Primitive drilling of carapace and horn
David Barnett - Venice, FL
>Reverse? Maybe, although not likely. Reversible? Definitely, or more specifically, bidirectionally.
Earliest drilling of tortoiseshell employed straight shaft drills (a bone splinter or wooden stick spun back and forth between the palms of the hands, often with a sharp fragment of bone, shell or flint affixed to the end), bow drills, and later flywheel pump drills. Friction can easily generate enough heat to produce a hole, but as Oppi Untracht states in Jewelry Concepts & Technology: "Real tortoiseshell fuses to a black mass when heated and smells like burning hair." It also becomes brittle and flakey after melting.
As for metal drills for very thin materials (natural or otherwise), they gain very little if any advantage by fluting, so it's common to make simpler drills. You can do this easily: take a hand sewing needle of desired diameter. Sharply snap off the tapered pointed section. If it snaps cleanly it's good enough steel of proper hardness. Otherwise, find another needle. Now pull it along a honing stone or sandpaper, first one side, then the opposite until it is forms a centered wedge with a sharp arris. Chuck it in a pin vise and twiddle it back and forth with your fingers or between your palms. A more complicated centered V-point with opposing bevels works nicely, too, but is more often used on pearls and shell as it's less likely to delaminate nacre. An improvement is to flare the business end with a hammer blow to give more shank clearance. You'd need to anneal, forge and reharden, of course. A match will do.
Horn can be pierced, drilled and punched. Both tortoiseshell and horn can be boiled and soaked, rendering them more suitable for piercing/punching. Boiling and clamping scarfed sheets of either material will result in an iseperable and largely invisible weld and can be moulded/formed this way, as well.
As for Bill Lowrance's suggestion of drilling over Allcraft's excellent Red German pitch, I'm sure Tevel will gladly sell you a kilo to try (it's not cheap, mind you), but you can back your drilling just as well with wood or any non-brittle thermoplastic substrate (Delrin, Nylon, whatever). Scotch tape works, too.
