ISO 4579:2021

Aerospace - Drives, internal, TORX® PARALOBE® drive - Geometrical definition, gaging and technical requirements

This document specifies basic dimensions, characteristics and engineering requirements for TORX® PARALOBE® recesses in aerospace fasteners.

Aéronautique et espace — Empreintes, TORX® PARALOBE® entraînement — Définition géométrique, calibrage et exigences techniques

General Information

• Status: Published
• Publication Date: 04-Nov-2021
• ICS: 49.030.01 - Fasteners in general
• Technical Committee: ISO/TC 20/SC 4 - Aerospace fastener systems
• Drafting Committee: ISO/TC 20/SC 4/WG 3 - Supporting documents
• Current Stage: 6060 - International Standard published
• Start Date: 05-Nov-2021
• Due Date: 16-May-2023
• Completion Date: 05-Nov-2021

Overview - ISO 4579:2021 (TORX® PARALOBE® drive for aerospace)

ISO 4579:2021 specifies the geometrical definition, gaging and technical requirements for TORX® PARALOBE® recesses used in aerospace fasteners. The standard defines basic recess configuration, metric and inch recess dimensions, inspection/gaging methods and a fastener recess torque test procedure. It is intended for designers, manufacturers and quality personnel working with aerospace fastener drive systems. Note: TORX® PARALOBE® is a trademark and the standard notes possible patent licensing considerations.

Key topics and technical requirements

• Scope and terminology: Definitions for recess, driver bit, configuration and optimum recess torque.
• Recess geometry and dimensions: Detailed tables of recess diameters and inscribed diameters for drive sizes (drive codes 001–110 SI) given in both metric and inch units.
• Gaging and inspection:
  • Uses a penetration-type go/no‑go gage assembly (go and no‑go elements) to check recess depth and fit.
  • Gage identification, zero check on a flat surface, insertion and depth measurement procedures are specified.
  • Element diameters for each drive size are listed (see Table 2 in the standard).
• Fastener recess torque testing:
  • Test fixture requirements: alignment with fastener axis, non-rotation of fastener, and ability to apply specified end load while not preventing cam-out.
  • Torque device requirements: hand torque wrenches or torsion machines per applicable requirements.
  • Driver bits must conform to ISO 4580.
  • Test procedure: fixture the fastener, align driver bit within 1° of axis, apply end load per NASM1312-25, apply torque in install and removal directions and record results.
  • Optimum recess torque values: Table 3 provides minimum torsional strength/optimum torque values by drive size.

Practical applications and users

Who uses ISO 4579:2021:

• Aerospace fastener designers and engineers specifying internal drive recesses.
• Fastener manufacturers and tooling suppliers ensuring dimensional and functional conformity to TORX® PARALOBE® geometry.
• Quality control and inspection teams using go/no‑go penetration gages for acceptance testing.
• Maintenance, assembly and procurement teams selecting appropriate driver bits and torque requirements for installation/removal operations.

Practical benefits:

• Ensures interchangeability of driver bits and fasteners.
• Provides standardized inspection and torque-test methods to reduce drive failures and cam‑out.
• Supports certification and traceability in aerospace manufacturing and maintenance.

Related standards

• ISO 4580 - driver bit geometry, gaging and technical requirements for TORX® PARALOBE® bits.
• NASM1312-25 - driving recess torque quality conformance test (referenced for end‑load and test details).

Keywords: ISO 4579:2021, TORX PARALOBE, aerospace fasteners, recess dimensions, gaging, go/no‑go gage, torque test, driver bit.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 4579
First edition
2021-11
Aerospace — Drives, internal, TORX®
PARALOBE® drive — Geometrical
definition, gaging and technical
requirements
Aéronautique et espace — Empreintes, TORX® PARALOBE®
entraînement — Définition géométrique, calibrage et exigences
techniques
Reference number
© ISO 2021
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
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Basic fastener recess configuration .2
4.1 General . 2
4.2 Recess dimensions — metric and inch . 2
4.3 Recess drive designation . 3
5 Recess inspection .3
5.1 Gaging equipment . 3
5.2 Gaging procedure . 4
5.3 Penetration type gage dimensions — metric and inch . 5
6 Fastener recess torque test . 5
6.1 Fixture . 5
6.2 Torque wrench/torsion machine . 5
6.3 Driver bit . 6
6.4 Test specimen . 6
6.5 Fastener recess torque test procedure . 6
6.6 Fastener recess torque values. 6
iii
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
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
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 documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles,
Subcommittee SC 4, Aerospace fastener systems.
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
Introduction
The International Organization for Standardization (ISO) draws attention to the fact that it is claimed
that compliance with this document may involve the use of a patent.
ISO takes no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured ISO that he/she is willing to negotiate licences under
reasonable and non-discriminatory terms and conditions with applicants throughout the world. In
this respect, the statement of the holder of this patent right is registered with ISO. Information may be
obtained from the patent database available at www.iso.org/patents.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights other than those in the patent database. ISO shall not be held responsible for identifying
any or all such patent rights.
v
INTERNATIONAL STANDARD ISO 4579:2021(E)
Aerospace — Drives, internal, TORX® PARALOBE® drive —
Geometrical definition, gaging and technical requirements
1 Scope ®
This document specifies basic dimensions, characteristics and engineering requirements for TORX
®1)
PARALOBE recesses in aerospace fasteners.
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 4580, Aerospace — Drives, internal, TORX PARALOBE driver bit — Geometrical definition, gaging
and technical requirements
NASM1312-25, Fastener Test Methods – Method 25 – Driving Recess Torque Quality Conformance Test
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology dat
...