Threaded drill rods are also called hydraulic drill rods, heavy drill rods. The thread drill rod is a kind of rock drilling tool which is connected with the shank adpter, hydraulic rock drill and thread drill bit and transfers the impact power and rotary knob force of the hydraulic rock drill to the thread drill bit to break rock.

It is common practice to bump up the drive end of drifting drill steel for added strength at the rock drill end to accommodate larger diameter and shank adapters. Drill steel of rock drilling tools is available in many standard lengths to match the drill feeds on a multitude of available drifting jumbos. A rock drill bit diameter closer to the steel diameter can be used since the coupling does not enter the hole, this enhances flushing and hole accuracy.