I have a Jones and Shipman boring head, on a 40int arbor, I'm looking for a 30int arbor, it has a 1" unthreaded boss that centres it with 4 bolts that hold it on, all searches for this turn up fine threaded Chinese import style arbors, does anyone know where one could be bought? Maybe I'm not searching the correct name for this style of arbor or something?

Emgee, the head itself has 4 long grub screws that screw into the head, the the arbour is held on by 4 thin nuts that hold it on, you can just see in the photo.

Old mart, I did actually see that while looking, it's probably what I'll end using, as it's about the same cost of buying a good lump of tool steel to make into a straight shank arbour.

I just had a look through the sellers other items, they also have a m20 threaded version, I messaged the seller to ask the diameter of the location boss above the thread, if it's bigger than 1", that would be ideal, I could just cut the threads off then turn the boss to fit, and drill 4 holes as the original to hold it.