Half-Ground Round Bur
2 Minute Read
There are times during the setters workday where there is a need for a specific tool, but there nothing is available at the local tool supply store. With a little creativity you can modify many of the tools you have to make a wide selection of newer and improved tools that will accommodate any setting situation.
One requirement of a stone setter is to make a bezel "fit" a cabochon stone. The usual procedure is to grind away much of the bezel wall and then try to push the metal over. This is an absolute waste of precious metal, metal that has to hold the stone, and accommodate the clients wear and tear for years to come.
This newly modified tool is very easy to describe. It is a half ground round bur. I have selected many of my rarely used larger round burs just for this simple procedure. The actual grinding is done with the use of a simple bench grinder bought at the hardware store. Hold the bur in a wooden handled mini-vise, and apply careful pressure to the rotating grinding wheel. Slowly rotate the bur against the grinding wheel until you reach the final shape - a "half-round" ball bur.
Make sure the bur does not "burn" while grinding. If the bur is overheated it will lose its temper rendering it useless. To keep this from happening, always have on hand a little jar of water to dunk the bur into to keep it cool to the touch.
What you are creating is an "inner surfaced cutting angle" that will match the gentle curve of the cabochon stone. Using this bur is definitely a saving of metal and labor, and will ensure a clean corner around the base ofthe bezel, as well as the correct curved angle for the higher section of the bezel wall, thus ensuring a well fitting shape to the stone.
For the initial shaping, you should use a smaller sized bur, as this will initiate the lower edge of the cabochon. Then select a somewhat larger "Half-Round" bur to finish cutting the bezel wall matching the curvature of the stone. Once cut, fit the cabochon stone into the bezel. If the stone does not sit PERFECTLY, remove the stone and check with your 10X power loupe to see if there is a slight aberration to the seat. Then carefully grind away the section of the bezel where the stone is hitting.
I will not, in this article, attempt to describe how to set a Cabochon stone, but only describe to you, the setter/ jeweler, another great labor saving tool you can easily make in your shop. There is one thing I would like to emphasize however, and that is that it is important that you bright cut the inside of the bezel. I always make an honest effort to clean the top edge of the bezel to make the finished product presentable. After the stone is set, I clean the bezel with a #40 Flat Graver, or my "Right-Sided" #2, Onglette to create a "Bright Cut" around the top of the bezel. It's the final touch that shows best, and is the mark of a professional tradesman!
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With over 40 years experience as a stone setter, Gerry Lewy is known throughout the diamond setting community. Gerry started his 9-year apprenticeship with a jewelry manufacturer and tutored by a gentleman ‘setter’, in Haddon Gardens, London. Gerry has redeveloped himself into more than a master setter, his purpose is now to be a teacher of the art as well.
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