ISO 15872:2017

INTERNATIONAL ISO
STANDARD 15872
Second edition
2017-03
Aerospace — UNJ threads — Gauging
Aéronautique et espace — Filetage UNJ — Vérification par calibres
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
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ii © ISO 2017 – All rights reserved

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
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).
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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.
iv © ISO 2017 – All rights reserved

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
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
2 © ISO 2017 – All rights reserved

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
...