Rolls-Royce Silver Cloud - Section A3 Unified Screw Threads

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Silver
Cloud,
Silver
Cloud
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Chapter A
Workshop
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SECTION
A3
UNIFIED SCREW THREADS
The need for a common standard of
screw
threads
in
the United
Kingdom, Canada and
the United
States
of
America
has led
to an agreement between
the countries
concerned to use UNIFIED THREADS
of mutually
acceptable form,
pitch
and diameter.
There
are three
types of unified
thread:
1. Unified Coarse.
2.
Unified
Fine.
3. Unified
Special.
These unified threads are clearly identified
by the
standard system
of markings, as illustrated in
Figure
Al.
There is little
difference
between
the form
of
the
American national thread and the
unified thread;
therefore the new threads are largely interchangeable
with S.A.E. standards. They
are not, however,
interchangeable with
BSF, and although BSW have
the same number of threads
per
inch as
the Unified
National
Coarse series, interchanging is
not recom-
mended due to a difference
in
the thread form.
The following
types
of thread
are
used on nuts,
bolts
and castings fitted to Rolls-Royce and
Bentley
cars.
CASTELLATED
NUT
R.R
OESIGN
ON[Y
UNIFIED
NUTS
HIGH DUTY
NU-IS
NOTE AD]OINING
CIRCLES
NOTE
ADJOINING
CIRCLES
NOTE
RICISS AND
WASHER
'ACT
tr@IN
NOTE FACINGS
'@"
COUNTERSUNK
HEAD
SCRE\/vS
o
N
r
a
F
For all sizes
below
I
in. diameter,
BA
threads
are used.
For all sizes between
t
in. and
f
in.
diameter
inclusive,
the Unified
Fine
thread
is
used.
All sizes above
f
in. diameter
have been classified
by
Rolls-Royce and
Bentley
Motors
as Unified
Special
and have 16
threads
per
inch.
The Unified
Coarse Thread is not used.
USEO
ON COLD FOR6[D
HEADS ONIY
NOIE AOJOINING
clRctEl
NOTE TURRET ON
VISIBLE
END OF THREAD
NOTE TURRIT FOR
UNF IOENTIFICAT
A13
Fig.
Al
Identifcation
ofunified
threads