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#21
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"William Black" Sorry, it's complicated, 'scorper' is the generic name for a range of specialised gravers.used in stone setting. They are used to cut the silver away so that the stone sits on a 'shoulder' and also to remove surplus metal at teh top of the setting so as to allow it to be bent over the stone........... I guess the problem is that I do not have any idea of the your starting point. My experience has been with "easy set" type of stuff where the stone is plopped into the setting and the prongs are bent to keep it from falling out. Not even bottle rocket science. Where does all this micro machining fit in? js -- PHOTO OF THE WEEK: http://schmidling.netfirms.com/weekly.htm Astronomy, Beer, Cheese, Gems, Sausage, http://schmidling.netfirms.com |
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#22
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On , in Ìô Jack Schmidling wrote:
I guess the problem is that I do not have any idea of the your starting point. Properly made settings are the starting point. Then you have to fit the stone to it, so it correctly contact the prongs evenly, while allowing you to then, without breaking the stone set the metal over the stone that will hold it. Commonly, one does this cutting and fittinf of the prongs with various hand tools, such as jewelers saws, needle files, rotary burs in a flex shaft or other hand held motorized setup, or engraving tools. The later, also called gravers, burins, or scorpers, depening on where you're from, and which types of tool shape one is talking about, are basically just small hand driven, very sharp, chisels with which one can shave off very precise amounts of metal. My experience has been with "easy set" type of stuff where the stone is plopped into the setting and the prongs are bent to keep it from falling out. Not even bottle rocket science. You're right. But also not very good stone setting. The easy set type things are not all that well fitted to the stones as is. good enough to seem OK to an ameteur, or for cheap jewelery, but the poorer fit means the stones are less secure, more easily loosened from the mountings. Also, to minimize the percentage of stones that will be chipped and broken in using the easy sets, they're made rather thinner than a pro would usually do, and often of softer alloys, so they bend easily. Trouble with that is then they're just as easy to unbend if one puts some stress on the mounting during wear. And because the notches in the prongs are "generic" rather than fitted to the individual measurements and slight variances of the stone, the possibility of a prong not quite fitting exactly is much higher. That misfit greatly increases the chance of chipping or breaking a stone. But the process is essentially the same as you've seen. just taken to a whole new level. As well, properly done, stone setting needs to address such aspects as the prongs not catching on fabrics, a look for the finished stone that well balances the mounting (something that can differ from stone to stone), durability of the finished setting, long term security, and of course, managing to get it set without breaking it. The latter is of no great concern if one is selecting stones from the five dollar bin of synthetics for cheap birthstone jewelry. it becomes of major concern when one is setting better stones, stones that already belong to a customer, or stones one is selling for enough money that replacing it if broken would be a major expense. Where does all this micro machining fit in? not really machining, just usually hand fitting. The idea is that the notches need to properly fit the girdle of the stone all the way around, each prong in the same degree of contact and pressure on the stone. With custome precision cut stones, this is not that hard. But most commercially cut stones vary more, with different girdle heights, often girdles that are wavey or differ in height or thickness. And most good gems are not a precisely calibrated size and shape either. yes, it sounds simple. And in essence, the concepts are not complex. but the practice of stone setting takes exactly that. Practice. To get good at it takes a LOT of practice. Note too, that stone setting is a lot more than just notching and bending prong tips. Bezels may be thin rims, easily burnished over, or may be thicker metal that needs a punch and hammer to drive down over the stone. or it may involved precisely fitted tapered holes in a piece of metal, and then you use a graver to push bits of metal from the surrounding field of metal up and slightly over the stone, forming small hemispherical bead shapes holding in the stones. Again, it sounds simple. Doing it well is another matter entirely. And if doing one is not so bad, getting a hundred small diamonds set into a ring this way, all set identically so the appearance of all is the same, with all stones set properly level to each other, and almost touching each other... and doing it in, say, a high nickle 18K white gold, which is a hard, springy, sometimes brittle metal that makes mild steel look like clay to work with... And remembering that with this style of setting, there's often little or no extra metal at all to work with. Slip and cut off a bit you needed, and you're in deep do-do... yeah, maybe not rocket science. this can be a lot more work than just lighting a rocket... Peter |
#23
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William Black wrote: "Jack Schmidling" wrote in message ... "William Black" Usually the mount for a conventional round stone is a conic section made by forming it with a tool set in a die with the silver tube between them, you then belt it with a hammer and anneal.... Roger on that but what I am trying to do in minimize the height profile so they don't look like pretty warts. I have drilled holes and used cut down commercial heads and used a counter sink to form a conic hole but find that just selecting the right size hole puts the stone at the proper level. I was under the impression that the stone could not touch anything much without destroying the optics but I guess as long and it's not filled with glue or some such thing it does not matter. True, and hole right through the piece for the light to get through helps Correction please, a properly cut stone needs no light to enter it from behind or from the side. A few facet edges resting against a metal edge or 2 will not affect it's optical performance though most medium to low refractive index gems WOULD be compromised to varying degrees by having adhesives applied to the pavilion. Carl 1 Lucky Texan -- to reply, change ( .not) to ( .net) |
#24
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"Carl 1 Lucky Texan" Correction please, a properly cut stone needs no light to enter it from behind or from the side. A few facet edges resting against a metal edge or 2 will not affect it's optical performance though most medium to low refractive index gems WOULD be compromised to varying degrees by having adhesives applied to the pavilion.... That seems a bit of an understatement. I epoxied a nice CZ into a ring at the insistance of a friend and it totally destroyed it. I think the reason hard metal has little effect is that contact is minimal and only where facets meet. Adhesives cover everything and become visible through a perfectly cut stone because of the refractive index of the epoxy vs air. The RI of the stone makes no difference unless it is the same as epoxy. js -- PHOTO OF THE WEEK: http://schmidling.netfirms.com/weekly.htm Astronomy, Beer, Cheese, Gems, Sausage, http://schmidling.netfirms.com |
#25
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On , in Ìô Jack Schmidling wrote:
That seems a bit of an understatement. I epoxied a nice CZ into a ring at the insistance of a friend and it totally destroyed it. I think the reason hard metal has little effect is that contact is minimal and only where facets meet. Adhesives cover everything and become visible through a perfectly cut stone because of the refractive index of the epoxy vs air. The RI of the stone makes no difference unless it is the same as epoxy. the key is that the proper reflection of light from the pavilion of the stone depends on maintaining the difference in the refractive index of the stone, with what is optically in contact with the stone. Normally, this is air, and there is then enough of a difference in refractive index, that light is able to properly reflect from the paviolion facets. When any material with a refractive index higher than air, is in contact with the pavilion of the stone, the angle at which light mist strike a facet in order to internally reflect, rather than just passing out of the stone, is much shallower, greatly decreasing the angles at which light will reflect. So then light just passes out of the stone, and the stone appears dead, and you see through it, instead of seeing reflected light.. Glue forms an optical contact with the stone. So does stuff like dirt, oils, etc On the other hand, the metal of a mounting generally cannot "wet" the surface. Even when it appears in contact with the stone, it's not intimate enough contact to exclude the tiny film of air, and then the air is what is in optical contact with the stone, and the stone appears all right. In a few cases, especially with hard stones like diamond, and soft malleable metal like platinum, I've seen cases where some portion of a mounting was pressed hard enough to a back facet to exclude the air, and that spot, even with diamond, will appear as a dark shadow. Not as bad, though, as the glue, etc, since when metal is pressed hard to a diamond surface, if it's in optical contact, then what is in optical contact with the stone is, after all, highly reflective metal. A mirror. So then IT reflects the light back, and not all is lost. it just looks like a different spot. That principal is why the cheap glass rhinestones known as "foilbacks" work so well. Though they're just glass, they're coated on the back with an actual mirrored coating, so light reflects from a back coating that's actually metalic, and perfectly reflective, not depending on refractive index at all. Peter |
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