ISO 4161:2012

Hexagon nuts with flange, style 2 - Coarse thread

ISO 4161:2012 specifies the characteristics of hexagon nuts with flange (style 2), with metric coarse threads from M5 to M20 inclusive, of product grade A for threads up to and including M16 and product grade B for threads above M16.

Écrous hexagonaux à embase cylindro-tronconique, style 2 — Filetage à pas gros

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 4161:1999 - Hexagon nuts with flange - Coarse thread
• Effective Date: 16-Feb-2012

Overview

ISO 4161:2012 specifies the characteristics of hexagon nuts with flange, style 2 - coarse thread. It applies to metric coarse threads from M5 to M20 inclusive, and defines product grades: A for threads up to and including M16 and B for threads above M16. The standard covers dimensions, tolerances, mechanical properties references and gauging methods to ensure interchangeability and consistent quality for flange hex nuts.

Key topics and requirements

• Scope and designation
  • Applies to hexagon nuts with flange (style 2), coarse threads M5–M20.
  • Example designation: “Hexagon nut with flange ISO 4161 - M12 - 10”.
• Dimensions and geometry
  • Detailed nominal sizes, pitches and dimensional limits (height, flange thickness, width across flats/corners) are given in Figure 1 and Table 1.
  • Corner radii and edge contour guidance are included; certain sizes (e.g., M14) are noted as preferably avoided.
• Thread and tolerance
  • General-purpose metric thread standards and tolerance class 6H are referenced.
  • Thread tolerances and limits are to follow ISO 261 / ISO 965-2 where applicable.
• Product grades and mechanical properties
  • Product grade A for D ≤ M16 and B for D > M16 (per ISO 4759-1).
  • Mechanical property classes (e.g., 8, 9, 10, 12) and stainless grades (e.g., A2-70) are specified by reference to ISO 898-2 and ISO 3506-2.
• Gauging and acceptance
  • Annex A gives a recommended gauging method using two plain ring gauges (A and B) and a feeler or ring gauge (C) to check hexagon height, flange thickness, corner fill and width across corners.
  • Acceptance inspection references ISO 3269; surface discontinuities per ISO 6157-2.
• Finishes and coatings
  • Electroplating per ISO 4042, zinc flake per ISO 10683, and hot-dip galvanizing per ISO 10684. Additional finishes to be agreed between purchaser and supplier.

Applications and users

ISO 4161:2012 is intended for:

• Fastener manufacturers producing hexagon nuts with flange (style 2) to ensure dimensional conformity.
• Design and mechanical engineers specifying reliable, interchangeable flange hex nuts in assemblies.
• Quality inspectors and procurement teams performing gauging, acceptance and supplier audits.
• Supply chain and standards compliance professionals ensuring parts match international mechanical and coating requirements.

Typical applications include machinery assemblies, automotive components, construction connections and any bolted joint requiring integrated flange nuts for load distribution and assembly reliability.

Related standards

Key referenced standards for threads, tolerances, properties and testing:

• ISO 225, ISO 261, ISO 724, ISO 965-2
• ISO 898-2, ISO 3506-2 (mechanical properties)
• ISO 4759-1 (product grades)
• ISO 3269 (acceptance inspection), ISO 6157-2 (surface discontinuities)
• ISO 4042, ISO 10683, ISO 10684 (coatings)

Keywords: ISO 4161:2012, hexagon nuts with flange, style 2, coarse thread, M5–M20, product grade A, product grade B, gauging, fastener standards.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 4161
Third edition
2012-09-01
Hexagon nuts with flange, style 2 —
Coarse thread
Écrous hexagonaux à embase cylindro-tronconique, style 2 —
Filetage à pas gros
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
Bibliography . 7
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 4161 was prepared by Technical Committee ISO/TC 2, Fasteners, Subcommittee SC 12, Fasteners with
internal metric thread.
This third edition cancels and replaces the second edition (ISO 4161:1999), of which it constitutes a minor revision.
iv © ISO 2012 – All rights reserved

INTERNATIONAL STANDARD ISO 4161:2012(E)
Hexagon nuts with flange, style 2 — Coarse thread
1 Scope
This International Standard specifies the characteristics of hexagon nuts with flange (style 2), with metric
coarse threads from M5 to M20 inclusive, of product grade A for threads up to and including M16 and product
grade B for threads above M16.
If, in special cases, specifications other than those listed in this International Standard are required, they can be
selected from existing International Standards, for example ISO 261, ISO 724, ISO 898-2, ISO 965-2 and ISO 3506-2.
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 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 purpose metric screw threads — Tolerances — Part 2: Limits of sizes for general
purpose external and internal screw threads — Medium quality
ISO 3269, Fasteners — Acceptance inspection
ISO 3506-2, Mechanical properties of corrosion-resis
...