ISO 5858:2026

Aerospace — Nuts, self-locking, with maximum operating temperature less than or equal to 425 °C — Procurement specification

This document specifies the required characteristics for metric self-locking nuts, with MJ threads, for use in aerospace construction at a maximum temperature less than or equal to 425 °C. It is applicable to nuts as defined above, provided that reference is made to this document in the relevant definition document.

Aéronautique et espace — Écrous à freinage interne dont la température maximale d'utilisation est inférieure ou égale à 425 °C — Spécification d'approvisionnement

La présente Norme internationale spécifie les caractéristiques requises pour les écrous à freinage interne, métriques, à filetage MJ conformément à l'ISO 5855-2, utilisés dans les constructions aérospatiales à des températures maximales inférieures ou égales à 425 °C. Elle est applicable aux écrous à freinage interne répondant à la définition ci-dessus, à condition qu'elle soit référencée dans le document de définition les concernant.

General Information

• Status: Published
• Publication Date: 20-May-2026
• ICS: 49.030.30 - Nuts
• Technical Committee: ISO/TC 20/SC 4 - Aerospace fastener systems
• Drafting Committee: ISO/TC 20/SC 4/WG 3 - Supporting documents
• Current Stage: 6060 - International Standard published
• Start Date: 21-May-2026
• Due Date: 11-Feb-2027
• Completion Date: 21-May-2026

Relations

• Revises: ISO 5858:1999 - Aerospace — Nuts, self-locking, with maximum operating temperature less than or equal to 425 degrees C — Procurement specification
• Effective Date: 15-Feb-2025

Overview

ISO 5858: Aerospace - Nuts, self-locking, with maximum operating temperature ≤ 425 °C - Procurement specification is an essential international standard developed by the International Organization for Standardization (ISO). This standard details the procurement specification and required characteristics for metric self-locking nuts with MJ threads used in aerospace construction when the maximum operating temperature is 425 °C or less. ISO 5858 serves as a reference for manufacturers, suppliers, and engineers to ensure product reliability, quality assurance, and safety in critical aerospace assemblies.

Metric self-locking nuts described under ISO 5858 are critical components in aerospace fastener systems, tasked with resisting loosening under vibration and thermal stress. The specification is only applicable when explicitly referenced in a definition or procurement document relevant to a specific application.

Key Topics

ISO 5858 covers several core areas to standardize the procurement and quality requirements for aerospace self-locking nuts:

• Scope and Applicability: Focuses on metric self-locking nuts with MJ threads for aerospace use, limited to applications ≤ 425 °C.
• Material and Performance: Outlines acceptable materials, strength classes, hardness, corrosion resistance, and non-magnetism criteria.
• Quality Assurance & Testing: Specifies manufacturer qualifications, batch production requirements, and qualification versus acceptance inspections.
• Surface Treatments and Coatings: Details requirements for surface coating types, thickness, and adhesion - including corrosion and lubricant coatings.
• Dimensional and Functional Requirements: Sets standards for the geometry, threads, wrench engagement, and squareness of bearing surfaces.
• Testing and Inspection Methods: Lists mechanical and physical tests, such as axial load, locking torque, stress embrittlement, vibration resistance, and marking/identification.
• Packaging and Labelling: Stipulates procedures to ensure traceability and prevent damage or corrosion during transportation and storage.

Applications

ISO 5858 self-locking nuts are used in multiple aerospace applications where safety and performance under demanding environments are crucial. Practical applications include:

• Aircraft Assembly: For securing structural components, engine parts, avionics, and control systems where resistance to vibration and high temperatures is essential.
• Spacecraft Construction: Used in satellites, launch vehicles, and space modules where fastener integrity under variable thermal loads ensures mission success.
• Maintenance and Repair Operations (MRO): Facilitates standardized replacement, ensuring compatibility and compliance with international aerospace requirements.
• OEM and Supplier Procurement: Streamlines quality and conformity assessments between manufacturers, suppliers, and regulatory bodies by providing common benchmarks.

By adhering to ISO 5858, manufacturers benefit from reduced risk of fastener failure, improved assembly safety, ease of quality control, and compliance with global aerospace regulations.

Related Standards

ISO 5858 is often used in conjunction with several related standards for fastener and quality assurance requirements in aerospace:

• ISO 7481: Test methods for self-locking nuts with maximum operating temperature ≤ 425 °C.
• ISO 5855-2: Limit dimensions for bolts and nuts with MJ threads.
• ISO 691: Tolerances for wrench and socket openings.
• ISO 9227: Corrosion tests in artificial atmospheres (salt spray tests).
• ISO 7870-1/2/3: Control charts for quality management via statistical processes.
• ISO 8788: Tolerances of form and position for metric nuts.
• ISO 1463: Methods for metallic and oxide coating thickness measurements.
• ASTM E1417/E1444: Practices for penetrant and magnetic particle testing.
• EN/AS 9138: Aerospace quality management and product acceptance.

Conclusion

By following ISO 5858, organizations ensure that self-locking nuts for aerospace applications consistently meet rigorous requirements for material properties, thermal performance, and quality assurance, supporting both airworthiness and international market acceptance. Manufacturers, suppliers, engineers, and procurement professionals in the aviation and aerospace sectors should reference ISO 5858 to guarantee compliance and product reliability in all relevant activities.

Standards Content (Sample)

International
Standard
ISO 5858
Third edition
Aerospace — Nuts, self-locking, with
2026-05
maximum operating temperature
less than or equal to 425 °C —
Procurement specification
Aéronautique et espace — Écrous à freinage interne dont la
température maximale d'utilisation est inférieure ou égale à 425
°C — Spécification d'approvisionnement
Reference number
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Quality assurance . 3
4.1 General .3
4.1.1 Manufacturer's approval .3
4.1.2 Qualification of nuts .3
4.1.3 Production acceptance of nuts .3
4.2 Qualification inspection and test conditions .3
4.3 Production acceptance inspection and test conditions .4
4.4 Use of statistical process control (SPC) .4
5 Technical requirements . 5
Annex A (normative) Types of permissible surface discontinuity .28
Annex B (informative) Cross-sectional area formula .29
Bibliography .30

iii
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 www.iso.org/directives).
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 20, Aircraft and space vehicles, Subcommittee
SC 4, Aerospace fastener systems.
This third edition cancels and replaces the second edition (ISO 5858:1999), which has been technically
revised.
The main changes are as follows:
— normative references have been updated;
— the structure of Table 1 has been changed;
— new tables for sampling have been added.
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.

iv
International Standard ISO 5858:2026(en)
Aerospace — Nuts, self-locking, with maximum operating
temperature less than or equal to 425 °C — Procurement
specification
1 Scope
This document specifies the required characteristics for metric self-locking nuts, with MJ threads, for use in
aerospace construction at a maximum temperature less than or equal to 425 °C.
It is applicable to nuts as defined above, provided that reference is made to this document in the relevant
definition document.
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.
ISO 691, Assembly tools for screws and nuts — Wrench and socket openings — Tolerances for general use
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 3887, Steels — Determination of the depth of decarburization
ISO 5855-2, Aerospace — MJ threads — Part 2: Limit dimensions for bolts and nuts
ISO 7403, Aerospace — Spline drives — Wrenching configuration — Metric series
ISO 7481, Aerospace — Nuts, self-locking, with maximum operating temperature less than or equal to 425 °C —
Test methods
ISO 8788, Aerospace — Nuts, metric — Tolerances of form and position
ISO 9227, Corrosion tests in artificial atmospheres — Salt spray tests
ISO 9934 , Non-destructive testing — Magnetic particle testing
ISO 21920-3, Geometrical product specifications (GPS) — Surface texture: Profile — Part 3: Specification
operators
ASTM E1417, Standard Practice for Liquid Penetrant Testing
ASTM E1444, Standard Practice for Magnetic Particle Testing
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
definition document
document specifying all the requirements for nuts, i.e.:
— metallurgical requirements;
— geometrical and dimensional requirements;
— functional requirements (strength and temperature classes)
Note 1 to entry: The definition document may be an International Standard, a national standard, or an in-house
standard or drawing.
3.2
finished nut
nut ready for use, inclusive of any possible treatments or surface coatings, as specified in the definition
document (3.1)
3.3
production batch
quantity of finished nuts (3.2), manufactured using the same process, from a single material cast (single
heat of alloy), having the same number of definitiondocument (3.1), same thread and diameter code, heat
treated together to the same specified condition and produced as one continuous run in the course of the
same production cycle, following the same manufacturing route and having undergone all the relevant heat
treatments and surface treatments
3.4
crack
rupture in the material which can extend in any direction and which can be intercrystalline or
transcrystalline in character
3.5
seam
open surface defect resulting from extension of the metal
3.6
lap
folding over of unwelded metal that can arise when the material is formed (drawing) or in the finished
product (pressing or forging)
3.7
inclusion
non-metallic particle originating from the material manufacturing process
Note 1 to entry: These particles can be isolated or arranged in strings.
3.11
sampling plan
plan according to which one or more samples are taken in order to obtain information and possibly reach a
decision
Note 1 to entry: In this document, each sampling plan specifies the number of nuts to be inspected as a function of the
size of the batch (3.3) and the acceptance number [number of defective items acceptable (Ac)]. See ISO 2859-1.
3.12
simple random sampling
sampling 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

3.15
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 system being completely engaged with the bolt
(two pitches minimum protrusion, including the end chamfer)
3.16
seating torque
tightening torque to be applied to the nut or bolt to introduce or to increase the axial load in the assembly
3.18
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
3.19
wrench torque
tightening and untightening torques which the driving feature of the nut has to withstand repeatedly
without any permanent deformation which would prevent the appropriate wrench from being used or
preclude re-use of the nut
3.20
IRR
initial reliability requirement
inspection reliability requirement
minimum acceptable outgoing yield or probability of conformance
4 Quality assurance
4.1 General
4.1.1 Manufacturer's approval
The manufacturer shall be capable of continuous production of nuts meeting the quality requirements
specified in this document.
4.1.2 Qualification of nuts
The purpose of qualification inspections and tests of nuts is to check that the design and manufacturing
conditions for a nut allow it to satisfy the requirements of this document.
4.1.3 Production acceptance of nuts
The purpose of production acceptance inspection and tests of a nut is to check, as simply as possible, using
a method which is inexpensive but most representative of the actual conditions of use, with the uncertainty
inherent in statistical sampling, that the nuts satisfy the requirements of this document.
Production acceptance inspections and tests shall be carried out by, or under the responsibility of, the
manufacturer.
The manufacturer is responsible for the quality of the nuts manufactured.
4.2 Qualification inspection and test conditions
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;

— 100 nuts selected from a single batch by simple random sampling.
The test programme can be reduced, or qualification of a nut 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.
The inspections and tests shall be repeated on any nut if the supplier or the manufacturing conditions have
changed.
Qualification inspections and tests are summarized in Table 2.
4.3 Production acceptance inspection and test conditions
Production acceptance inspections and tests (requirements, methods, numbers 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 subjected to several inspections or tests.
The nuts to be subjected to destructive inspections or tests may be those on which non-destructive
inspections or tests have been carried out.
If a more stringent inspection is deemed necessary, all or part of the qualification inspections and tests may
be performed during the production acceptance inspections and testing. In this case, the number of nuts
submitted is the same as that submitted for qualification inspections and tests.
Batches declared unacceptable after the production acceptance inspections and tests shall be submitted
for re-inspection or testing only after either all the defective units have been removed or defects have been
corrected, or both. In this case, the attribute(s) which caused the rejection shall be verified using a sample
of twice the normal size but the maximum number of allowed defective items shall be the same as in the
original inspection.
Production acceptance inspections and tests are summarized in Table 2.
4.4 Use of statistical process control (SPC)
Where a characteristic is obtained by a controlled statistical process, in order to declare conformity of
the characteristic, the manufacturer may refrain from the final systematic sampling provided for in this
document, if he/she is can formally justify this choice by using the standards quoted in it as a basis.
This justification will include the following phases:
— analysis of the product's key characteristics;
— analysis of the risks for each implemented process;
— determination of either the parameters or characteristics, or both, to be respected under SPC;
— determination of the capabilities of each process;
— drawing up an inspection plan and integration in the manufacturing process;
— drawing up of routes and control charts (e.g. ISO 7870-1, ISO 7870-2, ISO 7870-3);
— use of control charts for data consolidation;
— determination of the audits to be run and the control to be carried out to ensure reliability of the device.
To be usable in production, this process shall be validated beforehand by the qualifying body, either during
the qualification phase or a posteriori, according to the case, by analysing the justificatory file and the
results of the qualification inspections such as provided for in Clause 5.

5 Technical requirements
The technical requirements are given in Table 1.
They complement the requirements of all other standards or specifications referenced in the definition
document for the nut.
If there is no International Standard specifying the method to be used, a prior agreement shall be reached
between the user and the manufacturer with respect to the following inspections and tests:
— spectrographic analysis or spectroscopic analysis of the material (Table 1, item-no 111);
— micrographic inspection of the structure of the material (Table 1, item-no 1-2);
— inspection for carburization or decarburization (Table 1, item-no 1-3);
— magnetoscopic or fluorescent inspection for surface discontinuities (Table 1, item-no 1-4);
— magnetic permeability inspection (Table 1, item-no 1-6);
— inspection by chemical reagent to determine type of surface coating (Table 1, item-no 2-2);
— tactile inspection or inspection using a profilometer to determine surface roughness (Table 1, item-
no 3-2).
Table 1 — Technical requirements
Inspection and test Sample
Item-no Characteristic Technical requirement Test category
method size
1 Material
a
1-1 Type The material shall be as Spectrographic analysis Qualification 3
specified in the definition or spectroscopic analysis
document. (method to be agreed upon
between the user and man-
ufacturer).
a
See Clause 4 for applicability conditions.
b
Inspections applicable only to nuts made of steel or steel alloy.
c
Inspection to be carried out before coating of the surface or after removal of the surface coating.
d
Inspection applicable only to nuts made of stainless steel.
e
Inspection applicable only to electrolytic coatings (cadmium, silver, etc.).
f
This inspection may be performed on nuts that have been subjected to the inspection of microstructure (see item no 1-2).
g
Test applicable only to all-metal self-locking wrench nuts.
h
For the qualification testing of all-metal self-locking nuts, the nuts shall be exposed for 6 h to the maximum operating
temperature specified in the definition document before the load is applied.
i
Test applicable only to wrench nuts.
j
Test applicable only to nuts heat-treated to a hardness equal to or greater than 44 HRC.
k
Test applicable only to floating-anchor nuts, gang channel nuts and fixed-anchor nuts, produced in several parts and
assembled by brazing or clinching.
l
Test applicable only to gang channel and anchor nuts, with the exception of corner nuts (see ISO 7481) and of reduced-
series single-lug nuts.
m
For all-metal self-locking nuts made of stainless steel with MoS -type dry-film lubrication, this test shall be carried out
over five cycles in order to avoid any risk of seizing.
n
Test applicable only to nuts of diameter 5 mm, 6 mm, 7 mm, 8 mm, 10 mm and 12 mm (see ISO 7481).
o
Test applicable only to sealing nuts.
p
Test applicable only to clinch nuts.

TTabablele 1 1 ((ccoonnttiinnueuedd))
Inspection and test Sample
Item-no Characteristic Technical requirement Test category
method size
a
1-2 Microstructure Nuts shall be free from Micrographic inspection Qualification 5
cracks. The inclusions of a transverse section
shall not exceed the values (method to be agreed upon
specified in the material between the user and man-
standard, when specified ufacturer).
therein.
a
1-3 Carburization or No area of carburization and Microscopic examina- Qualification 5
b
decarburization no area of total decarburiza- tion in accordance with
tion is permissible. An area the method agreed upon
of partial decarburization between the user and man-
is permissible provided ufacturer or Vickers micro-
that the thickness over the hardness measurement
area is less than or equal to (using a 300 g load) in
0,1 mm. accordance with ISO 3887,
or an equivalent method,
shall be carried out.
b a
1-4 Surface disconti- The types of permissible Magnetoscopic (method Qualification 5
c
nuities surface discontinuity shall to be agreed upon between
be in accordance with the user and manufacturer,
Production Ac- Tables 11
Annex A. The maximum shall in accordance with.
ceptance and 12
depth allowed for these ISO 9934 or ASTM E1444)
discontinuities is given in or penetrant inspection in
Table 17. accordance with ISO 3452-
1 or ASTM E1417.
Nuts shall be free from In the event of any doubt
cracks. arising as to the nature
of the defects detected,
inspect defective nuts at a
magnification of × 10 after
sectioning.
a
See Clause 4 for applicability conditions.
b
Inspections applicable only to nuts made of steel or steel alloy.
c
Inspection to be carried out before coating of the surface or after removal of the surface coating.
d
Inspection applicable only to nuts made of stainless steel.
e
Inspection applicable only to electrolytic coatings (cadmium, silver, etc.).
f
This inspection may be performed on nuts that have been subjected to the inspection of microstructure (see item no 1-2).
g
Test applicable only to all-metal self-locking wrench nuts.
h
For the qualification testing of all-metal self-locking nuts, the nuts shall be exposed for 6 h to the maximum operating
temperature specified in the definition document before the load is applied.
i
Test applicable only to wrench nuts.
j
Test applicable only to nuts heat-treated to a hardness equal to or greater than 44 HRC.
k
Test applicable only to floating-anchor nuts, gang channel nuts and fixed-anchor nuts, produced in several parts and
assembled by brazing or clinching.
l
Test applicable only to gang channel and anchor nuts, with the exception of corner nuts (see ISO 7481) and of reduced-
series single-lug nuts.
m
For all-metal self-locking nuts made of stainless steel with MoS -type dry-film lubrication, this test shall be carried out
over five cycles in order to avoid any risk of seizing.
n
Test applicable only to nuts of diameter 5 mm, 6 mm, 7 mm, 8 mm, 10 mm and 12 mm (see ISO 7481).
o
Test applicable only to sealing nuts.
p
Test applicable only to clinch nuts.

TTabablele 1 1 ((ccoonnttiinnueuedd))
Inspection and test Sample
Item-no Characteristic Technical requirement Test category
method size
a
1-5 Hardness The hardness of the finished In accordance with Qualification 5
nuts shall be within the lim- ISO 7481.
Production accept- Table 16,
its specified in the definition
ance
column B
document for the nut or in
the material standard.
d a
1-6 Non-magnetism The magnetic permeability Method to be agreed upon Qualification 5
of the finished nuts shall be between the user and man-
less than 2 (air = 1) in a mag- ufacturer.
netic field of 15 916 A/m.
2 Surface coating
a
2-1 Presence Surface coating shall be Visual examination. Qualification 100
specified in the definition
Production accept- Tables 11
document applied at the
ance and 13
locations.
e a
2-2 Type Surface coating shall be as Visual examination or Qualification 3
specified in the definition inspection by chemical
Production accept- Table 16,
document. reagent in case of doubt
ance column A
(method to be agreed upon
between the user and man-
ufacturer).
e a
2-3 Thickness The thickness of the surface Device for measuring the Qualification 5
coating shall be within the thickness of surface coat-
Production accept- Table 16,
limits specified in the defini- ings, e.g.
ance column B
tion document.
ISO 1463 for micro graphic
for ISO
If no limits are specified in method or ISO 3497 for
the definition document, the X-Ray method

measurement position is
In case of doubt, micro-
Table 16,
specified as the functional
graphic inspection shall be
Column
surfaces: bearing surface
carried out in accordance
A for ISO
f
and thread surface
with ISO 1463
a
2-4 Adhesion Qualification
a
See Clause 4 for applicability conditions.
b
Inspections applicable only to nuts made of steel or steel alloy.
c
Inspection to be carried out before coating of the surface or after removal of the surface coating.
d
Inspection applicable only to nuts made of stainless steel.
e
Inspection applicable only to electrolytic coatings (cadmium, silver, etc.).
f
This inspection may be performed on nuts that have been subjected to the inspection of microstructure (see item no 1-2).
g
Test applicable only to all-metal self-locking wrench nuts.
h
For the qualification testing of all-metal self-locking nuts, the nuts shall be exposed for 6 h to the maximum operating
temperature specified in the definition document before the load is applied.
i
Test applicable only to wrench nuts.
j
Test applicable only to nuts heat-treated to a hardness equal to or greater than 44 HRC.
k
Test applicable only to floating-anchor nuts, gang channel nuts and fixed-anchor nuts, produced in several parts and
assembled by brazing or clinching.
l
Test applicable only to gang channel and anchor nuts, with the exception of corner nuts (see ISO 7481) and of reduced-
series single-lug nuts.
m
For all-metal self-locking nuts made of stainless steel with MoS -type dry-film lubrication, this test shall be carried out
over five cycles in order to avoid any risk of seizing.
n
Test applicable only to nuts of diameter 5 mm, 6 mm, 7 mm, 8 mm, 10 mm and 12 mm (see ISO 7481).
o
Test applicable only to sealing nuts.
p
Test applicable only to clinch nuts.

TTabablele 1 1 ((ccoonnttiinnueuedd))
Inspection and test Sample
Item-no Characteristic Technical requirement Test category
method size
a)  of molybde- There shall be no sign of Heat the nuts to the max- 5
num disulfide flaking, cracking or soften- imum operating tempera-
(MoS2) ing after test. ture specified in the defi-
nition document for 3 h,
then cool the nuts slowly to
ambient temperature.
b)  of silver There shall be no sign of Heat the nuts to the
blisters or exfoliation after maximum operating tem-
test. perature specified in the
definition document for
4 h, then rapidly cool the
nuts with compressed air
(at a pressure of 0,3 MPa
to 0,4 MPa) by means of a
nozzle with a diameter of
1,5 mm held close to the
surface of the nuts.
a
2-5 Corrosion resist- The surface coating speci- Neutral salt spray (NSS) Qualification 8
b
ance fied in the definition docu- test shall be carried out in
ment (protective treatment accordance with ISO 9227.
and, possibly, lubrication)
Exposure for 336 h with-
shall ensure effective pro-
out signs of corrosion.
tection against corrosion.
3 Surface condition
a
3-1 Appearance Finished nuts shall be free Visual examination. In Qualification 100
from burrs and bumps. the event of any doubt
Production accept- Tables 11
arising as to the nature
ance and 13
of the defects detected,
inspect defective nuts at a
magnification of × 10 after
sectioning.
a
3-2 Surface Rough- The surface roughness of the In accordance with ISO Qualification 5
c
ness nuts shall be as specified in 21920-3.
the definition document.
Visual examination.
a
See Clause 4 for applicability conditions.
b
Inspections applicable only to nuts made of steel or steel alloy.
c
Inspection to be carried out before coating of the surface or after removal of the surface coating.
d
Inspection applicable only to nuts made of stainless steel.
e
Inspection applicable only to electrolytic coatings (cadmium, silver, etc.).
f
This inspection may be performed on nuts that have been subjected to the inspection of microstructure (see item no 1-2).
g
Test applicable only to all-metal self-locking wrench nuts.
h
For the qualification testing of all-metal self-locking nuts, the nuts shall be exposed for 6 h to the maximum operating
temperature specified in the definition document before the load is applied.
i
Test applicable only to wrench nuts.
j
Test applicable only to nuts heat-treated to a hardness equal to or greater than 44 HRC.
k
Test applicable only to floating-anchor nuts, gang channel nuts and fixed-anchor nuts, produced in several parts and
assembled by brazing or clinching.
l
Test applicable only to gang channel and anchor nuts, with the exception of corner nuts (see ISO 7481) and of reduced-
series single-lug nuts.
m
For all-metal self-locking nuts made of stainless steel with MoS -type dry-film lubrication, this test shall be carried out
over five cycles in order to avoid any risk of seizing.
n
Test applicable only to nuts of diameter 5 mm, 6 mm, 7 mm, 8 mm, 10 mm and 12 mm (see ISO 7481).
o
Test applicable only to sealing nuts.
p
Test applicable only to clinch nuts.

TTabablele 1 1 ((ccoonnttiinnueuedd))
Inspection and test Sample
Item-no Characteristic Technical requirement Test category
method size
a
4 Marking The nuts shall be marked as Visual examination. Qualification 100
specified in the definition
Production accept- Tables 11
document.
ance and 14
5 Dimensions
a
5-1 General dimen- The dimensions and any Suitable limit gauges or Qualification 20
sions deviations in form and po- measuring instruments.
Production accept- Tables 11,14
sition, measured at ambient
ance and 15
temperature, shall be within
the limits specified in the
definition document.
a
5-2 Thread The thread shall be in con- Qualification 20
formity with the definition
Production accept- Tables 11
document.
ance and 13
— Nuts with locking by
plastic insert
The threaded GO gauge shall Threaded GO/NO GO
be capable of being freely gauges.
screwed up to the locking
device
— All-metal selflocking
nuts
The threaded GO gauge shall Threaded GO/NO GO
be capable of being freely gauges.
screwed for at least one
turn.
For nuts with molybdenum Bolt with standard threads
disulfide dry lubrication, a in accordance with
bolt with standard threads ISO 5855-2 shall be used.
shall be capable of being
freely screwed for at least
one turn.
a
See Clause 4 for applicability conditions.
b
Inspections applicable only to nuts made of steel or steel alloy.
c
Inspection to be carried out before coating of the surface or after removal of the surface coating.
d
Inspection applicable only to nuts made of stainless steel.
e
Inspection applicable only to electrolytic coatings (cadmium, silver, etc.).
f
This inspection may be performed on nuts that have been subjected to the inspection of microstructure (see item no 1-2).
g
Test applicable only to all-metal self-locking wrench nuts.
h
For the qualification testing of all-metal self-locking nuts, the nuts shall be exposed for 6 h to the maximum operating
temperature specified in the definition document before the load is applied.
i
Test applicable only to wrench nuts.
j
Test applicable only to nuts heat-treated to a hardness equal to or greater than 44 HRC.
k
Test applicable only to floating-anchor nuts, gang channel nuts and fixed-anchor nuts, produced in several parts and
assembled by brazing or clinching.
l
Test applicable only to gang channel and anchor nuts, with the exception of corner nuts (see ISO 7481) and of reduced-
series single-lug nuts.
m
For all-metal self-locking nuts made of stainless steel with MoS -type dry-film lubrication, this test shall be carried out
over five cycles in order to avoid any risk of seizing.
n
Test applicable only to nuts of diameter 5 mm, 6 mm, 7 mm, 8 mm, 10 mm and 12 mm (see ISO 7481).
o
Test applicable only to sealing nuts.
p
Test applicable only to clinch nuts.

TTabablele 1 1 ((ccoonnttiinnueuedd))
Inspection and test Sample
Item-no Characteristic Technical requirement Test category
method size
a
5-3 Wrench engage- The deformation necessary Female gauge satisfying Qualification 20
g
ment to achieve internal locking the following dimensional
Production accept- Tables 11
shall not prevent a wrench requirements:
ance and 14
from being used.
A female gauge, of identical a)  Hexagonal and bihex-
form to the driving feature agonal drive
of the nut being inspected,
Minimum tolerances spec-
shall be capable of being
ified shall be in accordance
freely installed over a length
with ISO 691.
equal to the wrenching
b)  Spline drive
height specified in the defi-
nition document.
Maximum material condi-
tion of female wrenching
device shall be in accord-
ance with ISO 7403.
a
5-4 Squareness of Any out-of-squareness of In accordance with Qualification 20
bearing surface the bearing surface, relative ISO 7481.
Production accept- Tables 11
to the thread, shall be
ance to 14
within the limits specified in
ISO 8788.
6 Performance
a
6-1 Axial load The finished nuts shall In accordance with Qualification 8 for 80 %
withstand the axial load ISO 7481. load and 8
specified for their tensile for 100 %
strength class, as laid down load
in the definition document.
Production accept- Table 16,
ance column B
a)  80 % test The nuts shall not display: The load to be applied is
specified in Table 3.
a
See Clause 4 for applicability conditions.
b
Inspections applicable only to nuts made of steel or steel alloy.
c
Inspection to be carried out before coating of the surface or after removal of the surface coating.
d
Inspection applicable only to nuts made of stainless steel.
e
Inspection applicable only to electrolytic coatings (cadmium, silver, etc.).
f
This inspection may be performed on nuts that have been subjected to the inspection of microstructure (see item no 1-2).
g
Test applicable only to all-metal self-locking wrench nuts.
h
For the qualification testing of all-metal self-locking nuts, the nuts shall be exposed for 6 h to the maximum operating
temperature specified in the definition document before the load is applied.
i
Test applicable only to wrench nuts.
j
Test applicable only to nuts heat-treated to a hardness equal to or greater than 44 HRC.
k
Test applicable only to floating-anchor nuts, gang channel nuts and fixed-anchor nuts, produced in several parts and
assembled by brazing or clinching.
l
Test applicable only to gang channel and anchor nuts, with the exception of corner nuts (see ISO 7481) and of reduced-
series single-lug nuts.
m
For all-metal self-locking nuts made of stainless steel with MoS -type dry-film lubrication, this test shall be carried out
over five cycles in order to avoid any risk of seizing.
n
Test applicable only to nuts of diameter 5 mm, 6 mm, 7 mm, 8 mm, 10 mm and 12 mm (see ISO 7481).
o
Test applicable only to sealing nuts.
p
Test applicable only to clinch nuts.

TTabablele 1 1 ((ccoonnttiinnueuedd))
Inspection and test Sample
Item-no Characteristic Technical requirement Test category
method size
— any cracks;
— any permanent set;
— any significant
reduction in their
locking torque.
b)  100 % test The nuts shall not display: The load to be applied is
h
specified in Table 4 .
— any cracks;
— any fractures.
Permanent set and resultant
effects (reduction or disap-
pearance of locking torque)
are permissible.
a
6-2 Wrenching fea- Finished nuts shall with- In accordance with Qualification 3
i
ture (wrench stand the torque specified ISO 7481.

torque) for the tensile strength
The torque shall be as
Production accept- Not appli-
class, as laid down in the
specified in Table 5 and
ance cable
definition document, and
shall be applied 15 times
shall not display any crack
by alternately tightening
or deformation preventing a
and untightening the nut.
standard socket or spanner
from being used.
a
See Clause 4 for applicability conditions.
b
Inspections applicable only to nuts made of steel or steel alloy.
c
Inspection to be carried out before coating of the surface or after removal of the surface coating.
d
Inspection applicable only to nuts made of stainless steel.
e
Inspection applicable only to electrolytic coatings (cadmium, silver, etc.).
f
This inspection may be performed on nuts that have been subjected to the inspection of microstructure (see item no 1-2).
g
Test applicable only to all-metal self-locking wrench nuts.
h
For the qualification testing of all-metal self-locking nuts, the nuts shall be exposed for 6 h to the maximum operating
temperature specified in the definition document before the load is applied.
i
Test applicable only to wrench nuts.
j
Test applicable only to nuts heat-treated to a hardness equal to or greater than 44 HRC.
k
Test applicable only to floating-anchor nuts, gang channel nuts and fixed-anchor nuts, produced in several parts and
assembled by brazing or clinching.
l
Test applicable only to gang channel and anchor nuts, with the exception of corner nuts (see ISO 7481) and of reduced-
series single-lug nuts.
m
For all-metal self-locking nuts made of stainless steel with MoS -type dry-film lubrication, this test shall be carried out
over five cycles in order to avoid any risk of seizing.
n
Test applicable only to nuts of diameter 5 mm, 6 mm, 7 mm, 8 mm, 10 mm and 12 mm (see ISO 7481).
o
Test applicable only to sealing nuts.
p
Test applicable only to clinch nuts.

TTabablele 1 1 ((ccoonnttiinnueuedd))
Inspection and test Sample
Item-no Characteristic Technical requirement Test category
method size
a
6-3 Stress embrittle- Heat treatment and surface In accordance with Qualification 3
j
ment treatment shall not cause ISO 7481.
any embrittlement that
The tightening torque ap-
can prevent the nuts from
plied shall be as specified
withstanding continuously,
in Table 6.
without cracking or ruptur-
The axial load shall be
ing, the axial load specified
applied for 168 h.
for their tensile strength
class, as laid down in the
definition document.
k a
6-4 Torque-out The retention device in the See ISO 7481. Qualification 3
body of the nut shall be
The torque specified in
capable of withstanding the
Table 7 shall be applied in
torque arising during screw-
both directions.
ing, tightening, unscrewing
and untightening, and the
body of the nut shall not
become detached from the
plate, cage or gang channel.
No crack or deformation
shall be present which is
likely to prevent the nut
from being re-used.
a
6-5 Non-rotation of During application of the See ISO 7481. Qualification 5
captive washer captive washer seating
The squeeze torque
torque, the washer shall not
applied shall be equal to
rotate on the bearing plate.
0,5 × the value specified in
The test is not applicable Table 6.
to nuts with a diameter
The seating torque applied
< 4 mm.
shall be the torque speci-
The test shall be carried out fied in Table 6.
on one cycle only.
a
See Clause 4 for applicability conditions.
b
Inspections applicable only to nuts made of steel or steel alloy.
c
Inspection to be carried out before coating of the surface or after removal of the surface coating.
d
Inspection applicable only to nuts made of stainless steel.
e
Inspection applicable only to electrolytic coatings (cadmium, silver, etc.).
f
This inspection may be performed on nuts that have been subjected to the inspection of microstructure (see item no 1-2).
g
Test applicable only to all-metal self-locking wrench nuts.
h
For the qualification testing of all-metal self-locking nuts, the nuts shall be exposed for 6 h to the maximum operating
temperature specified in the definition document before the load is applied.
i
Test applicable only to wrench nuts.
j
Test applicable only to nuts heat-treated to a hardness equal to or greater than 44 HRC.
k
Test applicable only to floating-anchor nuts, gang channel nuts and fixed-anchor nuts, produced in several parts and
assembled by brazing or clinching.
l
Test applicable only to gang channel and anchor nuts, with the exception of corner nuts (see ISO 7481) and of reduced-
series single-lug nuts.
m
For all-metal self-locking nuts made of stainless steel with MoS -type dry-film lubrication, this test shall be carried out
over five cycles in order to avoid any risk of seizing.
n
Test applicable only to nuts of diameter 5 mm, 6 mm, 7 mm, 8 mm, 10 mm and 12 mm (see ISO 7481).
o
Test applicable only to sealing nuts.
p
Test applicable only to clinch nuts.

TTabablele 1 1 ((ccoonnttiinnueuedd))
Inspection and test Sample
Item-no Characteristic Technical requirement Test category
method size
l a
6-6 Push-out Finished nuts shall be capa- See ISO 7481. Qualification 3
ble of withstanding the axial
The load specified in
load which can arise during
Table 8 shall be applied.
screwing without any cracks
appearing.
Any deformation at the
thread axis shall be less
than 0,8 mm and shall not
prevent a standard bolt
being installed over at least
one turn.
6-7 Locking The locking device shall
enable:
— the nuts to be re-used
after several removal
operations;
— correct tensioning
of the bolts when a
normal tightening
torque is applied, and
there shall be no risk of
causing the bolts to fail
under tension.
a
See Clause 4 for applicability conditions.
b
Inspections applicable only to nuts made of steel or steel alloy.
c
Inspection to be carried out before coating of the surface or after removal of the surface coating.
d
Inspection applicable only to nuts made of stainless steel.
e
Inspection applicable only to electrolytic coatings (cadmium, silver, etc.).
f
This inspection may be performed on nuts that have been subjected to the inspection of microstructure (see item no 1-2).
g
Test applicable only to all-metal self-locking wrench nuts.
h
For the qualification testing of all-metal self-locking nuts, the nuts shall be exposed for 6 h to the maximum operating
temperature specified in the definition document before the load is applied.
i
Test applicable only to wrench nuts.
j
Test applicable only to nuts heat-treated to a hardness equal to or greater than 44 HRC.
k
Test applicable only to floating-anchor nuts, gang channel nuts and fixed-anchor nuts, produced in several parts and
assembled by brazing or clinching.
l
Test applicable only to gang channel and anchor nuts, with the exception of corner nuts (see ISO 7481) and of reduced-
series single-lug nuts.
m
For all-metal self-locking nuts made of stainless steel with MoS -type dry-film lubrication, this test shall be carried out
over five cycles in order to avoid any risk of seizing.
n
Test applicable only to nuts of diameter 5 mm, 6 mm, 7 mm, 8 mm, 10 mm and 12 mm (see ISO 7481).
o
Test applicable only to sealing nuts.
p
Test applicable only to clinch nuts.

TTabablele 1 1 ((ccoonnttiinnueuedd))
Inspection and test Sample
Item-no Characteristic Technical requirement Test category
method size
After the test has been
completed, the thread of the
b
...