Thread is 5/8-11. Next time I'd go more course. No need for fine adjustment. Cut from 6061 1.5" round bar.
Overall there's 5" of thread there, you only need 3. Less if you use a stiffer spring.
Knurl nut is like 1.5" od.
It's a custom piece made on a 109 year old lathe and a 60s era Bridgeport knockoff. For the hours I have into it, I'd have to charge far more than anyone in their right mind would be willing to pay.
You could easily draw this up in solidworks and have it 3d printed.
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Moe Colontonio
Cherry Hill, NJ
RV-8 N495T