Please help with design specs

[sunshineandlemons]

Story problem of the day: I have twelve (12) 3 mm round stones and want to make a floral pendant similar to the design below except with a round center. What do I need the diameter of the round center stone to be? And who said you don't need algebra skills for important things later in life?

 

[0515vision]

I think 8.4-8.5mm stone but that’s not taking into account prongs, spacing and other practical life things. That’s calculated with circles touching circles.

Someone can check my work:
You have 12 3mm stones. So the circumference of the circle going through the center of those stones is 36mm. The diameter of that circle is 36/pi = 11.46mm. You need to subtract the width of the outer 3mm melee so 8.46mm.

Again these are theoretical measurements of exact circles. Life is so easy when it’s just on paper lol!

Edit: Realized the 3mm stones actually make a dodecagon and not a circle, but I’m in the general ballpark.

 

[maryjane04]

I was getting something made for my 8.8mm cushion/omc centre.

My melee are ever so slightly bigger than yours at 3.15mm average and this is what the jeweller mocked up.

Hope that helps.