ISO 261:1998
(Main)ISO general purpose metric screw threads - General plan
ISO general purpose metric screw threads - General plan
This International Standard specifies ISO general purpose metric screw threads (M) having basic profile according to ISO 68-1. Basic dimensions are given in ISO 724. For tolerances see ISO 965-1.
Filetages métriques ISO pour usages généraux — Vue d'ensemble
La présente Norme internationale spécifie les filetages ISO métriques (M) pour usages généraux, dont le profil de base est conforme à l'ISO 68-1. Les dimensions de base sont données dans l'ISO 724. Pour les tolérances, voir l'ISO 965-1.
General Information
Relations
Overview
ISO 261:1998 provides the general plan for ISO general-purpose metric screw threads (M). The standard establishes the framework for selecting nominal diameters and thread pitches and ties the metric thread form to the basic profile in ISO 68-1, with basic dimensions in ISO 724 and tolerances referenced to ISO 965-1. ISO 261 is intended as a practical guide for designers, manufacturers and engineers working with standard metric threads.
Key Topics
- Scope: Specifies ISO general-purpose metric screw threads (M) with the basic profile defined by ISO 68-1. Basic dimensions are given in ISO 724; tolerances are specified in ISO 965-1.
- Designation: Thread designation shall follow the rules in ISO 965-1.
- Diameter and pitch selection:
- Preference is given to diameters listed in the standard in a prioritized set of columns (choose column 1 first, then column 2, then column 3).
- For each selected nominal diameter (or diameter range), select one of the pitches shown on the corresponding line.
- The standard distinguishes “coarse” and “fine” pitches to reflect common practice; these terms do not imply quality differences.
- Some pitches shown in parentheses are to be avoided where possible.
- A specific list of finer pitches that may be used when finer than table values are required is provided: 3 mm, 2 mm, 1.5 mm, 1 mm, 0.75 mm, 0.5 mm, 0.35 mm, 0.25 mm, 0.2 mm.
- The standard notes increasing difficulty in meeting tolerances for larger diameters with a given pitch.
- Special cases: Certain diameters and pitches are reserved for specific applications (for example, some sizes are noted only for spark plugs or for locking nuts for bearings).
Applications
ISO 261 is useful for:
- Mechanical designers specifying fasteners for assemblies where ISO metric threads are required.
- Manufacturers and procurement teams looking to standardize screw, bolt and nut sizes across product ranges.
- Quality and inspection personnel referencing the appropriate system for designation, pitch selection and conformity checks.
By following ISO 261, users ensure compatibility with ISO profile and dimension standards, simplify interchangeability, and reduce the need for bespoke thread forms.
Related Standards
- ISO 68-1 - Basic profile for metric screw threads (referenced for thread form)
- ISO 724 - Basic dimensions for ISO metric screw threads
- ISO 965-1 - Principles and basic data for tolerances and designation
- ISO 262 and ISO 5408 are additional normative references related to sizes and vocabulary
Following ISO 261:1998 ensures a harmonized approach to metric thread selection and designation in line with international practice.
Frequently Asked Questions
ISO 261:1998 is a standard published by the International Organization for Standardization (ISO). Its full title is "ISO general purpose metric screw threads - General plan". This standard covers: This International Standard specifies ISO general purpose metric screw threads (M) having basic profile according to ISO 68-1. Basic dimensions are given in ISO 724. For tolerances see ISO 965-1.
This International Standard specifies ISO general purpose metric screw threads (M) having basic profile according to ISO 68-1. Basic dimensions are given in ISO 724. For tolerances see ISO 965-1.
ISO 261:1998 is classified under the following ICS (International Classification for Standards) categories: 21.040.10 - Metric screw threads. The ICS classification helps identify the subject area and facilitates finding related standards.
ISO 261:1998 has the following relationships with other standards: It is inter standard links to ISO 261:1973. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
You can purchase ISO 261:1998 directly from iTeh Standards. The document is available in PDF format and is delivered instantly after payment. Add the standard to your cart and complete the secure checkout process. iTeh Standards is an authorized distributor of ISO standards.
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 261
Second edition
1998-12-15
ISO general purpose metric screw
threads — General plan
Filetages métriques ISO pour usages généraux — Vue d’ensemble
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 261 was prepared by Technical Committee ISO/TC 1, Screw threads, Subcommittee
SC 1, Basic data.
This second edition cancels and replaces the first edition (ISO 261:1973) 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 iso@iso.ch
Printed in Switzerland
ii
©
INTERNATIONAL STANDARD ISO ISO 261:1998(E)
ISO general purpose metric screw threads — General plan
1 Scope
This International Standard specifies ISO general purpose metric screw threads (M) having basic profile according
to ISO 68-1. Basic dimensions are given in ISO 724. For tolerances see ISO 965-1.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the editions indicated were valid. All standards are subject to
revision, and parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
ISO 68-1:1998, ISO general purpose screw threads — Basic profile — Part 1: Metric screw threads.
ISO 262:1998, ISO general purpose metric screw threads — Selected sizes for screws, bolts and nuts.
ISO 724:1993, ISO general purpose metric screw threads — Basic dimensions.
ISO 965-1:1998, ISO general purpose metric screw threads — Tolerances — Part 1: Principles and basic data.
ISO 5408:1983, Cylindrical screw threads — Vocabulary.
3 Definitions
For the purposes of this International Standard, the definitions given in ISO 5408 apply.
4 Designation
A screw thread in conformity with this International Standard shall be designated according to ISO 965-1.
©
ISO
5 Choice of diameter and pitch
5.1 Choose, for preference, diameters in column 1 of table 2 and, if necessary, in column 2 and then in column 3.
Diameter 35 mm, and pitch
...
NORME ISO
INTERNATIONALE 261
Deuxième édition
1998-12-15
Filetages métriques ISO pour usages
généraux — Vue d’ensemble
ISO general purpose metric screw threads — General plan
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 261 a été élaborée par le comité technique ISO/TC 1, Filetages, sous-comité SC 1,
Données fondamentales.
Cette deuxième édition annule et remplace la première édition (ISO 261:1973), dont elle constitue une révision
technique.
© ISO 1998
Droits de reproduction réservés. Sauf prescription différente, aucune partie de cette publication ne peut être reproduite ni utilisée sous quelque
forme que ce soit et par aucun procédé, 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 iso@iso.ch
Imprimé en Suisse
ii
©
NORME INTERNATIONALE ISO ISO 261:1998(F)
Filetages métriques ISO pour usages généraux —
Vue d’ensemble
1 Domaine d'application
La présente Norme internationale spécifie les filetages ISO métriques (M) pour usages généraux, dont le profil de
base est conforme à l'ISO 68-1. Les dimensions de base sont données dans l'ISO 724. Pour les tolérances, voir
l'ISO 965-1.
2 Références normatives
Les normes suivantes contiennent des dispositions qui, par suite de la référence qui en est faite, constituent des
dispositions valables pour la présente Norme internationale. Au moment de la publication, les éditions indiquées
étaient en vigueur. Toute norme est sujette à révision et les parties prenantes des accords fondés sur la présente
Norme internationale sont invitées à rechercher la possibilité d'appliquer les éditions les plus récentes des normes
indiquées ci-après. Les membres de la CEI et de l'ISO possèdent le registre des Normes internationales en vigueur
à un moment donné.
ISO 68-1:1998, Filetages ISO pour usages généraux — Profil de base — Partie 1: Filetages métriques.
ISO 262:1998, Filetages métriques ISO pour usages généraux — Sélection de dimensions pour la boulonnerie.
ISO 724:1993, Filetages métriques ISO pour usages généraux — Dimensions de base.
ISO 965-1:1998, Filetages métriques ISO pour usages généraux — Tolérances — Partie 1: Principes et données
fondamentales.
ISO 5408:1983, Filetages cylindriques — Vocabulaire.
3 Définitions
Pour les besoins de la présente Norme internationale, les définitions données dans l’ISO 5408 s’appliquent.
4 Désignation
Un filetage conforme à la présente Norme internationale doit être désigné conformément à l'ISO 965-1.
©
ISO
5 Choix du diamètre et du pas
5.1 Choisir, de préférence, les diamètres dans la colon
...
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