On 29 Apr 2002, at 19:40, Mike Faggart wrote:
> anybody on the list that can tell me what size bolts go where for the front
> suspension pics from gordon's pages. I have the front susp. in boxes with
> loose bolts. Yes, I will get new ones to replace the old.
> HHHHHEEEELLLLLPPPP!!!!
> looks like I am relearning the alphabet with A bolt, B bolt, C bolt,
>
> mike faggart
> seroc
Here's a little history of bolts and nuts I got off another car list. I
know it does not have datsun in it but it will give people some idea
of all the different and weird sizes of bolts and nuts and why some
cars have both metric and standard faseners.
John F.
History of Whitworth
Although written for a British motorcycle audience, this
also applys to
many earlier British cars. It was reproduced on the
British Cars list
with
permission from the author Charles Falco.
A lecture on the meaning of "Whitworth"
First, a tiny bit of history. In the 19th Century every British
factory
which needed to bolt something to something else
devised their own
fasteners to do it. Clearly, this caused all sorts of
compatibility
problems. So, along came Mr. Whitworth (I forget his
first name right
now)
who invented a standardized
system of coarse threads (with 55 degree thread angle
and rounded roots
and
crests).
This standardization was a Good Thing. Along with his
threads came heads
for the bolts that were based on the length *along* the
side of one
flat,
rather than across the flats. Hence, there is no simple
fractional
number
for the length across the flats, which is why your
American wrenches
don't
fit. The fractional number on your English wrenches
refers to the
diameter
of the bolt (which is 1/4", 3/8" etc. just like in the U.S.);
not to the
distance across the flats (which ends up being various
weird
dimensions).
Some years later the Brits decided they needed a finer
pitch for some
applications, so another thread series was introduced
(same 55 degrees).
They also decided that the heads were too big for the
bolts, so for most
applications they switched to using the next size smaller
heads. Because
of
this, and to add one more bit of confusion to life, one
manufacturer
will
mark a particular wrench (spanner) "3/8BS," while a
different
manufacturer
will mark the same sized wrench "7/16W." They fit the
same diameter bolt.
The first thing any fledgling Brit biker learns is that his (or
her)
motorcycle has "Whitworth bolts." They think this is
interesting, buy a
set
of "Whitworth wrenches," discover these wrenches fit
their bolts, and
believe they now know everything they need to know
about British
fasteners.
Unfortunately, at this point they know only enough to
make themselves
dangerous. Instead, what they *should* have said to
themselves is
"Ohmygod,
what other weird and incomprehensible things have the
Brits done to the
fasteners on my machine?" The answer to this question
is:
British Standard Whitworth (BSW)
These are the original, 19th Century, coarse-threaded
industrial bolts
designed to hold locomotives together. Because of their
coarse pitch,
they
are more prone to vibrating loose, so are little used on
motorcycles.
_Except_ for threading into Aluminum (e.g. crankcase
studs), where a
coarse
thread is
less prone to stripping than a fine one. It turns out that,
except for
1/2"
(where the Brits use 12 tpi, and the Americans 13 tpi)
the thread
pitches
are the same as for American Unified Coarse (UNC).
However, the thread
*form* is different; Whitworth = 55 degrees; UNC = 60
degrees. In spite
of
this, mismatched nuts and bolts mate nicely, so you're
likely to find
UNC
bolts or studs where BSW should have been.
British Standard Fine (BSF)
A finer pitch series, analogous to the American Unified
Fine (UNF),
although--unlike the case of BSW/UNC--with none of the
pitches in common
with UNF. Many motorcycle manufacturers commonly
used a lot of BSF
threads.
CEI (Cycle Engineers' Institute) or BSC (British
Standard Cycle)
-these are different names commonly used for the same
threads.
60 degree thread angle, rather than the 55 degree of
BSW and BSF. For
sizes
from 1/4" through 1/2" by far the most common are 26
tpi, although 24
tpi
appear as well. *Most*, but by no means all, fasteners on
post-War BSA's
(through the late '60's, when it got more complicated)
were CEI.
Although
the thread form and pitch is different, the head sizes on
CEI-threaded
fasteners use the same wrenches as BSW/BSF.
British Association (BA)
47-1/2 degree thread angle. This is a metric thread
system devised by
the
British for small screws used in components like
speedos. Not metric
like
you might expect, but with diameters determined by a
factor proportional
to
a power of the logarithm to the base 10 of the thread
pitch in
millimeters.
I couldn't possibly be making this up. Ah, the English.
You'll find lots
of
BA threads on any British bike, but only for fasteners
smaller than
1/4".
BA fasteners have their own set of wrench sizes.
Typically, a set of
"Whitworth" sockets will include a 0BA (and maybe a
2BA--bigger number =
smaller size) socket.
British Standard Pipe (BSP)
A tapered, self-sealing thread system used to seal fluids
(interestingly,
the US *and* the metric world standardized on the BSP system for
threading
all their pipes).
UNF and UNC
In the late 1960's, when even the U.S. was thinking of going metric, the
giant BSA corporation decided it was finally time to scrap that old 19th
Century Whitworth-based system, and switch to....yes, you guessed it,
American. Since they had lots of money invested in tooling, the switch
wasn't made suddenly
(or completely), so bikes from the late '60's and later had a mix of all
sorts of thread forms. Typically, engine internals (e.g. the thread on
the
end of a camshaft) stayed with whatever form it used to have, while
simple
fasteners (e.g. holding the fenders on) switched to UNF.
"None of the Above"
While the above systems account for well over 95% of all threads you'll
ever run across on a British bike, some manufacturers--again BSA springs
to
mind, but others were guilty as well--couldn't restrain themselves from
inventing a few oddball pitches of their own. This is why, when dealing
with British bikes, you should assume nothing. You must have a pitch
gauge
and calipers.
So, let's get back to the question someone asked a few days ago about
buying a set of "Whitworth" taps and dies to last him the rest of his
Brit
biking life. The first thing I'd say is that if you wants it to last, be
sure you buy a HSS set (rather than carbon steel), even though it will
be
at least 2x the price. Then, in order of overall usefulness, I believe
you'll find in first place it will be a CEI set, then BSF, then BA.
Unless/until you really get deeply involved, make do with UNC to
"simulate"
BSW (although you'll want to buy an individual 1/2"-12 at
some point to
supplement the UNC set). Thus, if you follow my
recommendation, the very
*last* thing you'll want to buy for working on your British
motorcycle is
a
"Whitworth" set (I have one, by the way, but only got it
after I'd had
CEI,
BSF etc. for a long time).
Charles Falco
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