Greetings,
The greatest challenge with Star is that there are few fully dimensioned drawings remaining. When Bruce Williams bought the company from Pioneer, lots of tooling was supplied; but, few drawings.
Seems like "Tribal Knowledge" prevailed at Star...
So, this begins the task of Reverse Engineering the parts.
What were the original Star designers thinking?
Fortunately with the aid of thread gauges, hardness testers, microscopes and an abundance of existing spare parts a lot of reconstruction has taken place.
Oh yes, I forgot the Internet. Via the Internet, I was able to locate that weird powder hopper thread. It is not listed in any of the standard tables in the Machinery Handbook. I stumbled on it merely by accident.
Star's primary products were sprinkler heads for the Citrus farmers in California. Perhaps this is why the odd threads? Look at the Expander Plug and decapping rods for the Sizing dies. Both are 27 pitch!
Cheers,
Dave