Hints and Tips - Headlamp Nuts

From: TA TERRY
Sent: 14 September 1999
To: british-cars-pre-war
Subject: Large size nuts , fine threads...??

Those large nuts on the bottom of most Lucas headlights, Anyone know what standard that is??


From: Barry Riseley
Sent: 14 September 1999
To: TA TERRY; british-cars-pre-war
Subject: Re: Large size nuts , fine threads...??

Hullo Terry,

I assume that you are referring to the threaded "mounting tube" and associated nut which is used to affix the Lucas lamps to the mudguard, headlight bar or whatever.

If that is the case then I think you will find the thread is British Standard Brass (BSB) and I think generally somewhere in the region of 9/16" OD. The tread is Whitworth form and is 26TPI. I know that I have got taps and dies for them and think that there may well be several different OD's but all are 26TPI.

Best regards

Barry Riseley
Tasmania


From: davidw
Sent: 14 September 1999
To: british cars; TA TERRY
Subject: RE: Large size nuts , fine threads...??

You can still buy the nuts from Lucas.


From: TA TERRY
Sent: 14 September 1999
To: Barry Riseley
Subject: Re: Large size nuts , fine threads...??

I think Barry has it right on these Lucas mounts but I cannot find a chart for BSB or BSC threads. I am pretty sure BSC, British Standard Cycle, are all 26 tpi regardless of size but I doubt there are sizes above 1/2" dia. Anyone know of a web site with these standards?

Now how about those tie rod ends which seem to be 9/16 x 20 tpi? What thread standard are those?

Tnx Barry and all....


From: Barry & Shirley
Sent: 14 September 1999
To: TA TERRY
Subject: Re: Large size nuts , fine threads...??

Terry, I think you will find they are cycle threads

Barry Lafbery
Membership Secretary
Rover Car Club of Canada
1963 P5 1971 P6B


From: Stan Fickes
Sent: 14 September 1999
To: TA TERRY
Subject: Re: Large size nuts , fine threads...??

> Anyone know of a web site with these standards?

Terry-

Try http://www.livsteam.demon.co.uk/threads.htm.

Stan


From: Barry Riseley
Sent: 14 September 1999
To: TA TERRY
Subject: Re: Large size nuts , fine threads...??

Hullo Terry and Co.

Please be assured that BSB threads (all 26TPI) are certainly well known way above 1/2" OD.

I must say that I have forgotten the arcane details of the difference between BSB and British Standard Cycle threads, as I have always assumed that they are based on Whitworth Standard thread forms. I will try and look that one up!

I have BSB Taps and Dies in my workshop up to at least 1" OD.

On the subject of the tie rod end threads, they could well be specials, although somewhere I have a book which lists a whole range of "standards" for various "TPI" based threads. I will see if I can find the book.

The thread in the ends of the "track rod arms" (is that what they are called, I can't remember} that attach to the beam front axle of the ubiquitous Austin Seven are also of doubtful heritage, from memory 5/8" OD 16TPI Whitworth Form, and can be a real trap for the uninitiated.

Anyway, I will try and "expose" the difference between BSB and BSC threads and would really like to know an address in UK where I could get a supply of the nuts as Lucas is just about extinct in my part of the world.

Barry Riseley


From: TA TERRY
Sent: 15 September 1999
To: Barry Riseley
Subject: Re: Large size nuts , fine threads...??

In a message dated 9/14/99 Barry Riseley writes:

<< On the subject of the tie rod end threads, they could well be specials, although somewhere I have a book which lists a whole range of "standards" for various "TPI" based threads. I will see if I can find the book. >>

I'm now told that these track rod end threads are of a "Admiralty Standard" with a Whitworth form. Like BSC all sizes are the same tpi...in this case 20 tpi. I'll bet the story on how this standard became the one for track rods would be interesting.

Can anyone confirm?

A useful URL for BSB and BSC is http://www.livsteam.demon.co.uk/threads.htm Thanks to Stan Fickes for this....


From: Stuart Ulph
Sent: 15 September 1999
To: Barry Riseley
cc: TA TERRY
Subject: Re: Large size nuts , fine threads...??

Barry Riseley writes:

>Hullo Terry and Co.
>Anyway, I will try and "expose" the difference between BSB and BSC threads
>and would really like to know an address in UK where I could get a supply
>of the nuts as Lucas is just about extinct in my part of the world.
>
>Barry Riseley

May I suggest you try Keith Ardley,14, Bridge Rd., Mepal, Ely, Cambs. Tel. 01353 778493 for almost anything to do with headlamps. He recently supplied me with some 26 tpi nuts for Butlers lamps. Incidentally, up til then I had been using BSA M/cycle hub spindle nuts-cycle thread- but they are a bit meaty!

Regards,

Stuart Ulph


From: Barry Riseley
Sent: 04 October 2001
To: Guy Weatherall
Subject: Lucas Headlamp etc Mounting Spigot Threads

Hello Guy,
I was browsing through your much appreciated and valuable Vintage Knowledge pages the other day and came across the item in the "Technical Info" area on "Head lamp Nuts" and found some e-mails from myself, giving a most learned dissertation on the intimate details of "Brass Threads."

I note in one of them that I said that I would come back with some further details on the differences between "Brass" and "Cycle" Threads. I had forgotten about this whole affair, but since reading your archive notes, I have dug out my copy of "Machinery's Screw Thread Book" 18th edition, published circa 1961.

This book, a later edition of which has so far eluded me, is veritable tome when it comes to screw threads, and is the most comprehensive work on threads that I have ever seen. It even covers such erudite things as "Bottle closure threads" and the unique thread system use for Telephone Line insulator fitting to pole cross arms!

Suffice to say that I can now confirm that British Standard Cycle Thread is a comprehensive thread system for bicycle use, and entertains thread pitches from 56tpi to 8tpi, with a range of threads between 1/4" to 3/4" at the familiar 26tpi.

The British Standard Cycle Thread is not based on the Whitworth form, but rather has a thread angle of 6o degrees. In 1961 it was specified by the British Standards Association in BS811:1950

In the case of the Brass Thread, my reference reads as follows:

British Brass Thread
The origin of the British "Standard" Brass Thread is obscure; for although there exists no British Standard for it, this thread has been in use for many years for gas fittings, brass tubing and general brass work........

Whatever the diameter, it consists of 26 threads to the inch of Whitworth form.

The tables contained in my reference give "Brass Thread" specifications from 1/8" to 2" diameters.

I have no doubt that the various "Lucas" lamp fittings under discussion which gave rise to your Archive reference, are in fact British"Standard" Brass Thread.

So, somewhat belatedly, I hope I have met the commitment I gave earlier to sort out the difference between BSB and BSC.

Best regards,

Barry Riseley
Tasmania
Australia


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