ISO 15872:2017

Aerospace — UNJ threads — Gauging

ISO 15872:2017 provides methods for the gauging of ISO UNJ threads complying with ISO 3161. Other methods of ensuring that the product is within the specified limits can be used, provided that correlation with the specified gauges is established.

Aéronautique et espace — Filetage UNJ — Vérification par calibres

General Information

• Status: Published
• Publication Date: 22-Mar-2017
• ICS: 49.030.10 - Screw threads
• Technical Committee: ISO/TC 20/SC 4 - Aerospace fastener systems
• Drafting Committee: ISO/TC 20/SC 4 - Aerospace fastener systems
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 31-Oct-2022

Relations

• Revises: ISO 15872:2002 - Aerospace — UNJ threads — Gauging
• Effective Date: 29-Mar-2014

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 15872
Second edition
2017-03
Aerospace — UNJ threads — Gauging
Aéronautique et espace — Filetage UNJ — Vérification par calibres
Reference number
ISO 15872:2017(E)
©
ISO 2017

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ISO 15872:2017(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
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ii © ISO 2017 – All rights reserved

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ISO 15872:2017(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Symbols and abbreviated terms. 2
4 Types of gauges . 3
4.1 Gauges and setting plugs for external threaded products . 3
4.2 Gauges for internal threaded products . 3
5 Reference temperature . 3
6 Function, design and use of gauges . 4
6.1 Gauges for external threads . 4
6.1.1 Virtual pitch diameter indicating thread gauges . 4
6.1.2 Solid or adjustable GO screw ring gauges . 4
6.1.3 Simple pitch diameter indicating thread gauges . . 4
6.1.4 Major diameter gauges . 5
6.1.5 Minor diameter gauges. 5
6.1.6 Optical comparator checks . 5
6.2 Gauging for internal threads . 5
6.2.1 GO screw plug gauges . 5
6.2.2 NOT GO screw plug gauges . 5
6.2.3 Minor diameter gauges. 5
6.2.4 Virtual pitch diameter indicating thread gauges . 5
6.2.5 Simple pitch diameter indicating thread gauges . . 6
7 Setting of gauges . 6
7.1 Setting gauges for external threads . 6
7.2 Setting ring gauge for indication thread gauges . 6
8 Gauging of threads . 6
8.1 General . 6
8.2 Internal threads evaluation . 7
Bibliography .22
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ISO 15872:2017(E)

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
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established 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.
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 on 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 the following
URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by ISO/TC 20, Aircraft and space vehicles, Subcommittee SC 4, Aerospace
fastener systems.
This second edition cancels and replaces the first edition (ISO 15872:2002), which has been technically
revised and includes the following changes:
— unused symbols have beenremoved from Table 1: WGO, WNG, Z1, ZPL, and ZR.
— Figures have been changed to align with 8.1.
— Normative references have been updated.
— Terminology has been updated.
— The document has been editorially revised.
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INTERNATIONAL STANDARD ISO 15872:2017(E)
Aerospace — UNJ threads — Gauging
1 Scope
This document provides methods for the gauging of ISO UNJ threads complying with ISO 3161.
Other methods of ensuring that the product is within the specified limits can be used, provided that
correlation with the specified gauges is established.
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 1, Geometrical product specifications (GPS) — Standard reference temperature for the specification of
geometrical and dimensional properties
ISO 3161, Aerospace — UNJ threads — General requirements and limit dimensions
3 Terms, definitions, symbols and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5408 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1.1
best wire size
cylinder or sphere which has a radius so that it will contact the thread flanks at the pitch cylinder
intersection
Note 1 to entry: The radius of the best wire or sphere is theoretically equal to 0,288 68P.
3.1.2
indicating gauge
device having contacts which will precisely compare the size of a work piece thread to a setting
standard of known dimensions
Note 1 to entry: The value for the indicated characteristic thus established is the dimensional value attributed
to the work piece. An indicating gauge can have contacts designed to measure any thread characteristic. This
document specifies the characteristics and designs for ISO UNJ threads.
3.1.3
simple pitch diameter
diameter of an imaginary cylinder intersecting an actual thread over the width of one groove where
that width is equal to one half of the basic pitch
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ISO 15872:2017(E)

3.1.4
virtual pitch diameter
pitch diameter of the smallest (for external threads) or largest (for internal threads) perfect thread
form with GO gauge profile which can engage the product threads for a distance equal to the GO gauge
thread engagement
3.2 Symbols and abbreviated terms
See Table 1.
Table 1 — Symbols, abbreviated terms and definitions
Symbol or Symbol or
abbreviated Definition abbreviated Definition
term term
Basic minor diameter of the internal Tolerance for each flank angle of a
D T /2
1 α1
thread of a workpiece profile with complete flanks
Basic pitch diameter of the external Tolerance for each flank angle of a
d T /2
2 α2
thread of a workpiece profile with truncated flanks
Tolerance on the pitch diameter of
Fundamental deviation of the exter-
es T GO and NOT GO screw check plugs,
CP
nal thread of a workpiece
wear check plugs and setting plugs
Fundamental deviation of the inter- Tolerance for the major diameter of
EI T
d
nal thread of a workpiece the external thread of a workpiece
Height of the triangle of a thread Tolerance for the pitch diameter of the
H T
d2
profile external thread of a workpiece
Tolerance for the diameter of plain Tolerance for the minor diameter of
H T
1 d3
plug gauges the external thread of a workpiece
Tolerance on the size of check plug Tolerance for the minor diameter of
H T
P D1
gauges for plain calliper gauges the internal thread of a workpiece
(LSL) Lower specification limit T Pitch tolerance
P
Distance between the middle of the
Tolerance for the pitch diameter of the
m tolerance zones TR of a screw ring T
D2
internal thread of a workpiece
gauge and TCP of a GO check plug
Tolerance for the pitch diameter of GO
(USL) Upper specification limit T
PL
and NOT GO screw plug gauges
Tolerance for the pitch diameter of GO
P Pitch T
R
and NOT GO screw ring gauges
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ISO 15872:2017(E)

4 Types of gauges
4.1 Gauges and setting plugs for external threaded products
The function, design and use of gauges and setting plugs for external threads are explained in the
following subclauses.
Gauge type Subclause
a)  GO screw ring gauges 6.1.2
b)  Setting plug for adjustable GO screw ring and indicating thread gauges 7.1.1
c)  Virtual pitch diameter indicating thread gauges 6.1.1
d)  Simple pitch diameter indicating thread gauges 6.1.3
e)  Flat contact gauges for major diameter 6.1.4
f)  Point contact indicating thread gauges for minor diameter 6.1.5
g)  Optical comparator for root radius and minor diameter 6.1.6
4.2 Gauges for internal threaded products
The function, design and use of gauges for internal threads are explained in the following subclauses.
Gauge type Subclause
a)  GO screw plug gauges 6.2.1
b)  NOT GO screw plug gauges 6.2.2
c)  Plain gauges for minor diameter (plug gauge) 6.2.3.1
d)  GO full form screw plug gauges 6.2.3.2
e)  Virtual pitch diameter indicating thread gauges 6.2.4
f)  Simple pitch diameter indicating thread gauges 6.2.5
g)  Setting ring gauge for indicating thread gauges (solid type) 7.2
5 Reference temperature
In accordance with ISO 1, the dimensions of the gauge and the product shall be checked at the
temperature of 20 °C.
If the product and the gauge have the same coefficients of linear expansion, the temperature may
deviate from 20 °C, provided the temperature of the product and the gauge are the same.
If the product and the gauge have different coefficients of linear expansion, the temperature of both, at
the time of gauging, shall be:
a) 20 °C ± 2 °C for sizes 1,000 UNJ and smaller;
b) 20 °C ± 1 °C for larger threads.
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ISO 15872:2017(E)

6 Function, design and use of gauges
6.1 Gauges for external threads
6.1.1 Virtual pitch diameter indicating thread gauges
6.1.1.1 It measures, on two or three segments or rolls, the maximum material virtual pitch diameter
taking into account variations of form such as pitch variation, helix and flank variations, roundness and
taper which produces an enlargement of the virtual pitch diameter. In addition, virtual pitch diameter
control ensures the flank angle contact is sufficient to ensure that the root radius does not exceed the
maximum limit. Measurement of virtual pitch diameter with indicating gauges shall be obtained to
calculate virtual minus simple pitch diameter differential unless the simple pitch diameter limits, gauged
in accordance with 6.1.3, are within the limits defined by the maximum pitch diameter and the form
variation limits in ISO 3161.
6.1.1.2 Indicating gauges have two or three contacts at 180° or 120°, respectively. Gauges with
segments or rolls are designed with the length of the GO virtual maximum material gauging elements
equal to the GO ring gauge length equal to nine pitches (P) or the basic major diameter of the thread,
whichever is the smallest. For configuration and profile requirements, see Figure 1.
6.1.1.3 The minor diameter of the GO virtual maximum material thread segments and the diameter of
the circle surrounded by the roll cluster of GO virtual maximum material rolls shall be equal to the pitch
diameter of the product minus 0,375H, less the T value in Table 2 minus tolerance when assembled in
PL
the gauge frame. This corresponds to a flat width of 0,312 5P on the minor crest for the thread. The crest
shall be flat in an axial plane and parallel to the axis of the segments or rolls.
6.1.1.4 The major diameter of the GO virtual maximum material segments and the root of the GO virtual
maximum material rolls shall be cleared beyond a 0,125P flat either by an extension of the flanks of the
thread toward a sharp vee or by an undercut no greater than 0,125P maximum width and approximately
central. The root clearance shall be such that the major diameter of the full form section of the thread
setting plug gauge is cleared after the assembled gauge has been properly set to size.
6.1.1.5 The pitch diameter cylinder axis of threaded segments and rolls shall be straight within the
diameter tolerance zone equal to T specified in Table 2. The half-angle variations in the segment or roll
PL
thread shall be within the limits specified in Table 3. For the pitch variations, see Table 4.
6.1.2 Solid or adjustable GO screw ring gauges
To ensure the ease of assembly of product threads and conformance to the maximum material virtual
pitch diameter limits, solid or adjustable, GO screw ring gauges with thread form in accordance with
Figure 1 and setting gauges in accordance with 7.1.1 may be used. Solid GO screw ring gauges shall
not be permitted to exceed the product thread dimensional limits. The gauge thickness/length shall be
standardized (see 6.1.1.2). Details on adjustable GO thread ring gauges and truncated setting plugs may
be obtained from ASME B1.2.
6.1.3 Simple pitch diameter indi
...