Hi Kammo, I've tried to make my own tap out of a piece of 12x3 trapezoidal leadscrew (didn't really want to pay £40 plus for a tap for 3 nuts) but I think I've flattened the profile a bit when cutting a taper on it as it's very loose on the leadscrew.

Nathan, any chance for a remuneration I could borrow the tap after Kammo?