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Two-prong settings for irregular stones

Use sturdy, strategically-placed prongs to set a custom stone. 

Think two prongs can’t secure a stone? Think again!

There's a trick to using only two prongs to secure a stone to a piece of metal, and it’s not using epoxy. Our custom-carved spider stone has side indents that allow us to secure it with just two sturdy prongs. Because the prongs are made of thick wire, there’s plenty of room to file a little notch on the inside of each prong. Once pushed against the stone’s edge, those notches, coupled with the stone’s indents, help grip the stone securely. If your stone isn’t shaped like ours, you can still use the notched prongs to hold it, but you may need more than two.

SUPPLIES

Two faceted prong-set garnets accent a spider carved from a solid piece of Andamooka opal in this 2 x 11⁄2 -in. (51 x 38 mm) pierced pendant.

  • Large center stone 
  • Sterling silver:
    • 16-gauge (1.3 mm) sheet: 2 x 3 in. (51 x 76 mm)
    • 12-gauge (2.1 mm) wire: 1 in. (25.5 mm) or longer if your stone needs more than two prongs 
  • Two 3 mm round prong settings
  • Two 3 mm faceted accent stones
  • Chain with 2 jump rings at ends
  • Gorilla Glue or Elmer’s white glue 
  • Boric acid
  • Denatured alcohol
  • Abrasive radial bristle disks: fine
  • Burs: 2.9 mm setting bur, 2.3 mm cup bur, 1 mm cup bur 

TOOLBOXES

Sawing/piercing
Soldering
Stone setting
Finishing


NOTE: The center stone in this pendant was carved from a solid piece of Andamooka matrix opal, a type of opal that contains flecks of color throughout a background material.

To learn how to plan out, carve, and polish your own spider-shaped stone, check out the articles Carve a custom stone with your Flex Shaft, Part 1 and Part 2. 


INSTRUCTIONS
PREPARATION

Select your center stone
. Choose a large center stone that has a flat back. Our stone is a custom-carved rainbow Andamooka opal. It’s special because it has two indents opposite each other; these indents allow us to use only two large prongs to securely set it. To secure your stone with just two prongs, you could use any material with indents on opposite sides, such as rough drusy rock, irregular beach glass, or freeform cabochons. If your stone doesn’t have indents, you’ll need at least three prongs equally spaced around the stone to ensure that it’s securely set.

Draw your template. Draw a cross on graph paper, and center your stone on top of the cross. Trace an outline around your stone, leaving a 0.5 mm (or smaller) border around it. After you pierce the backplate, you’ll file this border away so the metal will be flush with the set stone.

Remove the stone, and then draw the outline and design for your backplate, using a pencil to mark all the areas you want to pierce. 

NOTE: 
Make all the supporting lines in your design of similar weight and no less than 2 mm (5⁄64 in.) wide, which is thick enough that the metal will remain durable after you pierce and file it. 

Note on your template where you want to position each 2 mm (5⁄64-in.) wire prong for the center stone. If you want to add accent stones, as we did, note the positions for the stones’ settings. 
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PHOTO 1
Draw at least one place to attach a jump ring so you can connect your pendant to a chain. We wanted two jump rings at the top of the design, so we drew two 5 mm (3⁄16-in.) circles of metal; they’re just large enough for us to drill a 2 mm (5⁄64-in.) hole to fit each jump ring.

Glue your template to the metal. Using white glue, attach your template to a clean, flat piece of 16-gauge (1.3 mm) sterling silver sheet. Use a small amount of glue, and smooth the paper with your fingers. Allow the glue to dry completely.
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PHOTO 2
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PHOTO 3
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PHOTO 4
BACKPLATE

Drill the areas to be pierced. Using a center punch on a steel block, create a dimple at each pencil mark. Place your metal sheet on a wooden surface, and drill out all the holes, using a #60 drill bit [PHOTO 1].

Pierce the design. Thread your saw blade through the drill hole closest to the center of the design. Carefully saw out that pierced section, following the lines on your template. When you’re piercing, always cut out the inner areas of a design first [PHOTO 2], and work outward from the center. Because the outer edge of the backplate provides extra support and stability, always saw it last [PHOTO 3].

TIP: Use sharp, high-quality saw blades to achieve clean results with intricate piercing work.

Remove the template.
To remove the glue and paper from the template, soak your pierced backplate in a solution of warm water and dish detergent. Using a soft bristle toothbrush, clean the metal thoroughly, and allow it to dry.

Clean up the backplate. Using needle files, clean up the interior [PHOTO 4] and exterior pierced edges [PHOTO 5] until they’re smooth. Sand the front and back of the backplate with sandpaper [PHOTO 6] until the metal is smooth and even.

Using a flex shaft or buffing machine and soft buffs, pre-polish the metal with white diamond or tripoli compound.

It’s much easier to get a clean, polished metal surface after soldering if you do a thorough polishing job at this phase. Make sure you’ve removed all traces of the sanding process so the metal is smooth and polished.
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PHOTO 5
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PHOTO 6
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PHOTO 7
PRONGS AND ACCENT SETTINGS

Drill the prong holes.
Place your center stone on the backplate, and carefully mark where your prongs will be. Remove the stone, place your backplate on a steel block, and use a center punch to dimple the spots you’ll drill for the prongs [PHOTO 7]. 

Place the backplate on a wooden surface. Using a 2 mm drill bit, carefully drill a hole for each prong [PHOTO 8]. 

Make the prongs. Using a jeweler’s saw, cut two 11 mm (7⁄16-in.) pieces of 12-gauge (2.1 mm) sterling silver wire. Use a coarse flat file to flatten the ends of each wire.

Insert the wires into the backplate’s holes until the end of each wire is flush with the back of the backplate. This will be a tight fit; simple pressure should hold the wires in position [PHOTO 9]. If it’s not a tight enough fit, you may have to adjust the position of the prongs in the charcoal block prior to soldering.
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PHOTO 8
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PHOTO 9
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