[kbryt]

I have found NOS  1/2 x 20 tpi cycle nuts if you want one.

3/8 spanner size and one 7/16.

thin but you may need to skin them a bit more if you want really thin.

Probably got more in my old dirty nuttery box, but that takes time to rummage in.

[phutton]

Both 1/2"-20 BSCY and 1/2"-20 UNF are 60 degree included angle threads. Whit form is 55 degrees. In small threads, this doesn't make a lot of difference, but at 1/2" it possibly does.

According to BS811:1950 (the standard for cycle threads) after 1950, 20tpi cycle threads are Whit form i.e. 55 degree. Prior to that they would have been 60 degrees.

P.

[kbryt]

I will have a rummage during the weekend and see how many nut I can find.

[VicYouel]

I have struggled with spindle nuts in the past of the 20tpi variety that do not fit....... and of course I did not resort to lapping them with fine grinding paste!!!! Just wondering whether BSF form was adopted in 1932 on front and rear spindles.
Vic
PS Must research  the part number data base sometime for more clues.

[kbryt]

I know that, but unf forms and cycle are not compatible.

I've a huge collection of obscure 26 and 20 tpi cycle  taps and dies, almost to the point of OCD.

my first answer should have been more precise.

[AndyB]

Cycle thread form comes in both 26 and 20tpi

HTH

[kbryt]

Don't mix UNF and Whit even though they look like they might interchange.

Bad practice if nowt else.

I have 20tpi whit taps and may even be able to find you a nut, several makes used that size.

[Tom Snow]

Hi Old_Timer,

The spindle I have is indeed 1/2" X 20 TPI but with Whit thread form I believe; you will need to check this with a gauge to be sure as 1/2" X 20 TPI is also a UNF size. A good tap and die supplier should be able to supply the size in either thread forms.

Regards,

Tom.

[OLD_TIMER]

Can anyone tell me the thread size for the front wheel spindle. I have measured at 1/2" 20tpi I have guessed and tried Cycle thread but does not fit.  I am missing the thin (locking nut) spacer nuts.