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Drilling and carving slate

Greetings Orchidians: I have an upcoming grad school project on which
I seek advice. I have cut some pieces of slate. I would like to both
carve some pieces (carving and smoothing top surface, in a very
simple, undetailed way), and to drill some to put decorative rivets
through, and insert a tube setting in others. I know slate is easily
cracked, and layers flake off too. The finished pieces will have
straight sides, and be set into a thick-walled sterling silver
"frame", and backed in silver. I can bevel the sides if that will
work better. The pieces vary in thickness between about 1/4 - 3/8
inch (around 5- 8 mm) thick. For the rivets or tube setting, I
thought of carefully drilling a pilot hole first with a hand drill,
and then widening it with larger drills in my drill press. But before
I start I’d like advice! I’ve already put a lot of time into cutting
the shapes, or blanks. The slate is very even-grained. Both front and
back are in their original “flaked off the parent rock” texture. They
have a certain amount of what I think is washed-in mud imbedded in
the surface. A scrubbing with toothbrush and water has not removed it
all. I would like to keep the “flaked” texture in some areas, but
need to know the best way to clean the stone, too.

These are the tools I thought I’d use, and already have, so far:

hand stone-carving rasps, tiny riffler style
regular drill bits
diamond drill bits
diamond burs
usual flex-shaft carving bits (aluminum oxide and silicon oxide, etc.)
usual steel burs
usual rubber metal polishing wheels, in various grits

I thank you in advance for your suggestions!

Hi Lin; Try cleaning it with a little full strength muriatic acid.
You can get it from most building supply stores and quite a few
hardware stores. It’s used for cleaning concrete. Careful to use eye
protection and rubber gloves and appropriate protective clothing.
Dispose of excess by neutralizing with sodium bicarbonate. Check the
Orchid archives. Others, particularly John Burgess, have posted a few
pieces on the disposal of acids.

David L. Huffman

Hi Lin, I would recommend doing the “set up” first, you’re holes for
fitting, etc., before you do your decorative work. That way, if it
breaks you won’t have the time invested in the carving. As for
carving, my favorite tools are flat, knife edge, and rounded gravers.
I draw out the design with a sharpie if the stone is light or a
metallic pen if the stone is black then go over the lines with a
sharp scribe. Depending on how deep you intend to go, do it bit by
bit rather than trying to take big chunks at a time. Try a couple of
scrap pieces first, you can get slate from a Home Depot type place to
practice with. Also, when done, you can color with the metallic pens
for highlights if desired. I carve Celtic designs and color them in.

Marta in Sacto