This sub-class covers methods or apparatus specific to mining or quarrying. [3]
Even though disclosed only for mining or quarrying, drill bits, bore reamers, core taking devices, drilling pipes or rods, handling, racking or connecting arrangements for drilling pipes or rods, counterboring or enlarging drilled holes, flame drilling, or other drilling apparatus not provided for in this sub-class, are covered by sub-class Fulltext... Hierarchy... Expanded...E21B. [3]