Extension handle for a Starrett solid-rod inside micrometer set

[Toolmaker51]

Another home engineer conquers proprietary threads!
Paul Jones, you've assembled a first rate setup to accomplish what few can outside 'our' circle. Even less would understand why.

Many products use bastard threads or components, with varied justifications.
Naturally, some were in place before standardization was standard, and continue using original manufacturing equipment. I say that makes sense.
Other products want control of who is getting inside, I like that less.
I'm certain a lower tier exists, thinking their item is so exclusive, special bits will protect it. More likely the design flaws are masked yet easily remedied, they think you'll just buy another of theirs.
That's a challenge if ever there was one!