Ed Huntress wrote:


"Suga Moto Soy" wrote in message
...

Jimmy Suarez wrote:
can somebody tell what kind of thread is this?
http://www.signaturehardware.com/product8636

it is for an old fashined door knob spindle,the thicknes is 9/32
square stock, and 20TPI,is there a nut or bolt made for this thing?
Thanx

I don't know what the thread is, but those things are so soft it
usually doesn't even matter. They'll mush in anything.

I can't believe this Jimmy, nobody can give you an answer,I thought
some great machinists are posting here.I heve seen this type of door
knobs in many houses built from the 1900s to 1940s.

Well, mine was built in 1924, but assuming it was a long-time
standard, the thread is 18 tpi (0.072" pitch) (Starrett thread gage)
and the major diameter of the threads is around 0.375" (Starrett
mike). The spindle is a little worn from old age and use, so I'll let
you guess at what nut might fit. It looks to me like a 3/8 x 18. I
don't believe that's a standard; UNC is 3.8 x 16 and UNF is 3/8 x 24.

I'd double-check that 20 tpi; it's close, but no cigar on the spindles
on my doorknobs.

I suggested 3/8" BSF which is 20 TPI but the OP doesn't seem to have
responded to any poster regarding their comments. If the OP is in the US
then BSF won't be that common unless they're next to gunner's motorbike
but for me my neighbour has quite a selection of BA, BSF, BSW, BSP, and
more recently UNF and UNC, and staggeringly a few metric, I also know a
guy that would have many such spindles from various periods so could
measure if required.

The period of manufacture would be of some use in pinning down standards
or not. I recently repaired a ceiling light, most likely of Dutch
manufacture in the 19th century, and the main thread holding it together
appeared to be M10.7 x 1.5. From the design with solid arms no provision
had been made for gas or electric so candles were the original light and
I reckon it dated from the first half of the 19th century. The 1.5 mm
thread pitch would be 17 TPI, which I have never seen anywhere , but
1.5mm pitch might make sense. IIRC at that date no real standards
existed, BSW coming in around the mid 19th century in the UK, so I
expect the threads were produced to suit in the factory which certainly
seems to be supported by the other mish-mash of threads else where in
the items. In the end I single point cut the main suspension rod thread
at one end to suit the female piece it mated with and the non-visible
end I fitted with a M10 helicoil.