Marcus,
The stud that came out will be one that threads into the hub. When installed the back of the stud is deformed so that it doesn't come out.
Unfortunately when you then drag the deformed end through the hub it often damages the thread......I have a hub with two studs out where one hole is OK the other has no thread so the hub is probably past saving.
Welding cast to steel is a possibility, not ideal though (and certainly not 'original')
Thread is 9/16" BSF, I was chasing a tap today and they are about $50 each so now on the lookout for a NOS one as I have a few nuts that need to have the threads cleaned up.
I'll be in the shed tonight but I'll try & remember to take my phone with me.
Colin

