ISO 13809:2026

Fasteners — Hexalobular socket set screws

This document specifies the characteristics of hexalobular socket set screws with metric coarse pitch threads M3 to M30 for steel and M3 to M24 for stainless steel and with product grade A. Set screws are not intended for use under tensile load. If in certain cases other specifications are requested, hardness classes and stainless steel grades can be selected from ISO 898-5 or ISO 3506-3, and dimensional options from ISO 888, ISO 965-1 or ISO 4753.

Fixations — Vis sans tête à six lobes internes

General Information

• Status: Published
• Publication Date: 06-May-2026
• ICS: 21.060.10 - Bolts, screws, studs
• Technical Committee: ISO/TC 2/SC 11 - Fasteners with metric external thread
• Drafting Committee: ISO/TC 2/SC 11 - Fasteners with metric external thread
• Current Stage: 6060 - International Standard published
• Start Date: 07-May-2026
• Due Date: 11-Jan-2026
• Completion Date: 07-May-2026

Overview

ISO 13809:2026 establishes international requirements for fasteners known as hexalobular socket set screws. This standard covers characteristics specific to set screws with metric coarse pitch threads, with sizes ranging from M3 to M30 for steel and M3 to M24 for stainless steel, all corresponding to product grade A. Hexalobular socket set screws, also commonly called Torx® set screws, are widely used in mechanical and assembly applications for their superior drive capabilities and reduced risk of cam-out.

Notably, ISO 13809:2026 applies to set screws not intended for use under tensile loads. The standard provides guidance on the selection of hardness classes, stainless steel grades, and dimensional options by referencing additional ISO standards as needed.

Key Topics

• Scope & Product Grades:

  • Specifies metric coarse pitch threads: M3–M30 (steel), M3–M24 (stainless steel)
  • Applies to product grade A only
  • Set screws intended for compressive or shear applications, not tension

• Dimensional Specifications:

  • Details on thread forms, socket dimensions, and point types including flat, truncated cone, cup, and dog points, all conforming to referenced ISO thread and end standards
  • Dimensional tolerances and acceptance criteria guided by related ISO standards

• Material Options & Mechanical Properties:

  • Hardness classes and stainless steel grades in accordance with ISO 898-5 and ISO 3506-3
  • Surface condition options: as processed, electroplated, passivated, or zinc flake coated, with custom agreements possible between purchaser and supplier

• Marking & Packaging:

  • Marking on the product is typically not required unless specified by purchaser
  • Clear labeling on packaging required, specifying product reference, grade, dimensions, point type, surface condition, manufacturer, batch, and quantity

Applications

Hexalobular socket set screws offer enhanced torque transfer and are valued for high assembly efficiency. They are commonly used in:

• Mechanical assemblies: Securing components on shafts, pulleys, or collars
• Electronics & instrumentation: Fixing knobs, sensors, or adjustment screws that require non-slip engagement
• Automotive, aerospace, and industrial equipment: Where precise clamping without protrusion is crucial, especially where repeated assembly/disassembly may occur
• Stainless steel variants provide corrosion resistance for marine, chemical, and medical equipment applications

The standardized sizes and thread forms support global supply interoperability, quality control, and compliance for manufacturers and end-users.

Related Standards

ISO 13809:2026 references and aligns with several major international standards to ensure harmonized requirements for dimensions, performance, and materials, including:

• ISO 898-5: Mechanical properties of steel set screws
• ISO 3506-3: Mechanical properties of stainless steel set screws
• ISO 888: Nominal lengths and thread lengths for fasteners
• ISO 965-1: Tolerances for ISO metric threads
• ISO 10664: Hexalobular internal driving features for bolts and screws
• ISO 4042 / ISO 10683: Surface coatings and finishes for fasteners
• ISO 4753: Configurations of screw ends
• ISO 8991 / ISO 8992: Designation and general requirements

For those specifying or sourcing hexalobular socket set screws, referencing ISO 13809:2026 helps ensure robust product selection, quality assurance, and compliance with globally recognized standards in fastener technology.

Standards Content (Sample)

International
Standard
ISO 13809
First edition
Fasteners — Hexalobular socket set
2026-05
screws
Fixations — Vis sans tête à six lobes internes
Reference number
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Dimensions . 2
5 Requirements and reference International Standards .10
6 Marking and labelling .11
6.1 Marking on product . .11
6.2 Labelling on package .11
7 Designation .11
Annex A (informative) Cut-off slugs at machined set screws with dog point .12
Bibliography .13

iii
Foreword
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The procedures used to develop this document and those intended for its further maintenance are described
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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ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
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This document was prepared by Technical Committee ISO/TC 2, Fasteners, Subcommittee SC 11, Fasteners
with metric external thread.
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 13809:2026(en)
Fasteners — Hexalobular socket set screws
1 Scope
This document specifies the characteristics of hexalobular socket set screws with metric coarse pitch
threads M3 to M30 for steel and M3 to M24 for stainless steel and with product grade A.
Set screws are not intended for use under tensile load.
If in certain cases other specifications are requested, hardness classes and stainless steel grades can be
selected from ISO 898-5 or ISO 3506-3, and dimensional options from ISO 888, ISO 965-1 or ISO 4753.
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 724, ISO general purpose metric screw threads — Basic dimensions
ISO 888, Fasteners — Bolts, screws and studs — Nominal lengths and thread lengths
ISO 898-5, Mechanical properties of fasteners made of carbon steel and alloy steel — Part 5: Set screws and
similar threaded fasteners with specified hardness 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 3506-3, Fasteners — Mechanical properties of corrosion resistant stainless steel fasteners — Part 3: Set
screws (and similar fasteners not under tensile stress) with specified grades and hardness 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 this document.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Dimensions
Dimensions shall be in accordance with Figures 1 to 6 and Tables 1 to 4.
Dimensions for cut-off slugs at machined set screws with dog point are given in Annex A.
Symbols and designations of dimensions are specified in ISO 225.

a
For regular standard lengths, α shall be 90° or 120° at the choice of the manufacturer.
ref
b
For short standard lengths (see Tables 1 to 4), α shall be 120°.
ref
c
Thread end FL (flat point – Figure 3 and Table 1), TC (truncated cone point – Figure 4 and Table 2), CP (cup
point – Figure 5 and Table 3) or SD/LD (short/long dog point– Figure 6 and Table 4) as specified in ISO 4753.
The dimensions specified therein shall apply.
d
d is the diameter of the chamfer at the socket side.
f
NOTE The contour of the bottom of the hexalobular socket outside the gauging area is at the discretion of the
manufacturer.
Figure 1 — Hexalobular socket set screw
It is not required that burrs from broaching are removed except it is agreed between customer and supplier.
Figure 2 — Permissible alternative form of socket (broached socket)

a
The 45° angle applies only to the portion of the point situated below the minor diameter of the thread.
b
Incomplete thread u < 2P.
Figure 3 — Thread end: flat point (FL)
Table 1 — Dimensions for set screws with flat point (FL)
Dimensions in millimetres
Thread, d M3 M4 M5 M6 M8 M10 M12 M16 M20 M24 M30
a
P 0,5 0,7 0,8 1 1,25 1,5 1,75 2 2,5 3 3,5
b
d min. ≈ Minor thread diameter d
f 3
max. 2,00 2,50 3,50 4,00 5,50 7,00 8,50 12,00 15,00 18,00 23,00
d
p
min. 1,75 2,25 3,20 3,70 5,20 6,64 8,14 11,57 14,57 17,57 22,48
Socket No. 6 8 10 15 25 30 40 50 55 60 70
A ref. 1,75 2,4 2,8 3,35 4,5 5,6 6,75 8,95 11,35 13,45 15,7
Hexalobular
c
socket
max. 0,95 1,20 1,55 1,90 3,10 3,30 3,60 4,75 5,75 7,25 8,20
t
min. 0,80 1,00 1,30 1,60 2,70 2,90 3,20 4,30 5,30 6,80 7,70
l
Range of standard lengths between the stepped bold lines (white area)
nom. min. max.
3 2,8 3,2
d
4 3,76 4,24
d
5 4,76 5,24
d
6 5,76 6,24
d Screws with
too short lengths
8 7,71 8,29
d
10 9,71 10,29
d
12 11,65 12,35
d
16 15,65 16,35
d
20 19,58 20,42
d
25 24,58 25,42
d
30 29,58 30,42
d
35 34,5 35,5
40 39,5 40,5
45 44,5 45,5
Lengths by agreement in accordance with
ISO 888
50 49,5 50,5
55 54,4 55,6
60 59,4 60,6
a
P is the pitch
...