ISO 273:1979

Fasteners - Clearance holes for bolts and screws

Specifies diameters for general purpose applications; tabulates the hole diameters for fine, medium and coarse series for thread diameters from 1 mm up to 150 mm; holes for special applications should be selected on the basis of design requirements.

Éléments de fixation — Trous de passage pour vis

La présente Norme internationale spécifie les diamètres des trous de passage pour applications générales. Ces valeurs résultent des calculs de la surface d'appui des têtes de vis et des écrous conformes aux normes de produit ISO. NOTE -- Les trous de passage pour applications spéciales devraient être sélectionnés sur la base des exigences de la conception.

General Information

• Status: Published
• Publication Date: 31-May-1979
• ICS: 21.060.01 - Fasteners in general
• Technical Committee: ISO/TC 2/SC 7 - Reference standards
• Drafting Committee: ISO/TC 2/SC 7 - Reference standards
• Current Stage: 9093 - International Standard confirmed
• Start Date: 10-Jul-2024
• Completion Date: 13-Dec-2025

Relations

• Revises: ISO/R 273-1:1962 - Withdrawal of ISO/R 273/1-1962
• Effective Date: 15-Apr-2008
• Revises: ISO/R 273-2:1968 - Withdrawal of ISO/R 273/2-1968
• Effective Date: 15-Apr-2008

Overview

ISO 273:1979 is an international standard published by the International Organization for Standardization (ISO) that specifies clearance hole diameters for bolts and screws used in general purpose applications. The standard covers hole sizes appropriate for a range of bolt thread diameters, from 1 mm up to 150 mm. It provides tabulated diameters for clearance holes corresponding to fine, medium, and coarse thread series to ensure proper fit and mechanical performance in fastening assemblies.

The standard was developed by ISO Technical Committee 2 (Fasteners) and serves as a technical revision of the earlier ISO Recommendation R 273-1962. It ensures consistency and interchangeability in the design and manufacturing of fastened joints worldwide. Special applications requiring non-standard hole sizes should consider bespoke design requirements.

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Key Topics

• Clearance Hole Diameters: ISO 273 details precise diameters for clearance holes in three thread series-fine, medium, and coarse.
• Thread Diameter Range: The standard covers thread diameters from as small as 1 mm to as large as 150 mm.
• Dimensional Tolerances: Recommended tolerance fields are provided for holes to ensure optimal fit:
  • Fine thread series: H12 tolerance
  • Medium thread series: H13 tolerance
  • Coarse thread series: H14 tolerance
• Chamfer Recommendations: To avoid interference between the hole edge and the bolt underhead fillet, chamfering the hole is advised.
• Application Scope: General purpose clearance holes based on standard bolt and nut dimensioning. Custom clearance holes for special applications should be designed as per specific requirements.

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Applications

ISO 273:1979 is essential for engineers, designers, and manufacturers in the fastener and mechanical assembly industries. Its practical value includes:

• Mechanical Design: Assisting mechanical engineers in selecting correct hole sizes for bolts and screws to ensure smooth assembly and load transfer.
• Manufacturing Processes: Providing machining and quality control teams with standard diameters and tolerances, reducing trial and error and improving productivity.
• Product Assembly: Ensuring compatibility and interchangeability of parts in global supply chains by adhering to internationally accepted hole sizes.
• Maintenance and Repair: Facilitating easier replacement of fasteners by using standardized clearance hole sizes.

Industries benefiting from ISO 273 include automotive, aerospace, construction, machinery manufacturing, and electronics, where reliable fastening is critical.

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Related Standards

To complement ISO 273, the following standards are relevant for a comprehensive understanding of fastener dimensions and performance:

• ISO 4032 - Hexagon nuts, product grades A and B
• ISO 4762 - Hexagon socket head cap screws
• ISO 261 / ISO 262 - Metric screw threads - General pitch and limits of sizes
• ISO 965 - Tolerances for metric screw threads
• ISO 898-1 - Mechanical properties of fasteners made of carbon steel and alloy steel

These standards work in conjunction to cover the entire range of fastener design parameters, from thread dimensions and mechanical properties to nut sizes and torque specifications.

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By complying with ISO 273:1979, organizations can assure the design, manufacture, and maintenance of bolted joints meet global standards for safety, performance, and interchangeability, streamlining international trade and engineering collaboration. This makes the standard an invaluable tool in any mechanical engineering or fastener-related project.

Standards Content (Sample)

International Standard
INTERNATIONAL ORGANIZATION FOR STANDARDIZATlONWlE)I(C1YHAPOflHAR OPTAHM3AUMR n0 CTAH,QAPTbl3ALWl~RGANlSATlON INTERNATIONALE DE NORMALISATION
Clearance holes for bolts and screws
Fasteners -
&men ts de fixa tion - Trous de passage pour boulons et vis
First edition - 1979-06-01
Ref. No. IS0 273-1979 (El
UDC 621.882.15
Descriptors : fasteners, screws, dimensions, bolts, hole size, dimensional tolerances.
Price based on 2 pages
FOREWORD
IS0 (the International Organization for Standardization) is a worldwide federation
of national standards institutes (IS0 member bodies). The work of developing
International Standards is carried out through IS0 technical committees. Every
member body interested in a subject for which a technical committee has been set
up 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.
Draft International Standards adopted by the technical committees are circulated
to the member bodies for approval before their acceptance as International
Standards by the IS0 Council.
International Standard IS0 273 was developed by Technical Committee lSO/TC 2,
Fasteners, and was circulated to the member bodies in December 1977.
It has been approved by the member bodies of the following countries :
New Zealand
Australia Hungary
Belgium India Norway
Bulgaria Ireland Romania
Canada Italy . Spain
Czechoslovakia Japan Sweden
Denmark Korea, Dem. P. Rep. of Switzerland
Finland Korea, Rep. of Turkey
France Mex ice USA
Germany, F. R. Netherlands Yugoslavia
The member bodies of the following countries expressed disapproval of the
.
document on technica tounds
1 Y
South Africa, Rep. of
United Kingdom
USSR
This International Standard cancels and replaces IS0 Recommendation R 273-1962
of which it constitutes a technical revision.
0 International Organization for Standardization, 1979 l
Printed in Switzerland
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...

Norme internationale
@ 273
INTERNATIONAL ORGANIZATION FOR STANDAROIZATION~MEXflYHAPOflHAfl OPrAHM3AUMfl fl0 CTAHflAPTM3AUMM.ORGANISATlON INTE RNATIONALE DE NORMALISATION
Elements de fixation - Trous de passage pour vis
Fasteners - Clearance holes for bolts and screws
Premigre edition - 1979-06-01
Corrigee et reimprimbe - 1992-07-15
- CDU 621.882.15 Ref. no : IS0 273-1979 (F)
U
-
Descripteurs : element de fixation, vis partiellement filetee, vis entierement filetee, dimension, dimension de trou, tolerance de dimension.
R
z
F?
R
E Prix base sur 2 pages
AVANT-PROPOS
L’ISO (Organisation internationale de normalisation) est une federation mondiale
d’organismes nationaux de normalisation (comites membresde I’ISO). L’elaboration
des Normes internationales est confiee aux comites techniques de I’ISO. Chaque
comite membre interesse par une etude a le droit de faire partie du comite technique
correspondant. Les organisations internationales, gouvernementales et non
gouvernementales, en liaison avec I’ISO, participent egalement aux travaux.
Les projets de Normes internationales adoptes par les comites techniques sont
soumis aux comites membres pour approbation, avant leur acceptation comme
Normes internationales par le Conseil de I’ISO.
&a Norme internationale IS0 273 a ete Blaboree par le comite technique ISO/TC 2,
El6rnenis de fixation, et a et6 soumise aux comites membres en decembre 1977.
Les comites membres des pays suivants I’ont approuvee :
Allemagne, R. F. Finlande Nouvelle-ZClande
Australie France Pays-Bas
Belgique Hongrie Roumanie
Suede
Bulgarie lnde
Su isse
Canada lrlande
ltalie Tchecoslovaquie
Coree, RBp. d6m. p. de
Coree, Rep. de Japon Turquie
Danemark Mexique USA
Norvege Yougoslavie
Espagne
Les comites membres des pays suivants I‘ont desapprouvee pour des raisons
techniques :
Afrique du Sud, Rep. d’
Royaume-Uni
U RSS
Cette Norme internationale annule et rempla
...