Out Of The Blue Artifacts A Library of a lifetime of collecting
Coal Mining Rock Borer Drill Bits.
Made from iron and tungsten. Sizes – Large 4″ x 2″ inches. Small 2 1/2″ x 2″ inches.
The smaller bit has two points for drilling and two water infusion holes. The larger one has three points with two water infusion holes. The both bits have an internal screw thread.