MF50 ram ? How tight the piston?

Dipper ram developed a leak so took it apart to seal it. The piston is threaded onto the rod with a set screw to hold it.
When I took it apart I was surprised when the piston started to turn when I was loosening the set screw.
I have the factory manual & parts book, neither show a cylinder like this one although they seem to have a dozen different cylinders in the manual.
So today I replaced the seals and putting it back together. Threaded the piston on and it stopped at just hand tight at...

MF50 ram ? How tight the piston?

MF50 ram ? How tight the piston?