[Jewelry making - Article 00055] - Re: [Orchid] How to Tighten Princess Cut Diamonds?

[David Huffman]

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Hi Noel;

>     I took stone-setting with Blaine Lewis at the New Approach School.
>     One of the settings we did was a princess cut in a four-prong
>     setting. 

    Blaine has his reasons, and I respect his abilities as a setter and
    a teacher. I've been setting for 35 years, and I've also been doing
    repairs that long. I can imagine how he does it, but his theatrics in
    that lesson point more to his skill as an educator than a setter. He
    must have had the culet of the stone set down in the bottom of the
    head to pull that off. Can't imagine that looking very good: a little
    squatty. And there's another thing. There is a head that looks like
    the Tiffany for a round, but it's made for a princess cut, and there
    are subtle differences in prong angle, thickness, etc. Again, setting
    it in a round head can be done, but what's the point if there's
    better choices? But I still think there's problem with the basic
    geometry of setting a princess in a head designed for a round stone. 

    Here's what it is. 

    When you have 4 prongs as in a typical Tiffany setting, in the cross
    section they are wider in one direction than the other. That means,
    they can bend sideways more easily than they can outward. They lean
    up at an angle that is pretty close to that of a diamond's pavilion,
    a little steeper, of course. When you cut notches in the prongs for a
    round stone, the pavilion of, say, a 1 carat stone will make contact
    with with about 2 millimeter's of metal per each prong, and the prong
    tip will bend over touching another 1.5 millimeters. Now, cut all
    those notches and bend down the prongs, it's very difficult for the
    prong to bend sideways (which is the easier way for that cross
    section of metal to bend). When the stone is locked down that way,
    the top tip of the prong actually has to lift up a tad for it to be
    able to bend a prong sideways. Not so with a princess cut because the
    entire stone can rotate and change the relationship of the square to
    the prongs. The top of the prong doesn't have to lift, it only has to
    twist a bit, which, because of that cross section, is easier than
    lifting the tip of a prong. Rotate a round stone and nothing changes. 


>     Are you master-jewelers saying this is dead wrong? 

    In my shop, it's wrong. Oh, I can set them like that, and I believe,
    when I worked for others and they required it, I did that. But there
    are plenty of heads that have the aesthetic of that classic Tiffany
    head that are designed to do a superior job of holding a princess
    cut. Just get out Stuller's findings catalog and browse their setting
    for princess cuts. 

    The thing about a proper head for a princess cut is that it should
    have enough prong width to allow cutting a slight longitudinal notch
    to accommodate that long facet juncture that goes from the point down
    about half the length of the pavilion. And I NEVER rely on downward
    pressure on the point of the stone to hold it. It's actually held by
    sideways pressure at the corners on the girdle of the stone. When you
    bring the "V" in, it makes contact, then the angle of the "V" get's
    tightened and begins to fold over the top of the stone. With a
    Tiffany made for a round stone, there is nothing to "squeeze" in to
    hold that corner, you have to push the prong down onto the point,
    which is dangerous if you put too much pressure on it, and there's no
    "vector" tightening possible because you can't slide the prong
    sideways, that means, there's no way to compensate for that "bounce"
    you get from the white gold. 

    Well, sorry to go on like this, but I suspect others on this forum
    are going to blast me for this, so this is for them too. By the way,
    if there's anything you need done that Blaine Lewis does, just send
    it to me and get ready to cut a check. I'll match my setting skills
    against his, but boy, if I were able to teach like that, I'd make a
    lot more money and probably have a life too. 

David L. Huffman
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