Sometimes we find a stone that has a non standard size or shape. This rose quartz is a good example. It is a high dome cabochon that has lovely color and is 19x22 mm in size. A standard calibrated mounting is not available in this size. So we will make one to fit. Because the base should be fairly thick and sterling is expensive in 20 gauge I chose single clad silver filled sheet http://www.riogrande.com/Product/3-1-10-Silver-Filled-Single-Clad-Sheet-20-Ga/105379?pos=3. This is bronze with a layer of sterling 10% by weight on one side of the sheet. In the picture you can see the bronze side. I also used gallery wire 4mm wide and a double half round sterling wire for the shank.
First step is to cut a piece of gallery wire close to the circumference of the stone making sure it will be able to overlap by 1/4 inch. Form it roughly to the cabochon by wrapping and pressing it to the stone.
Next using a sharpie fine point marker and holding the wire wrapped around the stone mark the length on both ends at once.
It should look like this. The pattern wont always match but don't try to make it match because it wont fit the stone if you do.
Here it is sitting on a ceramic soldering taper. I soldered the bezel with hard solder. You will want to have 3-4 grades of solder to do a project like this at first because the hard melts at a higher temperature than the medium which is used to solder the bezel to the plate..and use soft or easy for the shank attachment. This keeps previous joins from coming apart.
next insert the stone and form the bezel to fit exactly by pushing on the base of the bezel all around.
Next trace the shape loosely onto the backing sheet and cut it out. I use a jewelers saw for this...shears will distort the metal and you want this to be perfectly flat to solder on the bezel.
Set the stone and bezel on the cutout sheet to confirm it fits The remove the stone and pickle both pieces to clean and prepare them for soldering. I place the pieces on a wire grid on top of a soldering tripod..you can use a charcoal block or ceramic soldering block as well. Place chips of solder around the inside edge of the bezel wire and apply flux to the whole thing. Then heat the base with a soft flame and when the flux melts begin to move the point of the flame around the inside heating the area to be joined until the solder flows.
You can see the solder flowed well and has round all around the edge attaching the bezel to the plate. Put this in the pickle pot and when it is clean the silver will be white and ready for the next step.
I chose this traditional double wire and bent it around the ring mandrel after sawing through the center to form the Y shape which will be supporting the large stone.
Here the shank wire is prepared and the points of attachment filed flat. At this point it is good to file the ends smooth and remove sharp edges.
Place it on the base and using easy solder attach the shank, then pickle again and begin the finishing process. File first, any rough edges then using emery boards or sandpaper in 400 grit wrapped around a stick smooth the file marks away. Then using your favorite rotary tool like a heatless mizzy wheel polish all surfaces.
The inside should be finished with clear or milky stones because the surface will show through the stone. Here I used a rotary nylon brush and tripoli to give a smooth finish.
The all that is left is to mount the stone. If you are successful in making the bezel the right size the stone should sit with no wiggle in the bottom of the plate. If you are using an opaque stone glue can be used.. In my case I used the tall prong tops to hold the stone by pushing them against the stone all around. I always start at 1-3-6-9 around the clock then when the stone is locked in do the rest of the prongs until the stone doesn't rattle.