The Fencepro Standard Hydraulic auger system is ideal for hard clay, Papa clay, hard pan, Rhyolite etc. It has a 400NM motor and is fast. There are two tips available - the Tungsten Pilot which is best for rock, and the Silver Earth Pilot which is best for clay.
The kit has its own hydraulic ram, giving excellent control with optimal down pressure maximising drilling capability. This will not pull out posts however.
Alternatively, the standard auger system can be mounted to the rock spike extractor. This is quite common as it gives operators the option of spiking or drilling with the same unit. Also the ability to pull posts out.
Auger options are;
75mm, 100mm, 125mm, 150mm, 175mm, 200 mm diameter augers.
These all drill to 1200mm deep, which can be extended with the 250mm auger extension.