It’s another typical drill job in the sculptor’s studio. Assemble a sculpture from three pieces of stone. Fix them together with 5/16 inch stainless pins, either sleeved for disassembly and transport, or epoxied for permanent placement and strength. Topmost is this black and red marble wing, scorched brittle by the SW desert heat. A carbide-tipped drill bit could work if done carefully. The hole must go through a narrow area and the tangential force of the drill flutes could wedge an unseen fracture into disaster.
I chicken out and opt for an electroplated diamond holesaw. These look like a piece of pipe dipped into diamond dust. Chuck one into a 3/8 inch variable speed drill motor and turn it fairly slowly to minimize heat buildup. Hold the alignment stable and use light pressure to smoothly penetrate about 3/8 inch then pull the bit out to clear the stone dust and cool the bit. Do it again. Occasionally point the drill at the floor and tap the side of the drill shaft to clear the buildup of dust or stone in the hollow bit. A small screwdriver snaps out the stone core remaining in the hole.
The marble fin sits on a layered black sand flagstone. A carbide-tipped masonry drill starts the hole precisely and smoothly at medium speed. Withdrawal pulls out the drilling residue and cools the tip. The varying cross-grain density of the stone layers is similar to drilling plywood. A piece of masking tape on the shaft clears the mounding stone dust away from the hole and informs approach of the required depth.
The flagstone stands on edge and must be pinned to a base for stability. Holes are marked equidistant from the ends. The holes are nearly parallel to the layers. Splitting is a threat. The edge is C-clamped between pieces of plywood to stabilize the layers. The masonry bit starts at the mark, then skews across the grain. Wrong! An anxiously applied electroplated diamond holesaw nimbly rescues the holes and the pinning.
A red granite base laughs at the spinning masonry bit. Rotary hammer drill. . . .no problem!