ISO/FDIS 18669-1

Internal combustion engines -- Piston pins

Moteurs à combustion interne -- Axes de pistons

General Information

• Status: Published
• ICS: 43.060.10 - Engine block and internal components
• Technical Committee: ISO/TC 22/SC 34 - Propulsion, powertrain and powertrain fluids
• Drafting Committee: ISO/TC 22/SC 34/WG 9 - Piston Pins
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 12-May-2021
• Completion Date: 12-May-2021

RELATIONS

• Revised: ISO 18669-1:2013 - Internal combustion engines -- Piston pins
• Effective Date: 15-Dec-2017

Standards Content (sample)

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 18669-1
ISO/TC 22/SC 34
Internal combustion engines — Piston
Secretariat: ANSI
pins —
Voting begins on:
2021-05-12
Part 1:
Voting terminates on:
General specifications
2021-07-07
Moteurs à combustion interne — Axes de pistons —
Partie 1: Spécifications générales
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 18669-1:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. ISO 2021
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ISO/FDIS 18669-1:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

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on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

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Published in Switzerland
ii © ISO 2021 – All rights reserved
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ISO/FDIS 18669-1:2021(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

3.1 General ........................................................................................................................................................................................................... 1

3.2 Geometrical and manufacturing features of piston pins .................................................................................... 1

3.2.1 Bore types .............................................................................................................................................................................. 1

3.2.2 Outside-edge configurations ................................................................................................................................. 2

3.2.3 Other features ..................................................................................................................................................................... 3

4 Symbols .......................................................................................................................................................................................................................... 3

5 Nomenclature .......................................................................................................................................................................................................... 4

5.1 Outside, inside and end features ............................................................................................................................................. 4

5.2 Outside edge and inside chamfer configurations ...................................................................................................... 6

5.2.1 Chamfered outside-edge configuration ........................................................................................................ 6

5.2.2 Double-chamfered outside-edge configuration .................................................................................... 6

5.2.3 Radiused outside-edge configuration ............................................................................................................ 7

5.2.4 Chamfer-locking outside-edge configuration ......................................................................................... 7

5.3 Outside-edge drop-off configuration ................................................................................................................................... 8

6 Codes ................................................................................................................................................................................................................................. 9

7 Designation of piston pins .......................................................................................................................................................................10

7.1 Designation elements and order ..........................................................................................................................................10

7.1.1 Mandatory elements ..................................................................................................................................................10

7.1.2 Additional elements ...................................................................................................................................................10

7.2 Designation examples ....................................................................................................................................................................10

8 Piston pin types, dimensions and tolerances ......................................................................................................................11

8.1 Manufacturing types .......................................................................................................................................................................11

8.2 Dimensions and tolerances .......................................................................................................................................................11

8.2.1 Outside diameter and form and location tolerances .....................................................................11

8.2.2 Inside diameter tolerance .....................................................................................................................................13

8.2.3 Length (l ) and gauge length (l ) tolerances ........................................................................................13

1 5

8.2.4 Outside-edge form .......................................................................................................................................................14

8.2.5 Inside-edge profile ......................................................................................................................................................15

8.2.6 Tapered bore dimensions ......................................................................................................................................16

8.2.7 Centre-web dimensions (see Figure 17) ..................................................................................................18

9 Material and heat treatment .................................................................................................................................................................18

9.1 Type of material ..................................................................................................................................................................................18

9.2 Core hardness l core strength .................................................................................................................................................19

9.3 Carburised and nitrided case depth ..................................................................................................................................20

9.4 Surface hardness ................................................................................................................................................................................21

9.5 Volume change .....................................................................................................................................................................................21

10 Common features ..............................................................................................................................................................................................22

10.1 Roughness of surfaces ...................................................................................................................................................................22

10.1.1 Roughness of machined surfaces ....................................................................................................................22

10.1.2 Roughness of coated surfaces ............................................................................................................................22

10.1.3 Roughness of extruded and seamless drawn bore surfaces ....................................................23

10.2 Marking of piston pins ...................................................................................................................................................................23

10.3 Miscellaneous ........................................................................................................................................................................................23

10.3.1 Cleanliness .........................................................................................................................................................................23

10.3.2 Corrosion protection .................................................................................................................................................23

10.3.3 Residual magnetism ...................................................................................................................................................23

10.3.4 Packaging.............................................................................................................................................................................23

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ISO/FDIS 18669-1:2021(E)

11 Quality requirements ...................................................................................................................................................................................24

11.1 Material characteristics ................................................................................................................................................................24

11.1.1 Decarburisation .............................................................................................................................................................24

11.1.2 Cementite network .....................................................................................................................................................24

11.1.3 Nitride coating ................................................................................................................................................................24

11.1.4 Grinder burn .....................................................................................................................................................................24

11.2 Material defects ...................................................................................................................................................................................24

11.2.1 Cracks .....................................................................................................................................................................................24

11.2.2 Forming streaks .............................................................................................................................................................24

11.3 Visual defects .........................................................................................................................................................................................25

Bibliography .............................................................................................................................................................................................................................26

iv © ISO 2021 – All rights reserved
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ISO/FDIS 18669-1:2021(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 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 22, Road vehicles, Subcommittee SC 34,

Propulsion, powertrain and powertrain fluids.

This third edition cancels and replaces the second edition (ISO 18669-1:2013), which has been

technically revised.
The main changes compared to the previous edition are as follows:
— Clause 2 added,
— Table 4 “Waviness” added,
— Table 18 “Roughness machined surfaces” changed,
— Subclause 10.1.2 “Roughness of coated surfaces” added,
— Table 21 “Visual defects” changed,
— editorial changes.
A list of all parts in the ISO 18669 series can be found on the ISO website.

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.
© ISO 2021 – All rights reserved v
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 18669-1:2021(E)
Internal combustion engines — Piston pins —
Part 1:
General specifications
1 Scope

This document specifies the essential dimensional characteristics of piston pins with a nominal outer

diameter from 8 mm up to and including 100 mm, for reciprocating internal combustion engines for

road vehicles and other applications. In certain applications, except road vehicles, and provided that

mutual agreement is made between the customer and the manufacturer, this document can be used

with suitable modifications.

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 document can require a manufacturer and customer statistical process control

agreement.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological 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/
3.1 General
3.1.1
piston pin

precision cylindrical component that connects the piston to the connecting rod and has a smooth hard

peripheral surface
3.2 Geometrical and manufacturing features of piston pins
3.2.1 Bore types
3.2.1.1
cylindrical bore
pin having a straight cylindrical bore
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ISO/FDIS 18669-1:2021(E)
3.2.1.2
centre web
pin bore with 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.

3.2.1.3
tapered bore

pin with conical-shaped inside diameter near the ends that reduces the weight of the piston pin (3.1.1)

3.2.1.4
machined bore
pin with inside diameter produced solely by machining
3.2.1.5
seamless drawn tube

hollow steel product which does not contain any line junctures resulting from the method of

manufacture
3.2.1.6
end web
pin bore with 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.
3.2.2 Outside-edge configurations
3.2.2.1
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.
3.2.2.2
outside-edge form angle

region of outside-edge form that provides a smooth transition to the peripheral surface to facilitate

ease of assembly
3.2.2.3
outside-edge form angle end face
region of outside-edge form that provides a smooth transition to the end face
3.2.2.4
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.
3.2.2.5
inside-edge chamfer

bevelled edge between the bore surface and the end faces of the piston pin (3.1.1)

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ISO/FDIS 18669-1:2021(E)
3.2.2.6
gauge point

locating point on the pin outside-edge chamfer (3.2.2.1) from where the gauge diameter (d ) and gauge

length (l ) are measured
3.2.3 Other features
3.2.3.1
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
3.2.3.2
slag line
linear flaw of non-metallic inclusions
4 Symbols
Symbol Description
a Wall thickness
b Outside-edge drop-off length
c Outside-edge drop-off height
d Outside diameter
d Inside diameter
d Tapered bore diameter
d Centre-web diameter
d Gauge diameter
d End face diameter
e Tapered bore runout
f Outside-edge length
g Outside-edge chamfer length
H Limit hardness
h End face concavity
h End face step
k Tapered bore relief
l Length
l Tapered bore length
l Centre-web length
l Gauge length
r Outside-edge radius
R Core strength
s End face runout
t Inside-edge chamfer length
t Outside-edge form length
α Tapered bore angle
β Outside-edge chamfer angle
γ Outside-edge form angle end face
δ Outside-edge form angle
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ISO/FDIS 18669-1:2021(E)
5 Nomenclature
5.1 Outside, inside and end features

Terms commonly used to describe pins with a cylindrical bore are shown in Figure 1.

Key
1 end face
2 bore surface
3 peripheral surface
d outside diameter
d inside diameter
l length
a wall thickness
For detail W 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
h end face step
d end face diameter
End face concavity and end face step are not recommended for end face locking.
Figure 2 — Detail W of Figure 1
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ISO/FDIS 18669-1:2021(E)
Terms commonly used to describe pins with a centre web are shown in Figure 3.
Key
1 centre-web radius
l centre-web length
d centre-web diameter
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
l tapered bore length
Figure 5 — Pin with tapered bore
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ISO/FDIS 18669-1:2021(E)
5.2 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
For detail X see Figures 7 and 8.
For detail Y see Figure 9.
NOTE This can be used with either a round or rectangular retainer ring.
Figure 6 — Outside-edge configuration (detail X: chamfered; detail Y: radiused)
5.2.1 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)
5.2.2 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/FDIS 18669-1:2021(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)
5.2.3 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)
5.2.4 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/FDIS 18669-1:2021(E)
Key
1 gauge points
l gauge length
d gauge diameter
For detail Z see Figure 11.
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
d gauge diameter
δ outside-edge form angle
β outside-edge chamfer angle
Figure 11 — Detail Z of Figure 10
5.3 Outside-edge drop-off configuration

Terms commonly used to describe outside-edge drop-off configurations are shown in Figure 12 a),

12 b) and 12 c).

The outside-edge drop-off is for manufacturing purposes and is therefore a chamfer that is very small

in height but long in length.
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ISO/FDIS 18669-1:2021(E)

a) Chamfered edge and drop-off b) Double-chamfered edge and c) Radiused edge and drop-

drop-off 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)
6 Codes

Codes used for piston pins shall be as given in Table 1 with their explanatory descriptions.

Table 1 — Codes and descriptions
Relevant sub-
Code Description clause of this
document

P1…P6 Pin-type classification according to manufacturing method of the pin centre hole 8.1

X Piston pins in combination with needle bearing 9.3
F1, F2, F3 Outside-edge configuration tolerance class 8.2.4
K Carburising steel class K 9.1 / 9.2
S Carburising steel class S 9.1 / 9.2
L Carburising steel class L 9.1 / 9.2
M Carburising steel class M 9.1 / 9.2
N Nitriding steel class N 9.1 / 9.2
V Piston pins with limited volume change 9.3 / 9.4 / 9.5
H1, H2 Surface hardness class 9.4
R1, R2 Peripheral surface roughness class 10.1.1
G Chamfer-locking outside-edge configuration (gauge point) 7.2 / 8.2.4
R Outside-edge radiused 8.2.4 / 7.1.2
C1 Outside-edge chamfered 8.2.4
C2 Outside-edge double chamfered 8.2.4
LA, LB Length tolerance class 8.2.3
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ISO/FDIS 18669-1:2021(E)
Table 1 (continued)
Relevant sub-
Code Description clause of this
document
MM Manufacturer’s mark 10.2
TC Piston pins with bore surface cold formed 8.2.6
7 Designation of piston pins
7.1 Designation elements and order

To designate piston pins, the following details shall be given, in the order shown below. The codes given

in Table 1 shall be used.
7.1.1 Mandatory elements

The following mandatory elements shall constitute the designation of a piston pin:

— designation, i.e. piston pin;
— number of International Standard: ISO 18669-1;
— 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.
7.1.2 Additional elements

The following optional elements may be added to the designation of a piston pin; in this case they shall

be separated from the mandatory elements by a slash (/):
— code for outside-edge configuration, e.g. R, C1, C2, G;
— size of chamfer-locking gauge dimensions, d × l × β when code G is specified;
5 5
— code for limited volume change, V;
— code for surface hardness, H1, H2;
— code for surface roughness, R1, R2.
7.2 Designation examples

The following are examples of piston pin designation in accordance with this document.

EXAMPLE 1 Designation of a piston pin complying with the requirements of this document, manufacturing

type P5 (P5) of outside diameter d = 20 mm (20), inside diameter d = 11 mm (11) and length l = 50 mm (50)

1 2 1

made of carburising steel, class L (L) with double chamfered outside-edge configuration (C2), selected chamfer-

locking outside-edge configuration (G) of gauge diameter d = 18,9 mm (18,9), gauge length l = 49 mm (49) and

5 5

outside-edge chamfer angle β = 45° (45), limited volume change (V), class 2 surface hardness (H2) and class 1

roughness on peripheral surface (R1). Parameters in parenthesis are used in the ISO piston pin designation:

Piston pin ISO 18669-P5, 20 × 11 × 50-L / C2 G-18,9 × 49 × 45 V H2 R1.
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ISO/FDIS 18669-1:2021(E)

EXAMPLE 2 Designation of a piston pin complying with the requirements of this document, manufacturing

type P2 (P2) of outside diameter d = 22 mm (22), tapered bore diameter d = 18 mm (18), tapered bore angle

1 3

α = 20 (20), inside diameter d = 12 mm (12) and length l = 60 mm (60) made of nitriding steel, class (N).

2 1
Parameters in parenthesis are used in the ISO piston pin designation:
Piston pin ISO 18669-P2, 22/18-20 × 12 × 60-N.
8 Piston pin types, dimensions and tolerances
8.1 Manufacturing types
See Table 2.
Table 2 — Piston pin manufacturing types
Permissible manufacturing methods
Manufacturing
Cold-formed Seamless
code
Machined Cold-formed
centre web drawn tube
P1 x x x X
P2 x x x no
P3 no x x no
P4 x x no no
P5 no x no no
P6 x no no no
8.2 Dimensions and tolerances
8.2.1 Outside diameter and form and location tolerances

Terms commonly used to describe outside-edge drop-off configurations are shown in Figure 13a), 13b)

and 13c).
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ISO/FDIS 18669-1:2021(E)

a) Chamfered edge and drop-off b) Double-chamfered edge and c) Radiused edge and drop-

drop-off off
Key
b outside-edge drop-off length
c outside-edge drop-off height
f outside-edge length
g outside-edge chamfer length
δ outside-edge form angle
β outside-edge chamfer angle
See Figure 14.
Figure 13 — Drop-off configurations (detail X and Y of Figure 6)

Table 3 shows the outside diameter tolerances and the permissible cylindricity, circularity and edge

drop-off.
Table 3 — Outside diameter (d ) and form and location
...