Hi Michael,

Yes, I used Network to create the top half of the ring, then used the Finger size to Trim it & get the required shape.
I then found those arc shaped Edges I needed to form the bottom section from that trimmed Network Surface by using Copy & Paste.
Those newly made Curves would be the Profiles for a Sweep to create the lower section which would be the rings band.

So obviously that difference in the Network tolerance & Sweep tolerance was what helped to throw the Join off.
Not a big problem, at least I know I can work around this by scaling the model, Thanks again for all of that tip.

regards Colin