Ancient ultrasonic drill holes found along an old granite quarry in Saxony, Germany.
The best way to understand ultrasonic drilling is to observe the work created in rock or stone, especially along ancient rock cliffs and quarries.
(Above) ultrasonic drilling round shape holes in granite using a soft brass tube. A copper-based tube will wear down a little faster than a harder steel tube (below).
A portion of a round steel tube was made into a star shape tube (drawplate required). As the star portion of the drill tube disintegrates from drilling, the tube transitions to the round portion of the tube.
The resulting hole will be part star shape (with geometry) and part round shape.
The star portion of the hole will appear as if a cookie cutter went through the stone.
Star shape holes are better than round holes when using explosives to split blocks of rock for quarrying due to their pointed structure in the stone. The only drawback to ultrasonic core drilling is the core is stuck in the hole
A clogged-up hole with a core stuck inside is ineffective for quarry blasting. The core must be removed for explosives.
To eliminate the core while drilling, a honeycomb-like structure welded inside the tube would break up the core and keep a fast-drilling pace.
The inside honeycomb design of the tube will not only crush up the core while drilling, but it will also leave its image or its mark in the stone.
A hole that transitions from star shape to round shape is ultrasonically created using a shaped metal tube. A twist or spiral appearance when looking through the star hole is the result of a twist made in the tube caused from stress in metal shaping. An internal star twist is a common occurrence in ancient star shaped drill holes.
