A loose crown underreamer apparatus (10) for boring into earth and other materials includes a crown (28) loosely coupled to a bit shank (12). The loose coupling mechanism (34) employed in the present invention reduces the occurrence of friction welds occurring between crown (28) and bit shank (12). Coupling mechanism (34) employed in the present invention includes a plurality of deformable polyurethane retainer balls (36) disposed in shank sockets (38) and corresponding crown sockets (40). Coupling mechanism (34) employed in the present invention allows for crown (28) to be uncoupled and re-coupled to bit shank (12) at will.
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