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 60mm of tubes with greater wall thickness. At the ends of the pipes cut trapezoidal threaded, length 60 mm.
The outer diameter - 108 mm
The inner diameter - 98 mm
Wall thickness - 5 mm
Mark steel - 45
Pipe length from 1 to 5 meters by agreement.