Men , whats the thread on these ? Now have the female and need to make the plugs for them . Damned fine thread there.
Steve

Hello Steve
3/16 - 32
John

I'd assumed you were referring to the thread joining these two parts....
I don't know the size or the threadform but I'd hazard a guess at a Whitworth instrument thread or possibly UNEF, although it seems finer than that.

Thats the one Nick.
Looks like 30 tpi with the Thread gauge internally. Will dismantle a full one to check out the male --- its easier to get a better look.-- nothing i can find that fine --even on the Machinist forums .
Steve

Ahh, just clicked on your link Nick , believe it or not -- i've never heard of whit fine . looks like the one !!! Cheers

Just had one apart , its 28tpi 3/4"

It won't be Whitworth, that's a coarse thread, it can be BSF or BSP in Imperial or it's a UNF in Unified, BSP do have some weird tpi to diameter. Highly unlikely to be metric, I still think it origin is not the auto industry more industrial kitchen origin, i.e large fridge, freezer or oven doors.

Ian , to my surprise there is a BSW Fine ( never seen it myself , but then i dont move in exotic circles ) It is likely as you say to had another org. application. Probable pre war --- possibly timber Coach building. Brass is 26tpi , whit fine is 30 tpi and this particular thread is 28 tpi.
Steve

Thanks Steve, you live and learn every day I did come across these units way back in the 70's but can't remember where but certainly not specific to the SP, perhaps there is a reference to them in the Driving Member around 71 -73, normally they are not a unit one loses.

Anyone --- Thread ?