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. 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. The increase in the surface roughness extends at least
over the auger length necessary for feed purposes.