ISO 3191:1998

Aerospace - Nuts, anchor, self-locking, fixed, single lug, reduced series, with counterbore, with MJ threads, classifications: 1 100 MPa (at ambient temperature)/235 degrees C, 1 100 MPa (at ambient temperature)/315 degrees C and 1 100 MPa (at ambient temperature)/425 degrees C - Dimensions

This International Standard specifies the dimensions of self-locking, fixed, single lug anchor nuts, reduced series, with counterbore, with MJ threads, for classifications: 1 100 MPa1)/235 °C2), 1 100 MPa1)/315 °C2) and 1 100 MPa1)/425 °C2). This International Standard is only applicable for the compilation of aerospace product standards.

Aéronautique et espace — Écrous à river, à freinage interne, fixes, simple patte, série réduite, avec chambrage, à filetage MJ, classifications: 1 100 MPa (à température ambiante )/235 degrés C, 1 100 MPa (à température ambiante) /315 degrés C et 1 100 MPa (à température ambiante )/425 degrés C — Dimensions

La présente Norme internationale prescrit les dimensions des écrous à river, à freinage interne, fixes, simple patte, série réduite, avec chambrage, à filetage MJ, de classifications: 1 100 MPa1)/235 °C2), 1 100 MPa1)/315 °C2) et 1 100 MPa1)/425 °C2). La présente Norme internationale est applicable uniquement à l'élaboration de normes de produit destinées aux constructions aérospatiales.

General Information

• Status: Published
• Publication Date: 02-Dec-1998
• ICS: 49.030.30 - Nuts
• Technical Committee: ISO/TC 20/SC 4 - Aerospace fastener systems
• Drafting Committee: ISO/TC 20/SC 4 - Aerospace fastener systems
• Current Stage: 9093 - International Standard confirmed
• Start Date: 19-Oct-2021
• Completion Date: 13-Dec-2025

Relations

• Consolidated By: ISO 14589:2000 - Blind rivets - Mechanical testing
• Effective Date: 06-Jun-2022
• Revises: ISO 3191:1985 - Aerospace - Self-locking, fixed, single-lug anchor nuts, reduced series, with counterbore, strength classification 1 100 MPa and maximum operating temperature 235 degrees C
• Effective Date: 15-Apr-2008

Overview

ISO 3191:1998 is an international standard developed by ISO's Technical Committee ISO/TC 20/SC 4, which specializes in aerospace fasteners. This standard specifies the dimensions of self-locking, fixed, single lug anchor nuts, a specialized type of aerospace fastener characterized by a reduced series size, a counterbore design, and MJ threads. It covers nuts classified to withstand tensile stresses of 1,100 MPa at ambient temperature and high-temperature endurance at 235 °C, 315 °C, and 425 °C.

This standard is critical for the aerospace industry, ensuring uniformity and reliability in components that require secure fastening under extreme conditions. ISO 3191:1998 supports aerospace product standardization, providing precise dimensional requirements for anchor nuts used in structural and mechanical assemblies.

Key Topics

• Nut Type: Anchor nuts that are self-locking and fixed with a single lug for secure attachment in aerospace structures.
• Thread Standard: MJ threads, which are specific metric threads used in aerospace fasteners.
• Dimensional Specifications: Detailed dimensions and tolerances expressed in millimeters, including nut height, diameter, lug size, and counterbore dimensions.
• Material Stress Classifications:
  • 1,100 MPa at ambient temperature / 235 °C
  • 1,100 MPa at ambient temperature / 315 °C
  • 1,100 MPa at ambient temperature / 425 °C
• Surface Treatment Considerations: Dimensions apply post surface coating but before lubrication, with the requirement that optional metallic caps must remain fixed at maximum use temperature.
• Tolerance Compliance: Must adhere to ISO 8788 for shape and positional tolerances to ensure interchangeability and reliable performance.
• Purpose: To support the development and application of aerospace product standards ensuring nut reliability under mechanical stress and thermal exposure.

Applications

ISO 3191:1998 nuts are widely used in:

• Aerospace Structural Assemblies: Ensuring secure fastening of critical airframe components subjected to vibration and thermal cycling.
• High-Temperature Aerospace Environments: Suitable for applications requiring integrity at elevated temperatures, such as engines, exhaust systems, and thermal protection elements.
• Precision Mechanical Systems in Aircraft: Ideal for fixed attachment points where self-locking capabilities prevent loosening under aerodynamic forces.
• Manufacturing of Aerospace Fasteners: Provides manufacturers with strict guidelines for nut dimension compliance when producing self-locking anchor nuts.
• Maintenance and Spare Part Standardization: Facilitates replacement with certified nuts that meet stringent aerospace standards, ensuring safety and compatibility.

Related Standards

ISO 3191 references and complements several important aerospace fastener standards, including:

• ISO 5855-2:1988 – Covers limits for dimensions of MJ threads used in screws and nuts.
• ISO 5858:1991 – Specifications for self-locking nuts with maximum service temperatures up to 425 °C.
• ISO 8788:1987 – Defines tolerances of shape and position specifically for aerospace fastener nuts.
• ISO 5858 – Guidelines for procurement specifications related to internal locking nuts.

By aligning with these standards, ISO 3191:1998 ensures compatibility and consistency across various aerospace components and fasteners, facilitating quality control, interoperability, and safety in the aerospace sector.

---

Adopting ISO 3191:1998 is essential for aerospace manufacturers, designers, and quality assurance professionals who require standardized, reliable fasteners that perform under stringent mechanical and environmental conditions. This standard supports the aerospace industry's commitment to safety, durability, and international compatibility in fastener design.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 3191
Second edition
1998-12-01
Aerospace — Nuts, anchor, self-locking,
fixed, single lug, reduced series, with
counterbore, with MJ threads,
classifications: 1 100 MPa (at ambient
temperature) / 235 °C, 1 100 MPa (at
ambient temperature) / 315 °C and 1 100 MPa
(at ambient temperature) / 425 °C —
Dimensions
Aéronautique et espace — Écrous à river, à freinage interne, fixes, simple
patte, série réduite, avec chambrage, à filetage MJ, classifications:
1 100 MPa (à température ambiante) / 235 °C, 1 100 MPa (à température
ambiante) / 315 °C et 1 100 MPa (à température ambiante) / 425 °C —
Dimensions
A
Reference number
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.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard ISO 3191 was prepared by Technical Committee
ISO/TC 20, Aircraft and space vehicles, Subcommittee SC 4, Aerospace
fastener systems.
This second edition cancels and replaces the first edition (ISO 3191:1985),
which has been technically revised.
©  ISO 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet [e-mail]
Printed in Switzerland
ii
©
ISO ISO 3191:1998(E)
Introduction
The dimensions specified in this International Standard have been
determined to satisfy the requirements of the procurement specification of
ISO 5858.
iii
©
INTERNATIONAL STANDARD  ISO ISO 3191:1998(E)
Aerospace — Nuts, anchor, self-locking, fixed, single lug, reduced
series, with counterbore, with MJ threads, classifications:
1 100 MPa (at ambient temperature) / 235 °C, 1 100 MPa
(at ambient temperature) / 315 °C and 1 100 MPa (at ambient
temperature) / 425 °C — Dimensions
1  Scope
This International Standard specifies the dimensions of self-locking, fixed, single lug anchor nuts, reduced series,
1) 2) 1) 2)
with counterbore, with MJ threads, for classifications: 1 100 MPa /235 °C , 1 100 MPa /315 °C and
1)
2)
1 100 MPa /425 °C .
This Intern
...

NORME ISO
INTERNATIONALE 3191
Deuxième édition
1998-12-01
Aéronautique et espace — Écrous à river,
à freinage interne, fixes, simple patte, série
réduite, avec chambrage, à filetage MJ,
classifications: 1 100 MPa (à température
ambiante) / 235 °C, 1 100 MPa
(à température ambiante) / 315 °C et
1 100 MPa (à température ambiante) /
425 °C — Dimensions
Aerospace — Nuts, anchor, self-locking, fixed, single lug, reduced series,
with counterbore, with MJ threads, classifications: 1 100 MPa (at ambient
temperature) / 235 °C, 1 100 MPa (at ambient temperature) / 315 °C and
1 100 MPa (at ambient temperature) / 425 °C — Dimensions
A
Numéro de référence
Avant-propos
L'ISO (Organisation internationale de normalisation) est une fédération
mondiale d'organismes nationaux de normalisation (comités membres de
l'ISO). L'élaboration des Normes internationales est en général confiée aux
comités techniques de l'ISO. Chaque comité membre intéressé par une
étude a le droit de faire partie du comité technique créé à cet effet. Les
organisations internationales, gouvernementales et non gouvernementales,
en liaison avec l'ISO participent également aux travaux. L'ISO collabore
étroitement avec la Commission électrotechnique internationale (CEI) en
ce qui concerne la normalisation électrotechnique.
Les projets de Normes internationales adoptés par les comités techniques
sont soumis aux comités membres pour vote. Leur publication comme
Normes internationales requiert l'approbation de 75 % au moins des
comités membres votants.
La Norme internationale ISO 3191 a été élaborée par le comité technique
ISO/TC 20, Aéronautique et espace, sous-comité SC 4, Éléments de
fixation pour constructions aérospatiales.
Cette deuxième édition annule et remplace la première (ISO 3191:1985),
dont elle constitue une révision technique.
©  ISO 1998
Droits de reproduction réservés. Sauf prescription différente, aucune partie de cette publi-
cation ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun pro-
cédé, électronique ou mécanique, y compris la photocopie et les microfilms, sans l'accord
écrit de l'éditeur.
Organisation internationale de normalisation
Case postale 56 • CH-1211 Genève 20 • Suisse
Internet [e-mail]
Imprimé en Suisse
ii
©
ISO ISO 3191:1998(F)
Introduction
Les dimensions prescrites dans la présente Norme internationale ont été
définies pour satisfaire aux exigences de la spécification d'approvisionnement
de l'ISO 5858.
iii
©
NORME INTERNATIONALE  ISO ISO 3191:1998(F)
Aéronautique et espace — Écrous à river, à freinage interne, fixes,
simple patte, série réduite, avec chambrage, à filetage MJ,
classifications: 1 100 MPa (à température ambiante) / 235 °C,
1 100 MPa (à température ambiante) / 315 °C et 1 100 MPa
(à température ambiante) / 425 °C — Dimensions
1  Domaine d'application
La présente Norme internationale prescrit les dimensions des écrous à river, à freinage interne, fixes, simple patte,
1) 2) 1) 2)
série réduite, avec chambrage, à filetage MJ, de classifications: 1 100 MPa /235 °C , 1 100 MPa /315 °C et
1) 2)
1 100 MPa /425 °C .
La présente Norme internationale est applicable uniquement à l'élaboration de normes de produit destinées aux
construction
...