Hello everyone. New here and happy to have joined 
I’m working on a solitaire sunstone channel set ring in Sterling and need some help. The stone is a 7mm round and as a larger solitaire setting the channel will not be able to be squeezed tighter after seating the stone. The metal is just too thick. I’ve attached a couple of images.
Thus far I’ve made decent seats (for a beginner) and have worked one deeper to allow room for the stone to slip in on the other side. Currently I’ve cut about as deep as I’d like to but the stone still sits with the girdle just touching the top of the channel. Definitely too tight to force down into place without breaking the stone.
So, do I continue cutting one seat deeper until it nudges into the opposite seat? I’m worried I’ll have an uneven setting with some back and forth slop on the stone. Or, would the hammering down of my channels correct this possibly? Thanks for your time folks 
Sunstone, like all feldspars, has poor toughness. An unprotected girdle, as in this design, is a recipe for a broken stone.
I’m definitely aware of its lacking in hardness. I would not attempt this for a client. It’s for my wife and will only be worn “out” if you will, so not really concerned with the potential for damage. Just hoping to get it into place safely.
Welcome
Well, how much do you value your sunstone? In my experience sunstones need a tremendous amount of care in being set and worn. Saying that, although the mounting you have chosen is very popular, there are some structural issues with this particular design that puts the stone at risk.
The ring design has heavy sides of the ring and the bridge under the stone is much thinner next to the heavy walls holding the stone. Most rings, over time bend and the ring will bend where the metal is the thinest, sometimes cracking. This will loosen the center stone, which puts the stone at risk.
When we would do similar designs, we use an arch under the stone and have arch thick enough where that area won’t bend. It Isolates the stone and makes it much more secure. From what I’m seeing, I’d allow more distance between the walls, where the stone just barely doesn’t fit, so when the seat is cut, the stone will drop in.
Now comes the harder part, hammering the metal over the stone to secure it. This is where the sunstone is most at risk, probably as much as from wearing. There is hardness and durability, or toughness. Hardness is the ability to withstand scratching. Durability and toughness is the ability to withstand a blow or pressure. Sunstone is neither hard nor durable.
When we would set this style of ring up for hammering the metal over the stone, we would build up the channels with additional metal. This additional metal, in the process, will be compressed over stone, when hammered, which enables the metal to be cleaned up and made to look like the stone is suspended between the walls. If you don’t add the additional metal, the clean up and finishing will be more difficult and will not look as clean. But a slip with a tool, or a graver, … a soft stone or a stone that’s not durable will be toast.
Sorry, this probably isn’t what you want to hear.
Hello Hendrijk,
Welcome to Orchidland!
Here’s an idea for your setting. Cut the channel on EACH side of the mounting ALL THE WAY to one end of each side. The goal is to slide the stone in from the open end. No pressure on the stone. It may even rotate (depending on the precision of the stone’s cut) a bit.
When the stone has been slid into place, close up the open ends to trap the stone. If the mounting has a metal “tag” protruding at the edge of each open channel, that “tag” could be forced over and used to plug the open channels.
This mounting has been used with diamonds - the open channel ends are soldered closed. Soldering won’t work with a sunstone, but perhaps a laser welder?
You must share your solution when the piece is finished. Lucky your wife!
Judy in Kansas, where the weather is lovely. The art show I did yesterday, suffered in attendance because so many people were enjoying being outside.