Fabricating a Platinum Three Stone Ring
Part I
By Tom Weishaar
1. Recently a woman brought in her old platinum ring with a loose marquise diamond to be worked on. After some debate she decided that it would be better to reset the 1.33 ct. diamond with an updated new three stone mounting. She picked out a matched pair of trilliants to go on either side of the center and the job came to my bench for fabrication. Fabricating a three stone mounting is one of the three requirements for becoming a JA®, Certified Master Bench Jeweler™ and is the project that seems to give bench jewelers the most difficulty. I thought I would describe the process I use, but it will require three separate articles to complete the complicated process. I hope you enjoy this series.
2. In part I of this trilogy, I will fabricate the platinum shank for my project. A size six ring requires 60 mm of 3mm square stock to complete. I’m starting with 2 inches (or 50 mm) of stock, but I will reduce the center to avoid filing away the shank. I start by locating the center of the piece of stock and marking its position.
I want to reduce the center section from 3mm square down to 2mm. To help me visualize where to roll the metal I am marking a center zone of metal (approximately 20mm) with a black Sharpie.
3. I slide the stock into the reduction gears of my rolling mill and clamped it down tightly. I can now roll the metal back and forth over the center section tightening the mill with each pass. The black ink helps me see where to stop and then reverse the mill.
When the rolling is complete my stock is now 60mm long. Both ends of the stock are still 3mm square, but the center section has been reduced to 2mm square. The rolling has saved me the expense of needing to use a longer piece of platinum and the time it would take to file the center down to the correct thickness.
4. This tool is an antique shank bender. If you ever come across one at a flea market or on E-bay they are handy for bending a piece of thick metal into a nice circle. In this picture I am using a size 6 die and bending my stock into a perfect ring.
5. This picture needs a bit of explanation. I like to use some modeling clay to approximate the curvature of the finished ring. By placing these three rather large stones in the clay I can visualize the correct angles of the stones and their relationships to each other. I want to tuck the side trilliants up under the center stone and angle then down toward the finger so that my completed ring will not be too wide.
6. In this picture you can see that the three stones will have a total width of 17mm. That is the maximum I can allow for a size 6 ring. This process, the “layout”, is very important in the planning of a custom mounting. If I skipped this process then I would lose control of my design and the ring could turn out badly.
7. The classic three-stone ring has a recessed center section and two “wings” that come up to hold the side stones. To achieve this look I like to mark a line that splits the thicker top of the shank into two 1.5mm sections. The purpose will become apparent in the next few pictures.
8. I use a thin 6/0 saw blade to slice an 8mm long cut down each half of the center of the ring. I like to make about a 1mm diagonal cut, then flip the ring over and cut from the other side. I go back and forth carefully cutting from both sides of the ring to help ensure that my saw blade stays on the lines and doesn’t wander during the cutting. I will only get one chance at this so it has to be correct the first time.
9. I think this picture best illustrates what I am trying to produce. Here I am lifting the two top sections of the shank creating a classic cathedral style mounting. For lack of a better term, I’ll call these sections metal wings.
10. Once the cutting and lifting is completed the center section can be soldered together. I like to use high-quality 1700 platinum solder to complete this first solder joint. I always use natural gas and oxygen for my soldering because it burns so cleanly. I always encourage bench jewelers to use high quality solders. The Mill and Refining Director of Hoover and Strong, Stewart Grice, recently told me that some solder manufactures omit the platinum from solders as high as 1500. Hoover and Strong’s platinum solders contain platinum down to the 1300 level. I believe that when you want a great product them you must use high quality ingredients – thanks Stewart!
11. Since the two upright supports will taper toward the trilliants, I am going to use this opportunity to tap them down a bit. The hammering will thicken the metal and reduce the amount that I will need to file down.
My shank is now nearly completed. I have already pre-finished it with a 200 grit sanding stick and I have now switched over to using a 1000 grit sanding stick. I find that if I take to time to finish the metal with fine-grade sandpaper then it reduces the amount of time I spend polishing.
12. I also like to make my own sanding discs that I use on the flex shaft. The disc is nothing more than a piece of fine grit sandpaper with a thin plastic backing. The paper and plastic are flexible and can be maneuvered into some very tight places. They work very well for pre-polishing down in crevices.
13. Since I have taken the time to pre-finish my shank I do not have to use any aggressive polishing compounds. I am only using a compound called “Diamond 8000”. This
compound is sold through Otto Frei. At $25.00 per bar it is expensive, but it is the best platinum polishing compound I have ever used and well worth the price. I just use a small amount on a soft felt wheel or a muslin buff and it does an amazing job on polishing platinum.
14. I always polish each section of my jewelry before going on to the next procedure. The shank is complete and ready to have the custom made crowns added to it. This shank took just over two hours to fabricate. I would like to share some design thoughts with you. The shank is 2mm square on the bottom. This is a good thickness and it should last for 30 years of normal wear. Between the fingers the shank increases to 2.4mm square. I hardly ever make a shank more than 2.5mm between the fingers as it becomes uncomfortable to wear. The middle/top section measures 1.5 by 3mm. This shank will be a great platform to hold those three large diamonds. I hope this article has helped answer any question about fabricating three-stone ring shanks.
This article first appeared in Bench Magazine http://www.BenchMagazine.com
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