Bsi bs au 264 1995 (1999) iso 2345 1994

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BRITIS H S TAND ARD AUTO MO BILE S E RIE S

BS AU
2 64 : 1 995
IS O 2 3 4 5 : 1 994

Road vehicles —
M1 8

×

1 ,5 spark-plugs

with conical seating
and their cylinder head
housing

IC S 43 . 0 60 . 5 0


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BS AU 264:1995

Committees responsible for this
British Standard
The p rep aration of this Britis h S tandard was entrus ted to Technical
C ommittee MC E /9, Ignition equip ment for sp ark ignition engines , up on which
the following b odies were rep res ented:

S ociety of Motor Manufacturers and Traders Ltd.
C oop ted memb ers

This Britis h S tandard, having
b een p rep ared under the
direction of the E ngineering
S ector Board, was p ub lis hed
under the authority of the
S tandards Board and comes
into effect on

Amendments issued since publication

1 5 D ecemb er 1 9 9 5

Amd. No.
© BS I 1 1 - 1 9 9 9

The following BS I references
relate to the work on this
s tandard:
C om mittee reference MC E /9
D raft for comment 9 3 /71 5 401 D C

ISBN 0 580 24944 1

D ate

C omments

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BS AU 264:1995

Contents
Page
C ommittees res p ons ib le
National foreword

ii

1

S cop e

1

2

Normative references

1

3

Requirements

1

Figure 1 — M1 8

×

1 , 5 sp ark- p lugs with conical s eating

3

Figure 2 — H ous ing of sp ark- p lug in cylinder head

4

Tab le 1

1

Lis t of references

© BS I 1 1 - 1 99 9

Ins ide front cover

Ins ide b ack cover

i


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BS AU 264:1 995

National foreword

This British Standard has been prepared by Technical Committee MCE/9. It is
identical with ISO 2345: 1 994

Road v ehicles — M1 8

×

1 , 5 sp ark- p lugs w ith co nical

, published by the International

seating and their cylinder head hous ing

Organization for Standardization (ISO) .
Cross-references
Publication referred to

ISO 68: 1 973
ISO 261 : 1 973
ISO 965- 1 : 1 980
ISO 965- 3: 1 980

C orresponding British Standard



BS 3643



Part 1 : 1 981




ISO m etric screw threads
Princip les and b asic data

(Technically equivalent)




A British Standard does not purport to include all the necessary provisions of a
contract. Users of British Standards are responsible for their correct application.
Compliance with a British Standard does not of itself confer immunity
from legal obligations.

Summary of pages

This document comprises a front cover, an inside front cover, pages i and ii,
pages 1 to 4, an inside back cover and a back cover.
This standard has been updated (see copyright date) and may have had
amendments incorporated. This will be indicated in the amendment table on the
inside front cover.
ii

© BSI 1 1 - 1 999


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BS AU 2 64 : 1 995

The Z length of the spark- plug housing in the

1 S cop e

This International Standard specifies the main
characteristics of M1 8

×

1 , 5 spark- plugs with

conical seating and their cylinder head housing, for
use with spark- ignition engines.

cylinder head shall be sufficient to ensure that the
end of the spark- plug thread does not proj ect into
the combustion chamber at any point when the
spark- plug is tightened to the maximum torque
specified in

3.4.

Threads

2 Normative re fe re nce s

3.2.3

The following standards contain provisions which,

3.2.3.1

through reference in this text, constitute provisions

The threads of M1 8

of this International Standard. At the time of

corresponding tapped holes in the cylinder head

Spark-plug and cylinder head

×

1 , 5 spark- plugs and the

publication, the editions indicated were valid. All

shall conform to ISO 68, ISO 261 , ISO 965- 1 and

standards are subj ect to revision, and parties to

ISO 965- 3. Their limiting dimensions and their

agreements based on this International Standard

tolerance classes shall be as specified in

are encouraged to investigate the possibility of

and

applying the most recent editions of the standards
indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
ISO 68: 1 973, ISO general purpose screw threads —

3.2.3.1 .2

3.2.3.1 .1

Limiting dimensions

The limiting dimensions shall be as given in
Table 1 .
Tab le 1

Basic profile.

Dimensions in millimetres

ISO 261 : 1 973, ISO general purpose metric screw

threads — General plan.

ISO 965- 1 : 1 980, ISO general purpose metric screw

D i me nsio n

threads — Tolerances — Part 1 : Principles and basic
data.

ISO 965- 3: 1 980, ISO general purpose metric screw

Maj or diameter

threads — Tolerances — Part 3: Deviations for
constructional threads.

Pitch diameter

3 Require me nts

Minor diameter

3 . 1 Te rminals

The spark- plug terminal may be either the solid
post or the threaded type. A spark- plug with
threaded terminal on which a nut is applied shall
respect the dimensions specified for spark- plugs
with solid post terminal. See Figure 1 .
3 . 2 D ime nsions and thre ad s

See Figure 1 and Figure 2.
3.2.1

3.2.3.1 .1

respectively.

Length dimensions

a

With a root radius

3.2.3.1 .2

Plu g thre ad

Tap p e d ho le

(on finished

i n cyli nd e r

plug)

he ad

max.

1 7, 933

not specified

min.

1 7, 697

18

max.

1 6, 959

1 7, 21 6

min.

1 6, 81 9

1 7, 026

max.

1 6, 092

min.

1 5, 845

1 6, 676
a

1 6, 376

W 0, 1 50 mm (0, 1 P) .

Tolerance classes

The tolerance classes of thread M1 8

× 1 , 5 of finished

spark- plugs and of the corresponding tapped holes
in the cylinder head shall be as follows:
— 6e for spark- plugs (see note 1 );
— 6H for tapped holes in the cylinder head.

The length dimensions are measured from a

NOTE 1

gauging plane defined by diameter 1 9 mm on the

International Standard can be fitted in existing heads also in

seating.
Dimension 1 0, 9 mm

± 0, 3 mm may be increased for

certain spark- plug types.
3.2.2

Dimensions of spark-plug housing in

cylinder head
The length dimensions Z and 9 mm max. in the

In order that spark- plugs complying with this

extreme cases, the value for the maximum truncation of the
minor diameter of the spark- plug base has been slightly reduced
with respect to the ISO value.
This maximum value of the minor diameter is calculated from a
distance of H/6 for the maximum truncation instead of the value
given by the formula in ISO 965- 1 : 1 980, clause

11,

according to

the formula given below:
Minor diameter, maximum

= d1 – es – 2(H/4 – H/6)

cylinder head are measured from a gauging plane
defined by diameter 1 9 mm on the seating.

= 1 6, 376 – 0, 067 – 0, 21 7
= 1 6, 376 – 0, 284 = 1 6, 092
The value for the basic profile remains the same as for the
ISO thread (1 6, 376 – 0, 067 = 1 6, 309) .

© BSI 1 1 - 1 999

1


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BS AU 264:1 995

NO TE 2

The initial clearance

e

= 0, 067 mm between the pitch

diameters of the thread and of the tapped hole is intended to
p revent the possibility of seizure, as a result of combustion
deposits on the bare threads, when removing the spark- plugs.

The contour of the insulator is optional; however,
between the reference planes defined for
spark- plugs with solid post terminal by the

This clearance is also intended to enable spark- plugs with

dimensions 2 9 mm and 3 3 mm, and for spark- plugs

threads in accordance with this International Standard to b e

with threaded terminal b y the dimensions 2 6 mm

fitted in existing tapped holes.

3.2.3.2

Threaded terminal

and 30 mm, its largest diameter shall
be 1 2 , 2 mm

± 0, 3 mm.

For spark- plugs with a threaded- type terminal, the

D etails not specified are left to the manufacturer’s

thread tolerance class of the terminal

choice.

[see Figure 1 b) ] is 6e.
NO TE 3

D epending on manufacturing processes, class 7e is

acceptab le on the finished product.

Nuts for use with threaded terminals shall have
internal threads to 6H tolerance prior to assemb ly
on the threaded post.

3.4 Installation tightening torque
The installation torque values apply to new
spark- plugs without lub ricant on the threads. If
threads are lubricated, the torque value shall be
reduced b y approximately one- third to avoid
overstressing. The spark- plugs shall be tightened

3.3 Other dimensions of spark-plug and
housing in cylinder head

with a torque of 2 0 N·m to 30 N·m in cast iron
cylinder heads.

The other dimensions shall be as indicated in

NO TE 4

Figure 1 and Figure 2 .

for the first spark- plug installation.

2

E ngine manufacturers may specify a different torque

© BSI 1 1 - 1 999


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BS AU 2 64: 1 995

1 ) Spark- plug manufacturers are encouraged to
adopt 1 5 °

±

5 ° for future products.

2 ) 0, 7 mm pitch complying with ISO 68 and ISO 2 61 .
3) D epending on manufacturing processes, class 7e is
acceptable on the finished product.
4) Length of usable thread.
5) Cylindrical part.
6) O ther dimensions: see Figure 1 a) .

Figure 1 — M1 8

â BSI 1 1 - 1 999

ì

1 ,5 spark-p lugs with conical se ating

3


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BS AU 264:1 995

4

Figure 2 — Housing of spark-plug in cylinder head

© BSI 1 1 - 1 999


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List of references

See national foreword.

© BSI 1 1 - 1 999

BS AU 264:1995


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BS AU

264:1995
ISO 2345:1994

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