Gear box castellated nut

[nth]

Hello again.
More sage advice requested- does anyone know the sixe / thread of the castellated nut at the back of the gearbox that retains the propshaft coupling?
I've gone to change the oil seal which was pouring out oil to find a previous owner had refitted the nut with permanent threadlock and no split pin. Had to split the nut off but no thread gauge handy to check it.
Thnks
Neil

[telco.2]

Hi, Just checked 5/8" diameter 16tpi.
Bill

[nth]

Thanks Bill - any idea where to purchase as can't find at my stockist or internet sales. appears to be Unified 16 series?
Thanks
Neil

[telco.2]

Hi Neil,
I'll have a look over the week end & see if I have a spare one. How is it that Singer used such an odd thread form in the '30's?
Bill

[nth]

Thanks Bill.
You'd have thought they would have used BSF / UNF off the shelf. Seems no reason to me as 18 TPI in UNF as standard if extra tension needed.
Cheers
Neil

[telco.2]

Hi Neil,
I have found ONE spare in all the 60 years collection (!) & is the only spare I have. It is 1"A/F on the hex but screws perfectly onto the shaft. A bit rusty on the outside but otherwise A1. Let me know if you're interested
kind regards
Bill

[nth]

Hello Bill
PM'd you.
Cheers
Neil