MG T-ABC

I am in the process of tidying up the panel warning lights and I need some of the small brass nuts that attach the wire.

Does anyone know what size nut is used and where I might get some. ?

Incidentally, the repros have a different thread.

I don't know for sure, but I suspect they are BSF/BA. The repro is probably metric.

Steve Simmons wrote: ↑

Sat Jan 29, 2022 10:07 am

I don't know for sure, but I suspect they are BSF/BA. The repro is probably metric.

I would like to know for sure as I suspect they might be BA. There again, they could be BSB.?

BSB and BSF are 55 degree Whitworth thread forms. Variations in TPI. Something that small on an electrical/instrument I suspect would be BA, but just a guess. BA is a 47.5 degree thread. BA nuts should not be that hard to find online. If it is BA and you try a 55 degree thread, or 60 degree (metric) thread that is a similar size and thread count it may screw on, but you will not be able to tighten it-- as it buggers the threads.
https://www.madmodder.net/index.php?topic=12952.0

If it is BA and you can get a precise measurement of the stud (widest measurement) the nut would fit on, you can look on this chart for major diameter to get size. BA size 0 - 12. Ebay has most BA sizes.

I never even considered BSB. Can't remember the last time I heard someone even mention them! As I recall, British Brass is used more for plumbing pipe and the like?

BA is likely right. A lot of those tiny threads are BA.

I've heard of BSC cycle threads, but this is the first time I've heard of BSB.
But Smiths and Lucas stuff is usually BA threads.
I get them from British Tools & Fasteners in New York.
https://britishfasteners.com/help.html

Thanks guys. I am surprised that this is not a more common question. The diameter of the stud is 9.5mm - so not on the BA table above. The nuts are quite shallow - half nuts.? and there should be two of them.

The item is threaded brass with a spring loaded plunger (that the bulb compresses).

If you measure in millimeters I suspect you are in a metric country.
9.5 mm = .374" so my first guess is it is probably a 3/8-20 BSF thread.
Does the thread pitch look to be about 1.25 mm?

My apologies to everyone. I made an error with the size. It's NOT 9mm (of course it's not!!) It measures 4.7 mm ........so the size nut I need is 2 BA.

Sorry again......and thanks for your help!

So I ordered some 2 BA 1/2 nuts (Ebay) and they have arrived. Unfortunately although quite close, they won't go on.

I don't know if the thread in the nuts is not 2BA as described or if the original thread is not BA after all.?

I received some 3/16" BSF brass nuts today....and they don't fit either!!!

Thread identification shouldn't be this hard. I may or may not have the same lights, but they are in a box so I can easily look at them. Maybe you could post a picture of what you are doing.

As previously mentioned, the repros have a different thread again...I suspect metric.

I would like to establish what the original thread should be.

Well I would have put money on an electrical item being 2BA, but now I'm stumped.
I measure .181" OD and 40 threads per inch.
What is that? I found something called 3/16-40 Model Engineer's thread here.
https://britishfasteners.com/threads-ME
It seems to be used by people who build model steam railroads.
https://journeymans-workshop.uk/baandme.php
I think that must be it, though why Lucas would use it is beyond my comprehension. This site, which is my supplier of choice for British screws, has all the British thread charts.
https://britishfasteners.com/help.html

Many thanks, Rob. I have sourced some here in the U.K.

I would imagine they are the right nuts for the job.

Will post again when I get them.

Cheers,
Ray.

Believe it or not...those are not the right nuts either!

I have now spent enough on nuts. I could have bought a new light for the money.!

I have resolved the issue in a different way. I now have a small rubber grommet acting as an insulator and being compressed under pressure allows me to get away with just the one nut..