Correctly Sizing rings with stone settings

[Amy]

Hello, I am a new member to the forum and I just want to say that I really enjoy reading the posts and advice given. I feel that I'm learning a lot.
I started making silver jewellery 9 months ago, I have been trying to master making some basic bezel set rings but I have a question about sizing.
I am making a ring for a customer that will have a 16 mm round moonstone cabochon set in it, the shank is attached to either side of the circle bezel rather than being a complete circular ring that is soldered to the underneath of the bezel. It has been trial and error to get the sizing correct- as the shank is not a complete circle and has a flat section that is the bezel. I understand the principal of using the diameter for the desired size, adding the shank wire thickness and times by pie to get the cut length of the shank and this has worked fine for completely circular rings but is there a calculation for when there is a bezel setting within the shank?
The customer measured as a uk o and half and that corresponds correctly to my sizing mandrel- the ring fits her just right but when I check it on the ring mandrel it measures as a m and a half/ n .... Is there some magic that I'm missing or a gap in my knowledge? What if a customer orders the same ring but in a different size would I have to meet the customer and do a size check ? Ideally I'd like to make the ring and be able to check its size on my ring mandrel rather than doing a fit test. I've attached an image of the ring shank and the ring on the sizing mandrel in the hope that it might make some sense ??!
I'd really appreciate some advice, many thanks :D

[theresa]

In my opinion you need to file the back of the setting with a half round file and check the size. You can then gently hammer it with a rawhide hammer to make it bigger if necessary. Anyway, that's what I would do.
Perhaps a more experienced jeweller will advise you of a better way.

[Aurarius]

The customer measured as a uk o and half and that corresponds correctly to my sizing mandrel- the ring fits her just right but when I check it on the ring mandrel it measures as a m and a half/ n ....
That sounds about what you'd expect for a ring of that shape - in other words that it comes up that bit smaller on the ring stick but still fits. Fingers in cross section aren't round, unlike ring sticks.

[Dennis]

Hi Amy, what you are really asking is how to size a ring with a D-shaped interior and as you can't use a ring stick, this requires what I call the memory game:

First get some ring sizers, and ascertain the size as usual. Then try it on you own fingers until you find a knuckle it will just snugly pass snugly over. This will give you the size to use for an hour or so until your own fingers might change.
Be sure to remember which one of the ten useful first or second knuckles you have chosen.

To make the ring shank conform, solder one end, and then before soldering the other, adjust it until your chosen knuckle feels right in it.
After a while you get pretty good at this and can also use it for normal rings, for instance if they are wider than usual. Dennis.

[Amy]

Thankyou so much for replying Theresa, for future rings I might have a go at gently filing as you suggested- it might help the ring to slide over the knuckles a bit better too. All the best, Amy 😊

[Amy]

Thankyou that's useful to know ��

[Goldsmith]

Hi Amy, have you had a look at this old posting;http://www.cooksongold.com/forum/showthread.php?t=6295

It shows how I made a simple bezel set silver ring.

James

[Amy]

Thankyou so much Dennis- I understand. I'm amazed that you managed to summarise my rambling explanation with just one sentence �� I hadn't thought of it as a d shape but yes that makes perfect sense... ��

[Amy]

Thanks James, what a lovely ring...your post has been really helpful...
It's good to see how much you filed off the top of the shank before soldering the bezel cup to it, I like the little clamps too!
I've always started with d shape wire if that's the look I was going for so it's interesting to see how you have filed the rectangle wire to become d shaped - was that with just a regular straight file?
Also would you start half or a full size smaller ?
On my original post of the moonstone ring I wanted the light to come through the back of the stone so that's why I made the kind of step bezel setting ( think that's what it is ) , I guess I could have made a bezel cup and then pierced a shape out. Many thanks for your reply and the link to your other post. Amy