Device for producing bored piles

Device for producing bored piles having an auger, which along at least part of the auger length is surrounded by a rotating encasing tube and during boring the encasing tube is rotated in or counter to the rotation direction of the auger and in which the auger and the encasing tube are introduced essentially simultaneously into the ground during boring, wherein to facilitate material discharge, the surface roughness of the auger helix surface pointing in the feed direction is increased compared with the roughness of the rolled surfaces in a complete or partial surface manner by additional machining, and the increase in the surface roughness extends at least over the auger length necessary for feed purposes.