Terminal stud thread for the Bomb style starter ?

[foster461]

On the rear end of the early TR3 and I assume TR2 starter motor, the so-called Bomb type, there is a threaded stud for the starter cable connection. I am missing the nut that goes on this stud. The starter motor still has the brass jam nut that secures the stud to the case so I took that nut to the hardware store expecting it to match something but it does not. The stud is around .25 inches diameter but what the heck is the thread ?

Stan

[Dic Doretti]

BSF.

[BlueTR3A-5EKT]

As stated it is 1/4" BSF 

Also same thread as used on the later TR3A-4A  starter terminal post.  Lots of other British cars of the era with the 418G type Lucas starter will have the same threaded terminal post. (MGB, AH 3000, Jag. etc)

Cheers

Peter W

PS If stuck I do have a couple of spares - That said there ought to be someone in your part of the world with a spare.

[foster461]

Thanks guys, I would never have figured that out.

I see BSF threads have a tpi number, is 1/4 bsf always 26 tpi ? and is this brass nut from Moss USA what I need ?

 

https://mossmotors.com/hex-nut-brass-1-4-26-bsf

[BlueTR3A-5EKT]

Yes 1/4" x 26 BSF is a standard form.

see here

https://www.ring-plug-thread-gages.com/PDChart/BSF-thread-data.html

my only concern is that I think the hexagon size of the Moss nut will be smaller than the original  Lucas item.   Not the end of the world  if the thread fits ok.

cheers

Peter W

[Dic Doretti]

On 6/25/2020 at 11:54 PM, BlueTR3A-5EKT said:

my only concern is that I think the hexagon size of the Moss nut will be smaller than the original  Lucas item.   Not the end of the world  if the thread fits ok.

That could be an advantage, the original nut need a 1/4" whitworth spanner while the smaller nut needs a much more readily available 1/2" unf spanner unless, horror of horrors Moss has gone metric.

           Cheers Richard

[foster461]

I will know in a few days when Moss ships the order. They have a couple of different nuts so I'll see which works the best. This starter doesnt fit my 1960 TR3a so I'm going to try and sell it to someone who can use it but it works and I'd like it to be complete. Moss has a minimum order and a couple of nuts doesn't come close so I had to add some toys for ballast.