The drill collar is at the bottom of the drill string and is a major component of the lower hole assembly. Its main feature is that the wall thickness is large (generally 38~53mm, which is equivalent to 4~6 times of the wall thickness of the drill pipe), and it has greater gravity and rigidity. In order to facilitate the drilling work, the elevator slot and the slip groove can be processed on the outer surface of the internal thread of the drill collar.
Drill collar introduction
Made of rolled or forged AISI 4145H chrome-molybdenum alloy steel for effective control of chemical and trace element content.