ISO 12126:2012

Prevailing torque type all-metal hexagon nuts with flange with metric fine pitch thread, style 2 - Product grades A and B

ISO 12126:2012 specifies the characteristics of prevailing torque type all metal hexagon nuts with flange (style 2), and metric fine pitch thread with nominal thread diameters from 8 mm up to and including 20 mm, in product grade A for diameter sizes less than or equal to 16 mm and product grade B for diameter sizes greater than 16 mm, and with property classes 6, 8 and 10.

Écrous hexagonaux à embase, autofreinés, tout métal, à filetage métrique à pas fin, style 2 — Grades A et B

General Information

• Status: Published
• Publication Date: 16-Aug-2012
• ICS: 21.060.20 - Nuts
• Technical Committee: ISO/TC 2/SC 12 - Fasteners with metric internal thread
• Drafting Committee: ISO/TC 2/SC 12 - Fasteners with metric internal thread
• Current Stage: 9093 - International Standard confirmed
• Start Date: 01-Jul-2022
• Completion Date: 13-Dec-2025

Relations

• Revises: ISO 12126:1997 - Prevailing torque type all-metal hexagon nuts with flange with metric fine pitch thread - Product grades A and B
• Effective Date: 16-Feb-2012

Overview

ISO 12126:2012 defines the standards for prevailing torque type all-metal hexagon nuts with flange, specifically with metric fine pitch threads. These nuts are style 2 and cover nominal thread diameters from 8 mm up to and including 20 mm. The standard classifies the nuts into two product grades: Grade A for diameters up to 16 mm and Grade B for diameters above 16 mm, with mechanical property classes 6, 8, and 10. These nuts ensure reliable fastening through their prevailing torque feature, preventing loosening under vibration or dynamic loading conditions.

This international standard is essential for manufacturers, suppliers, and quality inspectors to ensure consistency, performance, and interchangeability in engineering applications where precise torque retention and fine threads are needed.

Key Topics

• Product Scope: Covers prevailing torque all-metal hex flange nuts (style 2) with metric fine pitch threads sized 8 mm to 20 mm.
• Grades and Property Classes:
  • Grade A: For thread diameter ≤ 16 mm
  • Grade B: For thread diameter > 16 mm
  • Property classes: 6, 8, and 10 provide mechanical performance specifications.
• Dimensional Specifications: Dimensions are aligned with ISO 10663 but with added prevailing torque features. Detailed sizes and tolerances are specified in tables for thread pitch, flange thickness, hexagon size, and nut height.
• Material and Mechanical Properties: Steel material requirements meeting ISO 8992 and mechanical properties conforming to ISO 898-2 and ISO 2320.
• Gauging and Inspection:
  • Recommended gauging methods using ring gauges ensure adherence to hexagon and flange dimensions.
  • Surface discontinuity limits and finish requirements are specified via ISO 6157-2, ISO 4042 (electroplating), and ISO 10683 (zinc flake coatings).
• Related Normative References:
  • ISO 261, ISO 724, ISO 965-2 for metric thread geometry and tolerances.
  • ISO 4759-1 for tolerance classes and product grades.
  • ISO 3269 for acceptance inspection procedures.
• Designation Format: Nuts are designated by the standard number, thread size, and property class (e.g., ISO 12126 - M12 × 1.5 - 8).

Applications

ISO 12126:2012 nuts are critical components for industries requiring secure fastening with fine pitch threads and reliable torque resistance, such as:

• Automotive Engineering: Used in engine assemblies and precision components where vibration resistance and fine adjustment are essential.
• Aerospace: Applications demanding high strength, precise torque, and resistance to loosening under dynamic stresses.
• Machinery Manufacturing: For devices requiring precise assembly with fine pitch threads enhancing clamping stability.
• Electronics and Electrical Equipment: Where compact assemblies with fine threads provide better torque control.
• Construction and Structural Engineering: Applied when high-strength fasteners with reliable retaining torque are necessary.

The standard supports manufacturers and engineers in achieving high reliability and safety by specifying mechanical properties, thread precision, and flange dimensions.

Related Standards

ISO 12126:2012 references and complements several international standards for comprehensive fastener specification and quality control:

• ISO 10663 - Dimensions for hexagon nuts with flange.
• ISO 898-2 - Specifies mechanical properties of nuts with specified classes.
• ISO 261, ISO 724, ISO 965-2 - Define metric screw thread geometry and tolerances.
• ISO 2320 - Addresses mechanical and performance properties of prevailing torque steel nuts.
• ISO 4759-1 - Provides tolerance specifications for bolts, screws, studs, and nuts across product grades.
• ISO 4042 and ISO 10683 - Define electroplated coatings and zinc flake coating requirements.
• ISO 6157-2 - Specifies acceptable surface discontinuities.
• ISO 3269 - Outlines acceptance inspection for fasteners.
• ISO 8992 - Covers general requirements for bolts, screws, studs, and nuts.

These interconnected standards ensure a harmonized approach to fastener design, manufacturing, coating, inspection, and performance verification.

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Keywords: ISO 12126, prevailing torque hexagon nuts, all-metal flange nuts, metric fine pitch thread, product grade A, product grade B, fastener standards, mechanical property classes, ISO fastener specifications, hex nuts with flange, torque retaining nuts, fine pitch thread fasteners, quality inspection fasteners.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 12126
Second edition
2012-09-01
Prevailing torque type all-metal hexagon
nuts with flange with metric fine pitch
thread, style 2 — Product grades A and B
Écrous hexagonaux à embase, autofreinés, tout métal, à filetage
métrique à pas fin, style 2 — Grades A et B
Reference number
©
ISO 2012
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 either ISO at the address below or ISO’s
member body in the country of the requester.
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ii © ISO 2012 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Dimensions . 1
4 Requirements and reference International Standards . 4
5 Designation . 4
Annex A (informative) Gauging of hexagon nuts with flange . 5
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. 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.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 12126 was prepared by Technical Committee ISO/TC 2, Fasteners, Subcommittee SC 12, Fasteners with
metric internal thread.
This second edition cancels and replaces the first edition (ISO 12126:1997), of which it constitutes a minor revision.
iv © ISO 2012 – All rights reserved

INTERNATIONAL STANDARD ISO 12126:2012(E)
Prevailing torque type all-metal hexagon nuts with flange with
metric fine pitch thread, style 2 — Product grades A and B
1 Scope
This International Standard specifies the characteristics of prevailing torque type all metal hexagon nuts with
flange (style 2), and metric fine pitch thread with nominal thread diameters, D, from 8 mm up to and including
20 mm, in product grade A for sizes D ≤ 16 mm and product grade B for sizes D > 16 mm, and with property
classes 6, 8 and 10.
NOTE The dimensions of the nuts correspond to those given in ISO 10663 plus prevailing torque feature.
If other specifications are required, they can be selected from existing International Standards, for example
ISO 261, ISO 724, ISO 898-2, ISO 965-2, ISO 2320 and ISO 4759-1.
2 Normative references
The following referenced documents are indispensable for the application 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 225, Fasteners — Bolts, screws, studs and nuts — Symbols and descriptions of dimensions
ISO 261, ISO general purpose metric screw threads — General plan
ISO 724, ISO general-purpose metric screw threads — Basic dimensions
ISO 898-2, Mechanical properties of fasteners made of carbon steel and alloy steel — Part 2: Nuts with
specified property classes – Coarse thread and fine pitch thread
ISO 965-2, ISO general purp
...