In the casing in difficult soils used casing pipe of high strength steel. For repeated use of expensive pipe for joining pipes used nipple with a straight thread 40 mm from the pipe with greater wall thickness. At the ends of the pipes cut internal trapezoidal thread, length 40 mm.
The outer diameter 89 mm
The inner diameter of 79 mm
Wall thickness 5 mm
Mark steel - 45
Pipe length from 1 to 5 meters by agreement.