6.2.5 SHAPING THE PAVILION – BREAK FACETS
Now, the pavilion can be formed – the Break Facets are done
first.
You are still using the coarse lap, (switch to a medium lap as you
approach the target angle—or, use a medium lap all the way—
it’s not so slow). Set a speed of 4 or 5 (later on, when you are
more comfortable with your faceting, you will--probably--increase
the speeds). The water drip, from the Water Tank, is at a rate of
one or two drops per second.
Set the Index Gear at 3 (same settings as for the girdle). Set the
Angle Dial at 45 degrees.
Set the stone down onto the lap, in the quadrant of the lap nearest to yourself, lower the vertical position a bit
(so you get a reading higher than the 45.00), and slowly sweep the stone back and forth from the center to the
edge of the lap and back, grinding a flat. Watch the Angle Dial go down—and finally reach the target of 45.00.
You can repeat this—and as you get closer to where the facets will join at the tip (the “culet”), switch to the
medium lap. You can observe where that depth of cut is getting closer by cutting several of these index
positions (say, at 3 and the opposite index, 51)—repeatedly examining the stone as you adjust the depth of the
cut
Then, with the medium lap, continue going down in vertical position—repeatedly examining the stone as you
adjust the depth of the cut—the vertical setting—until the facets come to a tip at the bottom (or almost--it will be
the Main facets that finally form the tip—the “culet”). That establishes the final depth for the Break facets.
With the first break facet in place at Index position 3 (and another position too, at 51), move to the next index
position. Proceed to add the remaining break facets, in the sequence shown:
Pavilion Break Facets—set Angle Dial at 45:
96 Index at: 3, 9, 15, 21...etc…steps of 6…to 93
Now, proceed to the:
6.2.6 SHAPING THE PAVILION MAIN FACETS
In shaping the main facets (the "mains") you will be removing very small amounts of material, Continue with the
600 (or1200) mesh lap. Approach this slowly and carefully since the material will be removed very quickly.
Inspect often. The main facet positions are:
Main Facets--Angle Dial setting at 42:
96 Index at: 96 (0),12, 24, 36, 48, 60, 72, 84
As you do this, inspect the stone and observe how the mains
develop--after just barely grinding you can see the
beginnings of the break facet. This observation helps you
understand the faceting process, and after some experience
you will know exactly where a new facet will appear.
The mains are cut until they meet the girdle, as shown in the
sketch. Make note of the position of the vertical adjustment.
To Next Page
Loading...