ISO 4755:1983

Fasteners - Thread undercuts for external metric ISO threads

Lays down the form and dimensions of undercuts for bolts, screws and similar externally threaded products, recommended for use in those cases where it is needed for components such as plugs.

Éléments de fixation — Gorges de dégagement pour éléments à filetage extérieur métrique ISO

Mehanski vezni elementi - Žlebovi za izteke zunanjih metrskih navojev ISO

General Information

• Status: Published
• Publication Date: 31-Jan-1983
• 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: 21-Jun-2023
• Completion Date: 13-Dec-2025
• Ref Project: SIST ISO 4755:1996 - Fasteners -- Thread undercuts for external metric ISO threads

Overview

ISO 4755:1983 - Fasteners: Thread undercuts for external metric ISO threads specifies the required form and dimensions of undercuts on externally threaded fasteners (bolts, screws and similar products). First published in February 1983 and developed by ISO/TC 2 (Fasteners), the standard defines when and how an undercut should be applied - typically where an undercut is needed to accommodate a mating component such as a plug - unless an applicable product standard specifies otherwise.

Key topics and requirements

• Scope and purpose: Defines the geometry of thread undercuts for external metric ISO threads to ensure consistent fit and function with mating parts.
• Dimensional data: Provides a tabulated set of dimensions in millimetres tied to thread pitch and nominal diameter. Designers and manufacturers use these values to size the undercut correctly.
• Form features: Specifies the shape and transition between the threaded portion and the undercut, including rules for transition angles (the document notes a minimum transition angle of 30° where relevant).
• Applicability: Recommended for bolts, screws and similar externally threaded products when undercuts are required (for example, to clear plugs or to provide clearance for sealing elements).
• Normative notes: Includes limits and special notes (for instance, provisions covering small thread diameters and related dimensional exceptions).

Practical applications

• Ensuring proper clearance for plugs, inserts, sealing parts or inspection gauges that interface with the end of an externally threaded fastener.
• Avoiding thread interference during assembly by providing a controlled run-out region at the end of the thread.
• Guiding machining and thread-rolling operations to produce correct undercut geometry and minimize rework.
• Specifying inspection criteria and acceptance limits in quality control and manufacturing documentation.

Who should use this standard

• Mechanical and product designers specifying fasteners for assemblies where end-fit or plug engagement is critical.
• Fastener manufacturers, thread-rolling and CNC shops producing metric ISO threaded parts.
• Quality engineers and inspection personnel verifying undercut dimensions and transition geometry.
• Procurement and standards specialists ensuring purchased fasteners meet established ISO requirements.

Related standards

ISO 4755 complements general ISO metric thread standards and product-specific fastener standards developed by ISO/TC 2. Refer to applicable ISO thread and fastener product standards for full mating-thread and product requirements.

Keywords: ISO 4755:1983, thread undercuts, external metric ISO threads, fasteners, bolts, screws, undercut dimensions, plug clearance, fastener standards.

Standards Content (Sample)

SLOVENSKI STANDARD
01-april-1996
Mehanski vezni elementi - Žlebovi za izteke zunanjih metrskih navojev ISO
Fasteners -- Thread undercuts for external metric ISO threads
Éléments de fixation -- Gorges de dégagement pour éléments à filetage extérieur
métrique ISO
Ta slovenski standard je istoveten z: ISO 4755:1983
ICS:
21.040.10 Metrski navoji Metric screw threads
21.060.01 Vezni elementi na splošno Fasteners in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

International Standard
INTERNATIONAL ORGANIZATION FOR STANDARDIZATIONWE~YHAPO~HAR OPrAHM3AUMR fl0 CTAHI1APTH3Al#Wl.ORGANISATlON INTERNATIONALE DE NORMALISATION
Thread undercuts for external metric ISO
Fasteners -
threads
&men ts de fixa tion - Gorges de dkgagement pour Mments 2 filetage extkieur metrigue ISO
First edition - 1983-02-01
w UDC 621.882.14
Ref. No. ISO 47551983 (E)
-
Descriptors : fasteners, bolts, screws, dimensions.
Price based on 2 pages
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of
national Standards bodies (ISO member bedies). The work of developing International
Standards is carried out through ISO technical committees. Every member body
interested in a subject for which a technical committee has been authorized 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 CS0 Council.
International Standard ISO 4755 was developed by Technical Committee ISO/TC 2,
Fasteners, and was circulated to the member bodies in December
...

International Standard
INTERNATIONAL ORGANIZATION FOR STANDARDIZATIONWE~YHAPO~HAR OPrAHM3AUMR fl0 CTAHI1APTH3Al#Wl.ORGANISATlON INTERNATIONALE DE NORMALISATION
Thread undercuts for external metric ISO
Fasteners -
threads
&men ts de fixa tion - Gorges de dkgagement pour Mments 2 filetage extkieur metrigue ISO
First edition - 1983-02-01
w UDC 621.882.14
Ref. No. ISO 47551983 (E)
-
Descriptors : fasteners, bolts, screws, dimensions.
Price based on 2 pages
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of
national Standards bodies (ISO member bedies). The work of developing International
Standards is carried out through ISO technical committees. Every member body
interested in a subject for which a technical committee has been authorized 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 CS0 Council.
International Standard ISO 4755 was developed by Technical Committee ISO/TC 2,
Fasteners, and was circulated to the member bodies in December 1981.
lt has been approved by the member bodies of the following countries:
New Zealand
Australia Germany, F.R.
Austria Hungary Norway
Poland
Belgium India
Brazil Ireland Romania
China Italy South Africa, Rep. of
Czechoslovakia Japan Spain
Denmark Korea, Dem. P. Rep. of Sweden
Egypt, Arab Rep. of Korea, Rep. of Switzerland
Finland United
...

Norme internationale
.
INTERNATIONAL ORGANIZATION FOR STANDARDIZATIONWlEIKJlYHAPOflHAR OPI-AHM3AUMR fl0 CTAH~APTbl3Al.Wl~RGANISATION INTERNATIONALE DE NORMALISATION
Éléments de fixation - Gorges de dégagement pour
éléments à filetage extérieur métrique ISO
Thread undercuts for external metric /SO threads
Fasteners -
Première édition - 1983-02-01
CDU 621.882.14 Réf. no : ISO 4755-1983 (F)
Descripteurs : élément de fixation, boulon, vis, dimension.
Prix basé sur 2 pages
Avant-propos
L’ISO (Organisation internationale de normalisation) est une fédération mondiale
d’organismes nationaux de normalisation (comités membres de I’ISO). L’élaboration
des Normes internationales est confiée aux comités techniques de I’ISO. Chaque
comité membre intéressé par une étude a le droit de faire partie du comité technique
correspondant. Les organisations internationales, gouvernementales et non gouverne-
mentales, en liaison avec I’ISO, participent également aux travaux.
Les projets de Normes internationales adoptés par les comités techniques sont soumis
aux comités membres pour approbation, avant leur acceptation comme Normes inter-
nationales par le Conseil de I’ISO.
La Norme internationale ISO 4755 a été élaborée par le comité technique ISO/TC 2,
fiéments de fixation, et a été soumise aux comités membres en décembre 1981.
Les comités membres des pays suivants l’ont approuvée:
Afrique du Sud, Rép. d’ Égypte, Rép. arabe d’
Norvège
Allemagne, R.F. Espagne Nouvelle-Zélande
Australie Finlande Pay-Bas
France
Autriche Pologne
Belgique Hongrie Roumanie
Inde
Brésil Royaume-Uni
Chine Irlande
Suède
Corée, Rép. de Italie Suisse
Corée, Rép. dém.
...

Norme internationale
.
INTERNATIONAL ORGANIZATION FOR STANDARDIZATIONWlEIKJlYHAPOflHAR OPI-AHM3AUMR fl0 CTAH~APTbl3Al.Wl~RGANISATION INTERNATIONALE DE NORMALISATION
Éléments de fixation - Gorges de dégagement pour
éléments à filetage extérieur métrique ISO
Thread undercuts for external metric /SO threads
Fasteners -
Première édition - 1983-02-01
CDU 621.882.14 Réf. no : ISO 4755-1983 (F)
Descripteurs : élément de fixation, boulon, vis, dimension.
Prix basé sur 2 pages
Avant-propos
L’ISO (Organisation internationale de normalisation) est une fédération mondiale
d’organismes nationaux de normalisation (comités membres de I’ISO). L’élaboration
des Normes internationales est confiée aux comités techniques de I’ISO. Chaque
comité membre intéressé par une étude a le droit de faire partie du comité technique
correspondant. Les organisations internationales, gouvernementales et non gouverne-
mentales, en liaison avec I’ISO, participent également aux travaux.
Les projets de Normes internationales adoptés par les comités techniques sont soumis
aux comités membres pour approbation, avant leur acceptation comme Normes inter-
nationales par le Conseil de I’ISO.
La Norme internationale ISO 4755 a été élaborée par le comité technique ISO/TC 2,
fiéments de fixation, et a été soumise aux comités membres en décembre 1981.
Les comités membres des pays suivants l’ont approuvée:
Afrique du Sud, Rép. d’ Égypte, Rép. arabe d’
Norvège
Allemagne, R.F. Espagne Nouvelle-Zélande
Australie Finlande Pay-Bas
France
Autriche Pologne
Belgique Hongrie Roumanie
Inde
Brésil Royaume-Uni
Chine Irlande
Suède
Corée, Rép. de Italie Suisse
Corée, Rép. dém.
...