Archive for April 2010 | Monthly archive page

Hart bur is a cutter that is the exact size and shape as the gemstone.

We have begun producing our own bezel settings in-house. These are the silver (or gold) tubes used to hold a gemstone (like in the eyes of one of the birthstone Thor’s Hammers). So much work was going into fitting the commercially made bezels that it became time and cost effective to make them from raw materials ourselves. This will also help to keep costs down in a market of rising precious metal prices.

To start out, a silver rod, slightly larger than the diameter of the stone it will be setting is selected and carefully straightened. Since we work with a lot of 3mm stones, the material selected is 6 gage wire; about 4.1mm.

 

A 6 gauge sterling silver rod is selected as the raw materials to make bezel settings for this 3mm emerald.

 

The silver rod is taken over to the micro lathe and a facing cut is made across the cut end to clean up the part where it was sheared off the spool of wire.

 

A facing cut to clean up the end.

 

Next the wire is turned into a tube by center drilling and then boring a hole into the end of the rod. The drill bit is held stationary in the lathe’s tailstock chuck and the workpiece is spun at high speed to produce a smooth internal bore. This will provide the clearance for the setting bur to do its work and also will make the bezel hollow so light can pass through it to back-light the gemstone that will be set in it. The diameter of the bore is not critical, as long as there is enough “wall” left to form a step to set the gemstone on. Here a #42 (.096″) drill bit is used.

Boring out the wire to form a tube

With the tube formed, the next step is to form the seat upon which the gemstone will rest. This is done with a hart bur. It is a tiny cutter that is the exact shape and size as the stone it is cutting for.  It is held in the tailstock chuck and introduced to the spinning silver tube just as with the drilling operation.  It is plunged in so that the back of the cutter head just passes into the tube. This leaves enough wall above the top of the gemstone to burnish down and secure the stone in place.

 

Hart bur is a cutter that is the exact size and shape as the gemstone.

 

After a light polishing , the finished bezel setting is “parted off” from the tube with a cutter mounted in the lathe’s cross slide. A light filing is all that is needed to remove any burs that might have been raised in the fabrication. It is then ready to be soldered into place on a piece of jewelry and a stone set in it. The whole process takes about 5 minutes.

And what about all the silver that is being cut away? Nothing goes to waste. That is collected together and will later be melted down to be cast into a pendant or something.

 

Parting off the finished bezel on the lathe.

 

A closeup of the finished gemstone bezel setting ready to be soldered onto a piece of jewelry.

The bezel setting soldered into the eye of a raven necklace terminal and set with a 3mm emerald birthstone.