Specifications
1071
GENERAL FIITING INSTRUCTIONS
1.
2
3.
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~~
METRIC NUT IDENTIFICATION
A
A
nut with an
IS0
metric thread is marked on one
face or on one of the flats of the hexagon with the
strength grade symbol
8,12
or
14. Some nuts with
a
strength 4,
5
or
6
are also marked and some have
the metric symbol
M
on the flat opposite
the
strength grade marking.
A
clock face system is used as an alternative
method of indicating the strength grade. The
external chamfers or a face
of
the nut is marked in
a position relative to the appropriate hour mark on
a clock face to indicate the strength grade.
A
dot is used to locate the 12 o'clock position and a
dash to indicate the strength grade. If the grade
is
above 12, two dots identify the
12
o'clock position.
1
2
m
STl036M
HYDRAULIC FITTINGS
-
Metrication
WARNING: Metric and Unified threaded hydraulic
parts. Although pipe connections to brake system units
incorporate threads of metric form,
those
for power
assisted steering are of UNF type. It
is
vitally important
that these two thread forms are not confused, and
careful study should be made
of
the following notes.
Metric threads and metric sizes are being introduced
into motor vehicle manufacture and some duplication
of parts must be expected. Although standardisation
must in the long run be good,
it
would be wrong not to
give warning of the dangers that exist while UNF and
metric threaded hydraulic parts continue together in
service. Fitting UNF pipe nuts into metric ports and
vice
-
versa should not happen, but experience of the
change from BSF
to
UNF
indicated that there is no
certainty in relying upon the difference
in
thread size
when safety is involved.
To provide permanent identification of metric parts is
easy
hut
recognitinn
has
been
assistpd
h\r
"
J
the
following means. (Illustration A Metric,
B
Unified.)
1.
2.
3.
4
U
@B
ST1033M
A
B
ST1034M
The metric female nut
is
always
used with a trumpet
flared pipe and the metric male nut is
always
used with
a convex flared pipe.
4.
AI1
metric ports in cylinders and calipers have no
counterbores, but unfortunately a few cylinders
with UNF threads also have no counterbore. The
situation is, all ports with counterbores are UNF,
but ports not counterbored are most likely to be
metric.
5.
The colour
of
the protective plugs
in
hydraulic
ports indicates the size and the type of the threads,
but the function of the plugs is
protcctive and not
designed as positive identification.
In
production
it
is
difficult
to
use the wrong plug but human error
must be taken into account.
The Plug colours and thread sizes are:
UNF
RED
iinx24UNF
GREEN
6
in
x
20
UNF
YELLOW
4
in
x
20
UNF
PINK
B
in
x
18
UNF
METRIC
BLACK
1Ox
1
mm
GREY 12x1 mm
BROWN 14 x 1,5 mm
6.
Hose
ends differ slightly between metric and UNF.
Gaskets are not used with metric hoses. The UNF
hose is sealed
on
the cylinder or caliper face by a
copper gasket by the metric hose seals against the
bottom of the port and there is a gap between faces
of
the hose and cylinder.
Pipe sizes for UNF are
&
in,
in
and
&
in outside
diameter.
Metric pipe sizes are 4,75 mm,
6
mm and
8
mm.
c-
..
All
metric pipe nuts, hose ends, unions and bleed
screws are coloured black.
letter
'M'.
Metric and UNF pipe nuts are slightly different in
shape.
4,75 mm pipe is exactly the same as
+
in pipe.
6
mm pipe is 0.014 in smaller than
i
in pipe.
8
mm
Convex pipe flares are shaped differently for
f
J'
metric sizes and when making pipes
for
metric
equipment, metric pipe flaring tools must be used.
The hexagon area
of
pipe nuts is indented with the
pipe is 0.002 in larger than
&
in pipe.
-
.