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Setting flat oddly shaped cabochons on rounded surfaces

Hi All,

I am probably going at this all backwards so I need help! I have made a bracelet with a sweat soldered pattern (not really necessary information but…) and I have crudely filed down my bezels to conform to the surface of the bracelet… They are odd shapes, large enough and are placed horizontally so they take a lot of conforming… (anyone with really good techniques for matching a curve, please let me know.) Now I want to set the different cabochons which I have shaped and I’m trying to figure out the best way to back them in addition to grinding a curve into them (perhaps) so they are stable and will not crack. My first idea is to solder an inner ring for them to rest flat on but I wonder if there is other material I should put in there just to give them more support or if I can use a packing material to provide a flat surface. I know this is odd… very odd designs for sure. Any help is greatly appreciated.
Thanks!

Hi Marge,

I have an odd suggestion for your odd circumstance that might do the trick.

I had a customer who requested a pendant for a relative using a cab that he had cut. I went right to work and when attempting a trial fit I discovered that the cab was rocking. It had a slight high spot on the bottom. I was careless in not checking sooner because he’s a very experienced lapidary and I assumed that the cab was perfect. He admitted later that it was one of his very first cabs and had forgotten that it had that flaw.

What to do?! I didn’t want to scrap and remake the piece. Eventually I settled on one of the sculpting materials (like Sculpey) that can be baked in an ordinary oven. I placed two small pieces on either side of the high spot and pressed the cab down to flatten them. When I had a good, supporting surface I baked the clay in the setting in the oven. Setting the stone went fine.

Before I decided to do this I had examined items that our children and I had sculpted many years ago when they were young. We had used several different products and all were still strong and stable.

Gary

Thank you Gary!

I did some more research after I entered the question on Orchid and I found these products called Apoxie Clay and Apoxie Sculpt. Do you know anything about them? The users said that they had switched to these after using polymer clay. I hadn’t thought of using polymer clay like you suggested but that seems to be a perfect solution. Thank you! One question, did the polymer clay shrink after baking? Did you bake it in the bezel setting or flat after shaping?

You’re welcome, Marge. The polymer clay showed no shrinkage and I baked it in place in the setting. I am not familiar with Apoxie products.

Thank you Gary, that’s a great help!

HI, add find saw dust in bezel to level .

Thank you Tony! I have taken apart some 1st nations cabochon set rings and was unable to identify the material below the cabochon that was used to level it but it looked liked it might have been fine saw dust as you suggested… is that right? Do you know where I can find it or do I need to make my own?

I have worked on several pieces of Native American turquoise jewelry and found sawdust inside the bezel for leveling. Sometimes the cab may also have hardened liquid steel added to the back of an irregularly shaped cab to level it out. I suppose that this could also be used to conform to a curved shape. Fitting a bezel to a curved surface is a chore. I have done it, but I don’t like to. Shimming the bezel with a wire insert is the traditional way to go and as long as it is soldered in well should be fine. You might leave your bezel high until after you add the insert and then trim the bezel to fit once the stone has a seat. You can’t easily undo the insert once it is soldered in place. I have also poured resin into an irregular bezel like you describe, but it tends to either dome or ride up along the bezel edge, so it will need to be trimmed. You have lots of options. Good luck…Rob

Indeed! Thank you, Rob… since you have done this before, do you have any tricks for mapping out the curve before shaping the bottom of the bezel?

Other than trial and error, I really don’t have a suggestion. If I were to try this again, I would explore using Plasticine or some other type of clay to make a mold of the stone and curve that you are trying to fit and then translate this into a fitted bezel. Form a solid clay bezel in the shape of the stone and transfer the shape to an index card cutout and then metal once the card seems to fit the curve of the bracelet. Keep in mind that, once you assemble the bezel to the bracelet, you are defining the shape of the bracelet and it will be very difficult to change that shape without damaging the bracelet should it be necessary. In other words, make sure to shape the bracelet to the wrist that is will be worn on before you add the bezel. Good luck, if I have more thoughts, I will pass them on…Rob

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Another idea - unless the bracelet has a compound curve where the stone will sit you can try this:
Get close to the bezel shape you’ll need (as described in earlier posts) and cut the pattern from cardstock. Wrap it around the cab and tape edges together to test the fit on the bracelet and modify if needed.
Using the pattern, cut the bezel material a bit taller than you need.
Place an abrasive sheet over the bracelet curve and tape the edges to bracelet. Now you can sand the bezel base on the proper contour.

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Thanks, Rob. I did try shaping a wire that fit around the stone and bezel to the curved surface and then put the wire back over the bezel and trace the outline on the bezel… it came closer but not good enough. Plasticine may be the way to go… I’ll try it out, thanks!

  1. Thank you Pam. I like the idea of putting an abrasive over the curve I just wonder if I could find one thin enough or maybe use sticky backed sanding material. Unfortunately all of my curves are compound more from the deforming after sweat soldering the top layer and bending because the bottom layer is not at the same level, it tends to bow a little and when I flatten it for the bezel, well… I’m thinking that problem arises because my bottom layer is too thin or the open spaces of just bottom layer are too large. Also I texture the bottom layer before sweat soldering the top and I’m wondering if the texturing weakens it further. The problem is, I want the cabochons to sit on the bottom layer so they are recessed. Maybe I just need heavier material. Any special tricks to forming a bracelet that has two layers?

For mounting a bezel to a bracelet I have taped 400 grit wet dry sandpaper to a bracelet mandrel that you used to form the bracelet. Rub the bezel back and forth until you get the bezel to fit the formed bracelet. You will need a bezel that is tall enough to fit the curved bracelet and the height of the stone. I fill the voids on either side of the bezel with saw dust to form a flat level area for mounting the stone. I have also used the same procedure with rings by attaching sandpaper to a ring mandrel to sand a curve into the bezel for mounting on the ring shank.

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Wow, Patrick, thank you so much! That makes perfect sense to use the mandrel to shape the bezel, that way I don’t have to worry so much about adding to the dimensions of the curve with the sandpaper. I’m still wondering where I get the sawdust though or if I just use my jig saw to make a bunch… and which wood would be best… cedar, pine?

I’m not sure what type of sawdust. I bought a package of it from Thunderbird Supply a very long time ago and don’t have the label anymore. I rarely use sawdust except for this type of application where I’m mounting a flat stone to a curved base and bezel. Sorry

Thanks, Patrick. I looked up Thunderbird and they carry it in 2.75 oz and 1lb bags.

I’m a little late to the party here, and I’m a bit of a traditionalist, but I wouldn’t use sawdust on a piece of noble metal jewelry if I could help it. Native Americans did it out of necessity, but it’s easy enough to design a step bezel and then file the concavity into the bottom. If you don’t want to put in a step and then file most of it off, just use a wire and get it at the right height with a couple of sheet shims on either side where you won’t be filing. Seems a fairly easy solution. Prolly you could solder the bezel and the wire step and the two shims at the same time. -royjohn

Thanks, Royjohn for your suggestion. I’ll try it out and see. Were you suggesting that I shape the bezel to conform to the curves on the bracelet and then solder it together with the wire step and shims?

Actually I was suggesting putting in the shoulder first and then filing. If the shims were put at 9 and 3 o’clock, then you’d have only the bezel strip to cut or file away on the 12 and 6 o’clock axis and nearby. As I understand it, there’s hole where the bezel is to fit, so it’s not possible to put sandpaper on the bracelet, so the filing might have to be cut and try. I guess if you couldn’t get the bezel to fit seamlessly, you could add a single wire or twisted wire decoration or some such at the bezel base, but maybe that’s not in your conception. The filing’s the only dodgy part and maybe you could make a strip of paper, cut it to fit, glue it to the outside of the bezel and file to that…might be easier to cut the paper to fit than file the bezel with cut and try…-royjohn