provides information on . . .
SHAPING and FINISHING
Jack's Cabbing Technique
I use a "
flat lap" machine with variable speed.
Some people use the vertical
wheels like the "
" or "
Some don't want to spend the money
and, therefore, purchase a
Flat lap machines and vertical wheel machines having a
range of at least 180 to 600 mesh grits plus final polish are best, in My opinion,
for grinding and shaping the stone and quickly
getting rid of the unwanted material. I like flat lap machines that
have speed controls so that I can contol the speed which is very important
when grinding softer stones like opals.
Whereas, the Spool Polisher is mainly utilized
for the latter stages of finishing a stone.
One cannot grind quickly with a Spool Polisher
like one does with 60 to 180 mesh wheel or flat lap.
But if one does not have the money for the other machines,
by all means, buy the Spool polisher.
When one uses the phrase "cut and polish" or "cut opal",
it does not mean literaly "cut", like with a saw.
The term "cut" refers to the grinding process to shape a stone.
- Use a
with a thin blade to cut out the opal area
desired on large pieces if:
Use the trim saw also to trim off large areas of waste or excess
material. Some of the cutoff remnant pieces can also be
shaped and finished. Always apply water to cool down the
stone and blade and to wash away the debris.
- It cannot be used as one whole piece, or
- To obtain a certain size.
- Get rid of all remaining unwanted material on the stone
by the grinding process using diamond laps or wheels.
Always apply water to cool down the
stone and to wash away the debris.
Start with 180, 220, 240, or 260 mesh grit for quick removal
and shaping into a preform.
- If you are going to
use dops, prepare the dopping surface of the opal so that the
dop will fit securely in place. Most preparation consists of
developing an almost flat area and working it with 600 mesh
grit. If you are planning on polishing the backside or underside of the stone,
be sure it has some curvature to make it easier to polish.
- I usually set up about 30 stones to do at one time.
- Some of the smaller ones are put on top of nails (shape the
nail heads for best fit)
and attach by using a minimal
amount of "Goop"and let set over night.
The opal can be removed later by applying a candle flame to the nail shaft
nearest the nail head but be sure flame does not touch the opal.
Heat until opal can be easily removed.
"Goop" can be obtained from a hardware store.
- When using a flat lap machine, use a
5" Dish Lap
(600 or 1200 mesh) for final shaping before the sanding
process. Use lower speed on machine. Again, always apply water to cool down the
stone and to wash away the debris. Use certain parts of
the dish that best fits the curved surface desired. Learn
to twirl, swirl, and rotate the stone at different angles on the dish's surface.
This technique will give a better uniform curved surface.
- I make my own sanding disks for My flat lap machine.
- Use any round disk (metal, wood, or plastic or whatever)
with a 1/2" hole in the center.
- Attach a 1/8" to 1/4" thick medium soft rubber backing material
("closed-cell" preferred and cut to match disk)
to the disk using water resistant glue or "
3M Feathering Adhesive".
Or, you can purchase Foam Pads PSA backed
Those labeled "PSA" already have
a Pressure Sensitive Adhesive to hold the foam in place...all you have
to do is peel off the paper backing and apply to a clean surface.
- Attach 600 or 1200 mesh grit wet/dry sandpaper (cut, to match
disk) to the rubber backing material after applying
"3M Feathering Adhesive" to the top surface of the
rubber backing material.
Wait till the adhesive has dried and is slightly tacky
(about 20 minutes) before applying the sandpaper.
- The sand paper is initially too rough at first,
so use something you are not afraid to grind down on.
Eventually the grit on the sandpaper wears out and this is
where it really comes into play. Stop applying water. Apply
dabs of 1200 mesh "diamond
compound" in various spots on the used, pliable sandpaper.
Apply your stone to the surface where the compound has been
placed pressing lightly and gently allowing the compound to
spread over and across the lap while rounding off and
finalizing all of the stone's surfaces.
Get rid of all flats and scratches. I never go
to the final polishing stage until I am satisfied with all of the
surfaces of the stone.
Apply more compound if need be. If it gets too dry or
starts to grab the stone, apply a little clean water while working
the stone. Too much water will wash away the compound.
Use this sandpaper until it starts to come apart.
Then make another one.
- For polishing, I again make my own disks the same way
as the sanding type but instead of sandpaper, I attach a
to the rubber backing material in the
same manner the foam or rubber backing material was attached.
Use very clean water and allow it to slightly
drip during this process just to dampen the material but
not flood it. It is good to have some friction during
this process which aids in the polishing of the surfaces.
Bear down on this process to some degree, but
not enough to touch the hard disk below the rubber or too
much force that causes the stone to come off the dop.
Always keep the stone moving at all times in any process so
as not to get any part of the stone hot. Heat will destroy
opals when not careful. Polish until you are satisfied that
there are no scratches or unpolished areas. Improve your
techniques with experience.
Not all opals can be shaped into rounds or ovals, so use
your imagination and good eye for shaping them into
interesting objects of beauty at the same time considering
You don't have to use or stick with Jack's method. Develop
your own and enjoy being creative, clever, and resourceful.
If you have a better way, we want to hear about it.
Any flat lap or cabbing machine will work.
Some come with various laps, accessories, and some supplies.