Practical Stone Setting



Part 24: Setting Square Stones In Channels

NOTE: The procedures in this article are standard practices for bench jewelers at this time. If not executed properly, however, they can cause harm. Neither the author nor the publisher is responsible for injuries, losses, or damage that may result from the use or misuse of this information.

Safety Alert: Gravers and burs are extremely sharp and, if used improperly, can cause serious injury. Be sure that your hands are firmly secured and safely protected from the graver at all times.

“The path to mastery has many stepping stones.”
—Ancient Chinese proverb

After learning to set round stones in a channel (see “Practical Stone Setting—Part 19: Channel Round Setting,” JCK, October 2009, p. 104), the next step on the path to mastery is setting square or princess cut stones in channels. The procedures are pretty straightforward; the tricky part is cutting seats into the channel walls at the correct height and depth. Your first few attempts may be less than satisfactory, but with practice you will build skill and confidence.

A key concept in channel setting is that the stones rest on very small horizontal shelves or grooves cut into the vertical channel walls with burs. The opening of the channel should be slightly smaller than the stones. For 2 mm stones like these, there should be a gap of 1.75 mm. If the stone overlaps 0.25 mm on both sides, the seat on each side is only 0.125 mm deep. In other words, the seat is cut very shallow. This setting is accomplished best with such narrow ledges.

Prior to setting, measure and arrange the stones by size, with the two smallest stones reserved for the sides. Arrange the remaining five stones for the top from smallest to largest.

1. Here is a cast 14k gold ring from Stuller, along with seven matching square faceted stones measuring 2 mm. Five of the stones will be set into the top and one each down the sides.

  Fig. 1. Casting with seven 2 mm square-cut stones

2. Place the stones on top of the channel to determine the layout. It is helpful to rub some sticky wax along the edge of the channel so the stones stay in place. Use a scribe to mark the ends of the stones on top of the channel. Set a pair of dividers slightly larger than the height of the crown, from the girdle to the table when viewed from the side.

Use this measurement to inscribe a line inside each channel, to indicate where the seat will be cut. In this example from Stuller, the casting has a little groove in the metal already. Run the line down the side channels as well.

  Fig. 2. Marking the layout of the stones

3. Use a 0.5 mm round bur on each end of the two channels to make four indentations, one at the end of each line. These marks delineate the length of the channels and provide a protective pocket for the stones’ corners that is beyond what can be removed with a hart bur. Rest the bur on the metal for support when carving the indentations. Carve a little deeper for these pockets than the 0.125 mm channel depth that the hart bur will cut.

  Fig. 3. Burring a deep pocket for the corners

4. Relieve the support bars as necessary to create space for the culets of the stones to pass. This step depends on the mounting. If the metal crossbars are too tall, they will not let the stones slide along. Use a tapered cutting bur like a Krause bur for this task.

  Fig. 4. Using a tapered bur to lower the support bars

5. Use a 1.3 mm hart bur to cut the channels for five top stones. Holding the bur perpendicular and very steady, gently move the bur sideways into the metal wall, along the line made with dividers. Use a scraping motion to drag the bur along the wall, leaving a shallow groove about 0.125 mm deep. This is a very small horizontal gully, and it takes practice to get the feel of burring so precisely. Practicing on a piece of scrap brass will help you gain control before attempting this on your gold setting. At this stage, cut down the side channels as well because it would be difficult to get the hart bur into the end of the channel with the top stones already in place.

  Fig. 5. Cutting the channels with a small hart bur

6. Starting with the smallest stone, try to slide it into the channel from one end. If it does not enter, rotate the stone ¼ turn and try again because stones are rarely square.

  Fig. 6. Testing the first stone to see if it enters

7. If the first stone does not fit into the channel, use a flat graver to remove a very small sliver of metal widening the opening at the end, on one side and only as wide as the stone, and enabling it to enter.

  Fig. 7. Using a graver to open the channel

8. Place the first stone in the channel and use a brass or copper pusher to guide it along to the end of the channel.

  Fig. 8. Using a brass pusher to guide the first stone in the channel

9. Continue by inserting the second-smallest stone and continue in order of increasing size, making any necessary adjustments to the seats as needed.

  Fig. 9. Inserting the rest of the stones into the top channel

10. With all of the stones sitting in the top channel, tighten the metal with a hammer and punch. Carefully place the small rectangular face of a punch on the top, along the inner edge of one side. Tap very gently with a chasing hammer to bring the metal down onto the stones. Angling the punch a degree or two past 90 degrees can direct the force to the area closest to the stones without marring too much metal on the surface.

  Fig. 10. Using a punch to tighten the channels

11. Before setting the side stones, tilt the work in the block for better access. As in step 3, complete the channels by using the 0.5 mm round bur on each end to ­protect the corners of the stone.

  Fig 11. Burring the corners of the channel

12. Insert the end stones and tighten them as in step 10.

   Fig. 12. Tightening the end stones

13. Remove tool marks and even the surface with a #4 cut barrette needle file along the length of the channel, not over the stones. Ideally the two sides of the channel are co-planar, without any dips. Use a flat pumice wheel to bring the surfaces to a smooth pre-finish to be followed by Zam or Tripoli. Keep the surface flat. Do not over-polish and round the edges. Add a bright cut to clean up the edge and finish the surface before the final rouge. Check stones for security.

   Fig. 13. Removing the tool marks with a pumice wheel

14. Completed ring with seven square stones in a channel setting.

   Fig. 14. Completed setting

© 2011 Revere Academy of Jewelry Arts Inc.; first publication rights assigned to JCK magazine