Michael,
I'm going to guess 1/4" BSP. 0.518" OD - 19TPI.
https://britishfasteners.com/threads-bsp
Cheers,
Bob Haskell
Austin Healey 3000 BN7/BT7 registrar
On 12/23/20 11:30 AM, Michael Salter wrote:
> Well I have one for you Curt.
> The thread on the oil drain back pipe on the 100 engine (1B1236) has
> me stumped.
> The tube is 0.500" O.D. with an I.D. of 0.362"
> The OD of the thread is 0.511" and it is 19 T.P.I.
> I cannot find a 19 TPI x 1/2" pipe or tube spec anywhere .... any ideas?
>
> M
>
>
> On Wed, Dec 23, 2020 at 10:54 AM Curtis Arndt <cnaarndt@gmail.com
> <mailto:cnaarndt@gmail.com>> wrote:
>
> Here is an excerpt from one of my articles...
>
> On Tue, Dec 22, 2020 at 1:48 PM Curtis Arndt <cnaarndt@gmail.com
> <mailto:cnaarndt@gmail.com>> wrote:
>
> The bolt is 5/16" BSW!  Don't let anyone tell you different.
>
> Even my 45K original mile '60 Bugeye has its original 5/16"
> BSW bolt in the generator front plate. The problem arises
> since a 5/16" UNC bolt has the same tpi (threads per inch) as
> the 5/16" BSW bolt. The issue is that UNC has a thread pitch
> angle of 60° and Whitworth by definition is 55°. The wrong
> bolt will never torque properly and will eventually wear the
> aluminum generator front plate.
>
> Cheers,
>
> Curt
>
> On Mon, Dec 21, 2020 at 3:53 PM Roger Grace
> <roggrace@telus.net <mailto:roggrace@telus.net>> wrote:
>
> My understanding is that they are close but not
> interchangeable ?
> Thread angles are slightly different.
>
> For AH generator adjusting link is this 5/16 W or 5/16 UNC ?
>
> At back of my mind think they should be Whitworth -Â think
> you told me that is why they come loose if you use UNC ?
>
> Finding it difficult to identify one from the other.
> Any tips to do this welcome.
> Have a definite W bolt and comparing to UNC can only see
> slight rounding of UNC ?
>
> Moss sent me a UNC bolt for this link - well that is what
> they called it ?
>
> Would appreciate your expert input.
>
> Regards,
> Roger Grace
>
>
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