If you like to use a flat ended dop stick for any purpose other than as a target dop, or if you are a glue or adhesive dopster I recommend skipping this post.

Apparently glue doesn’t bond well to a polished surface and as you obviously don’t need the stones in a hurry, you might as well continue cutting with your favourite procedure.

Although not original, I have found very few cutters that cut ‘regular’ size stones that have adopted the polished table first, pavilion second, crown last, cutting procedure. Very large stones, very small stones and almost all diamonds have their tables cut and polished before any other cutting proceeds.

There are many advantages to polishing a table by hand before cutting any other facets

Discovery, finding out what you have.  As you start cutting the table a window develops in the rough,  it is quite easy to see even small uglies through a wet 600 window and you will be able to easily rethink your orientation before very much material is removed.

A facet is only polished quickly when its entire surface is in contact with the lap. The table is easily held flat against a polishing lap with finger pressure but it is not quite so easy to ensure 100% contact if dopped.

With a polished table you now have a perfect window into your stone, it can be readily checked for any problems that might occur and can even be mounted in a microscope for close scrutiny in fact this can be done at any time during the table cutting and polishing process. A dopped stone prohibits this.

During this process you learn the characteristics of the stone, the cutting action and the polishing technique and a big plus, you dispose of the most difficult and important facet first. Furthering this confidence in success is the knowledge that you will not have to make any design or angle adjustments to compensate for hidden inclusions showing up.

You now have a reference for a mathematical model. Measuring the depth of the stone will allow you to calculate exactly the width of the finished gem cut to the exact angles required by the design. You can also predict not only the size but also the finished weight, within a couple of points usually, and the stone hasn’t been dopped yet.

If the rough has insufficient width then all that you do is cut away some depth until you have a sufficiently lesser need that does fit. You never have to compromise and use inefficient angles because you have run out of stone.

You now have a cutting reference.  The girdle will easily cut
parallel to the table. If the stone becomes detached at any point the finished table ensures perfect registration for replacing it, either redopping to the table for redopping during the pavilion cutting or using the target dop for redopping during the crown cutting.

Finally, the point of this post, which I really wish I could make shorter, is the ease in cutting numerous calibrated stones with little or no time consuming sidetrack procedures. If you have a piece of rough with a finished table you can cut it exactly to the required depth for any given girdle width. If you aren’t comfortable with cotangents there are computer models that will do the sums for you. If you want the trig, I have an article in the Archives called ‘Cutting Mathematics”

Cutting to an accurate depth for the preform can easily be accomplished by holding the stone in your fingers but if a hand held dop stick is used you need to measure the stone, determine the amount to be removed and then dop it. Now measure the dop and stone together and simply grind away the unnecessary material.

That’s all there is to it, matched depth=matched width. Sorry but it needed the pre-amble.

Tony.