Hello Elizabeth, Is your problem one of diameter or of thickness? I
wasn’t clear.
The best way to deal with this is to avoid it. If you are picking
out the stones yourself, then bring a mm gauge with you and know the
maximum height you can buy and avoid those that are too thick or
wide. If you are buying through the mail or over the phone, let you
supplier know the trouble you are having and ask them to ship you
cabs with thickness or width of no more than ‘x’ millimeters so you
avoid the problem altogether in the future.
For those fat cabs you still have on hand, all you need to do is dop
them. Dopping is where you “glue” the stone to a stick with wax or
some other adhesive. Then you can easily hold tiny stones while you
grind away to your hearts desire.
You can dop to just about any small, strong, stick-like thing. I
regularly use skewers, pencils and golf tees, but notice the dop
stick I use are always made of wood. Golf tee’s are my favorite
because they are strong and the perfect length. I use the fat end for
bigger stones and the small end for small ones . Since you are using
a flex shaft to grind the stone, the length of the dop stick can be
as long as you want, but if you ever got into lapidary you would want
to keep them about 3" in case it gets away from you so it doesn’t get
jammed into the wheels of your lapidary machine.
Whether you need to skinny up the diameter or reduce the thickness,
you will need to dop first. If you need to skinny up the diameter,
then dop the back to the stick. If you need to reduce the thickness,
you need to dop to the front of the stone. To dop, first make sure
your stone is clean so the wax will stick to it. You need a bit of
dop wax (I like the green stuff), melt it in a little cat food can or
something small and metal like that. You can set the can on a
soldering tripod and heat the bottom till it the wax melts. It should
be melted to the point of queso dip…kind of thick but not runny. If
it’s too hot it will be runny and won’t hold. Dip the dop stick into
the wax and stir it around until it gather a glob. Let it cool a
teensy bit. Then form the wax into a mound kind of quickly (the wax
will be hot and will burn your fingers mildly if you hold in one spot
too long…this is how you will know it’s the right temp) and press
your stone onto the blob of wax and let this cool completely. Then
you grind away the unwanted parts. If you are grinding the bottom,
don’t hold too hard against the grinding wheel or it could come loose
and you’d be hunting again. To get it off the dop stick when you are
done, put it in the freezer till it gets cold and then just pop it
off. If it’s an opal, skip the freezer part and just pry it off.
You can also dop with epoxy and then soak it in acetone to remove,
but you have to be sure the stone is not going to be damaged in the
process.
If you are reducing the thickness, the machine that would do this
the best is a flat lap. For such a small stone, you don’t need to
invest in such a machine. Just use an aggressive grit (100) wheel and
do what you are doing. Hope this helps!