Inverted cone burr for cabochon setting

[Claire D]

Yesterday I decided to teach myself how to tube set some cabochons. I find using bezel strip really fiddly on small (4mm and smaller) cabs and end up wasting it. It all went according to plan, I drilled out the seat with a ball burr and then remembered something I'd read on here about levelling the seat off with an inverted cone burr, or a wheel burr. I just wanted to ask what the best size would be to get, and a good place to get them from? I'm setting 4mm cabs at the mo but it seems pretty much impossible to find a 4mm inverted cone burr! Would a smaller size work?

Thanks!

[Wallace]

Hi Claire,

for a 4mm and smaller, you can grind down your ball burrs to make them half burrs and use them to help. The half burr will not cut underneath only to the sides where it touches. I just use a ball burr or a setting burr, even with cabochons as either work well. Just go slowly, keep checking your depth and use some lube to stop any 'chatter' (jagged marks that can be left by burrs).

[Claire D]

Thanks Wallace - how do I grind down a ball burr please? Sounds quite serious and not sure I will have the right tools for that!

[Wallace]

Thanks Wallace - how do I grind down a ball burr please? Sounds quite serious and not sure I will have the right tools for that!

you can use one of those little separating discs - usually come in a box of many! They can get quite hot, so go slowly and dip your burr in water to keep it cool as you take off the metal.

edit, I think Cookies sell them, they fit onto a screw on mandrel and are a reddish colour. They are quite fragile, and probably why they are sold in a box of many. I have found some (which I thought I might not). PM me your address and I will send a few out on Thursday

[Dennis]

Yes it is quite importat to get a good seat for small cabochons, as they have a habit of turning upside down during setting.

I find these burrs useful for perfecting the seat after using a ball burr, partly because they also give an idea of depth. As they are fairly expensive, I turn them by hand using a universal handle:

https://www.hswalsh.com/product/frai...se-select-size

Universal handle; Cookson999AZM. Dennis

[Claire D]

Ah, yes that's what I was looking for thanks Dennis. Could you give me any idea of the size I'd need for 4mm cabs? Do I need to try and match the burr size to the stone size?

Thanks.

[Dennis]

Yes Claire, make a start with a ball burr which can be slightly big, but not inserted to its middle. Then go for the setting burr to match the stone. if you turn it by hand with a tiny amount of oil, it will be very accurate.

I hope you are using callipers too, because stones of a nominal size will vary slightly. Dennis

[Claire D]

Yes I had discovered a while ago that two 4mm turquoise cabs were in fact more like 4.5mm! I am checking the sizes of everything now, and it's quite surprising how much they do vary (annoyingly). I quite like using a burr in a pin vice for finishing off, feels like I'm a bit more in control of it. I'll try and get some of those wheel burrs and let you know how I get on.

[mikethejeweller]

Excellent tip regarding grinding down a ball burr, never heared of that before but that could be perfect for certain jobs. I have one or two of those burrs from Walsh, they also come in handy now and again.

[janiebyford]

Can anyone help me. I am trying to set 3 cm opal cabouchon said into a silver bangle. I would like to use a gypsy setting and have been practising with absolutely no success. Any tips from anyone or should I try a different setting technique ?


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