ISO 7380-3:2026

International
Standard
ISO 7380-3
First edition
Fasteners — Button head screws
2026-03
with reduced loadability —
Part 3:
Hexalobular socket button head
screws
Fixations — Vis à tête cylindrique bombée plate à capacité de
charge réduite —
Partie 3: Tête cylindrique bombée plate à six lobes internes
Reference number
© ISO 2026
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Dimensions . 2
5 Requirements and reference International Standards . 4
6 Marking and labelling . 6
6.1 Marking on product . .6
6.2 Labelling on package .6
7 Designation . 6
Bibliography . 7

iii
Foreword
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in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
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This document was prepared by Technical Committee ISO/TC 2, Fasteners, Subcommittee SC 11, Fasteners
with metric external thread.
A list of all parts in the ISO 7380 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
International Standard ISO 7380-3:2026(en)
Fasteners — Button head screws with reduced loadability —
Part 3:
Hexalobular socket button head screws
1 Scope
This document specifies the characteristics of hexalobular socket button head screws with reduced
loadability due to head design, in steel and stainless steel, with metric coarse pitch threads M3 to M12, and
with product grade A.
If, in certain cases, other specifications are requested, property classes and stainless steel grades can be
selected from ISO 898-1 or ISO 3506-1, and the dimensional options from ISO 888 or ISO 4753.
NOTE The reduced loadability (related to the head dimensions in combination with penetration of the hexalobular
socket specified in this document) implies a limitation of ultimate tensile load shown by a specific marking (property
class preceded by a zero). The loadability in the head is assumed to be 80 % of that in the thread for all sizes and all
property classes, see Table 4.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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 888, Fasteners — Bolts, screws and studs — Nominal lengths and thread lengths
ISO 898-1, Mechanical properties of fasteners made of carbon steel and alloy steel — Part 1: Bolts, screws and
studs with specified property classes — Coarse thread and fine pitch thread
ISO 965-1, ISO general purpose metric screw threads — Tolerances — Part 1: Principles and basic data
ISO 1891-4, Fasteners — Vocabulary — Part 4: Control, inspection, delivery, acceptance and quality
ISO 3269, Fasteners — Acceptance inspection
ISO 3506-1, Fasteners — Mechanical properties of corrosion-resistant stainless steel fasteners — Part 1: Bolts,
screws and studs with specified grades and property classes
ISO 4042, Fasteners — Electroplated coating systems
ISO 4753, Fasteners — Ends of parts with external ISO metric thread
ISO 4759-1, Tolerances for fasteners — Part 1: Bolts, screws, studs and nuts — Product grades A, B and C
ISO 6157-1, Fasteners — Surface discontinuities — Part 1: Bolts, screws and studs for general requirements
ISO 8991, Designation system for fasteners
ISO 8992, Fasteners — General requirements for bolts, screws, studs and nuts
ISO 10664, Hexalobular internal driving feature for bolts and screws

ISO 10683, Fasteners — Non-electrolytically applied zinc flake coating systems
3 Terms and definitions
No terms and definitions are listed in thi
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