Step 1: Marking and Sawing the Cab

Cutting a Slab
Unless you belong to a club that has a slab saw, you have a friend that has a slab saw, or just feel like spending a lot of money ($2000 up), the best place to start is by buying your slabs. They are available at most rock shops and gem and mineral shows. If you have a rough rock that you would like to cut, save it until you have more experience. Unless you are very lucky, most rocks that are collected by beginners will have characteristics, hardness, fractures, undercutting, etc.. that make them unsuitable for your first cabs.

Marking the Slab
Using a cab outline template, find the place on the slab you want to use as your cab. Using a sharpened aluminum rod or permanent marking pen, outline the cab on the back of the slab. Resist the temptation to mark the front or top of the slab. It is difficult to avoid cutting the cab too small when it is marked on top. Choose a slab that has a pattern that will allow small misplacement of the template on the back side, later you can find special two-sided templates to allow precise marking.

Figure 1.

Marking Trim Lines
Using an sharpened aluminum rod, mark trim lines on the slab. You will be using these lines as a guide to cut to on the trim saw. The lines should allow you to cut close to the cab outline, but not touch it.

Figure 2.

Using the Trim Saw
Always use safety glasses when working with the trim saw. The blade uses coarse enough diamond to cause small chips of rock to be thrown from the rock during cutting. Use the 10" trim saw to cut the slab on the trim lines, being careful not to cut into the area of the cab. The trim saw uses water with a detergent added as a lubricant, and unless you are allergic to dishwater there is no hazard.

Figure 3.

Step 2: Grinding the Cab

100 Grit Grind to Mark
Using the 100 grit diamond grinding belt or wheel, grind the cab to the outline marked on the slab. Check the size frequently with the cab template. The cab should not quite go through the template.

Figure 4.

90 Degree Edge
During the grinding process occasionally turn the slab vertically and straighten any angle on the edge back to 90 degrees (square corners).

Figure 5.

15 Degree Edge
When the cab has been ground to the outline, again turn the cab 90 degrees, and this time cut a 15 degree bevel sloping toward the top of the cab. The cab should now go about half way through the template.

Step 3: Grinding 15 Deg. Bevel

Figure 6.

Step 4: Grinding 45 Deg. Bevel

45 Degree Bevel

Turn the cab so that the bottom edge is 45 degrees to the grinding wheel and cut a very small (1/32" ) bevel on the edge. This allows the cab to be set in a finding without cracking.

Figure 7.

Step 5: Mark Center, Oval & Side of Cab

Mark Grinding Lines

Using the aluminum rod or marking pen, measure and mark the center of the top of the cab. Measure and mark an outline of the cab 1/3 the size of the cab on the top. Mark a line around the edge of the cab 1/3 up from the bottom of the cab.

Figure 8.

Step 6: Dop the Cab

Dopping
Heat the dop wax in the small electric heater. The wax should flow, but should not boil. A few stones will not tolerate much heat. To cold dop a stone, I recommend using double-sided carpet tape and a used dop stick with enough dop wax to form a base almost as large as the cab. Some care is required as the tape is not as strong a bond as the wax. Another option is to use a hot glue gun or epoxy.
Heat Stone
Heat the stone on the burner. The stone should be hot enough to boil a drop of water on its surface.

Mount Stone on Dop Stick
Place a dop stick in wax. Using tweezers or pliers (the stone is hot) remove the stone from the heat. Place the dop stick on the back of the cab and form the wax around it holding the stick straight. Wet your fingers and use them to center the dop stick on the back of the cab. Place cab and dop stick in water to cool it.

Figure 9.

Step 7: Grind Four Side Angles

Figure 10.

100 Grit Rough Shape
Using the 100 grit grinder, grind a set of flats between the 1/3 grinding lines marked earlier.

Step 8: Grind Cone

Grind the flats into a cone on the 1/3 grinding lines. Using a rocking motion, grind the cone into the final cab shape.

Figure 11.

Step 9: Grind Dome

600 Grit Final Shape
Use the 220 or 600 fine grinding wheel to smooth the shape and remove all of the rough grinding marks.

Figure 12.

Next Month: Sanding and Polishing the Cabochon