Patent ID: 6994494

Claim:
A device for use in a rotary boring procedure to produce bored piles in the ground, the device comprising: an auger of predetermined length and rotating in a first direction during the boring procedure; an encasing tube surrounding at least a portion of the length of the auger and rotating in a second direction during the boring procedure; the auger and the encasing tube being essentially vertically introduced essentially simultaneously into the ground during the boring procedure, the direction of introduction into the ground defining a feed direction; a helix forming part of the auger, the helix having a helix surface pointing in the feed direction; and means for increasing the roughness of the helix surface in the feed direction for facilitating material discharge, the increased surface roughness extending over a portion of the auger length needed for feed purposes, wherein the increased surface roughness takes place by full or partial-surface coating of at least the helix surface directed in the feed direction, circular or angular grains of wear-resistant material being non-positively connected to the auger helix surface by means of an adhesive matrix.