| 摘要 |
The tool has a stem (12) with a tip (16), an upper end (18) and a longitudinal axis To be connected to at least one rotating follower tube. A helical flight (20) surrounds the stem. The external diameter of the stem decreases form the upper end to the tip. The helical flight has constant external diameter. A cutter (24) is provided and is fixed to the helical flight close to the tip. The cutter projects outside the helical flight, and extends is a direction perpendicular to the longitudinal axis of the stem. |
