For those Listers out there who aspire to maintain complete originality,
Lindsay Porter's "Guide to Purchase and DIY Restoration" (now that I have it
nearby) states that Spridgets use Unified National Fine (UNF) in "almost
all" applications, which is "completely compatible with American Fine (AF)
or SAE threads". He goes on to state that:
"A few applications use a Unified National Coarse (UNC) compatible with
American coarse threads (some studs into the block and gearcase). There are
only a few applications of BSF (British Standard Fine) or BSW (British
Standard Whitworth - coarse). The dampers (shock absorbers) use a BSF
thread for their filler screws. All Lucas electrics use Whitworth until
around 1969 when the change was made to metric."
Additional information is provided in the book.
My question is: Is there a distinction between what UNF and AF/SAE look
like when installed (particularly from a concours perspective). (Perhaps
symbols on the end of the bolts?)
(All of this assumes that Porter is correct, obviously. If there is some
question about this, please let me know).
Thanks for your assistance.
Geoff Muttart
gmuttart@mtdc.ns.ca
Nova Scotia, Canada
AH 'Bugeye' Sprite
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