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Half-Round, bur for Cab-stones


Instead of attempting to prepare the inside of a Tube Setting with undercutting or bearing-cutting burs, I came across an fantastic idea. This round bur that is ‘not bought in your tool supplier shop" but with a little modification of a round bur (of any size) greatly assists the preparation of the tube setting. The Cabochon stone will then nicely and tightly fit into the setting.
All it takes is a round bur of your choice and put the bur against the bench-grinding wheel and rotate it as it is grinding. The whole idea is not get the round bur too hot, or it will lose it’s tensile strength! Keep the bur cool to the touch. Just remove only half of the round shape of the bur as seen in the photographs. The remaining shape, will be the actual shape of the Cab-stone, interesting? the bottom of the bur as it is cutting will be the "resting seat’ for the stone.
So in essence, you are doing two things at once, creating a ‘curved inner-shape’ for the curved surface of the Cab. Then as well you are making a ‘resting seat’ for the stone, what could be easier? Have setting your Cabochon stone now!


Brilliant! Thank you!


Can’t wait to try this out. Great idea.


very nice Gerry. What simple and elegant way of making a job easier.


Why use a round burr at all? I was taught to use a 45-degree hart burr. Works great!


Thanks for your input. But with the curved
wall there won’t be any sharp corners!
If you are satisfied with your burs, so be it!
My technique works also fine, it’s just
another setting option.:wink:
Gerry! from my IPhone!


Typically, for setting a cabochon in a bezel I begin by using a small hart burr to set my depth, and then switch to an inverted cone burr to open up the setting, and cut the flat seat.
I then use whatever burr or graver it takes to get a truly good seat for the particular stone, making sure to mark and orient the gem in the same way each time as I make adjustments.
I can easily see how these customized round burrs would be another good tool/technique in the “box of tricks”.
I always like to experiment with the tools and techniques that others use or suggest.
Never stop learning and you will never stop improving.
Thank you for sharing.