Thanks for the ideas! I was about to quit this idea and just make a fixed lower grill block that I could take sections out of when needed (say 5 parts). Now I might try the grates again
One issue. When the grate is closed the holes (brass and others) slide in next to the vain pivot bracket
I might get around that by taking the red outlined piece of metal and making it bigger (to the right in that pic above).
As for threading the rod, no way, it is only about a pencil lead thickness.
Nylon nuts will only work on the main bracket pivot point point, the rod at the grate will need to be loose to work (and there is no room for a nut)