ISO 12125:2012

Prevailing torque type hexagon nuts with flange (with non-metallic insert) with metric fine pitch thread, style 2 - Product grades A and B

ISO 12125:2012 specifies the characteristics of prevailing torque type all metal hexagon nuts with flange (with non-metallic insert) of style 2, with 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 (à anneau non métallique), 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 12125:1997 - Prevailing torque type hexagon nuts with flange (with non-metallic insert) with metric fine pitch thread - Product grades A and B
• Effective Date: 16-Feb-2012

Overview

ISO 12125:2012 is an international standard that defines the specifications for prevailing torque type hexagon nuts with flange and non-metallic inserts, featuring metric fine pitch threads. The standard applies to style 2 nuts with nominal thread diameters ranging from 8 mm to 20 mm. It covers two product grades: Grade A for diameters up to 16 mm, and Grade B for diameters greater than 16 mm. These nuts come in property classes 6, 8, and 10, ensuring a range of mechanical strengths suitable for various engineering applications.

Prevailing torque hexagon nuts with flange are designed to provide reliable resistance to loosening under vibration and other dynamic loads, due to the integrated non-metallic insert which enhances the locking mechanism. The nuts specified in ISO 12125:2012 comply with tight dimensional and mechanical property requirements, making them ideal for critical fastening applications.

Key Topics

• Product Scope: Covers all-metal hexagon nuts with flange and a non-metallic insert, with metric fine pitch threads, style 2.
• Dimensions: Detailed thread and nut dimensions correspond to ISO 10663, with additional prevailing torque features specified.
• Grades and Property Classes:
  • Product Grade A: For nut sizes with diameters ≤ 16 mm
  • Product Grade B: For nut sizes with diameters > 16 mm
  • Property Classes: 6, 8, 10 transverse mechanical strength ratings.
• Materials and Inserts: Nut bodies typically made from steel with polyamide or similar non-metallic inserts for prevailing torque.
• Thread Standards: Complies with ISO 261, ISO 724, and ISO 965-2 for metric fine pitch threads.
• Mechanical Requirements: Conformance to ISO 898-2 and ISO 2320 for mechanical and performance properties.
• Tolerance and Surface Finish:
  • ISO 4759-1 tolerant grades for thread and dimensional accuracy.
  • Electroplated finishes follow ISO 4042; zinc flake coatings per ISO 10683.
  • Surface discontinuity limits per ISO 6157-2.
• Gauging and Inspection: Uses specific gauges for dimensional checks, detailed in Annex A, ensuring compliance with standards.
• Designation Format: Clearly defined nut identification includes type, thread size, and property class (e.g., ISO 12125 - M12 × 1.5 - 8).

Applications

ISO 12125:2012 prevailing torque hexagon nuts with flange are vital components in industries requiring secure, vibration-resistant fasteners. Typical applications include:

• Automotive engineering – For engine assemblies and chassis components where fine pitch threads and secure fastening are critical.
• Aerospace and aviation – In structural components requiring high performance locking nuts that withstand vibration.
• Mechanical and industrial machinery – Use in precision equipment and assemblies needing fine thread pitch and reliable locking.
• Electrical and electronic equipment – Where controlled fastening torque and thread engagement prevent loosening.
• Construction and heavy machinery – Providing strong locking nuts for heavy-duty applications involving dynamic loads.
• General engineering – Any application requiring high-quality metric fine pitch fastening solutions with prevailing torque properties.

These nuts ensure safety, reliability, and consistent performance under demanding conditions thanks to strict adherence to ISO standards.

Related Standards

ISO 12125:2012 references and complements several key international standards to ensure interoperability and quality:

• ISO 10663 – Dimensions for hexagon nuts with flange.
• ISO 898-2 – Mechanical properties of nuts with specified property classes.
• ISO 2320 – Mechanical and performance properties of prevailing torque steel nuts.
• ISO 261, ISO 724, ISO 965-2 – Thread profile and tolerance specifications for metric fine pitch screws.
• ISO 4759-1 – Tolerances for fastener product grades.
• ISO 4042 and ISO 10683 – Electroplated and zinc flake coatings for fasteners.
• ISO 6157-2 – Surface discontinuity requirements to ensure quality.
• ISO 3269 – Acceptance inspection procedures for fasteners.
• ISO 8992 – General requirements for bolts, screws, studs, and nuts.

These interconnected standards support adherence to consistent quality, performance, and compatibility in fastening components worldwide.

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Keywords: ISO 12125:2012, prevailing torque hexagon nuts, flange nuts, metric fine pitch thread, non-metallic insert, product grade A, product grade B, property classes 6 8 10, fastening standards, vibration-resistant nuts, ISO fasteners, industrial nuts, engineering nuts, metric nuts, locking nuts.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 12125
Second edition
2012-09-01
Prevailing torque type hexagon nuts
with flange (with non-metallic insert)
with metric fine pitch thread, style 2 —
Product grades A and B
Écrous hexagonaux à embase, autofreinés (à anneau non métallique),
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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Published in Switzerland
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 12125 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 12125:1997), of which it constitutes a minor revision.
iv © ISO 2012 – All rights reserved

INTERNATIONAL STANDARD ISO 12125:2012(E)
Prevailing torque type hexagon nuts with flange (with non-
metallic insert) 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 (with non-metallic insert) of style 2, with 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
...