Ovals in general have a long history of problems with me. I could not cut them with my original equipment that I purchased as a kid of 15. But when I got back into faceting after a long period of inactivity, I made sure that I purchased a machine (still a platform facetor) that could do the job.
I tried using the preformed that the manufacturer made for the facetor, but it didn’t make the grade. I even found that the template for the preformer had been permitted to deteriorate and loose the correct position for the registration hole.
I really did not want to facet the girdles of the ovals, but I decided after not cutting ovals for over a year that I had to use meet point to obtain a good oval shape. The first time I tried to use the shape information from the pavilion to cut a crown, it was a complete fiasco. And I have never used meet point to complete a crown since my machine is not accurate enough for such an exorcise.
The following is a case history of an average pink tourmaline that I cut into an oval. Its pavilion is a simple design found on the top of page C26 of Facet Design Volume 1A. Its length/width ratio is 1.33. This is the design that I use for most of my ovals in the different standard ratios.
The pink oval started out as a section of crystal with a more or less round cross section. After checking it for flaws I chose one of the natural faces and made it the table to be. I considered a square cut, but I usually end up with a round, it would depend on the thickness of the rough. As soon as I started preforming the pavilion to be I knew that I had more flaws than I expected. They were non reflective, but their opaque white presence was unacceptable. So a grinding down of the 10 carat piece of rough began. It soon became obvious that I would not have the depth needed for a square cut without reducing the spread of the finished gemstone too much. And by the time I had finished grinding out enough of the opaque pains, I had to make an oval to try get the best stone I could out of the much reduced piece of rough. A round would have had to have the diameter of the narrowest dimension of the oval with a lot more weight loss.
I have recently been forced to change dopping waxes and using the new waxes properties, I now grind a flat wax platform on the dop stick that is oriented with the sides of the oval preform. This helps ensure that the preform is level and properly oriented. I use epoxy to attach the preform to the wax platform.
Now practice might make my work perfect, but with a well positioned preform and a calm attitude, I was actually able to grind an oval with the correct ratio of 1.33. This is almost unheard of for me. I usually cut a longer stone because of my inclination to under cut the narrow facets that meet at narrow angles. I began to dream that I could use the “correct” angles for a 37 degree crown in the book adn make a picture perfect stone. Not that many people would notice or care about such an accomplishment.
Now I do NOT use the cutting sequence that meet point demands. Even with the proper ratio, I need to check the orientation, which might have changed, when I transfer it. I do this by seeing if the end star facets when cut to the same depth meet over the meeting of the two end facets on this cut. It turned out that the gemstone had not shifted during the transfer and I was one more step closer to a “perfect” cut.
Holding my breath, I coolly cut in the crown. I do this by completing the find grind on the table and all the stars or grinding all the mains. It rather depend on the stones thickness and how limiting it is to the finished piece. With the pink oval, I ground all the mains to make an evenly thick girdle. Then I completed the stars after finishing the table. (I may recut the table depending on how well I have leveled my hand piece parallel to the lap and judged it size.) Now I see how well I have done by cutting in the break facets. I always use the book values, but adjust liberally. I this case I was in the pink. Even the ends came in well, if not perfectly and I was coasting home.
But then there must have been a reason besides the correct ratio for me picking to write about a pink oval. And there is. When I finished all the facets on the crown, I checked the girdle and found an area of excessive thickness. Very unusual, since I started my way of using both my eye as a judge and meet point.
Well after thinking about it, I decided that I had cut one of the mains at the wrong index. I am using a different index than I have used recently and it is slightly off on its markings. And I have had the same problem before. So I set up the proper angle and double check the index and sure enough, the facet was one notch off. It amused me that I had not only missed indexed the main, but compensated for it with the brakes all without noticing it. Well I carefully started to recut the main and the breaks and while the fix would fall short of making the gem ” perfect”, I was on my way to make a very nice gemstone.
Then it happened. The epoxy is getting a bit old and it had been a tad rubbery so I let it set up over night. Well as I gently cut the repairs I needed on the gemstone, the epoxy failed. It did not fail completely, but the stone was so loose that the it bounced on the lap. I carefully kept the stone’s position on the dop and epoxied it up again. (Of course it was not perfect.)
Now I was faced with finishing an oval that was not perfectly positioned. I was in too delicate a position to try and do any more cutting on the gemstone. Trial cuts to adjust the hand piece could make too many problems. So I set out to polish the few facets that should have been ground along with all the rest. (Pink tourmaline generally polishes very nicely and this oval was no exception.) I could still get a really nice oval, without too much adjustment, with angles close to the “book” values.
And then it happened. As I stared to adjust the hand piece to polish a star facet, the table was done, I splintered off the edge of the associated main. It was not a big deep conchoidal fracture like I get on most tourmaline, but rather more like a cleavage failure. What was I to do? Well I couldn’t grind it out since the gemstone was only marginally position to work on, so I had to polish it out. Well the size of the gemstone was only about 1.5 carats so it wasn’t too big a deal, but my hope of finishing a gemstone with the “book” values was lost forever.
It probably took me twice as long as it should have to finish the crown, but after a great deal of polishing, it was in the storage box. It is eye clean and bright and flashy and without looking for my problems with a loop, I doubt you would notice anything out of the ordinary about this pink oval. I know its secrets and I must say that I have never had a tourmaline fracture on me like this one did and if it is ever set, great care must be taken.