Patent ID: 7836976

Claim:
A fluid pressure operated underground piercing tool, comprising: a) an elongate cylindrical body having a striking element at one end; b) a striker slidably received within a chamber defined by said cylindrical body; c) an end cap threadedly engaged with another end of said body, said end cap capturing said striker within said body chamber; d) a valve assembly for controlling the communication of pressurized fluid to said body and for controlling the discharge of pressurized fluid from said body, said valve assembly being operator adjustable in order to produce forward or rearward movement of said underground piercing tool; and e) said threaded engagement between said cylindrical body and said end cap being of a tapered buttress thread configuration and including a threaded segment formed on said cylindrical body and a complementally shaped threaded segment formed on said end cap and further including at least one substantial relieved section formed on one side of each of said threaded segments in order to reduce stress risers on the one side of each threaded segment.