Mechanic offered a possible way to check..... embed the thread in a block of plasticene. (Modelling clay) which i happen to have some in the shop.
I will brace the back and impress the front along the threads. That will give him something to neasure.
His tools have BSF and BSW but he said they weren't matching up with the sample nut (original CTL part on loan) nor SAE or Metric.
For BSF, he said it should be 55 degree pitch, and it doesn't match that.
Have I stumbled across some odd thread only used to trap the steering wheel on the shaft? I really doubt that -
- but odder things have happened!