kSIST FprEN 4048:2026

Aerospace series - Nuts, self-locking, MJ threads, in heat-resisting nickel base alloy NI-PH2601 (Inconel 718), MoS2 coated - Classification: 1 550 MPa (at ambient temperature)/425 °C - Technical specification

This document specifies the characteristics, qualification and acceptance requirements for self-locking nuts with MJ threads in NI-PH2601, MoS2 coated, for aerospace applications.
Classification: 1 550 MPa /425 °C .
It is applicable whenever referenced.

Luft- und Raumfahrt - Muttern, selbstsichernd, MJ-Gewinde, aus hochwarmfester Nickelbasislegierung NI-PH2601 (Inconel 718), MoS2-beschichtet - Klasse: 1 550 MPa (bei Raumtemperatur)/425 °C - Technische Lieferbedingungen

Dieses Dokument legt die Eigenschaften sowie die Qualifikations- und Annahmebedingungen für selbstsi
chernde Muttern mit MJ-Gewinde aus NI-PH2601, MoS2-beschichtet, fest.
Klasse: 1550MPa
1/425°C2.
Es ist anwendbar, wenn darauf verwiesen wird.

Série aérospatiale - Écrous, à freinage interne, à filetage MJ, en alliage résistant à chaud à base de nickel NI-PH2601 (Inconel 718), revêtus MoS2 - Classification : 1 550 MPa (à température ambiante)/425 °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 NI-PH2601, revêtus MoS2, pour les applications aérospatiales.
Classification : 1 550 MPa /425 °C.
Elle est applicable chaque fois qu'elle est citée en référence.

Aeronavtika - Matice, samozapiralne, navoj MJ, iz toplotnoodporne zlitine na nikljevi osnovi NI-PH2601 (Inconel 718), mazane z MoS2 - Klasifikacija: 1550 MPa (pri temperaturi okolice)/425 °C - Tehnična specifikacija

General Information

• Status: Not Published
• Public Enquiry End Date: 30-Jan-2025
• ICS: 49.030.30 - Nuts
• Technical Committee: I13 - Imaginarni 13
• Current Stage: 5020 - Formal vote (FV) (Adopted Project)
• Start Date: 02-Jun-2026
• Due Date: 21-Jul-2026
• Ref Project: FprEN 4048 - Aerospace series - Nuts, self-locking, MJ threads, in heat-resisting nickel base alloy NI-PH2601 (Inconel 718), MoS2 coated - Classification: 1 550 MPa (at ambient temperature)/425 °C - Technical specification

Relations

• Revises: SIST EN 4048:2005 - Aerospace series - Nuts, self-locking, MJ threads, in heat resisting nickel base alloy NI-PH2601 (Inconel 718), MoS2 coated - Classification: 1 550 MPa (at ambient temperature) / 425 °C - Technical specification
• Effective Date: 09-Jul-2024

Overview

kSIST FprEN 4048:2026 is part of the Aerospace series, specifying requirements for self-locking nuts with MJ threads manufactured in heat-resisting nickel base alloy NI-PH2601 (Inconel 718) and coated with molybdenum disulphide (MoS2). This standard sets out the technical specification for these nuts, with a classification of 1 550 MPa tensile strength at ambient temperature and an operational temperature up to 425 °C. Developed by SIST and aligned with European aerospace industry needs, this document outlines characteristics, qualification, and acceptance criteria vital for high-performance applications where secure fastening under extreme operating conditions is required.

Key Topics

• Material Specification: Defines the use of NI-PH2601 (Inconel 718), a high-strength, corrosion and heat-resistant nickel alloy, renowned for its reliability in demanding environments.
• Thread Type: Covers MJ threads, standardized for aerospace fasteners, providing high strength and fatigue resistance.
• Surface Coating: Requires MoS2 coating, reducing friction and enhancing wear resistance under elevated temperatures.
• Mechanical Properties: Specifies a minimum tensile strength of 1 550 MPa at room temperature and assured performance up to 425 °C.
• Quality and Acceptance: Covers qualification processes, sampling plans, and acceptance quality limits to ensure consistent product reliability.
• Surface and Dimensional Requirements: Defines maximal permissible discontinuities, roughness, and marking/identification for traceability.
• Testing Methods: Refers to standards like EN 2491, ISO 1463, ISO 3497, ISO 5855-2, and ISO 8642, ensuring verified product integrity via mechanical, metallurgical, and non-destructive testing.

Applications

kSIST FprEN 4048:2026 is specifically intended for aerospace applications, with wider relevance in critical engineering sectors where secure, high-strength fastening under thermal and mechanical stress is vital.

• Aerospace Structures: Used in aircraft and spacecraft assemblies, these self-locking nuts provide resistance to loosening from vibration and thermal cycles.
• Jet Engines and Turbines: Designed for use in areas subject to high temperatures and mechanical loads, such as engine housings, nacelles, and afterburners.
• Defense Systems: Suitable for fastening components in missiles, satellites, and military aircraft, where material selection and mechanical reliability are crucial.
• Extreme Environment Assemblies: Beyond aerospace, relevant to high-temperature industrial applications, including power generation and automotive sectors.

Related Standards

• EN 2491: Aerospace series - Molybdenum disulphide dry lubricants - Coating methods.
• ISO 1463: Metallic and oxide coatings - Measurement of coating thickness - Microscopical method.
• ISO 3497: Metallic coatings - Measurement of coating thickness - X-ray spectrometric methods.
• ISO 5855-2: Aerospace - MJ threads - Part 2: Limit dimensions for bolts and nuts.
• ISO 8642: Aerospace - Self-locking nuts with max operating temperature greater than 425 °C - Test methods.
• ASTM E112-96: Determining average grain size for material reliability.
• EN 9133: Aerospace series - Quality Management Systems - Qualification Procedure for Aerospace Standard Products.
• ISO 2859-1: Sampling procedures for inspection by attributes.

Practical Value

• Reliability and Safety: Ensures fasteners meet stringent requirements for critical aerospace applications, minimizing the risk of failure.
• Consistency: Detailed qualification and acceptance routines standardize product quality across manufacturers.
• Traceability: Marking and batch labelling requirements support supply chain integrity and maintenance traceability.
• Efficiency: Use of MoS2-coated Inconel 718 nuts reduces downtime for maintenance by ensuring long-lasting, vibration-resistant fastening in harsh conditions.

Adoption of kSIST FprEN 4048:2026 supports compliance with international aerospace fastening standards and enhances the safety and durability of assemblies exposed to extreme environments.

Standards Content (Sample)

SLOVENSKI STANDARD
oSIST prEN 4048:2025
01-januar-2025
Aeronavtika - Matice, samozapiralne, navoj MJ, iz toplotnoodporne zlitine na
nikljevi osnovi NI-PH2601 (Inconel 718), mazane z MoS2 - Klasifikacija: 1 550 MPa
(pri temperaturi okolice)/425 °C - Tehnična specifikacija
Aerospace series - Nuts, self-locking, MJ threads, in heat-resisting nickel base alloy NI-
PH2601 (Inconel 718), MoS2 coated - Classification: 1 550 MPa (at ambient
temperature)/425 °C - Technical specification
Luft- und Raumfahrt - Muttern, selbstsichernd, MJ-Gewinde, aus hochwarmfester
Nickelbasislegierung NI-PH2601 (Inconel 718), MoS2-beschichtet - Klasse: 1 550 MPa
(bei Raumtemperatur)/425 °C - Technische Lieferbedingungen
Série aérospatiale - Écrous, à freinage interne, à filetage MJ, en alliage résistant à chaud
à base de nickel NI-PH2601 (Inconel 718), revêtus MoS2 - Classification : 1 550 MPa (à
température ambiante)/425 °C - Spécification technique
Ta slovenski standard je istoveten z: prEN 4048
ICS:
49.030.30 Matice Nuts
oSIST prEN 4048:2025 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN 4048:2025
oSIST prEN 4048:2025
DRAFT
EUROPEAN STANDARD
prEN 4048
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2024
ICS 49.030.30 Will supersede EN 4048:2004
English Version
Aerospace series - Nuts, self-locking, MJ threads, in heat-
resisting nickel base alloy NI-PH2601 (Inconel 718), MoS2
coated - Classification: 1 550 MPa (at ambient
temperature)/425 °C - Technical specification
Série aérospatiale - Écrous, à freinage interne, à filetage Luft- und Raumfahrt - Muttern, selbstsichernd, MJ-
MJ, en alliage résistant à chaud à base de nickel NI- Gewinde, aus hochwarmfester Nickelbasislegierung NI-
PH2601 (Inconel 718), revêtus MoS2 - Classification : 1 PH2601 (Inconel 718), MoS2-beschichtet - Klasse: 1
550 MPa (à température ambiante)/425 °C - 550 MPa (bei Raumtemperatur)/425 °C - Technische
Spécification technique 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 4048:2024 E
worldwide for CEN national Members.

oSIST prEN 4048:2025
prEN 4048:2024 (E)
Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
3.3 Surface discontinuities . 5
4 Quality assurance . 7
4.1 Qualification . 7
4.2 Acceptance. 7
4.2.1 Purpose . 7
4.2.2 Responsibility . 7
4.2.3 Inspection and test report . 7
5 Requirements . 7
Bibliography . 21

oSIST prEN 4048:2025
prEN 4048:2024 (E)
European foreword
This document (prEN 4048:2024) has been prepared by the Aerospace and Defence Industries
Association of Europe — Standardization (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 4048:2004.
This document includes the following significant technical changes with respect to EN 4048:2004:
— Clause 2: EN 3497 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 5.3.6.2: thickness measurement methods added;
— Table 1, Clause 5.4.4.1: Axial load requirement at ambient temperature modified;
— Table 1, Clause 5.4.4.2: Axial load requirement after 425°C baking modified;
— Table 1, Clause 5.4.5.1: Self-locking torque at ambient temperature (five cycles) method modified;
— Table 1, Clause 5.4.9: Hardness requirement modified;
— Table 5: requirement modified (wrench feature torque, push out load and torque out test);
— Table 7: seating torque values and footnote modified.
oSIST prEN 4048:2025
prEN 4048:2024 (E)
1 Scope
This document specifies the characteristics, qualification and acceptance requirements for self-locking
nuts with MJ threads in NI-PH2601, MoS coated, for aerospace applications.
1 2
Classification: 1 550 MPa /425 °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 2491, Aerospace series — Molybdenum disulphide dry lubricants — Coating methods
ISO 1463, Metallic and oxide coatings — Measurement of coating thickness — Microscopical method
ISO 3497, Metallic coatings — Measurement of coating thickness — X-ray spectrometric methods
ISO 5855-2, Aerospace — MJ threads — Part 2: Limit dimensions for bolts and nuts
ISO 8642:2008, Aerospace — Self-locking nuts with maximum operating temperature greater than
425 °C — Test methods
ASTM E 112-96, Standard Test Methods for Determining Average Grain Size
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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 parts, of the same type and same diameter, produced from the same 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
3.2
inspection lot
quantity of parts from a single production batch with the same part number which completely defines
the part
Correspond 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.org/.
Published by: ASTM International (US) https://www.astm.org/.
oSIST prEN 4048:2025
prEN 4048:2024 (E)
3.3 Surface discontinuities
3.3.1
crack
rupture in the material which may extend in any direction and which may be intercrystalline or
transcrystalline in character
3.3.2
seam
open surface defect
3.3.3
lap
surface defect caused by folding over metal fins or sharp corners and then rolling or forging them into
the surface
3.3.4
inclusions
non-metallic particles originating from the material manufacturing process. These particles may be
isolated or arranged in strings
3.4
test temperature
ambient temperature unless otherwise specified
3.5
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
3.6
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
3.7
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
3.8
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
3.9
sampling plan
plan according to which one or more samples are taken in order to obtain information and possibly to
reach a decision
oSIST prEN 4048:2025
prEN 4048:2024 (E)
3.10
limiting quality
LQ
quality limit in a sampling plan which corresponds to a specified 10 % probability of acceptance
3.11
acceptance quality limit
AQL
quality limit 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.
3.12
finished nut
nut ready for use, inclusive of any possible treatments and/or surface coatings, as specified in the
product standard or definition document
3.13
definition document
document specifying all the requirements for finished nuts
3.14
self-locking torque
torque to be applied to the nut or bolt to maintain movement of rotation in relation to the associated
part, the assembly being under no axial load and the nut locking system being completely engaged with
the bolt (minimum protrusion of two pitches including end chamfer)
3.15
seating torque
tightening torque to be applied to the nut or bolt to introduce or to increase the axial load in the
assembly
3.16
unseating torque
untightening torque to be applied to the nut or bolt to reduce or remove the axial load in the assembly
3.17
breakaway torque
torque required to start unscrewing the nut or bolt with respect to the associated part, with the nut
locking device 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
3.18
wrench feature torque
torque to be applied to the wrenching feature of the nut
oSIST prEN 4048:2025
prEN 4048:2024 (E)
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 inspection lot by simple random sampling.
The test programme may possibly be reduced, or the qualification of a nut 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 samples for the inspections and tests.
4.2 Acceptance
4.2.1 Purpose
Acceptance inspections and tests (requirements, methods, numbers of nuts) are specified in Table 1;
they shall be carried out on each production batch or inspection lot. Nuts from the batch or lot 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 this case, the number of nuts
submitted to these inspections and tests is the same as that submitted for qualification inspection and
tests.
4.2.2 Responsibility
Acceptance inspections and tests shall be carried out by the manufacturer, or under his responsibility.
4.2.3 Inspection and test report
A test report showing actual numerical values shall be provided if specified in the purchase order.
5 Requirements
Requirements shall be according to Table 1.
The same test sample may be utilized for more than one test provided that none of the characteristics of
the samples are altered during the examination procedure (see Table 2).
oSIST prEN 4048:2025
prEN 4048:2024 (E)
Table 1 — Technical requirements and tests methods
Sample
a
Clause Characteristic Requirement Inspection and test method Q/A
size
5.1   Material In accordance with the product Chemical analysis or certificate Q
standard or definition of conformity issued by the
A
document. manufacturer of the semi-
finished product.
5.2   Dimensions, In accordance with the product Standard gauging. Q 43
tolerances and standard or definition
A Tables
tolerances of form document.
3 and 4
and position
5.3   Manufacturing
5.3.1   Forming Nuts shall be formed by a hot or The method of forming shall be Q
cold forming process. 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 production
batch.
5.3.2   Heat treatment The heat treatment medium or Calibration of the heat Q
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 940 °C to treatment specification.
1010 °C, hold 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 treatment at
(720 ± 5) °C, held at
temperature for at least 8 h,
furnace cooled at (55 ± 5) °C
per hour to (620 ± 5) °C, held at
620 °C for at least 8 h , followed
by air cooling or faster.
Instead of the 55 °C per hour
cooling rate to 620 °C, parts
may be furnace cooled at any
rate provided the time at 620 °C
is adjusted to give a total
precipitation time of 18 h min.

oSIST prEN 4048:2025
prEN 4048:2024 (E)
Sample
a
Clause Characteristic Requirement Inspection and test method Q/A
size
5.3.3   Bearing surface In accordance with the product ISO 8642. Q 43
perpendicularity standard or definition
A Tables
document.
3 and 4
For non-floating plate nuts
having a bearing surface
exceeding × 1,5 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
the thread nominal diameter.
5.3.4   Thread and thread T
...