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I will soon need to #drill a "blind" hole in an #obsidian sphere (to use it as a knob for a cane) hole diameter ~12 mm, depth, say 50 mm. Anyone can give me some hints what to use (#diamond #drill I guess, but I cannot find one) and how to do it, so I would not spoil the material?
I don't really have any suggestions (apart from the likely obvious warning to think about thermal stresses), but am curious how was it shaped into the ball shape in the first place.
I am drifting towards making high value walking/fighting sticks. The most versatile tool/weapon for the pre-postapocalyptic world.

Hm~ once you have a hole, do you intend to mount a (wooden?) cane rod in it using wooden wedges?

I started to wonder whether adhering things to obsidian by heating it to ~its glass transition temperature would work and gotten nerd sniped into reading about metal-glass seals. Thanks.

THAT is a bit beyond my reach (at least for now). My working hypothesis is that I would glue-in (epoxy or polyurethane) a threaded sleeve both into the knob and the stick, and connect them with a threaded rod, secured with loctite removable glue.