<div dir="auto">Thanks Bob ... I think you have nailed it. <div dir="auto"><br></div><div dir="auto">M</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed., Dec. 23, 2020, 12:46 p.m. Bob Haskell, <<a href="mailto:rchaskell@earthlink.net">rchaskell@earthlink.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Michael,<br>
<br>
I'm going to guess 1/4" BSP. 0.518" OD - 19TPI.<br>
<br>
<a href="https://britishfasteners.com/threads-bsp" rel="noreferrer noreferrer" target="_blank">https://britishfasteners.com/threads-bsp</a><br>
<br>
Cheers,<br>
<br>
Bob Haskell<br>
Austin Healey 3000 BN7/BT7 registrar<br>
<br>
On 12/23/20 11:30 AM, Michael Salter wrote:<br>
> Well I have one for you Curt.<br>
> The thread on the oil drain back pipe on the 100 engine (1B1236) has <br>
> me stumped.<br>
> The tube is 0.500" O.D. with an I.D. of 0.362"<br>
> The OD of the thread is 0.511" and it is 19 T.P.I.<br>
> I cannot find a 19 TPI x 1/2" pipe or tube spec anywhere .... any ideas?<br>
><br>
> M<br>
><br>
><br>
> On Wed, Dec 23, 2020 at 10:54 AM Curtis Arndt <<a href="mailto:cnaarndt@gmail.com" target="_blank" rel="noreferrer">cnaarndt@gmail.com</a> <br>
> <mailto:<a href="mailto:cnaarndt@gmail.com" target="_blank" rel="noreferrer">cnaarndt@gmail.com</a>>> wrote:<br>
><br>
> Here is an excerpt from one of my articles...<br>
><br>
> On Tue, Dec 22, 2020 at 1:48 PM Curtis Arndt <<a href="mailto:cnaarndt@gmail.com" target="_blank" rel="noreferrer">cnaarndt@gmail.com</a><br>
> <mailto:<a href="mailto:cnaarndt@gmail.com" target="_blank" rel="noreferrer">cnaarndt@gmail.com</a>>> wrote:<br>
><br>
> The bolt is 5/16" BSW! Don't let anyone tell you different.<br>
><br>
> Even my 45K original mile '60 Bugeye has its original 5/16"<br>
> BSW bolt in the generator front plate. The problem arises<br>
> since a 5/16" UNC bolt has the same tpi (threads per inch) as<br>
> the 5/16" BSW bolt. The issue is that UNC has a thread pitch<br>
> angle of 60° and Whitworth by definition is 55°. The wrong<br>
> bolt will never torque properly and will eventually wear the<br>
> aluminum generator front plate.<br>
><br>
> Cheers,<br>
><br>
> Curt<br>
><br>
> On Mon, Dec 21, 2020 at 3:53 PM Roger Grace<br>
> <<a href="mailto:roggrace@telus.net" target="_blank" rel="noreferrer">roggrace@telus.net</a> <mailto:<a href="mailto:roggrace@telus.net" target="_blank" rel="noreferrer">roggrace@telus.net</a>>> wrote:<br>
><br>
> My understanding is that they are close but not<br>
> interchangeable ?<br>
> Thread angles are slightly different.<br>
><br>
> For AH generator adjusting link is this 5/16 W or 5/16 UNC ?<br>
><br>
> At back of my mind think they should be Whitworth - think<br>
> you told me that is why they come loose if you use UNC ?<br>
><br>
> Finding it difficult to identify one from the other.<br>
> Any tips to do this welcome.<br>
> Have a definite W bolt and comparing to UNC can only see<br>
> slight rounding of UNC ?<br>
><br>
> Moss sent me a UNC bolt for this link - well that is what<br>
> they called it ?<br>
><br>
> Would appreciate your expert input.<br>
><br>
> Regards,<br>
> Roger Grace<br>
><br>
><br>
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</blockquote></div>