I am wanting to drill a hole, 1.2mm in diameter and 2mm deep,
in the center of a 18x25 leopardskin jasper cab. What is the best
way to find the centerpoint?
G’day; Coat the cab in either Chinese white, ‘whiteout’ or black
marker pen. Set the points of a pair of dividers to a guessed centre
point of the cab. Now, whilst pressing one leg of the dividers
against the side of the stone, make a mark in the coating with the
other leg. Do this in several places, and the true centre will be in
the middle of the marks. You can even reset the dividers and repeat
the process if you are too far out in your original guess.
You must get a diamond drill bit; they are cheap enough. You can
first put the bit into a flexidrive, or Dremel, then make a little
shallow depression with the edge of the drill in the marked centre of
the stone, so it looks like a centrepunch mark. But I very strongly
advise that the actual drilling be done with the stone just submerged
in water in a shallow dish, and the drill used with an up and down
motion to keep the ‘swarf’ clear of the hole. You should be able to
drill a piece of 3mm agate in about 5 minutes, maybe slightly less.
A drill press is much preferred, but the hole cane be drilled using a
flexishaft or dremel - with care.
what kind of glue would be the strongest for holding an
ornamental sterling "peg" in this hole?
I would suggest a good epoxy resin, like araldite. Use the 24 hour
setting type, not the rapid setting one. I personally prefer to drill
right through, then rivet the post in position using tiny personally
made ornamental washers. But epoxy does work. Happy drilling - and
cheers, – John Burgess; @John_Burgess2 of Mapua Nelson NZ