| 摘要 |
PROBLEM TO BE SOLVED: To provide an auger casing with which smooth drawing can be performed even on a hard ground such as a boulder layer or a rock ground.SOLUTION: An auger casing comprises a tubular casing body in which an auger screw is disposed, and a dot-like protrusions which become convex outwardly from an outer circumferential surface of the casing body. A plurality of protrusions are arrayed to be uniform along a circumferential direction of the casing body. Thus, a contact area with a wall surface of a pore wall formed on a hard ground can be reduced, thereby suppressing resistance during drawing. |
