Lopsided drill bit produced flared cavities for trumpet-bell earrings. The Lingjiatan drill is deliberately lopsided, with both bit ends offset from the center of the shaft Off-center rotation creates a flared cone-shaped cavity, matching the trumpet-bell earring profile exactly Cutting action delivered by an abrasive slurry of hard mineral sand and water
The Lingjiatan drill is deliberately lopsided, with both bit ends offset from center. This off-center rotation sweeps a wider arc, carving flared cavities matching the trumpet-bell earring profile perfectly! Using abrasive mineral sand slurry at 1-3 mm depth per hour in jade, craftsmen achieved astonishing 0.5 mm walls through precise control. 🔬
Key Facts
- The Lingjiatan drill is deliberately lopsided, with both bit ends offset from the center of the shaft
- Off-center rotation creates a flared cone-shaped cavity, matching the trumpet-bell earring profile exactly
- Cutting action delivered by an abrasive slurry of hard mineral sand and water
- Smaller offset bit produces a larger flared cavity because off-center rotation sweeps a wider arc
- Drilling rate of 1-3 mm of depth per hour in hard jade provided real-time control over wall thickness
- Minor drilling irregularities were smoothed away in subsequent polishing stages
- 0.5 mm walls achieved through a precisely controlled, mechanically assisted process rather than reckless grinding
Related site: 凌家滩遗址考古保护大棚 — view location, images, and history on the Ancient Nerds map.
Source: Lost Prehistoric Engineering: The Mystery of the 0.5mm Jade Artifact by Curious Being