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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!

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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!

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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.

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I LOVE this idea. How does it compare to using an inverted cone bur with a Setter’s Helper?

My half-round but has the same curved smoothed surface as a Cab stone.
Those inverted burs do not have the same shape. My designed bur can be created on any bench-grinder.
I’m not familiar with the others.Try them, you might just like the shape and curvature. These will indeed match the bur to the shape of the stone.
Gerry Lewy

“Gerry, on my iPhone”

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I enjoyed your featured article on bezel setting. But I was wondering about this as well. How do you shape a bur to the same contour as a cabochon without grinding off the teeth that make it work? Or are you just grinding off the tip of the bur without changing the shape of the rest of it?

I’m removing less than half of the round shaped bur. But just stopping short of removing the curvature or shape of the Cabochon stone. This is quite a delicate process, and it does take some practice.
REMEMBER, keep rotating bur and keeping it ‘cool to your touch’ if it changes colour to brown or black, you’ve burned the bur.!!!
If this happens, the bur steel is now softened and it won’t be useful for long durations.
Have a little jar of water nearby and immerse your bur into your water, as often as you can. If it’s getting hot, stop and keep it cool to your finger…Gerry Lewy!

I use a modified round burr like this to clean up the inside solder joint between a bezel strip and the backing plate…Rob