This question is asked quite a bit on here, most recently by me.
I have been and sourced some nuts for the `85 UK made plastic hubbed tuffs that were strewn all over MK this year.
the size is-
3/8" UNF 24 TPI.
if anyone has the `Definitive' sizes for other ones, older, newer, rear, coaster etc, please post them here, I will add them to the list and maybe a kindly MOD could add it to the T&R stickies list.
I could only get full nuts yesterday, but am trying to locate a box of flange nuts (hens teeth), which they would have had OG.
MM