[Healeys] Whitworth vs UNC

[Curtis Arndt]

Here is an excerpt from one of my articles...

On Tue, Dec 22, 2020 at 1:48 PM Curtis Arndt <cnaarndt at 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 at 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 -  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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