Because most gemstones cannot withstand the heat of soldering, most gems are cold joined. Cold joining is the technique of using mechanical, rather than heat-induced, connections to bind two objects together. There are several ways to set stones. Though the type of setting used is based on the stone, the two most general settings are bezel and prong. A bezel is a strip of metal that surrounds a stone and is pressed down over its sloping contour to secure it in place, while prong settings are mountings in which "fingers" of metal secure the gem. There are several ways to make each of these types of settings. Bezel come as box, shelf, fancy, step, reverse, tube and gypsy setting. Prong can be made as crown, fabricated, pedestal.

The type of stone you are using plays a big part in what kind of setting you will use. For instance, tumbled stones are free-form lumps that are mass-finished by being tumbled in a drum with water and abrasives. Although they can be pretty, they are difficult to set. Cabochon stones, or cabs, are smooth, convex forms, most often with flat undersides. Of any shape, they look like a rounded mound from the side. Although some cabs are translucent, most are opaque. A faceted stone is translucent or transparent and come in a variety of shapes. Although they are no more difficult to set than a cab, precision is required to properly complement the extreme geometry of the cut.

Here is a basic guide to making an asthetically pleasing setting for any stone:

1. The stone must be securely held.
2. The setting should complement the stone.
3. The setting must not snag on clothing or hair.

The setting should relate to the piece around it.

Both bezel and prong settings each have their own requirements. Here I will list the basic steps to make a box bezel and then the three main guidelines for making a prong setting.

Making a Box Bezel

1. Fit the bezel to the stone.

Bend a loop of flattened wire around the stone and solder this bezel closed with a tiny piece of hard solder. Fine silver is good to use because it it malleable enough to press safely over the stone, though sterling, gold, copper, and brass can also be used. Make sure that the stone fits like a hand in a glove into the bezel. Time spent making it right at this stage will save twice the time fixing it later on, not to mention making a better setting.

2. Solder on the backing, trim and clean the seam.

After testing the bezel for proper fit on the stone, you are ready to solder it to the backing sheet. The size and thickness of the backing sheet depends on the size of the stone used, but a stong under 5mm might be set on 24 gauge sheet, while large stones would do better on 20 gauge sheet. After soldering, trim away the excess sheet with a saw or shears. You can leave an edge to decorate, or just trim up to the bezel wall. File and sand the seam until it disappears. If you are attaching the bezel to a piece of jewelry, do it now and use easy solder.

3. Adjust the height of the bezel walls.

Determine height by laying the stone next to the bezel, taking the thickness of the bottom sheet into account. If the bezel is too tall, either trim it with a file or insert an interior bezel or piece of sheet to raise the stone.

4. Set the stone.

On a cushioned surface, press the stone into place. If it doesn't fit, examine the problem and, after removing the stone, file, sand, or scrape the bezel to fit. Now, reset the stone and using a bezel pusher, press the bezel over the stone at each of four compass points (ie. N, S, E, W) Continue this back and forth method to evenly distribute the bezel closure and until all the bumps have been pressed down. This process could involve anywhere from 12 to over 100 pushes, depending on the size of the stone, height of the bezel, and power of each push.

5. Smooth and shape the bezel

Use a fine needle file or pumice wheel to smooth and shape the bezel. Never use sandpaper of any grain near a stone! After filing, use a burnisher or leather polishing stick to give the setting its final finish. Be patient, though. After putting in so much time, don't detract from the gem by hurrying through the cleanup.

Prong Settings Guidelines

1. Use strong metals.

Because prongs do a lot of work with a small amount of metal, the metal must be tough. Copper isn't hard enough and brass and sterling should only be used when the size of the stone allows for a hefty gauge and broad shape. Although practicing with sterling is a good idea, most prong settings are made of gold.

2. Prongs must be symmetrical.

To look good and assure a proper fit, prong settings must be perfectly accurate. They allow for no flaws, so it is important to stop after each step and examine your work from all angles.

3. Fit is critical.

A proper fit refers to both diameter and depth of the stone, as well as the contour of the pavilion. Irregularities in stones make setting them more difficult, so be familiar with them, exploring especially the girdle and the area just below it.
 

OOC Sources:
"Jewelry, Fundamentals of Metalsmithing" by Tim McCreight
"Beginning Jewelry" by James F. Warwick
"The Design and Creation of Jewelry, 3rd Edition" by Robert Von Neumann