Resetting Diamonds In Old Jewelry
We are often approached by customers asking us to remove a gemstone or diamond from one ring and place it in another ring. In many instances this a straight forward repair and can be done with a minimal amount of trouble. But there are also times when this is simply not possible and requires replacing the head or rebuilding the prongs. In some cases it's simply not possible at all.
This first set of pictures shows a diamond set in 4 prongs. The space that is cut into the prong for the diamond is called the seat. Generally the seat is cut half way or less into the prong. This removes enough metal from the prong to allow it to bend over the stone and still be strong enough to not break. This is where the first problem can come in. We see a lot of seats that are cut far more than 50% making resetting with that head impossible. The tip simply breaks off when it is bent back.
The angles of the cuts are designed to fit each diamond. The pavillion, bottom, of the diamond sits flat on the seat and the prong tip that is bent over the stone also sits flat. This secures the diamond properly and helps reduce the chance of snags and breakage.
Here we see what happens when you put a smaller stone in a larger head that has already been cut. For this demo I started with an 8mm stone and then replaced it with a 7mm stone. Just a 1mm difference. If we use the original seats that were cut for the larger stone we get a pinching action on the stone. You can see the gap that is now under the stone so that the pavilion is not supported properly. You can also see the gap above the stone. This leads to loose stones at best. If pressed down to hold the gemstone more securely you run the very real risk of snapping the girdle of the stone.
Instead of pinching the new stone we can sometimes recut the seat and reset the diamond. But this leads to it's own problems. The left over old prong needs to be removed to give us a clean prong to use for setting. This can leave us with a very small prong tip that may not be secure enough to hold the stone, or, to make a longer tip, we have to cut more than 50% of the prong which leaves us with a weakened prong.
Here we see what happens when putting a larger stone in a setting. Again, I am just going up 1mm. If we leave the prong angles alone the stone pushes through the prongs and the setting becomes worthless. So the first thing that needs to be done is to bend the prongs out. As you can see in the third picture we are now supporting the pavilion with just a single point rather than a flat surface. This leads us to the same problem as before when bending the prong tip over. We rung the very serious risk of chipping the girdle. Adding to this problem is the new prong angle. With the prongs being opened up like this they are easier to bend out of shape and can cause you to loose a stone more easily.
And finally I want to show an extreme example of a fat bellied stone. From here you can easily see what can happen if the bottom of the stone is shaped different than the original stone in the setting.
As I stated in the beginning, there is a lot that we can do when swapping stones from one setting to another. But it is important to understand the variables that can affect the success of this type of repair and why in most cases it is better for your jewelry to replace or rebuild the head rather than "trying to make it work".