How much leeway with a semi mount

[bookworm240]

I have a center stone I want to replace on a ring. The stone is 7.8mm round. As I have been looking for stones,I am finding 7.5mm or 8.0 mm. How exact do I need to be with a stone size? Is each setting different?

 

[chrono]

It also depends on the depth of the stone. The best thing to do (if you have the setting in hand) is to bring both the stone and setting to a local jeweller for a fitting. If that is not possible, bring the stone to the jeweller anyway and get his recommendation on the setting size. He''ll be able to give you a better answer because he''ll see the stone in person and be able to take accurate measurements.