 Surface discontinuities . 5
4 Quality assurance . 7
4.1 Qualification . 7
4.2 Acceptance. 7
4.2.1 Purpose . 7
4.2.2 Conditions . 7
4.2.3 Responsibility . 7
4.2.4 Inspection and test report . 7
5 Requirements . 7
Bibliography . 23

prEN 3004:2024 (E)
European foreword
This document (prEN 3004:2024) 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 3004:1997.
This document includes the following significant technical changes with respect to EN 3004:1997:
— Clause 2: EN 2516, ISO 3497 and ISO 1463 added;
— Table 1, Clause 5.3.2: heat treating temperature tolerances and duration modified;
— Table 1, Clause 5.3.4: thread and thread deformation requirements modified;
— Table 1, Clause 5.3.6.1: EN 2516 visual requirements added;
— Table 1, Clause 5.3.6.2: thickness measurements only applicable to silver plated parts and thickness
measurement methods added;
— Table 1, Clause 5.3.6.3: adhesion requirements only applicable to silver plated parts;
— Table 1, Clause 5.4.1.1: axial load requirements at ambient temperature modified and axial load at
100 % load added;
— Table 1, Clause 5.4.9: hardness requirements modified and Vickers method added;
— Table 5: push out load and torque out test torque values modified for diameters range from MJ5x0,8
to MJ10x1,25.
prEN 3004:2024 (E)
1 Scope
This document specifies the characteristics, qualification and acceptance requirements for self-locking
nuts with MJ threads in FE-PA2601.
1 2
Classification: 1 100 MPa /650 °C .
It is applicable whenever referenced.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 2516, Aerospace series — Passivation of corrosion resisting steels and decontamination of nickel or
cobalt base alloys
EN 2786, Aerospace series — Electrolytic silver plating of fasteners
ISO 1463, Metallic and oxide coatings — Measurement of coating thickness — Microscopical method
ISO 3452-1, Non-destructive testing — Penetrant testing — Part 1: General principles
ISO 3497, Metallic coatings — Measurement of coating thickness — X-ray spectrometric methods
ISO 21920-3, Geometrical product specifications (GPS) — Surface texture: Profile — Part 3: Specification
operators
ISO 8642:2008, Aerospace — Self-locking nuts with maximum operating temperature greater than
425 °C — Test methods
ASTM E 112-88, Standard Test Methods for Determining Average Grain Size
3 Terms and definitions
For the purposes of this document, the following terms and definitions.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
3.1
batch
quantity of finished nuts, of the same type and same diameter, produced from a material obtained from
the same melt, manufactured in the course of the same production cycle, following the same
manufacturing route and having undergone all the relevant heat treatments and surface treatments

Corresponds to the minimum tensile stress which the nut is able to withstand at ambient temperature without
breaking or cracking when tested with a bolt of a higher strength class.
Maximum test temperature of the parts.
Published by: ISO International Organization for Standardization http://www.iso.ch/.
Published by: ASTM International (US) https://www.astm.org/.
prEN 3004:2024 (E)
3.2 Surface discontinuities
3.2.1
crack
rupture in the material which may extend in any direction and which may be intercrystalline or
transcrystalline in character
3.2.2
seam
open surface defect
3.2.3
lap
surface defect caused by folding over metal fins or sharp corners and then compressing them into the
surface
3.2.4
inclusions
non-metallic particles originating from the material manufacturing process
Note 1 to entry: These particles can be isolated or arranged in strings.
3.3
test temperature
ambient temperature, unless otherwise specified
3.4
simple random sampling
taking of n items from a population of N items in such a way that all possible combinations of n items
have the same probability of being chosen
[SOURCE: ISO 3534:1977]
3.5
critical defect
defect that, according to judgement and experience, is likely to result in hazardous or unsafe conditions
for individuals using, maintaining, or depending upon the considered product, or that is likely to
prevent performance of the function of a major end item
[SOURCE: ISO 3534:1977]
3.6
major defect
defect other than critical, that is likely to result in a failure or to reduce materially the usability of the
considered product for its intended purpose
[SOURCE: ISO 3534:1977]
3.7
minor defect
defect that is not likely to reduce materially the usability of the considered product for its intended
purpose, or that is a departure from established specification having little bearing on the effective use
or operation of this product
prEN 3004:2024 (E)
[SOURCE: ISO 3534:1977]
3.8
sampling plan
plan according to which one or more samples are taken in order to obtain information and possibly to
reach a decision
[SOURCE: ISO 3534:1977]
3.9
limiting quality
in a sampling plan, the quality level which corresponds to the specified 10 % probability of acceptance
3.10
acceptable quality level
AQL
quality level which, in a sampling plan, corresponds to a specified but relatively high probability of
acceptance
Note 1 to entry: It is the maximum per cent defective (or the maximum number of defects per hundred units)
that, for purposes of sampling inspection can be considered satisfactory as a process average
[SOURCE: ISO 3534:1977]
3.11
finished nut
nut ready for use, inclusive of any possible treatments and/or surface coatings, as specified in the
product standard or definition document
3.12
definition document
document specifying all the requirements for finished nuts
3.13
self-locking torque
torque to be applied to the nut or bolt to maintain its movement of rotation in relation to the associated
part, the assembly being under no axial load and the nut locking zone being completely engaged with
the bolt (minimum protrusion of two pitches, including the end chamfer)
3.14
seating torque
tightening torque to be applied to the nut or bolt to introduce or to increase the axial load in the
assembly
3.15
unseating torque
untightening torque to be applied to the nut or bolt to reduce or remove the axial load in the assembly
3.16
breakaway torque
torque required to start unscrewing the nut or bolt with respect to the associated part, with the nut
locking zone still fully engaged on the bolt, but after the axial load in the assembly has been removed by
unscrewing half a turn followed by a halt in rotational movement
prEN 3004:2024 (E)
3.17
torque for testing the wrench feature
torque to be applied to the wrenching feature of the nut
4 Quality assurance
4.1 Qualification
The qualification procedure for aerospace standard products (e.g. according to EN 9133 or an
equivalent aerospace accepted and established qualification procedure) shall be used and documented
according to the specified tests if not otherwise agreed between customer and supplier.
Qualification inspections and tests (requirements, methods, numbers of nuts) are specified in Table 1.
They shall be carried out on:
— each type and diameter of nut;
— 46 nuts selected from a single batch by simple random sampling.
The test programme may possibly be reduced, or the qualification be granted without inspection or
testing: any such decision shall be based on the results obtained on similar types and diameters of nuts
provided that the design and manufacturing conditions are identical.
Table 2 indicates the allocation of nut sample for the inspections and tests.
4.2 Acceptance
4.2.1 Purpose
The purpose of acceptance inspections and tests is to check, as simply as possible, by a method
representative of actual use conditions, with the uncertainty inherent to statistical sampling, that the
nuts constituting the batch satisfy the requirements of this document.
4.2.2 Conditions
Acceptance inspections and tests (requirements, methods, number of nuts) are specified in Table 1.
They shall be carried out on each batch. Nuts from the batch to be tested shall be selected by simple
random sampling.
Each nut may be submitted to several inspections or tests.
If a more stringent inspection is deemed necessary, all or part of the qualification inspections and tests
may be performed during the acceptance inspection and testing. In case, the number of nuts submitted
to these inspections and tests is the same as that submitted for qualification inspection and tests.
4.2.3 Responsibility
Acceptance inspections and tests shall be carried out by the manufacturer, or under his responsibility.
4.2.4 Inspection and test report
A test report showing actual numerical values shall be provided if specified in the purchase order.
5 Requirements
Requirements and testing shall be according to Table 1.
prEN 3004:2024 (E)
Table 1 — Technical requirements and test methods
Sample
a
Clause Characteristic Requirement Inspection and test method Q/A
size
5.1  Material In accordance with the product Chemical analysis or Q
standard or definition document certificate of compliance A
issued by the manufacturer of
the semi-finished product
5.2  Dimensions, In accordance with the product Standard gauging Q 46
tolerances and standard or definition document  A Table 3 and
tolerances of Table 4
form and
position
5.3  Manufacturing
5.3.1  Forming Nuts shall be formed by a hot or The method of forming shall Q
cold forming process. be indicated
If hot formed, the forming
temperature shall not exceed
1 150 °C and they shall be air
cooled or faster.
The equipment shall ensure a
uniform temperature throughout
the batch.
5.3.2  Heat The heat treatment medium or Calibration of the heat Q
treatment atmosphere shall not cause any treatment equipment shall be
surface contamination except as confirmed.
permitted by 5.5.4.
Any scale which will not be Visual examination
removed by subsequent
machining shall be removed by
abrasive blasting with an
appropriate equipment.
Solution treat (if applicable) at a Examination of the heat
temperature of 900 °C ± 10°C to treatment specification
980 °C ± 10°C, held at the selected
temperature within ± 15 °C for
between 1 h min. and 2 h max.,
quench in oil, or alternative
medium or faster.
Precipitation treat at (720 ± 10) °C
held at temperature for at least
16 h cooled in air or faster.
Bearing In accordance with the product
5.3.3  ISO 8642 Q 46
surface standard or definition document.
perpendicular
ity
prEN 3004:2024 (E)
Sample
a
Clause Characteristic Requirement Inspection and test method Q/A
size
For non-floating plate nuts having  A Table 3 and
a bearing surface exceeding Table 4
1,5 times the thread nominal
diameter, the perpendicularity
requirement shall, unless
otherwise specified by the product
standard or definition document,
apply only to that portion of the
bearing surface of the part
contained within a diameter equal
to 1,5 times the thread nominal
diameter.
5.3.4  Thread and Threads in the locking region may Standard gauging Q 46
thread be deformed in any manner
deformation provided that the nut meets the
(form out-of- requirements of this standard.
round)
Tool marks and distortion are  A Table 3 and
permissible in the locking areas. Table 4
The marks shall be without any
abrupt changes.
The finish nuts shall allow for the
“GO” thread plug gauge to enter a
minimum of 3/4 of turn before
engagement of the locking
element.
5.3.5  Surface In accordance with the product ISO 21920-3 Q 3
Roughness standard or definition document Visual examination A Table 3 and
Table 4
5.3.6  Surface
coating
5.3.6.1    Ap pearance S ee EN 2786 for silver plated part. EN 2786 Q  4 3

See EN 2516 for passivated part. EN 2516 A Table 3 and
Table 4
5.3.6.2  Thickness In accordance with the product See 5.3.6.1. Inspection can Q 2
standard or definition document be carried out at the same A Table 6,
time as inspection per 5.5.1. column B
Only applicable for silver plated
for
part. Two methods are proposed
ISO 1463
either ISO 1463 for micro
graphic method or ISO 3497 Table 6,
for X-Ray method. column A
for
In case of dispute ISO 1463 is
ISO 3497
the reference method.
5.3.6.3
...