I've just checked with my neighbour as he has a Machinery Publications
thread book first printed in London 1915, although his copy is about
1935. The only threads listed with 19 TPI are Whitworth based and it
gives the thread details for the Whitworth thread of that TPI which my
21st edition Machinery's still does. It does list 2 copper tube threads
both Whitworth thread form but unfortunately neither uses 19 TPI. One
was called the Manchester thread used by Manchester plumbers and was 16
TPI constant pitch, the other Copper tube thread was similar to BSP but
used a 20 TPI in the size range you refered to so close but not the one.
Both are now likely obsolete.

I spoke briefly to the guy I know that has a thing about threads and he
wondered about BSPP (British Standard Parallel Pipe) as he has run
across this in gearboxes for bearing retaining nuts, this thread
apparently being useful for various engineering applications not just
pipe threads. He did mention a company, unfortunately now defunct, that
listed 158 different threads it could supply tooling for right down to
the Budapest fire department thread. I think he said he had or knew
where one of their catalogues was so if possibly i'll try to get a look.
Is your email address at ameritech good, if I turn anything up i'll
email you there if the thread falls off the end of my news reader.

Can you email me a picture of the units, i'll run it by the light guy I
know and see what he says. He has some french contacts and experience
with french lighting. I'm on broadband so don't worry about the size too
much unless its absolutely huge 2mb/picture.

Do I like a challenge? yes. Delving into our industrial heritage, so
much of it, and this may be touching the early fringes regarding
standards, or may predate it. I just happen to know a few people that
like this stuff.

From a quick look Whitworth introduced his standardised threads in
about 1841 and apparently take-up was quick although the BSI (Britsh
Standards Institute) didn't come about until much later (early 1900s ?).
Knowing the vintage of the items you are working on would help to pin
down an industrial environment and may help identify the thread.

Cheers

DB

Paul K. Dickman wrote:

"David Billington" wrote in message
k...

I do a number of modifications to lamps for a friend here in the UK and
have not run across this thread, but saying that one will probably turn up
next week. Are these items which have been in the US for many years or have
they recently been imported. Do you have any idea of the vintage. I presume
a tap is required as you are modifying a ready made part which would be a
pain to set-up for thread cutting.


These are recently imported, but of antique or certainly vintage
manufacture. In retrospect, they may mostly have been French lamps, but
almost all the sockets of British manufacture.

They make an adapter for the bi-pin base bulbs to our American style screw
shell bulbs, but through bad design, it is conceivable that the customer
could reverse the adapter or change the plug and end up with the entire
metal exterior of the fixture attached to the hot side of the wiring. Even
in proper assembly it leaves the body attached to the neutral lead.

Needless to say, I refuse to use them.

The pipe is slightly larger in diameter than our standard 1/8"- 27 pipe. The
simplest and cleanest fix is to ream out one of our socket bases and
re-thread it to match.

Because of clearance and mounting issues, it is usually extremely difficult
to re-thread the piping.

Paul K. Dickman