Why ancient star shaped drill holes in rock have equally spaced internal lobes or points.
(Below) An ancient square shaped drill hole in rock from Egypt (photo from Graham Hancocks website), shows the shape of the drilling tube.
When ultrasonically drilling rock, the drill hole will be nearly idenitcal to the shape of the tube.
(Below left) a square shaped drill hole made in Nephrite, Jade using a square shaped brass tube and (below right) a semi square drill hole made with a steel tube in Jadeite, Jade
If a square tube has rounded edges, it will drill a hole with rounded inside corners.
Below is a metal drawplate consisting of numerous calibrated 8-point star hole cut-outs.
The drawplate’s hole is precision cut in metal with equally spaced points, resulting in a tube with equally spaced lobes.
An 8-pointed metal tube, created from a drawplate, has 8 equally spaced lobes and will drill a hole in rock with 8 equally spaced internal lobes.
A rectangular tube with rounded corners will drill a hole in rock with curved corners.
Ultrasonic tube drilling rock leaves behind machined cores that match the inside shape of the tube.
Star holes having equally spaced internal lobes are created by the equally spaced lobes of a star shaped drilling tube.
Ancient precision star-shaped drill holes and some square-shaped drill holes in rock were created using ultrasonics and a shaped metal tube.
The above 8-point star shaped drill hole in rock from the Hualapai National Park in Arizona and the below square shaped drill hole in a rock from Egypt, both show signs of ultrasonic machining with a shaped metal tube.