ISO 18669-1:2013

INTERNATIONAL ISO
STANDARD 18669-1
Second edition
2013-07-15
Internal combustion engines —
Piston pins —
Part 1:
General specifications
Moteurs à combustion interne — Axes de pistons —
Partie 1: Spécifications générales
Reference number
ISO 18669-1:2013(E)
©
ISO 2013

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ISO 18669-1:2013(E)

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© ISO 2013
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ISO 18669-1:2013(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Terms and definitions . 1
2.1 General . 1
2.2 Geometrical and manufacturing features of piston pins . 1
3 Symbols . 2
4 Nomenclature . 3
4.1 Outside, inside and end features . 3
4.2 Outside edge and inside chamfer configurations . 6
4.3 Outside-edge drop-off configuration . 8
5 Codes . 9
6 Designation of piston pins .10
6.1 Designation elements and order .10
6.2 Designation examples .11
7 Piston pin types, dimensions and tolerances .11
7.1 Manufacturing types .11
7.2 Dimensions and tolerances .12
8 Material and heat treatment .17
8.1 Type of material .17
8.2 Core hardness l core strength .19
8.3 Carburised and nitrided case depth .19
8.4 Surface hardness .20
8.5 Volume change .20
9 Common features .20
9.1 Roughness of surfaces .20
9.2 Marking of piston pins .21
9.3 Miscellaneous .21
10 Quality requirements .22
10.1 Material characteristics .22
10.2 Material defects .22
10.3 Visual defects .23
Bibliography .24
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ISO 18669-1:2013(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. 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. 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.
The committee responsible for this document is ISO/TC 22, Road vehicles.
This second edition cancels and replaces the first edition (ISO 18669-1:2004), which has been
technically revised.
ISO 18669 consists of the following parts, under the general title Internal combustion engines — Piston pins:
— Part 1: General specifications
— Part 2: Inspection measuring principles
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INTERNATIONAL STANDARD ISO 18669-1:2013(E)
Internal combustion engines — Piston pins —
Part 1:
General specifications
1 Scope
This part of ISO 18669 specifies the essential dimensional characteristics of piston pins with an outer
diameter between 8 mm and 100 mm, for reciprocating internal combustion engines for road vehicles
and other applications. In addition, it establishes a vocabulary, a pin-type classification, material
description based on mechanical properties, common features and quality requirements.
The use of this part of ISO 18669 may require a manufacturer and customer statistical process
control agreement.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1 General
2.1.1
piston pin
precision cylindrical component that connects the piston to the connecting rod and has a smooth hard
peripheral surface
2.2 Geometrical and manufacturing features of piston pins
2.2.1 Bore types
2.2.1.1
cylindrical
pin having a straight cylindrical bore
2.2.1.2
centre web
pin inside diameter formed symmetrically from each end leaving a web in the pin centre
Note 1 to entry: The web is subsequently removed leaving a step as shown in Figure 3.
2.2.1.3
tapered
pin with conical-shaped inside diameter near the ends that reduces the weight of the piston pin
2.2.1.4
machined
pin with inside diameter produced solely by machining
2.2.1.5
seamless drawn tube
hollow steel product which does not contain any line junctures resulting from the method of manufacture
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ISO 18669-1:2013(E)

2.2.1.6
end web
pin inner diameter formed from one end leaving a web near the opposite end
Note 1 to entry: The web is punched out. The pin is then drawn over a mandrel and a forming line may result as
shown in Figure 4.
2.2.2 Outside-edge configurations
2.2.2.1
chamfer
outside-edge bevelled feature that is sometimes used to mate with a round retainer ring
Note 1 to entry: Referred to as “locking chamfer” when a round wire retainer ring is located on the chamfer angle
and used to secure the pin in the piston.
2.2.2.2
form angle δ
region of outside-edge form that provides a smooth transition to the peripheral surface to facilitate
ease of assembly
2.2.2.3
form angle γ
region of outside-edge form that provides a smooth transition to the end face
2.2.2.4
drop-off
non-functional machining feature that creates a transition between the outside edge and the
peripheral surface
Note 1 to entry: See Figure 12.
2.2.2.5
inside-edge chamfer
bevelled edge between the bore surface and the end faces of the piston pin
2.2.2.6
gauge point
locating point on the pin outside-edge chamfer from where the gauge diameter (d ) and gauge length
5
(l ) are measured
5
2.2.3 Other features
2.2.3.1
volume change
change detected as a permanent outside-diameter dimensional deviation at reference temperature after
being heated to a test temperature for a specified period of time
2.2.3.2
slag lines
linear flaws of non-metallic inclusions
3 Symbols
For the purposes of this part of ISO 18669, the symbols in Table 1 apply.
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ISO 18669-1:2013(E)

Table 1 — Symbols
Symbol abbreviation Description
a Wall thickness
b Outside-edge drop-off length
c Outside-edge drop-off height
d Outside diameter
1
d Inside diameter
2
d Tapered bore diameter
3
d Centre-web diameter
4
d Gauge diameter
5
d End face diameter
6
e Tapered bore runout
f Outside-edge length
g Outside-edge chamfer length
H Limit hardness
s
h End face concavity
1
h End face step
2
k Tapered bore relief
l Length
1
l Tapered bore length
3
l Centre-web length
4
l Gauge length
5
r Outside-edge radius
R Core strength
m
s End face runout
t Inside-edge chamfer length
1
t Outside-edge form length
2
α Tapered bore angle
β Outside-edge chamfer angle
γ Outside-edge form angle end face
δ Outside-edge form angle
4 Nomenclature
4.1 Outside, inside and end features
Terms commonly used to describe pins with a cylindrical bore are shown in Figure 1.
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ISO 18669-1:2013(E)

Key
1 end face
2 bore surface
3 peripheral surface
d outside diameter
1
d inside diameter
2
l length
1
a wall tickness
a
See Figure 2.
Figure 1 — Pin with cylindrical bore
Terms commonly used to describe end face concavity are shown in Figure 2a).
Terms commonly used to describe end face step are shown in Figure 2b).
a) End face concavity b) End face step
Key
h end face concavity
1
h end face step
2
d end face diameter
6
NOTE End face concavity and end face step not recommended for end face locking.
Figure 2 — Detail W of Figure 1
Terms commonly used to describe pins with a centre web are shown in Figure 3.
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ISO 18669-1:2013(E)

Key
1 centre-web radius
l centre-web length
4
d centre-web diameter
4
Figure 3 — Pin with cold-formed centre web
Terms commonly used to describe pins with a cold-formed end-web are shown in Figure 4.
Key
1 end-web forming line
Figure 4 — Pin with cold-formed end web
Terms commonly used to describe pins with a tapered bore are shown in Figure 5.
Key
1 tapered bore surface
α tapered bore angle
d tapered bore diameter
3
l tapered bore length
3
Figure 5 — Pin with tapered bore
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ISO 18669-1:2013(E)

4.2 Outside edge and inside chamfer configurations
Terms commonly used to describe the outside edge and inside chamfer configurations are shown in Figure 6.
Key
1 outside-edge chamfer or radius
2 inside-edge chamfer
t inside-edge chamfer length
1
a
See Figures 7 and 8.
b
See Figure 9.
NOTE This may be used with either a round or rectangular retainer ring.
Figure 6 — Outside-edge configuration (detail X: chamfered; detail Y: radiused)
4.2.1 Chamfered outside-edge configuration
Terms commonly used to describe the chamfered outside-edge configuration are shown in Figure 7.
Key
f outside-edge length
β outside-edge chamfer angle
Figure 7 — Chamfered configuration (detail X of Figure 6)
4.2.2 Double-chamfered outside-edge configuration
Terms commonly used to describe double-chamfered outside-edge configurations are shown in Figure 8.
The double chamfer is for assembly improvements of the piston pin.
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ISO 18669-1:2013(E)

Key
f outside-edge length
g outside-edge chamfer length
δ outside-edge form angle
β outside-edge chamfer angle
Figure 8 — Double-chamfered configuration (detail X of Figure 6)
4.2.3 Radiused outside-edge configuration
Terms commonly used to describe radiused outside-edge configurations are shown in Figure 9.
Key
r outside-edge radius
f outside-edge length
δ outside-edge form angle
Figure 9 — Radiused configuration (detail Y of Figure 6)
4.2.4 Chamfer-locking outside-edge configuration
Terms commonly used to describe chamfer-locking outside-edge configurations are shown in
Figures 10 and 11.
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ISO 18669-1:2013(E)

Key
1 gauge points
l gauge length
5
d gauge diameter
5
Figure 10 — Chamfer-locking outside-edge for round retainer ring
Key
1 gauge point
g outside-edge chamfer length
f outside-edge length
l gauge length
5
d gauge diameter
5
Figure 11 — Detail Z of Figure 10
4.3 Outside-edge drop-off configuration
Terms commonly used to describe outside-edge drop-off configurations are shown in Figure 12a),
12b) and 12c).
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ISO 18669-1:2013(E)

The outside-edge drop-off is for manufacturing purposes and is therefore a chamfer that is very small
in height but long in length.
a) Chamfered edge and drop-off b) Double-chamfered edge and c) Radiused edge and drop-off
drop-off
Key
b outside-edge drop-off length
c outside-edge drop-off height
g outside-edge chamfer length
f outside-edge length
δ outside-edge form angle
β outside-edge chamfer angle
Figure 12 — Drop-off configurations (detail X and Y of Figure 6)
5 Codes
Codes used for piston pins shall be as given in Table 2 with their explanatory descriptions.
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ISO 18669-1:2013(E)

Table 2 — Codes and descriptions
Relevant sub-
Code Description clause of this
part of ISO 18669
P1…P6 Pin-type classification according to manufacturing method of the pin centre hole 7.1
X Piston pins in combination with needle bearing 8.3
F1, F2, F3 Outside-edge configuration tolerance class 7.2.4
K Carburising steel class K 8.1 / 8.2
S Carburising steel class S 8.1 / 8.2
L Carburising steel class L 8.1 / 8.2
M Carburising steel class M 8.1 / 8.2
N Nitriding steel class N 8.1 / 8.2
V Piston pins with limited volume change 8.3 / 8.4 / 8.5
H1, H2 Surface hardness class 8.4
R1, R2 Peripheral surface roughness class 9.1.1
G Chamfer-locking outside-edge configuration (gauge point) 6.2 / 7.2.4
R Outside-edge radiused 7.2.4 / 6.1.2
C1 Outside-edge chamfered 7.2.4
C2 Outside-edge double chamfered 7.2.4
LA, LB Length tolerance class 7.2.3
MM Manufacturer’s mark 9.2
TC Piston pins with bore surface cold formed 7.2.6
6 Designation of piston pins
6.1 Designation elements and order
To designate piston pins, the following details shall be given, in the order shown below. The codes given
in Table 2 shall be used.
6.1.1 Mandatory elements
The following mandatory elements shall constitute the designation of a piston pin:
— designation, i.e. piston pin;
— number of International Standard: ISO 18669;
— type of piston pin, e.g. P1;
— hyphen;
— size of piston pin, d × d × l or d / d − α × d × l for a pin with tapered bore;
1 2 1 1 3 2 1
— hyphen;
— material code, e.g. L.
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