[Healeys] Whitworth vs UNC

Thu Dec 24 15:44:03 MST 2020

I've published this before, but there is also a good explanation of Unified
markings versus Whitworth in my vintage 1958 Machinery's Handbook.  A great
reference.

Regarding Michael Salter's question, I agree with Bob H...

*Nominal Size (inches)*

*TPI *

*Pitch (inches)*

*Major Diameter (inches)*

*Minor Diameter (inches)*

*Tapping Drill Size*

*1/4*

*19*

*0.0526*

*0.518*

*0.4546*

*11.8 mm (0.4646 inch)*

On Thu, Dec 24, 2020 at 11:53 AM <gradea1 at charter.net> wrote:

> When the British auto industry was switching over from BSF/W to UNF the
> explanation was published in the Austin Service Journal Volume 24. This is
> a good description of the differences.
> Also this chart has some very good measurements of the various hardware.
>
> Nice Christmas cards of Healeys in the snow...I don't have any snow, or my
> car out in the weather-it would be rain here in the Northwest.  Here is one
> of the sister car to Michael's at our local car show-last year...none this
> year ...or next? Season's Best...stay safe! Hank
>
> -----------------------------------------
> From: "Harold Manifold"
> To: "Michael Salter", "Bob Haskell"
> Cc: "Healey List"
> Sent: Wednesday December 23 2020 6:39:51PM
> Subject: Re: [Healeys] Whitworth vs UNC
>
> Understanding UNC and Whitworth is one thing but BSPP and BSTP fittings is
> a whole 'nother rabbit hole!
>
> ------------------------------
> *From:* Healeys [mailto:healeys-bounces at autox.team.net] *On Behalf Of*
> Michael Salter
> *Sent:* Wednesday, December 23, 2020 9:48 AM
> *To:* Bob Haskell
> *Cc:* Healey List
> *Subject:* Re: [Healeys] Whitworth vs UNC
>
> Thanks Bob  ... I  think you have nailed it.
>
> M
>
> On Wed., Dec. 23, 2020, 12:46 p.m. Bob Haskell, <rchaskell at earthlink.net>
> wrote:
>
>> Michael,
>>
>> I'm going to guess 1/4" BSP.  0.518" OD - 19TPI.
>>
>> <https://britishfasteners.com/threads-bsp>
>> 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 at gmail.com
>> > <mailto:cnaarndt at gmail.com>> wrote:
>> >
>> >     Here is an excerpt from one of my articles..
>> >
>> >     On Tue, Dec 22, 2020 at 1:48 PM Curtis Arndt <cnaarndt at gmail.com
>> >     <mailto: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 <mailto: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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