On the 19mm pins, what thread size and pitch are they?
With calipers im getting 15.75mm
what is the actual thread ?
There are no 19mm pins. Your options are:
5/8”
16mm
3/4”
28mm
Since you measured 15.75 that is in between 5/8” and 16mm The thread would be 5/8”-11 for either of those. My guess is you have 5/8” pins as there would be a little built in clearance from the nominal 15.875mm.