The spiral auger operates similar to a corkscrew and does not cut off the soil. The auger is usually applied when hard layers need to be penetrated. The spiral auger has a negative end, i.e. the centre of the auger end is whetted away. For profile research (soil mapping) the spiral auger is seldom used. Its use is confined to augering through very hard layers, e.g. boreore, brick layers, chalk and lime profiles in combination with other auger types. The single spiral auger is standard equiped with a contact for electrodes.