Rods, subs and adapters

In auger drilling, rods, subs, and adapters are the critical components that connect the drill rig’s power head to the augers and internal sampling tools.
1. Auger Rods (Center Rods)
Auger rods are smaller-diameter steel pipes that run through the hollow center of hollow stem augers.
Function: They connect the rig’s drive to the pilot bit (center plug) at the bottom of the auger string. This ensures the pilot bit rotates in tandem with the augers to clear the center path and prevent soil from entering the hollow stem.
Sampling: When the desired depth is reached, the center rods and pilot bit are withdrawn, allowing samplers or well materials to be lowered through the protected hollow stem.
2. Subs (Substitute Adapters)
Subs are short, threaded lengths of high-quality alloy steel used to bridge mismatched components.
Crossover Subs: Connect drill components with different thread sizes or types (e.g., connecting a large auger drive to a smaller center rod).
Saver Subs: Sacrificial components threaded onto expensive parts like the rig’s top drive or “Kelly”. They take the wear and tear of repeated connections, extending the life of the more costly equipment.
Bit Subs: Positioned directly above the drill bit, these often house float valves to prevent backflow of cuttings or fluids into the drill string.
3. Adapters
Adapters serve as the primary transition points between different types of machinery and tooling.
Drive Adapters: Connect the rig’s rotary head (often a hex or round drive) to the first section of the auger string.
Rod-to-Cap Adapters: Secure the internal drill rods to the auger’s drive cap, allowing the entire assembly to be advanced as one unit.
Lifting Adapters (Lift Subs): Provide a secure shoulder or hook point for the rig to hoist the heavy auger string out of the borehole.