Thread on a Lucas dynamo

[henk]

Can someone tell me which thread the nut is that's in front of the belt disk?
Is it like all Fordson UNF 7/16-20 or because it it Lucas BSF 7/16-20.

[Dandy Dave]

Are they not the same? Every bolt, nut, and screw on my Fordson Major is the same thread as what we call National Fine, or National Course over here. The nut on the end of the dynamo may be a Special Thread? Being an old hand at lathe work, when you cut threads on a shaft it is to the dimension of the shaft. Your in luck as 7/16 -20 is a common size. The shaft would be 0.4375. inch. The threads would be cut from there at 20 theads to the inch pitch. The threads inside of the nut would be cut a few thousands loose. The threads should have a 60 degree angle. Dandy Dave!

[Tubal Cain]

British imperial threads have an angle of 55 degrees and not 60 degrees as used on American and metric threads.

Gerald

[henk]

Sorry, due to bad English maybe I was not specific, but I mean is it UNF or BSF. Because all Fordson parts are UNC or UNF, but being a Lucas, so an English part, I have my doubts.
I know the difference in angle between the threads. Cutting BSF on UNC will weaken the threads.

[Aussie Frank]

Hi Henk,

My lucas parts list only lists the nut as 7/16" x 20 TPI no mention of BSF or UNF but the long through bolts are listed as 1/4" BSF so my guess is it should be 7/16 x 20 TPI BSF as I can't imagine that they would have mixed thread types when the generator was first designed.

Regards, Frank.

P.S. The lucas part number for the nut is 180740

[Dandy Dave]

British imperial threads have an angle of 55 degrees and not 60 degrees as used on American and metric threads.

Gerald

Okee Dokee. Learned something new today. Figures they had to do something different. And then there is Wentworth. ... Wonder If Rolls Royce still uses it in their autos. I have worked on a 1930. Good thing I have several lathes and can make all this stuff when necessary.

Henk, You should beable to see the difference with a thread gage. If you do not have one use a 1/4 - 20 UNC bolt and hold it up to a light, You will see a difference if there is any. Dandy Dave!

[henk]

Thanks you all.
I see if I can use the thread gage. The thread is pretty damaged.
My guess is that's BSF. tpi means turns per inches.

[Tubal Cain]

Henk,

BSF stands for British Standard Fine, BSW is British Standard Whitworth, which is a coarser thread. TPI stands for Threads Per Inch.

Gerald

[Dandy Dave]

Agreed. Anyboby that has ever threaded on a lathe would already know that TPI =Threads per inch. I could easily cut these threads. All I would need to do is sharpen a bit to 55 degrees rather than 60 degrees. The old lathes we had to pick out and fit the proper gears. With the newer lathes we just set it up with a quick change gear box. One thread the Quick thread change gear box is not capable of is pipe thread which is 27 TPI. I have 26 and 28... Another wonder of the world? Why did they do that. To Sell pipe threading machines, taps and dies??? Perhaps it is because pipe thread is tapered and would have to be done with a taper attacment. Dandy Dave!

[henk]

I have my dynamo disassembled and the plain bearing at the back and my rotor shaft at the rear is worn. This makes the rotor to wobble and the surface damaged.
During my search for new parts I found this site.
http://www.jcrsupplies.co.uk/products/DYNAMO_PARTS
So parts are still for sale. And the model is Lucas C40.
On another site I saw the thread on the rotor shaft is UNF.
http://www.limora.com/en/english-cars/m ... s-c40.html
So no English thread after all.
The roler bearing is in mm 35 x 15 x 11