Licensed Copy: Miss Anne Carty, British Standards Institution, 19/01/2012 15:56, Uncontrolled Copy, (c) The British Standards Institution 2012

BRITISH STANDARD AEROSPACE SERIES

Specification for
aluminium alloy,
mushroom-headed,
slotted drive, bolts
(unified thread)

ICS 49.030.20

NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW

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BS
BS4A
4A170:1999
170:1999

+A1:2012



Licensed Copy: Miss Anne Carty, British Standards Institution, 19/01/2012 15:56, Uncontrolled Copy, (c) The British Standards Institution 2012

BS
BS 4A
4A 170:1999
170:1999+A1:2012

Committees responsible for this
British Standard
The preparation of this British Standard was entrusted to Technical Committee
ACE/12, Aerospace fasteners and fastening systems, upon which the following
bodies were represented:
Civil Aviation Authority (Airworthiness Division)
Confederation of British Forgers
Ministry of Defence
Society of British Aerospace Companies Limited
Co-opted member

This British Standard, having
been prepared under the
direction of the Engineering
These Committee,
British Standards,
Sector
was published
having been
prepared
under
under

the authority
of the
the direction
of the Engineering
Standards
Committee
and comes
Sector
Committee,
into
effect
on 15 Junewas
1999
published under the authority of
the Standards Committee and
comes
into effect on

BSI 06-1999
15 June 1999
© The British Standards
Institution 2012
Published by BSI Limited 2012
The following BSI references
relate
to the work
on this
The
following
BSI references

standard:
relate
to the work on this
Committee reference ACE/12
standard:
Draft for comment
98/706176
Committee
reference
ACE/12 DC
12/30254205
Draft for comment 98/706176
DC DC

ISBN
580028286
4
ISBN0978
580 76867
5

Amendments issued since publication
Amd. No.
Date
Comments
Amendments issued since publication
Amd. No.

Date


Comments

A1

July 2012

See foreword


Licensed Copy: Miss Anne Carty, British Standards Institution, 19/01/2012 15:56, Uncontrolled Copy, (c) The British Standards Institution 2012

BS 4A 170:1999
BS 4A 170:1999+A1:2012

Contents
Page
Committees responsible
Inside front cover
Foreword
ii
1 Scope
1
2 Normative references
1
3 General requirements
1
4 Materials and manufacture
1
5 Dimensions and tolerances
1

6 Screw threads
1
7 Protective
Anti-corrosion
treatment
1
finish
8 Hardness values
1
9 Identifying and marking
1
10 Quality assurance procedure
1
Figure 1 Ð Dimensions of bolts
2
Figure 2 Ð Bearing length L, clamping length M and overall length E
2
Table 1 Ð Dimensions of bolts
3
Table 2 Ð Bearing length L, clamping length M and overall length E
4

© The British Standards Institution 2012
 BSI 06-1999

i
i


BS

BS 4A
4A 170:1999
170:1999+A1:2012

Licensed Copy: Miss Anne Carty, British Standards Institution, 19/01/2012 15:56, Uncontrolled Copy, (c) The British Standards Institution 2012

Foreword
This British
hasisbeen
prepared
Technical
Committee
ACE/12.
This
BritishStandard
Standard
published
byby
BSI
Standards
Limited,
underItlicence
supersedes
BS 3A 170:1962
which
is withdrawn.
from
The British
Standards
Institution.

This
British of
Standard
been
prepared
byrequirements
Technical Committee
This revision
BS A 170has
refers
to the
relevant
in BS A 100.ACE/12.
It
BS 4A
170:1999+A1:2012
incorporates
amendment 1. supersedes BS 4A 170:1999, which is withdrawn.
The
startStandard
and finish
of not
textpurport
introduced
or altered
Amendment
No. 1ofisa
A British
does
to include

all theby
necessary
provisions
indicated
in the
by Standards
tags and.
Minor editorial
are not tagged.
contract. Users
oftext
British
are responsible
for theirchanges
correct application.
This
revisionwith
of BSaABritish
170 refers
to the relevant
in BS
A 100.
Compliance
Standard
does notrequirements
of itself confer
immunity
from
legal
obligations.

This publication does not purport to include all the necessary provisions of a
contract. Users are responsible for its correct application.
Compliance with a British Standard cannot 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 7 and a back cover.

ii
ii

© The British Standards Institution 2012
 BSI 06-1999


Licensed Copy: Miss Anne Carty, British Standards In

icensed
Licensed
Copy:
Licensed
Copy:
Miss
Miss
Anne
Copy:
Licensed
Anne
Carty,

Miss
Carty,
Anne
British
Copy:
British
Carty,
Miss
Standards
Standards
British
Anne Institution,
Carty,
Standards
Institution,
British
19/01/2012
Institution,
Standards
19/01/2012
15:56,
19/01/2012
Institution,
15:56,
Uncontrolled
Uncontrolled
15:56,
19/01/2012
Uncontrolled
Copy,

Copy,
15:56,
(c) The
(c)Uncontrolled
Copy,
The
British
British
(c) Standards
The
Standards
Copy,
British
(c)
Institution
Standards
The
Institution
British
2012
Institution
2012
Standards
2012
Institution 2012

1 Scope

This British Standard specifies materials and
manufacture, dimensions, protective treatment and

quality assurance requirements for aluminium alloy,
mushroom-headed, slotted, drive bolts with unified
1 Scope
threads.
This British
Standard
materials
and is
NOTE
The latest
edition of specifies
an Aerospace
Series standard
indicated
by a prefix
number. protective treatment and
manufacture,
dimensions,
quality
assurance requirements for aluminium alloy,
1 Scope
mushroom-headed,
slotted, drive bolts with unified
2
references
1 Normative
Scope
This
British Standard
specifies materials and

threads.
manufacture,
dimensions,
protective
treatment
and
The
following
normative
documents
contain
The
following
documents,
inmaterials
whole
orand
in part,
This
British
Standard
NOTE
The
latest edition
of specifies
an Aerospace
standard
is
quality
assurance

requirements
forSeries
aluminium
alloy,
are
normatively
referenced
in
this
document
provisions
which,
through
reference
in
this
text,
manufacture,
dimensions,
protective
treatment
and
indicated by a prefix number.
mushroom-headed,
slotted,
drive
withFor
unified
and
areassurance

indispensable
its
application.
constitute
provisions
offor
this
British
Standard.
For
quality
requirements
forbolts
aluminium
alloy,
threads.
dated
references, subsequent
only
the edition
citedwith
applies.
dated
references,
amendments
to,
or
mushroom-headed,
slotted,
drive

bolts
unified
2
Normative
references
For
undated
references,
the
latest
edition
of
the
NOTE
The
latest
edition
of
an
Aerospace
Series
standard
is
revisions
of,
any
of
these
publications
do

not
apply.
threads.
indicated
by a document
prefix
number.
referenced
(including
any
amendments)
For
undated
references,
the
latest
edition
the
of
The
following
normative
documents
contain
NOTE The latest edition of an Aerospace Series standard is
applies
publication
referred
to applies.
indicated

by awhich,
prefix
number.
provisions
through
reference in this text,
constitute
provisions
of Specification
this British
Standard.
For
BSNormative
3A 100:1991,
Specification
for general
2
references
BS
4A 100:2003,
for general
dated
references,
subsequent
amendments
to, or
requirements
for
bolts
and

free
running
nuts
2
Normative
references
The
following normative
documents contain of
revisions
of, anynot
of these
publications
do not apply.
tensile
strength
exceeding
1 249 MPa.
provisions
which,
throughdocuments
reference
in this text,
The
following
normative
contain
For
undated
references,

the
latest
edition
of the
BS L 168:1978,
Specification
for barsStandard.
constitute
provisions
of this
British
For
provisions
which,
through
reference
inand
thisextruded
text,
publication
referred
to
applies.
sections
of
aluminium-copper-magnesium-silicondated
references,
subsequent
amendments
to,

or
constitute provisions of this British Standard. For
BS
3A 100:1991,
Specification
for general
manganese
alloy
(solution
treated
and
artificially
revisions
of,
any
of
these
publications
do
not
apply.
dated references, subsequent amendments to, or
requirements
for bolts200
andmm
free
running
nuts
of
aged)

(notof,exceeding
diameter
For
undated
references,
latest
edition
ofminor
the
revisions
any
of thesethe
publications
doornot
apply.
tensile
strength
not exceeding
1Mg
249
MPa.
sectional
dimension)
(Cu
4.4,
0.5,
Si
0.7,
publication
referred

to
applies.
For undated references, the latest edition of the
MnL
0.8).
BS
168:1978,
Specification
for
and extruded
BS
3A
100:1991,
Specification
forbars
general
publication
referred
to applies.
sections
of
aluminium-copper-magnesium-siliconBS
1580-1
Unified
screw
threads
–
Partnuts
1: of
BS

1580,
Specification
for
unified
screw
threads.
requirements
forSpecification
bolts and free
BS 3A 100:1991,
forrunning
general
manganese
alloy
(solution
treated
and
artificially
Screw
threads
with
diameters
¼
in
and
larger
–of
tensile
strength
not

exceeding
1
249
MPa.
BS 1580-1 andfor
-2:1962,
ï in. and
requirements
bolts Diameters
and free running
nutslarger.
aged) (not exceeding 200 mm diameter or minor
Requirements.
BS
L 168:1978,
barsMPa.
and extruded
tensile
strengthSpecification
not exceedingfor
1 249
sectional dimension) (Cu 4.4, Mg 0.5, Si 0.7,
sections
of Unified
aluminium-copper-magnesium-siliconBS
1580-3,
screw
threads
–
Part

3: extruded
Screw
BS
L
168:1978,
Specification
for
bars
and
Mn
0.8).
3 General
requirements
manganese
alloy
(solution
treated
artificially
threads
diameters
below
¼ in –and
Requirements
sectionswith
of aluminium-copper-magnesium-siliconBS
1580,
Specification
formm
unified
screwor

threads.
Bolts
shall
conform
to200
BS
A
100.
aged)
(not
exceeding
diameter
minor
manganese
(solution
treated
and
artificially
BS
EN 2284,alloy
Specification
for
sulfuric
acid
anodizing
sectional
dimension)
(Cu
4.4,
Mg

0.5,
Si
0.7,
BS
1580-1
and
-2:1962,
Diameters
ï
in.
and
larger.
aged)
(not exceeding
200 mm
diameteralloys.
or minor
of
aluminium
and wrought
aluminium
Mn
0.8).
sectional
dimension)
(Cu
4.4,
Mg
0.5,
Si

0.7,
4 Materials and manufacture
BS
1580,
for unified
screw
threads.
Mn
0.8).
3
General
The
boltsSpecification
shallrequirements
be machined
from bars
that
conform
BS
1580-1
and
-2:1962,
Diameters
ï
in.
and
larger.
1580,
Specification
for

unified
screw
threads.
to
L168.
4A 100:2003.
Bolts shall conform to BS
BS A 100.
BS 1580-1 and -2:1962, Diameters ï in. and larger.

3
5
Dimensions
and
tolerances
4 General
Materialsrequirements
and
manufacture
3
General
requirements
Bolts
shall
conform
to
BS
A conform
100.
The

shall bebolts,
machined
from barstothat
5.1 bolts
All finished
shall
the conform
Bolts
shallL conform
to BS Agiven
100. in Tables 1 and 2.
to
L168.
BS
168.
dimensions
and tolerances

4
and
manufacture
5.2Materials
The clamping
length
of the bolt shall conform to
4
and
manufacture
The
bolts shall be

machined
from
bars
conform
5 Materials
Dimensions
and
tolerances
the
dimensions
and
tolerances
given
in that
Table
2 and
to
L168.
shall
be such
when a standard
nutthat
without
The
bolts
shallthat,
bebolts,
machined
from bars
5.1

All finished
shall
conform
to the conform
countersink
or ring
gauge
without
countersunk
has
to
L168.
dimensions
and
given in by
Tables
1 and
been screwed
ontolerances
as far as possible
hand,
its 2.
5
Dimensions
and
tolerances
leading
is within
distance
from

the conform
underside
5.2 Theface
clamping
length
of theMbolt
shall
to
5
Dimensions
and
tolerances
of the
head.and
Thetolerances
runout
of given
the thread
not
5.1
Allbolt
finished
bolts,
shall
conform
to Table
theshall
the
dimensions
in

2 and
exceed
thetolerances
pitch.
dimensions
given
in Tables
1 and 2.
shall
betwice
suchand
that,
when
a standard
nut
without
5.1
All
finished
bolts,
shall
conform
to the
countersink
or
ring
gauge
without
countersunk
dimensions

and tolerances
in Tables
1 andhas
2. to
5.2
The clamping
length ofgiven
the bolt
shall conform
been screwed on as far as possible by hand, its
the
dimensions
and
tolerances
given
in
Table
2
and
5.2
Theface
clamping
length
of theMbolt
shall
to
leading
is within
distance
from

the conform
underside
shall
be such that,
when a standard
nut
without
the
dimensions
in Table
2 and
of the
bolt head.and
Thetolerances
runout of given
the thread
shall
not
countersink
ringwhen
gaugea without
shall
betwice
suchorthat,
standardcountersunk
nut withouthas
exceed
the pitch.
been
screwed

on
as
far
as
possible
by
hand, its has
countersink or ring gauge without countersunk
leading
face
is
within
distance
M
from
the underside
been screwed on as far as possible by hand,
its
of
the
bolt
head.
The
runout
of
the
thread
not
leading face is within distance M from the shall
underside

exceed
twice
the The
pitch.
of the bolt
head.
runout of the thread shall not
© The British
Institution 2012
exceed
twiceStandards
the pitch.
 BSI 06-1999

Bolts shall conform to BS A 100.

4 Materials andBS
manufacture
BS 4A 170:1999
4A 170:1999+A1:2012
The bolts shall be machined from bars that conform
to L168.

5 Dimensions and tolerances
BS 4A 170:1999
5.1 All finished bolts, shall conform to the
dimensions and tolerances given in Tables 1 and 2.

BSshall
4A be

170:1999
5.2 The nominal
clampinglength
lengthofofthe
thebolt
bolt
shall
conform
to
5.3
the
the dimensions
and
tolerances
given
Table
and
shall
be 2the
minimum
bearing
length
Lmin., which
BS in
4A
170:1999
shall be such
that, when
a standard
without

two
thread
minimum
clamping
length,
Mmin., lessnut
countersink or ring gauge without countersunk has
pitches.
been screwed
onlengths
as farL as
possible
hand,
itsinch
NOTE
The bearing
quoted
in Tableby
2 are
in 0.10
increments
but where
alength
0.05distance
length
increment
is required
this is
leading
is within

M
from
thebeunderside
5.3
Theface
nominal
of the
bolt
shall
the
permissible
agreement
between
manufacturer
and user
and
of the boltby
head.
The
runout
of
the thread
shall
not
, which
shall
be the
minimum
bearing
length

Lmin.
should be identified as follows: 8 ¯B, indicating a 6-32 UNC bolt of
exceed
twice
the
pitch.
, less
thread
minimum
clamping
bearing length
0.85 incheslength,
L, M andMEmin.
should
be two
adjusted
pitches.
accordingly.
5.3 The nominal length of the bolt shall be the
NOTE
The bearing
L quoted
Table 2shall
are in be
0.10the
inch
,inwhich
minimum
bearinglengths
length

Lmin.
5.3
The nominal
of
the
bolt shall
be the
increments
but where alength
0.05 length
increment
is required
this is
, less shall
two
minimum
clamping
length,
Mmanufacturer
6
Screwby
threads
min.
permissible
agreement
between
and thread
user
and
, which

be the
minimum
bearing
length
Lmin.
pitches.
should
be
identified
as
follows:
8
¯B,
indicating
a
6-32thread
UNC bolt of
two
minimum
clamping
length,
Mscrew
The
bolts
shall
have
unified
threads
of
the

min., less
bearing
length
0.85 inches
L, LMquoted
and E in
should
be
adjusted
NOTE
The
bearing
lengths
Table
2 are
inof
0.10 inch
pitches.
form
and
fit
specified
in the latest
edition
accordingly.
increments
but where a 0.05 length increment is required this is
NOTE
The by
bearing

lengths
L quoted
in Table 2 are
0.10 and
inch
BS
A 100.
permissible
agreement
between
manufacturer
andinuser
increments
but where
0.05 length
increment
is required
thisbolt
is of
should be identified
asafollows:
8 ¯B,
indicating
a 6-32 UNC
permissible
by 0.85
agreement
and user and
6 Screw
threads

bearing
length
inches between
L, M and manufacturer
E should be adjusted
should
be identified as follows:
8 ¯B, indicating a 6-32 UNC bolt of
7
Anti-corrosion
treatment
accordingly.
The
shall
have unified
of the
bearing
length
0.85 inches
L, M and screw
E shouldthreads
be adjusted
 BSIbolts
06-1999
All
finished
shallinbethe
anodized
and dyed
accordingly.

form
and fit bolts
specified
latest edition
of green.
NOTE
Because
of the use of the chromic acid process for
BS
A 100.
6
Screw
threads
anodizing, the bolts will not necessarily be uniformly coloured
6
Screw
threads
The
bolts shall
have unified screw threads of the
after
staining.

form
and fit
specified
intreatment
the screw
latest
of

BS
4A edition
100:2003.
7
Anti-corrosion
The
bolts
shall
have unified
threads
of the
BS
A
100.
form
and
fit
specified
in
the
latest
edition
of
All
finished
bolts
shall
be
anodized
and

dyed
green.
8 Hardness values
BS
A
100.
NOTE
Because
the use
ofnot
thecurrently
chromic applicable,
acid process
for they
NOTE
Hardnessofvalues
are
though

7 Protective
finish
anodizing, the bolts will not necessarily be uniformly coloured

7
mayAnti-corrosion
become applicable in thetreatment
near future.

afterfinished
staining. bolts shall be sulphuric acid anodized,

All
7
treatment
AllAnti-corrosion
finished bolts
shall be
anodized and dyed green.
coloured green and sealed in pure water in
NOTE
Because
of
the
use
of
the
chromic acid
process
for
9
Identifying
and
marking
All finished with
boltsBS
shall
be2284:1991,
anodized
and
dyed
green.

accordance
EN
Type
BC.
8 Hardness
values
anodizing,
the bolts will
not
necessarily
be uniformly
coloured
NOTE
Because
of
the
use
of
the
chromic
acid
process
for
The
bolts
shall
be
identified
in
accordance

with
the
after
NOTE 
Bolts arevalues
not always
uniformly
coloured
after
dyeing
NOTEstaining.
Hardness
are necessarily
not
currently
applicable,
though
they
anodizing,
the bolts
will not
be
uniformly
coloured
requirements
specified
in
BS
3A
100:1991

clause
8.
due
to
the
sulphuric
acid
anodizing
process.

may become applicable in the near future.
after staining.

8 Hardness values
10
Quality
assurance
procedure
9
and
marking
NOTE
Hardness values
are not
currently applicable, though they
8 Identifying
Hardness
values
may
become

applicable
in the near
future.
The
bolts
shall
conform
to the
requirements
The
shall
be identified
in quality
accordance
with the
NOTEbolts
Hardness
values
are not currently
applicable, though
they
specified
in
BS
A
100,
as
appropriate
to
method

may become applicable
in theinnear
requirements
specified
BSfuture.
3A 100:1991the
clause
8.

of
manufacture
9 Identifying

and marking
9 Identifying
and marking
The
bolts shall assurance
be identified
inprocedure
accordance with the
10
Quality
requirements
intoBS
3Aquality
100:1991
clause
The bolts shallspecified
be

identified
in
accordance
with 8.
the
conform
the
requirements
BS
4A 100:2003.
requirements
specified
in appropriate
BS
3A 100:1991
clause
8.
specified
in BS
A 100, as
to the
method
of
10manufacture
Quality assurance procedure

10
The Quality
bolts shall assurance
conform to theprocedure

quality requirements
specified
in
BS
A
100,
as
appropriate
the method
The bolts shall conform to the qualitytorequirements
of
manufacture
specified in
in BS
A 100,
appropriateas
toappropriate
the method
specified
BS
4A as
100:2003,
to
method of manufacture
of the
manufacture

1
1


The
spe
of m


Licensed Copy: Miss Anne Carty, British Standards Institution, 19/01/2012 15:56, Uncontrolled Copy, (c) The British Standards Institution 2012

BS
BS 4A
4A 170:1999
170:1999+A1:2012

Max. runout of
thread = 2 x pitch

D

F

(for ref.
only)

L*
(bearing length)

B

R rad
45 °


H

A

U rad

J
C

M*
(clamping length)

G

E*
(overall length)

Figure 1 Ð Dimensions of bolts
*

For bearing length L, clamping length M and overall length E see Table 2.

L

M

E

Figure 2 Ð Bearing length L,
clamping length M and overall

length E

22

 BSI 06-1999
© The British Standards Institution
2012


© The British Standards Institution 2012
 BSI 06-1999

0.189 5

0.249 5

0.312 0

0.190-32
UNF
No. 10-32UNF UNF 10–32
0.190
0

1/ in
0.250-28
UNF UNF 1/4–28
UNF
0.250
0

4

5/
0.3125-24
UNF
UNF
UNF 5/16–24
0.312
5 
16 in

0.309 0

0.246 5

0.186 5

0.160 5

0.134 5

in

min.
in

0.083

0.071


0.063

0.063

0.063

0.497

0.459

0.377

0.327

0.277

in

min.
ref
ref. only

Fa

0.690

0.565

0.441


0.378

0.316

in

max.

B

0.666

0.546

0.425

0.364

0.303

in

min.

0.183

0.150

0.118


0.102

0.086

in

max.

D

0.162

0.133

0.103

0.088

0.074

in

min.

Thickness of
head

0.030

0.025


0.020

0.015

0.010

in

approx.

C

Cylindrical
portion of
head

0.474

0.389

0.304

0.255

0.205

in

ref.

only

U

Radius
of
head

0.030

0.030

0.020

0.020

0.015

in

max.
in

min.

0.015

0.015

0.010


0.010

0.005

R

Radius under
bolt head

in

0.040

0.040

0.030

0.030

0.030

G

0.030

0.030

0.020


0.020

0.020

in

min.

Depth of
chamfer

max.

a This dimension is an absolute minimum associated with maximum length M and minimum length E. It is not intended for use for manufacturing or inspection purposes.
b To be measured from the top of the head to the point at which the slot breaks through see Figure 1.

0.163 5

0.164-32
UNC0
No. 8-32 UNCUNC 8–320.164

in

max.

A

Diameter of
head


Table 1 Ð Dimensions of bolts

Diameter of plain Thread
23
Min. length
portion of shank
pitch
of screwed
runout
portion of
(2 ×
shank
pitch)

0.137 5

in

Nominal
Decimal
equivalent
thread
size
of nominal
size

0.138-32
UNC0
No. 6-32 UNCUNC 6–320.138


Decimal
Nominal size
nominal
thread size

0.072

0.064

0.050

0.045

0.039

in

min.

H

0.084

0.075

0.060

0.054


0.048

in

max.

Width

in

0.090

0.073

0.055

0.046

0.038

0.100

0.083

0.065

0.056

0.048


in

max.

Jb

Depth
min.

Slot

Licensed Copy: Miss Anne Carty, British Standards Institution, 19/01/2012 15:56, Uncontrolled Copy, (c) The British Standards Institution 2012

BS 4A 170:1999
BS 4A 170:1999+A1:2012

3
3


Licensed Copy: Miss Anne Carty, British Standards Institution, 19/01/2012 15:56, Uncontrolled Copy, (c) The British Standards Institution 2012
Licensed Copy: Miss Anne Carty, British Standards Institution, 19/01/2012 15:56, Uncontrolled Copy, (c) The British Standards Institution 2012
Licensed Copy: Miss Anne Carty, British Standards Institution, 19/01/2012 15:56, Uncontrolled Copy, (c) The British Standards Institution 2012
Licensed Copy: Miss Anne Carty, British Standards Institution, 19/01/2012 15:56, Uncontrolled Copy, (c) The British Standards Institution 2012

BS
4A
170:1999
BS
4A

170:1999
BS
BS
4A
4A
170:1999
170:1999
BS
4A
170:1999+A1:2012

Table
2 2Ð
Bearing
length
L,L,L,
clamping
length
MMM
and
overall
length
EE(continued)
Table
22Ð
Bearing
length
clamping
length
overall

length
E
Table
Table
Table
2Ð
Ð
Ð
Bearing
Bearing
Bearing
length
length
length
L,
L,
clamping
clamping
clamping
length
length
length
Mand
Mand
and
and
overall
overall
overall
length

length
length
E(continued)
E(continued)
(continued)
(continued)
No.
6-32
UNC
No.
6-32
UNC
No.
No.
No.
6-32
6-32
6-32
UNC
UNC
UNC

No.
8-32
UNC
No.
8-32
UNC
No.
No.

No.
8-32
8-32
8-32
UNC
UNC
UNC

No.
10-32
UNF
No.
10-32
UNF
No.
No.
No.
10-32
10-32
10-32
UNF
UNF
UNF

Part
no.
MMM
E EE
no.
MMM

E EE
no.
MMM
E EE
Part
no.
Part
no.
Part
no.
Part
Part
Part
no.
no.
no. aLaLaaL
LaL
MM
E E Part
Part
Part
Part
no.
no.
no. aLaLaaL
LaL
MM
E E Part
Part
Part

Part
no.
no.
no. aLaLaaL
LaL
MM
EE
min.
+0+0+0
+0.04
min.
+0+0+0
+0.04
min.
+0.04
min.
+0.04
min.
+0.04
min.
+0.04
min.
min.
+0+0
+0.04
+0.04
min.
min.
+0+0
+0.04

+0.04
min.
+0.04
min.
+0.04
min.
+0.04
min.
min.+0+0+0
+0+0
+0.04
+0.04
20.03
20.03
20.03
20.03
20
20.03
20
20.03
20
20.03
20
20.03
20
20.03
20.03 20
20
20
20.03

20.03 20
20
20
20.03
20.03
20.03 20
20
20
20

ininin
inin
¯¯B
¯
B
0.05
¯B
¯
BB 0.05
0.05
0.05
0.05
1 1B11BB
0.1
0.1
1BB 0.1
0.1
0.1
2 2B22BB
0.2

0.2
2BB 0.2
0.2
0.2
3 3B33BB
0.3
0.3
3BB 0.3
0.3
0.3
4 4B44BB
0.4
0.4
4BB 0.4
0.4
0.4
5 5B55BB
0.5
0.5
5BB 0.5
0.5
0.5

ininin
inin ininin
inin
0.143
0.143
0.45
0.143

0.143
0.1430.45
0.45
0.45
0.45
0.193
0.193
0.50
0.193
0.50
0.193
0.1930.50
0.50
0.50
0.293
0.293
0.60
0.293
0.60
0.293
0.2930.60
0.60
0.60
0.393
0.393
0.70
0.393
0.70
0.393
0.3930.70

0.70
0.70
0.493
0.493
0.80
0.493
0.80
0.493
0.4930.80
0.80
0.80
0.593
0.593
0.90
0.593
0.90
0.593
0.5930.90
0.90
0.90

ininin
inin
¯¯C
¯
C
0.05
¯C
¯
CC 0.05

0.05
0.05
0.05
1 1C11CC
0.1
0.1
1CC 0.1
0.1
0.1
2 2C22CC
0.2
0.2
2CC 0.2
0.2
0.2
3 3C33CC
0.3
0.3
3CC 0.3
0.3
0.3
4 4C44CC
0.4
0.4
4CC 0.4
0.4
0.4
5 5C55CC
0.5
0.5

5CC 0.5
0.5
0.5

ininin
inin ininin
inin
0.143
0.143
0.50
0.143
0.143
0.1430.50
0.50
0.50
0.50
0.193
0.193
0.55
0.193
0.55
0.193
0.1930.55
0.55
0.55
0.293
0.293
0.65
0.293
0.65

0.293
0.2930.65
0.65
0.65
0.393
0.393
0.75
0.393
0.75
0.393
0.3930.75
0.75
0.75
0.493
0.493
0.85
0.493
0.85
0.493
0.4930.85
0.85
0.85
0.593
0.593
0.95
0.593
0.95
0.593
0.5930.95
0.95

0.95

ininin
inin
¯¯D
¯
D
0.05
¯D
¯
DD 0.05
0.05
0.05
0.05
1 1D11DD
0.1
0.1
1DD 0.1
0.1
0.1
2 2D22DD
0.2
0.2
2DD 0.2
0.2
0.2
3 3D33DD
0.3
0.3
3DD 0.3

0.3
0.3
4 4D44DD
0.4
0.4
4DD 0.4
0.4
0.4
5 5D55DD
0.5
0.5
5DD 0.5
0.5
0.5

ininin
inin ininin
inin
0.143
0.143
0.55
0.143
0.143
0.1430.55
0.55
0.55
0.55
0.193
0.193
0.60

0.193
0.60
0.193
0.1930.60
0.60
0.60
0.293
0.293
0.70
0.293
0.70
0.293
0.2930.70
0.70
0.70
0.393
0.393
0.80
0.393
0.80
0.393
0.3930.80
0.80
0.80
0.493
0.493
0.90
0.493
0.90
0.493

0.4930.90
0.90
0.90
0.593
0.593
1.00
0.593
1.00
0.593
0.5931.00
1.00
1.00

6 6B66BB
0.6
6BB 0.6
0.6
0.6
0.6
7 7B77BB
0.7
7BB 0.7
0.7
0.7
0.7
8 8B88BB
0.8
8BB 0.8
0.8
0.8

0.8
9 9B99BB
0.9
9BB 0.9
0.9
0.9
0.9
101010
B
B
1.0
10
1.0
1.0
10B
BB 1.0
1.0

0.693
0.693
1.00
0.693
0.6931.00
1.00
1.00
0.693
1.00
0.793
0.793
1.10

0.793
0.7931.10
1.10
1.10
0.793
1.10
0.893
0.893
1.20
0.893
0.8931.20
1.20
1.20
0.893
1.20
0.993
0.993
1.30
0.993
0.9931.30
1.30
1.30
0.993
1.30
1.093
1.093
1.40
1.093
1.0931.40
1.40

1.40
1.093
1.40

6 6C66CC
0.6
6CC 0.6
0.6
0.6
0.6
7 7C77CC
0.7
7CC 0.7
0.7
0.7
0.7
8 8C88CC
0.8
8CC 0.8
0.8
0.8
0.8
9 9C99CC
0.9
9CC 0.9
0.9
0.9
0.9
101010
C

C
1.0
10
1.0
1.0
10C
CC 1.0
1.0

0.693
0.693
1.05
0.693
0.6931.05
1.05
1.05
0.693
1.05
0.793
0.793
1.15
0.793
0.7931.15
1.15
1.15
0.793
1.15
0.893
0.893
1.25

0.893
0.8931.25
1.25
1.25
0.893
1.25
0.993
0.993
1.35
0.993
0.9931.35
1.35
1.35
0.993
1.35
1.093
1.093
1.45
1.093
1.0931.45
1.45
1.45
1.093
1.45

6 6D66DD
0.6
6DD 0.6
0.6
0.6

0.6
7 7D77DD
0.7
7DD 0.7
0.7
0.7
0.7
8 8D88DD
0.8
8DD 0.8
0.8
0.8
0.8
9 9D99DD
0.9
9DD 0.9
0.9
0.9
0.9
101010
D
D
1.0
10
1.0
1.0
10D
DD 1.0
1.0


0.693
0.693
1.10
0.693
0.6931.10
1.10
1.10
0.693
1.10
0.793
0.793
1.20
0.793
0.7931.20
1.20
1.20
0.793
1.20
0.893
0.893
1.30
0.893
0.8931.30
1.30
1.30
0.893
1.30
0.993
0.993
1.40

0.993
0.9931.40
1.40
1.40
0.993
1.40
1.093
1.093
1.50
1.093
1.0931.50
1.50
1.50
1.093
1.50

111111
B
B
1.1
11
1.1
1.1
11B
BB 1.1
1.1
121212
B
B
1.2

12
1.2
1.2
12B
BB 1.2
1.2
131313
B
B
1.3
13
1.3
1.3
13B
BB 1.3
1.3
141414
B
B
1.4
14
1.4
1.4
14B
BB 1.4
1.4
151515
B
B
1.5

15
1.5
1.5
15B
BB 1.5
1.5

1.193
1.193
1.50
1.193
1.1931.50
1.50
1.50
1.193
1.50
1.293
1.293
1.60
1.293
1.2931.60
1.60
1.60
1.293
1.60
1.393
1.393
1.70
1.393
1.3931.70

1.70
1.70
1.393
1.70
1.493
1.493
1.80
1.493
1.4931.80
1.80
1.80
1.493
1.80
1.593
1.593
1.90
1.593
1.5931.90
1.90
1.90
1.593
1.90

111111
C
C
1.1
11
1.1
1.1

11C
CC 1.1
1.1
121212
C
C
1.2
12
1.2
1.2
12C
CC 1.2
1.2
131313
C
C
1.3
13
1.3
1.3
13C
CC 1.3
1.3
141414
C
C
1.4
14
1.4
1.4

14C
CC 1.4
1.4
151515
C
C
1.5
15
1.5
1.5
15C
CC 1.5
1.5

1.193
1.193
1.55
1.193
1.1931.55
1.55
1.55
1.193
1.55
1.293
1.293
1.65
1.293
1.2931.65
1.65
1.65

1.293
1.65
1.393
1.393
1.75
1.393
1.3931.75
1.75
1.75
1.393
1.75
1.493
1.493
1.85
1.493
1.4931.85
1.85
1.85
1.493
1.85
1.593
1.593
1.95
1.593
1.5931.95
1.95
1.95
1.593
1.95


111111
D
D
1.1
11
1.1
1.1
11D
DD 1.1
1.1
121212
D
D
1.2
12
1.2
1.2
12D
DD 1.2
1.2
131313
D
D
1.3
13
1.3
1.3
13D
DD 1.3
1.3

141414
D
D
1.4
14
1.4
1.4
14D
DD 1.4
1.4
151515
D
D
1.5
15
1.5
1.5
15D
DD 1.5
1.5

1.193
1.193
1.60
1.193
1.1931.60
1.60
1.60
1.193
1.60

1.293
1.293
1.70
1.293
1.2931.70
1.70
1.70
1.293
1.70
1.393
1.393
1.80
1.393
1.3931.80
1.80
1.80
1.393
1.80
1.493
1.493
1.90
1.493
1.4931.90
1.90
1.90
1.493
1.90
1.593
1.593
2.00

1.593
1.5932.00
2.00
2.00
1.593
2.00

161616
B
B
1.6
16
1.6
1.6
16B
BB 1.6
1.6
171717
B
B
1.7
17
1.7
1.7
17B
BB 1.7
1.7
181818
B
B

1.8
18
1.8
1.8
18B
BB 1.8
1.8
191919
B
B
1.9
19
1.9
1.9
19B
BB 1.9
1.9
202020
B
B
2.0
20
2.0
2.0
20B
BB 2.0
2.0

1.693
1.693

2.00
1.693
1.6932.00
2.00
2.00
1.693
2.00
1.793
1.793
2.10
1.793
1.7932.10
2.10
2.10
1.793
2.10
1.893
1.893
2.20
1.893
1.8932.20
2.20
2.20
1.893
2.20
1.993
1.993
2.30
1.993
1.9932.30

2.30
2.30
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2.30
2.093
2.093
2.40
2.093
2.0932.40
2.40
2.40
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2.40

161616
C
C
1.6
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1.6
1.6
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CC 1.6
1.6
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C
C
1.7
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1.7

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CC 1.7
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C
1.8
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1.8
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1.9
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C
2.0
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2.0

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2.0

1.693
1.693
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1.793
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1.893
2.25
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2.25
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2.25
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1.993
2.35
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1.9932.35
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2.35
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2.093
2.45
2.093
2.0932.45
2.45
2.45
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2.45

161616
D
D
1.6
16
1.6
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DD 1.6

1.6
171717
D
D
1.7
17
1.7
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D
1.8
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1.8
1.8
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DD 1.8
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D
1.9
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1.9
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DD 1.9

1.9
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D
2.0
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2.0
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DD 2.0
2.0

1.693
1.693
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1.793
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1.7932.20
2.20
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1.893
1.893
2.30
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1.8932.30
2.30
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2.30
1.993
1.993
2.40
1.993
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2.40
2.40
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2.40
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2.093
2.50
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2.50
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2.50

212121
B

B
2.1
21
2.1
2.1
21B
BB 2.1
2.1
222222
B
B
2.2
22
2.2
2.2
22B
BB 2.2
2.2
232323
B
B
2.3
23
2.3
2.3
23B
BB 2.3
2.3
242424
B

B
2.4
24
2.4
2.4
24B
BB 2.4
2.4
252525
B
B
2.5
25
2.5
2.5
25B
BB 2.5
2.5

2.193
2.193
2.50
2.193
2.1932.50
2.50
2.50
2.193
2.50
2.293
2.293

2.60
2.293
2.2932.60
2.60
2.60
2.293
2.60
2.393
2.393
2.70
2.393
2.3932.70
2.70
2.70
2.393
2.70
2.493
2.493
2.80
2.493
2.4932.80
2.80
2.80
2.493
2.80
2.593
2.593
2.90
2.593
2.5932.90

2.90
2.90
2.593
2.90

212121
C
C
2.1
21
2.1
2.1
21C
CC 2.1
2.1
222222
C
C
2.2
22
2.2
2.2
22C
CC 2.2
2.2
232323
C
C
2.3
23

2.3
2.3
23C
CC 2.3
2.3
242424
C
C
2.4
24
2.4
2.4
24C
CC 2.4
2.4
252525
C
C
2.5
25
2.5
2.5
25C
CC 2.5
2.5

2.193
2.193
2.55
2.193

2.1932.55
2.55
2.55
2.193
2.55
2.293
2.293
2.65
2.293
2.2932.65
2.65
2.65
2.293
2.65
2.393
2.393
2.75
2.393
2.3932.75
2.75
2.75
2.393
2.75
2.493
2.493
2.85
2.493
2.4932.85
2.85
2.85

2.493
2.85
2.593
2.593
2.95
2.593
2.5932.95
2.95
2.95
2.593
2.95

212121
D
D
2.1
21
2.1
2.1
21D
DD 2.1
2.1
222222
D
D
2.2
22
2.2
2.2
22D

DD 2.2
2.2
2323
B
B
2.3
2323
B
23
2.3
2.3
23D
BB 2.3
2.3
2424
B
B
2.4
2424
B
24
2.4
2.4
24D
BB 2.4
2.4
2525
B
B
2.5

2525
B
25
2.5
2.5
25D
BB 2.5
2.5

2.193
2.193
2.60
2.193
2.1932.60
2.60
2.60
2.193
2.60
2.293
2.293
2.70
2.293
2.2932.70
2.70
2.70
2.293
2.70
2.393
2.393
2.80

2.393
2.3932.80
2.80
2.80
2.393
2.80
2.493
2.493
2.90
2.493
2.4932.90
2.90
2.90
2.493
2.90
2.593
2.593
3.00
2.593
2.5933.00
3.00
3.00
2.593
3.00

262626
B
C
D
B

2.6
2.693
3.00
C
2.6
2.693
3.05
D
2.6
2.693
3.10
26
2.6
2.6 2.693
2.693
2.6933.00
3.00
3.00 262626
26
2.6
2.6 2.693
2.693
2.6933.05
3.05
3.05 262626
26
2.6
2.6 2.693
2.693
2.6933.10

3.10
3.10
26B
BB 2.6
2.6
2.693
3.00
26C
CC 2.6
2.6
2.693
3.05
26D
DD 2.6
2.6
2.693
3.10
272727
B
C
D
B
2.7
2.793
3.10
C
2.7
2.793
3.15
D

2.7
2.793
3.20
27
2.7
2.7 2.793
2.793
2.7933.10
3.10
3.10 272727
27
2.7
2.7 2.793
2.793
2.7933.15
3.15
3.15 272727
27
2.7
2.7 2.793
2.793
2.7933.20
3.20
3.20
27B
BB 2.7
2.7
2.793
3.10
27C

CC 2.7
2.7
2.793
3.15
27D
DD 2.7
2.7
2.793
3.20
282828
B
C
D
B
2.8
2.893
3.20
C
2.8
2.893
3.25
D
2.8
2.893
3.30
28
2.8
2.8 2.893
2.893
2.8933.20

3.20
3.20 282828
28
2.8
2.8 2.893
2.893
2.8933.25
3.25
3.25 282828
28
2.8
2.8 2.893
2.893
2.8933.30
3.30
3.30
28B
BB 2.8
2.8
2.893
3.20
28C
CC 2.8
2.8
2.893
3.25
28D
DD 2.8
2.8
2.893

3.30
a See
a See
a aSee
a5.3.
5.3.
See
5.3.
See
5.3.
5.3.

4
4 4 44 4

© The British Standards Institution 2012

BSI
06-1999

BSI
06-1999
BSI

BSI
BSI
06-1999
06-1999
06-1999



Licensed Copy: Miss Anne Carty, British Standards Institution, 19/01/2012 15:56, Uncontrolled Copy, (c) The British Standards Institution 2012

BS 4A 170:1999
BS 4A 170:1999+A1:2012

Table 2 Ð Bearing length L, clamping length M and overall length E (continued)
No. 6-32 UNC
aL

+0
20.03

29 B
30 B
31 B
32 B
33 B

in
2.9
3.0
3.1
3.2
3.3

in
2.993
3.093
3.193

3.293
3.393

in
3.30
3.40
3.50
3.60
3.70

34 B
35 B
36 B
37 B
38 B

3.4
3.5
3.6
3.7
3.8

3.493
3.593
3.693
3.793
3.893

39 B
40 B

41 B
42 B
43 B

3.9
4.0
4.1
4.2
4.3

44 B
45 B

4.4
4.5

min.

a

M

No. 8-32 UNC
E
+0.04
20

Part no.

aL


+0
20.03

29 C
30 C
31 C
32 C
33 C

in
2.9
3.0
3.1
3.2
3.3

in
2.993
3.093
3.193
3.293
3.393

in
3.35
3.45
3.55
3.65
3.75


3.80
3.90
4.00
4.10
4.20

34 C
35 C
36 C
37 C
38 C

3.4
3.5
3.6
3.7
3.8

3.493
3.593
3.693
3.793
3.893

3.993
4.093
4.193
4.293
4.393


4.30
4.40
4.50
4.60
4.70

39 C
40 C
41 C
42 C
43 C

3.9
4.0
4.1
4.2
4.3

4.493
4.593

4.80
4.90

44 C
45 C

4.4
4.5


min.

M

No. 10-32 UNF
E
+0.04
20

Part no.

aL
min.

M
+0
20.03

E
+0.04
20

29 D
30 D
31 D
32 D
33 D

in

2.9
3.0
3.1
3.2
3.3

in
2.993
3.093
3.193
3.293
3.393

in
3.40
3.50
3.60
3.70
3.80

3.85
3.95
4.05
4.15
4.25

34 D
35 D
36 D
37 D

38 D

3.4
3.5
3.6
3.7
3.8

3.493
3.593
3.693
3.793
3.893

3.90
4.00
4.10
4.20
4.30

3.993
4.093
4.193
4.293
4.393

4.35
4.45
4.55
4.65

4.75

39 D
40 D
41 D
42 D
43 D

3.9
4.0
4.1
4.2
4.3

3.993
4.093
4.193
4.293
4.393

4.40
4.50
4.60
4.70
4.80

4.493
4.593

4.85

4.95

44 D
45 D

4.4
4.5

4.493
4.593

4.90
5.00

Part no.

See 5.3.

© The British Standards Institution 2012
 BSI 06-1999

5
5


Licensed Copy: Miss Anne Carty, British Standards Institution, 19/01/2012 15:56, Uncontrolled Copy, (c) The British Standards Institution 2012

BS
BS 4A
4A 170:1999

170:1999+A1:2012

Table 2 Ð Bearing length L, clamping length M and overall length E (continued)
1/ in UNF
4
aL

Part no.

min.

5/ in UNF
16

M

E

+0
20.03

+ 0.04
20

¯E
1E
2E
3E
4E
5E


in
0.05
0.1
0.2
0.3
0.4
0.5

in
0.151
0.201
0.301
0.401
0.501
0.601

in
0.65
0.70
0.80
0.90
1.00
1.10

6E
7E
8E
9E
10 E


0.6
0.7
0.8
0.9
1.0

0.701
0.801
0.901
1.001
1.101

11 E
12 E
13 E
14 E
15 E

1.1
1.2
1.3
1.4
1.5

16 E
17 E
18 E
19 E
20 E


aL

Part no.

M

E

+0
20.03

+ 0.04
20

¯G
1G
2G
3G
4G
5G

in
0.05
0.1
0.2
0.3
0.4
0.5


in
0.163
0.213
0.313
0.413
0.513
0.613

in
0.70
0.75
0.85
0.95
1.05
1.15

1.20
1.30
1.40
1.50
1.60

6G
7G
8G
9G
10 G

0.6
0.7

0.8
0.9
1.0

0.713
0.813
0.913
1.013
1.113

1.25
1.35
1.45
1.55
1.65

1.201
1.301
1.401
1.501
1.601

1.70
1.80
1.90
2.00
2.10

11 G
12 G

13 G
14 G
15 G

1.1
1.2
1.3
1.4
1.5

1.213
1.313
1.413
1.513
1.613

1.75
1.85
1.95
2.05
2.15

1.6
1.7
1.8
1.9
2.0

1.701
1.801

1.901
2.001
2.101

2.20
2.30
2.40
2.50
2.60

16 G
17 G
18 G
19 G
20 G

1.6
1.7
1.8
1.9
2.0

1.713
1.813
1.913
2.013
2.113

2.25
2.35

2.45
2.55
2.65

21 E
22 E
23 E
24 E
25 E

2.1
2.2
2.3
2.4
2.5

2.201
2.301
2.401
2.501
2.601

2.70
2.80
2.90
3.00
3.10

21 G
22 G

23 G
24 G
25 G

2.1
2.2
2.3
2.4
2.5

2.213
2.313
2.413
2.513
2.613

2.75
2.85
2.95
3.05
3.15

26 E
27 E
28 E
29 E
30 E

2.6
2.7

2.8
2.9
3.0

2.701
2.801
2.901
3.001
3.101

3.20
3.30
3.40
3.50
3.60

26 G
27 G
28 G
29 G
30 G

2.6
2.7
2.8
2.9
3.0

2.713
2.813

2.913
3.013
3.113

3.25
3.35
3.45
3.55
3.65

a

6
6

min.

See 5.3.

© The British Standards Institution 2012
 BSI 06-1999


Licensed Copy: Miss Anne Carty, British Standards Institution, 19/01/2012 15:56, Uncontrolled Copy, (c) The British Standards Institution 2012

BS 4A 170:1999+A1:2012
BS 4A 170:1999

Table 2 Ð Bearing length L, clamping length M and overall length E (continued)
1/ in UNF

4
aL

Part no.

min.

5/ in UNF
16

M

E

+0
20.03

+ 0.04
20

31 E
32 E
33 E
34 E
35 E

in
3.1
3.2
3.3

3.4
3.5

in
3.201
3.301
3.401
3.501
3.601

in
3.70
3.80
3.90
4.00
4.10

36 E
37 E
38 E
39 E
40 E

3.6
3.7
3.8
3.9
4.0

3.701

3.801
3.901
4.001
4.101

41 E
42 E
43 E
44 E
45 E

4.1
4.2
4.3
4.4
4.5

46 E
47 E
48 E
49 E
50 E

4.6
4.7
4.8
4.9
5.0

a


aL

Part no.

min.

M

E

+0
20.03

+ 0.04
20

31 G
32 G
33 G
34 G
35 G

in
3.1
3.2
3.3
3.4
3.5


in
3.213
3.313
3.413
3.513
3.613

in
3.75
3.85
3.95
4.05
4.15

4.20
4.30
4.40
4.50
4.60

36 G
37 G
38 G
39 G
40 G

3.6
3.7
3.8
3.9

4.0


3.713
3.701

4.25
4.35
4.45
4.55
4.65

4.201
4.301
4.401
4.501
4.601

4.70
4.80
4.90
5.00
5.10

41 G
42 G
43 G
44 G
45 G


4.1
4.2
4.3
4.4
4.5

4.213

4.313
4.312
4.413
4.513
4.613

4.75
4.85
4.95
5.05
5.15

4.701
4.801
4.901
5.001
5.101

5.20
5.30
5.40
5.50

5.60

46 G
47 G
48 G
49 G
50 G

4.6
4.7
4.8
4.9
5.0

3.213
3.313
3.413
3.513
3.613

5.25
5.35
5.45
5.55
5.65


3.801
3.813


3.901

3.913
4.001

4.013
4.101

4.113

See 5.3.

© The British Standards Institution 2012
 BSI 06-1999

7
7


Licensed Copy: Miss Anne Carty, British Standards Institution, 19/01/2012 15:56, Uncontrolled Copy, (c) The British Standards Institution 2012

BS
BS 4A
4A 170:1999
170:1999
+A1:2012

BSI
389 Chiswick High Road
London

W4 4AL

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