What is a flush setting in rings?

3.2mm. That's the diameter of the diamond I set into a 5mm platinum comfort-fit band last Tuesday. The client, a mechanic named Ben, had been back twice already with bent prongs on a previous ring - once after catching it on a carburetor, once after a gym session he "forgot" to remove it for. He'd had enough. He walked in and said, "Marin, I want something I can't break." I handed him a sample with a flush setting.

A flush setting - sometimes called a gypsy setting or a star setting - buries the stone directly into the metal band. The crown of the stone sits nearly level with the surface. No prongs, no beads, no raised edges. The metal around the stone is hammered down over the girdle, creating a smooth, continuous plane. You can run your thumb across it and feel almost nothing but polished metal and the flat, glinting face of the gem.

Getting it right takes patience and a steady hand, but the concept is simple: drill a tapered seat into the band with a burr sized to the stone's diameter, drop the stone in, and then push metal over the edge. In my shop, I use a Foredom flex shaft with a reciprocating hammer handpiece to peen the surrounding gold or platinum down. Some jewelers still use a manual burnisher and a chasing hammer. I do for antique repairs. Once the stone is locked, I clean up the edge with a tiny graver - a 90° - and finish the surface with pumice wheels and then polish. The stone isn't going anywhere. A .75 carat diamond, flush-set into an 18k yellow gold band, will survive a lifetime of engine work and eight-counts of jumping jacks. Ben's has made it six months now without a scratch.

The trade-off is light. A flush-set stone only shows its face. No pavilion angles catching light from the sides, no open culet, none of the fire you'd get from a prong or trellis setting. That's fine. If you want sparkle, get a prong-set solitaire. If you want a ring that can't snag on a glove, a seatbelt, or a patient's bedsheet, a flush setting is about as practical as it gets.

What stones work? Diamonds, sapphires, rubies - anything with a Mohs hardness of 9 or above. I'll set Moissanite flush too, though I'll warn you the higher refractive index can make it look a little glassy when all you see is the table. I won't set emerald, opal, or any softer stone flush. Don't ask. The pressure from the hammering can crack a stone with low toughness, and the repair means cutting the ring apart. I learned that one the hard way on a 2008 custom job with a client's heirloom emerald. She was insistent. It cracked on the third tap. I still think about that.

Resizing is another thing. A flush-set band can be sized up or down maybe half a size without jeopardizing the stone, as long as the jeweler knows to avoid the area right around the setting. Go beyond that and you risk distorting the seat and loosening the stone. For benched life, I recommend clients measure their finger accurately twice - once in summer, once in winter - before committing.

For anyone who works with their hands, I'll pick a flush-set diamond over a prong-set one every single time.