1/2 BSP on Austin 7?

[JonE]

I bought a tap and on looking again at the Cornwall club threads list, can't now remember why I have it! Can someone enlighten me so I can add a note to it please.

[Ilmoro]

Is it to modify a stripped gearbox drain plug thread?

[JonE]

that's the forum thread I found too! But no, I dont think I'd have bothered... which is why I'm head scratching again.

[Howard Wright]

Cancel that….. the king pin brass disc is 3/4” 20TPI

Hi Jon

Working from memory I have a feeling that the thread at the top of the king pin shaft that takes the brass closing disc is 1/2” BSP.

Do check with a thread gauge before you go tapping it.  The tap should be an end tap rather than a taper tap too.

I also think the filler plug on a 31 back axle could be the same thread but I’m not sure.

Cheers

Howard

[JonE]

I wonder if I had the same thinking as you, Howard i.e. I read something wrong and bought it.
Funnily enough, I have just been playing with the brass discs and wondering about their thread. I have little offcuts from my cross tube which is the same thread, and thought I could make some recycled plugs for the king pins, perhaps adding an allen key connector.

[Andy Bennett]

Were you doing some plumbing at the time, minds can wander?

[Howard Wright]

Hi Jon

I think the sump drain plug is 3/4” diameter and 14 tpi.  Which is, I believe, 1/2” BSP.

Cheers

Howard

[dickie65]

The drain plugs are a parallel thread so it would be BSPP Not BSPT
That is if in fact they are BSPP !

[Hedd_Jones]

They are neither. They are 3/4 diameter 14TPI whit threadform. 

A parallel 1/2 BSP tap, would clean the thread out nice, but the whole kaboodle would be bigger requiring a new plug. 

I've got a lot of 14tpi whitform threads on my steam roller, which is 1920. It is alledged that the 14tpi tooling was to some Great War ministry naval standard. I expect probably why Austin also had it. 

I've had to beg, borrow and make tooling to suit when carrying out repairs.

[dickie65]

Hedd.
My thoughts were that the drain plugs are a 3/4 Whitworth form so thanks for confirming it.