ISO 6624-2:2016

Internal combustion engines — Piston rings — Part 2: Half keystone rings made of cast iron

ISO 6624-2:2016 specifies the essential dimensional features of half keystone rings made of cast iron, types HK, HKB and HKBA, having nominal diameters from 38 mm up to, and including, 160 mm, used in reciprocating internal combustion piston engines for road vehicles and other applications.

Moteurs à combustion interne — Segments de piston — Partie 2: Segments demi-trapézoïdaux fabriqués en fonte moulée

General Information

• Status: Published
• Publication Date: 17-Feb-2016
• 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 4 - Piston rings
• Current Stage: 9092 - International Standard to be revised
• Completion Date: 18-Mar-2022

Relations

• Revises: ISO 6624-2:2003 - Internal combustion engines — Piston rings — Part 2: Half keystone rings made of cast iron
• Effective Date: 12-Feb-2011

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 6624-2
Second edition
2016-02-15
Internal combustion engines —
Piston rings —
Part 2:
Half keystone rings made of cast iron
Moteurs à combustion interne — Segments de piston —
Partie 2: Segments demi-trapézoïdaux fabriqués en fonte moulée
Reference number
ISO 6624-2:2016(E)
ISO 2016
---------------------- Page: 1 ----------------------
ISO 6624-2:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland

All rights reserved. Unless otherwise specified, 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
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. [phone]
Fax [phone]
[e-mail]
www.iso.org
ii © ISO 2016 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 6624-2:2016(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

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

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

3 Overview ....................................................................................................................................................................................................................... 1

4 Ring types and designation examples ............................................................................................................................................ 1

4.1 Type HK — Straight faced half keystone ring 7° ........................................................................................................ 1

4.1.1 General features................................................................................................................................................................ 1

4.1.2 Designation ........................................................................................................................................................................... 2

4.2 Type HKB — Barrel faced half keystone ring 7° ........................................................................................................ 2

4.2.1 General features................................................................................................................................................................ 2

4.2.2 Designation ........................................................................................................................................................................... 4

4.3 Type HKBA — Asymmetrical barrel faced half keystone ring 7°(h ≥ 1,2 mm) ............................. 4

4.3.1 General features................................................................................................................................................................ 4

4.3.2 Designation ........................................................................................................................................................................... 5

5 Common features ................................................................................................................................................................................................. 5

5.1 Type HK, HKB and HKBA — Half keystone ring ......................................................................................................... 5

5.1.1 Uncoated rings ................................................................................................................................................................... 5

5.1.2 Chromium plated or spray coated rings ...................................................................................................... 6

5.2 Chamfered edges — Type HK, HKB and HKBA rings — Outside and/or inside

chamfered edges (KA, KI) .............................................................................................................................................................. 7

5.3 Type HK, HKB and HKBA rings (fully faced, semi-inlaid) — Plating/coating thickness ......... 7

6 Force factors .............................................................................................................................................................................................................. 8

7 Dimensions and forces ................................................................................................................................................................................... 8

Annex A (normative) Calculation of measurement width h of half keystone rings .......................................17

Bibliography .............................................................................................................................................................................................................................18

© ISO 2016 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 6624-2:2016(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 meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical

Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 22, Road vehicles, Subcommittee SC 34,

Propulsion, powertrain and powertrain fluids.

This second edition cancels and replaces the first edition (ISO 6624-2:2003), which has been

technically revised.

ISO 6624 consists of the following parts, under the general title Internal combustion engines — Piston rings:

— Part 1: Keystone rings made of cast iron
— Part 2: Half keystone rings made of cast iron
— Part 3: Keystone rings made of steel
— Part 4: Half keystone rings made of steel
iv © ISO 2016 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 6624-2:2016(E)
Introduction

ISO 6624 is one of a number of series of International Standards dealing with piston rings for

[2][3][4][5] [6][7] [8]

reciprocating internal combustion engines. Others are ISO 6621, ISO 6622, ISO 6623,

[9] [10][11][12] [13]
ISO 6625, ISO 6626, and ISO 6627.
© ISO 2016 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 6624-2:2016(E)
Internal combustion engines — Piston rings —
Part 2:
Half keystone rings made of cast iron
1 Scope

This part of ISO 6624 specifies the essential dimensional features of half keystone rings made of cast

iron, types HK, HKB and HKBA, having nominal diameters from 38 mm up to, and including, 160 mm,

used in reciprocating internal combustion piston engines for road vehicles and other applications.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 6621-4, Internal combustion engines — Piston rings — Part 4: General specifications

3 Overview

The half keystone ring types are specified in Tables 1 and 2 and Figures 1 to 3. Their common features

and the dimensions of those features are specified in Tables 3 and 4 and Figures 4 to 9. Tables 5 and 6

give the force factors for the different ring types, while Table 7 gives the dimensions and forces of half

keystone rings.

The common features and dimensional tables presented in this part of ISO 6624 constitute a broad

range of variables and, in selecting a particular ring type, the designer shall bear in mind the conditions

under which it will be required to operate.
[4]

It is also essential that the designer refer to the specifications and requirements of ISO 6621-3 and

ISO 6621-4 before completing selection.
4 Ring types and designation examples

NOTE For the angle of half keystone rings, the same definition and measurement apply as for keystone rings

(see ISO 6621-2).
4.1 Type HK — Straight faced half keystone ring 7°
4.1.1 General features
Figure 1 shows the general features of piston ring type HK.
See Table 7 for dimensions and forces.
h values are calculated based on Annex A.
© ISO 2016 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 6624-2:2016(E)
Key
1 reference plane (ring is positioned flat against datum A)
2 top side identification mark
Nominal.
t = 0,006 × h .
Figure 1 — Type HK
4.1.2 Designation

EXAMPLE Designation of a piston ring complying with the requirements of ISO 6624-2, being a 7° half

keystone ring made of cast iron, with a straight-faced peripheral surface (HK), of d = 90 mm (90), of nominal

ring width h = 1,5 mm (1,5), made of heat treated martensitic spheroidal graphite cast iron, subclass 53 (MC53),

and having a chromium plated peripheral surface with a minimum thickness 0,1 mm (CR2). Parameters in

parenthesis are used in the ISO ring designation:
Piston ring ISO 6624-2 HK - 90 × 1,5 - MC53/CR2
4.2 Type HKB — Barrel faced half keystone ring 7°
4.2.1 General features
Figure 2 shows the general features of piston ring type HKB.
See Table 7 for dimensions and forces.
h values are calculated based on Annex A.
2 © ISO 2016 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 6624-2:2016(E)
Key
1 reference plane (ring is positioned flat against datum A)
2 top side identification mark
Nominal.
Figure 2 — Type HKB
Table 1 — Symmetrical barrel dimensions and gauge width (h )
Dimensions in millimetres
h h h h tol. h t , t h
1 25 26 26 27 2 3 8
1,2 0,30 0,60 ±0,20 0,90 0,002...0,012 0,60
1,5 0,35 0,75 ±0,25 1,15 0,80
1,75 0,35 0,85 ±0,30 1,35 1,00
0,003...0,015
2,0 0,40 1,00 ±0,30 1,60 1,20
2,5 0,45 1,25 ±0,40 2,05 1,60
3,0 0,50 1,50 ±0,50 2,50 2,00
0,005...0,020
3,5 0,55 1,75 ±0,50 2,95 2,40

Gauge width (h ) only informative; may be used only if agreed between the manufacturer and the customer.

© ISO 2016 – All rights reserved 3
---------------------- Page: 8 ----------------------
ISO 6624-2:2016(E)
4.2.2 Designation

EXAMPLE Designation of a piston ring complying with the requirements of ISO 6624-2, being a 7° half

keystone ring made of cast iron, with a barrel faced peripheral surface (HKB), of d = 90 mm (90), of nominal ring

width h = 1,5 mm (1,5), made of non-heat-treated grey cast iron, subclass 12 (MC12), and having a chromium

plated peripheral surface with a minimum thickness of 0,1 mm (CR2). Parameters in parenthesis are used in the

ISO ring designation:
Piston ring ISO 6624-2 HKB - 90 × 1,5 - MC12/CR2
4.3 Type HKBA — Asymmetrical barrel faced half keystone ring 7°(h ≥ 1,2 mm)
4.3.1 General features
See Table 7 for dimensions and forces.
h values are calculated based on Annex A.
Key
1 reference plane (ring is positioned flat against datum A)
2 top side identification mark
Nominal.
Figure 3 — Type HKBA
4 © ISO 2016 – All rights reserved
---------------------- Page: 9 ----------------------
ISO 6624-2:2016(E)
Table 2 — Asymmetrical barrel dimensions
Dimensions in millimetres
a b b
h h h h tol. h t t
1 25 26 26 27 2 3
1,2 0,28 0,43 0,90 0…0,005 0,005…0,016
±0,15
1,5 0,35 0,50 1,15 0...0,006 0,007...0,022
1,75 0,35 0,55 1,35 0,008...0,025
±0,20 0...0,007
2,0 0,40 0,60 1,50 0,009...0,030
2,5 0,45 0,70 1,80 0,011...0,035
±0,25 0...0,008
3,0 0,55 0,80 2,10 0,012...0,038
3,5 0,60 0,90 ±0,30 2,40 0...0,009 0,012...0,040
h may be lowered for rings with reduced edge dimensions.
t and/or t may be varied as agreed between the manufacturer and the customer.
2 3
4.3.2 Designation

EXAMPLE Designation of a piston ring complying with the requirements of ISO 6624-2, being a 7° half

keystone ring made of cast iron, with an asymmetrical barrel faced peripheral surface (HKBA), of d = 90 mm

(90), of nominal ring width h = 1,5 mm (1,5), made of non-heat-treated grey cast iron, subclass 12 (MC12),

and having a chromium plated peripheral surface with a minimum thickness of 0,1 mm (CR2). Parameters in

parenthesis are used in the ISO ring designation:
Piston ring ISO 6624-2 HKBA - 90 × 1,5 - MC12/CR2
5 Common features
5.1 Type HK, HKB and HKBA — Half keystone ring
5.1.1 Uncoated rings
1 1
a) Type HK b) Type HKB c) Type HKBA
Key
1 top side identification mark
Figure 4 — Uncoated rings
© ISO 2016 – All rights reserved 5
---------------------- Page: 10 ----------------------
ISO 6624-2:2016(E)
5.1.2 Chromium plated or spray coated rings
5.1.2.1 Fully faced
1 1
a) Type HK b) Type HKB c) Type HKBA
Key
1 top side identification mark
Figure 5 — Fully faced rings
5.1.2.2 Semi-inlaid
1 1 1
a) Type HK b) Type HKB c) Type HKBA
Key
1 top s
...

DRAFT INTERNATIONAL STANDARD ISO/DIS 6624-2
ISO/TC 22 Secretariat: AFNOR
Voting begins on Voting terminates on
2012-03-29 2012-08-29

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION • МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ • ORGANISATION INTERNATIONALE DE NORMALISATION

Internal combustion engines — Piston rings —
Part 2:
Half keystone rings made of cast iron
Moteurs à combustion interne — Segments de piston —
Partie 2: Segments demi-trapézoïdaux fabriqués en fonte moulée
[Revision of first edition (ISO 6624-2:2003)]
ICS 43.060.10

To expedite distribution, this document is circulated as received from the committee

secretariat. ISO Central Secretariat work of editing and text composition will be undertaken at

publication stage.

Pour accélérer la distribution, le présent document est distribué tel qu'il est parvenu du

secrétariat du comité. Le travail de rédaction et de composition de texte sera effectué au

Secrétariat central de l'ISO au stade de publication.

THIS DOCUMENT IS A DRAFT CIRCULATED FOR COMMENT AND APPROVAL. IT IS THEREFORE SUBJECT TO CHANGE AND MAY NOT BE

REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED AS SUCH.

IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT

INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME STANDARDS TO

WHICH REFERENCE MAY BE MADE IN NATIONAL REGULATIONS.

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 SUPPORTING DOCUMENTATION.
© International Organization for Standardization, 2012
---------------------- Page: 1 ----------------------
ISO/DIS 6624-2
Copyright notice

This ISO document is a Draft International Standard and is copyright-protected by ISO. Except as permitted

under the applicable laws of the user’s country, neither this ISO draft nor any extract from it may be

reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic,

photocopying, recording or otherwise, without prior written permission being secured.

Requests for permission to reproduce should be addressed to either ISO at the address below or ISO’s

member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Reproduction may be subject to royalty payments or a licensing agreement.
Violators may be prosecuted.
ii © ISO 2012 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/DIS 6624-2
Contents Page

Foreword ............................................................................................................................................................ iv

Introduction ......................................................................................................................................................... v

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

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

3 Overview ................................................................................................................................................. 1

4 Ring types and designation examples ................................................................................................ 1

4.1 Type HK — Straight faced half keystone ring 7° ................................................................................ 1

4.1.1 General features .................................................................................................................................... 1

4.1.2 Designation ............................................................................................................................................ 2

4.2 Type HKB — Barrel faced half keystone ring 7° ................................................................................ 2

4.2.1 General features .................................................................................................................................... 2

4.2.2 Designation ............................................................................................................................................ 4

4.3 Type HKBA — Asymmetrical barrel faced half keystone ring 7°(h1  1,2 mm) .............................. 4

4.3.1 General features .................................................................................................................................... 4

4.3.2 Designation ............................................................................................................................................ 6

5 Common features .................................................................................................................................. 6

5.1 Type HK, HKB and HKBA — Half keystone ring ................................................................................ 6

5.1.1 Uncoated rings ...................................................................................................................................... 6

5.1.2 Chromium plated or spray coated rings ............................................................................................. 7

5.2 Chamfered edges — Type HK, HKB and HKBA rings — Outside and/or inside chamfered

edges (KA, KI) ........................................................................................................................................ 8

5.3 Type HK, HKB and HKBA rings (fully faced, semi-inlaid) — Plating/coating thickness ................ 8

6 Force factors .......................................................................................................................................... 9

7 Dimensions and forces ......................................................................................................................... 9

Annex A (normative) Calculation of measurement width h of half keystone rings .................................. 18

Bibliography ...................................................................................................................................................... 19

© ISO 2012 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/DIS 6624-2
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.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

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.

ISO 6624-2 was prepared by Technical Committee ISO/TC 22, Road Vehicles.

This second edition cancels and replaces the first edition (ISO 6624-2:2003), which has been technically

revised.

ISO 6624 consists of the following parts, under the general title Internal combustion engines — Piston rings:

— Part 1: Keystone rings made of cast iron
— Part 2: Half keystone rings made of cast iron
— Part 3: Keystone rings made of steel
— Part 4: Half keystone rings made of steel
iv © ISO 2012 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/DIS 6624-2
Introduction

ISO 6624 is one of a number of series of International Standards dealing with piston rings for reciprocating

[2], [3], [4], [5] [6], [7] [8] [9]

internal combustion engines. Others are ISO 6621 , ISO 6622 , ISO 6623 , ISO 6625 ,

[10], [11], [12] [13]
ISO 6626 and ISO 6627 .

The common features and dimensional tables presented in this part of ISO 6624 constitute a broad range of

variables and, in selecting a particular ring type, the designer must bear in mind the conditions under which it

will be required to operate.
[4]

It is also essential that the designer refer to the specifications and requirements of ISO 6621-3 and

ISO 6621-4 before completing selection.
© ISO 2012 – All rights reserved v
---------------------- Page: 5 ----------------------
DRAFT INTERNATIONAL STANDARD ISO/DIS 6624-2
Internal combustion engines — Piston rings —
Part 2:
Half keystone rings made of cast iron
1 Scope

This part of ISO 6624 specifies the essential dimensional features of half keystone rings made of cast iron,

types HK, HKB and HKBA, having diameters from 38 mm to 160 mm, used in reciprocating internal

combustion piston engines.
2 Normative references

The following referenced documents are indispensable for the application 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 6621-4, Internal combustion engines — Piston rings — Part 4: General specifications

3 Overview

The half keystone ring types are specified in Table 1 and 2 and Figures 1 to 3. Their common features and the

dimensions of those features are specified in Tables 3 and 4 and Figures 4 to 9. Tables 5 and 6 give the force

factors for the different ring types, while Table 7 gives the dimensions and forces of half keystone rings.

4 Ring types and designation examples

NOTE For the angle of half keystone rings, the same definition and measurement apply as for keystone rings (see

ISO 6621-2).
4.1 Type HK — Straight faced half keystone ring 7°
4.1.1 General features
Figure 1 shows the general features of piston ring type HK.
See Table 7 for dimensions and forces.
h values are calculated based on h + 0,05 mm.
3 1
© ISO 2012 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO/DIS 6624-2
Key
1 reference plane
2 top side identification mark
Nominal.
t = 0,006  h .
Figure 1 — Type HK
4.1.2 Designation

EXAMPLE Designation of a piston ring complying with the requirements of ISO 6624-2, being a 7° half keystone ring

made of cast iron, with a straight faced peripheral surface (HK), of d = 90 mm (90), of nominal ring width h = 1,5 mm

1 1

(1,5), made of heat treated martensitic spheroidal graphite cast iron, subclass 53 (MC53), and having a chromium plated

peripheral surface with a minimum thickness 0,1 mm (CR2). Parameters in parenthesis are used in the ISO ring

designation::
Piston ring ISO 6624-2 HK - 90  1,5 - MC53/CR2
4.2 Type HKB — Barrel faced half keystone ring 7°
4.2.1 General features
Figure 2 shows the general features of piston ring type HKB.
See Table 7 for dimensions and forces.
h values are calculated based on h + 0,05 mm.
2 © ISO 2012 – All rights reserved
---------------------- Page: 7 ----------------------
ISO/DIS 6624-2
Key
1 reference plane
2 top side identification mark
Nominal.
t = 0,006  h .
Figure 2 — Type HKB
© ISO 2012 – All rights reserved 3
---------------------- Page: 8 ----------------------
ISO/DIS 6624-2
Table 1 — Symmetrical barrel dimensions and gauge width (h )
Dimensions in millimetres
h h h h tol. h t , t
1 25 26 26 27 2 3
1,2 0,30 0,60  0,20 0,90 0,002...0,012 0,60
1,5 0,35 0,75 1,15 0,80
 0,25
1,75 0,35 0,85 1,35 1,00
 0,30
0,003...0,015
2,0 0,40 1,00  0,30 1,60 1,20
2,5 0,45 1,25  0,40 2,05 1,60
3,0 0,50 1,50  0,50 2,50 2,00
0,005...0,020
3,5 0,55 1,75 2,95 2,40
 0,50

Gauge width (h ) only informative; may be used only if agreed between manufacturer and customer.

4.2.2 Designation

EXAMPLE Designation of a piston ring complying with the requirements of ISO 6624-2, being a 7° half keystone ring

made of cast iron, with a barrel faced peripheral surface (HKB), of d = 90 mm (90), of nominal ring width h = 1,5 mm

1 1

(1,5), made of non-heat-treated grey cast iron, subclass 12 (MC12), and having a chromium plated peripheral surface with

a minimum thickness of 0,1 mm (CR2). Parameters in parenthesis are used in the ISO ring designation:

Piston ring ISO 6624-2 HKB - 90  1,5 - MC12/CR2
4.3 Type HKBA — Asymmetrical barrel faced half keystone ring 7°(h1  1,2 mm)
4.3.1 General features
See Table 7 for dimensions and forces.
h values are calculated based on h + 0,05 mm.
4 © ISO 2012 – All rights reserved
---------------------- Page: 9 ----------------------
ISO/DIS 6624-2
Key
1 reference plane
2 top side identification mark
Nominal.
t = 0,006  h .
Figure 3 — Type HKBA
© ISO 2012 – All rights reserved 5
---------------------- Page: 10 ----------------------
ISO/DIS 6624-2
Table 2 —Asymmetrical barrel dimensions
Dimensions in millimetres
a b b
h h h tol. h
h t t
1 26 26 27
25 2 3
1,2 0,28 0,43  0,15 0,9 0…0,005 0,005…0,016
1,5 0,35 0,50 1,15 0,007...0,022
 0,15 0...0,006
1,75 0,35 0,55 1,35 0,008...0,025
 0,20
0...0,007
2,0 0,40 0,60  0,20 1,50 0,009...0,030
2,5 0,45 0,70  0,25 1,80 0,011...0,035
0...0,008
3,0 0,55 0,80  0,25 2,10 0,012...0,038
3,5 0,60 0,90 2,40 0,012...0,040
 0,30 0...0,009
h may be lowered for rings with reduced edge dimensions.
t and/or t may be varied as agreed between manufacturer and customer.
2 3
4.3.2 Designation

EXAMPLE Designation of a piston ring complying with the requirements of ISO 6624-2, being a 7° half keystone ring

made of cast iron, with an asymmetrical barrel faced peripheral surface (HKBA), of d = 90 mm (90), of nominal ring width

h = 1,5 mm (1,5), made of non-heat-treated grey cast iron, subclass 12 (MC12), and having a chromium plated peripheral

surface with a minimum thickness of 0,1 mm (CR2). Parameters in parenthesis are used in the ISO ring designation::

Piston ring ISO 6624-2 HKBA - 90  1,5 - MC12/CR2
5 Common features
5.1 Type HK, HKB and HKBA — Half keystone ring
5.1.1 Uncoated rings
a) Type HK b) Type HKB c) Type HKBA
Key
1 top side identification mark
Figure 4 — Uncoated rings
6 © ISO 2012 – All rights reserved
---------------------- Page: 11 ----------------------
ISO/DIS 6624-2
5.1.2 Chromium plated or spray coated rings
5.1.2.1 Fully faced
a) Type HK b) Type HKB c) Type HKBA
Key
1 top side identification mark
Figure 5 — Fully faced rings
5.1.2.2 Semi-inlaid
a) Type HK b) Type HKB c) Type HKBA
Key
1 top side identification mark
Figure 6 — Semi-inlaid rings
5.1.2.3 Inlaid (not recommended for chromium plated rings)
a) Type HK b) Type HKB c) Type HKBA
Key
1 top side identification mark
Figure 7 — Inlaid rings
© ISO 2012 – All rights reserved 7
---------------------- Page: 12 ----------------------
ISO/DIS 6624-2

5.2 Chamfered edges — Type HK, HKB and HKBA rings — Outside and/or inside chamfered

edges (KA, KI)
a) HK rings b) HKB rings c) HKBA rings
d) Chamfered edges
Key
1 top side ident
...