[Healeys] Whitworth vs UNC
michaelsalter at gmail.com
Wed Dec 23 09:30:16 MST 2020
Well I have one for you Curt.
The thread on the oil drain back pipe on the 100 engine (1B1236) has me
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?
On Wed, Dec 23, 2020 at 10:54 AM Curtis Arndt <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> 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.
>> 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.
>>> Roger Grace
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