ARCHAEOMETALLURGICAL STUDY OF AN ANCIENT BOW DRILL FROM THE MA‘AGAN MIKHAEL SHIP

The Ma‘agan Mikhael ship was discovered off the coast of Israel in 1985, and excavated in 1988 and 1989 by the Leon Recanati Institute for Maritime Studies at the University of Haifa. The shipwreck was dated to 400 BC. A bow drill, discovered in the shipwreck, was studied using nondestructive testing (NDT), and metallurgical methods. The bow drill is composed of a wooden drill-shaft and a metallic bit which survived in the form of particles. Some strongly magnetic fragments of the bit were carefully removed in order to study the quality of the steel and the manufacturing technology used by the ancient Greek smiths. Examination included a digital radiography nondestructive technique, optical microscopy, SEM, EDS chemical analyses, and micro-hardness tests. Radiographic analysis revealed the internal square inner hole of the shaft. The metallurgical analyses and micro-hardness test of the bit showed that it was made of high-carbon steel with a layered structure. The steel was heat-treated and strengthened by quenching without tempering, to form a coarse martensitic structure. The modified microstructure improved the mechanical properties, such as hardness and strength. This was the first metallurgical investigation of an ancient steel bit, and it is suggested that the Greek blacksmiths made the drill bit with state-of-the-art technology.