The entire process involves a total of 42 steps, if gold is used. This overview is simplified for stone - to- stone inlays, which are far simpler and more popular.
Slab the chosen host material to about 3/8 inch for pendants and 5/16 inch for earrings. Carve the host to the desired shape and size with a 4 inch trim saw blade, and bevel the edges. Pendants require a "hanging" hole for a bail or chain. Leave the areas where the hole will be, FLAT. (Fig. 1). Grind the piece to the desired shape and contour it on the most aggressive lap set wheel. With an aluminum pencil, scribe an outline of the inlay hole to be excavated and mark drill points on each side of the flat areas (Fig. 1).
Excavation requires the use of five diamond burrs of different sizes, shapes, and grits which are available as a set from Lasso Diamond Products (Fig. 2). Use the burrs in the order shown to excavate for the inlay (Fig. 3). To make the "hanging hole”, use a 2mm diamond core drill from each side's flat area (Fig. 1) so the two holes meet in the middle. To drill or excavate with diamond tools, use light pressure and lots of water. Enlarge the "hanging hole" with the bead reamer (Fig. 2), working from both sides alternately .with light pressure.
The inlay process is next. Select and cut an opal to about 1/8 inch thick. Orient the opal so it flashes best with the pendant (or earring) held vertically. Mark the opal's top, then start cutting it on the 240 grit lap wheel to fit the inlay hole. Work slowly, bit by bit, counter-clockwise around the opal (Fig. 4). Grind each small section to fit into the inlay hole as perfectly as possible before moving on.
Taper the inlay sides toward the bottom slightly to allow the opal to fit tighter into the host as it settles. When the inlay fits perfectly, stop working on it and decide whether to finish the piece as a flush or a cushion inlay. If the opal barely protrudes above the level of the host, choose flush. Clean both with steam or acetone, and epoxy the opal in with Devcon clear (Home Depot). Fill the hole and insert the opal, squeezing out any air bubbles. Leave overnight, then finish the piece as any cabochon.
For a cushion inlay, use the aluminum pencil to mark around the opal sides where it and the host excavation meet. Remove the opal and drop it onto a finish nail with Superglue. Contour cut the opal down to the aluminum line, then pre-polish and polish the opal as any cabochon. Do the same with the host, and epoxy the two together as above. Clean the piece well with acetone before the epoxy sets. When the epoxy has set, soften the epoxy by immersing the piece in acetone for a few minutes, then scrape off any excess epoxy with an X-Acto knife. Taper the sharp edges of the "hanging hole" with the No. 4 burr. For a professional touch, polish the inside of the hole using 1 1/2 inch pieces of bamboo skewer and successive diamond compounds of 325, 600, and 1200 grit. Use different pieces of bamboo for each grit, and clean the piece with soap, hot water, a toothbrush, and Q-tips between each grit.
For post earrings, before inlaying the opal, drill a 1mm hole through the piece near its top or through its inlay hole. Melt a small ball by heating the end of a 20 - gauge piece of round 14k gold wire. Cut the wire to its appropriate length for French hooks or posts Getting "stuck" is certain to happen. We will be standing by to help any who become stranded. Good luck.