Nice thought Brandon but the nut is steel and has no wear, it's the alloy that passes through it that is worn down causing the tap to disconnect under load.
I've got another idea, a mate at work makes miniature steam engines, about 1/100th scale and they pull carraiges of people around special little rail systems.
Anyway he is a really good miniature engineer and makes a lot of his own (all may be) parts, I gave him a whacking great brass rod I found in my shed when I bought my house so he said any time I needed some light engineering to contact him.
I'll take him up on that tomorrow.
Backup plan is to get a spare Scunny has in the South Island if he can find it and I can persude him to part with it.
I am so totally screwed without that damn tap!!!
In the states you just pop off down to the wreckers yard, something we have few of here in NZ.