Abstract: In a boring machine, rotation of a motor is transferred to a pipe spindle and a shaft, a cutting edge feeding mechanism arranged side by side with the pipe spindle moves the shaft toward a workpiece and a cutting edge attached to an end of the shaft drills a hole in the workpiece. The cutting edge feeding mechanism slidably but non-rotatably supports a chain holder around an outer circumference of the pipe spindle. A sprocket wrapped around by a chain is rotated by a handle to move the shaft. The radius of rotation of the handle is reduced to slowly move the shaft. The maximum torque of the motor rotating the shaft is controlled. The number of cutting edges falls within a range from six to eight.

Abstract: A reliable sleeve unit with a water-absorbing swelling rubber that provides a reliable seal to a branch hole and the branch stop while controlling the development of rust. The rubber layer is applied on a cylindrical metal sleeve having a flange on its outer circumference in a manner such that a certain height length of the metal sleeve from its bottom end face is left uncovered. The height length of the flange is set to be long enough for the flange to be inserted into the inner circumference of the branch pipe to be connected to the branch hole. The rubber layer is applied onto the metal sleeve in a manner such that the height length of the rubber layer coating the metal sleeve is approximately equal to the wall height of the branch hole, or in a manner such that the bottom edge of the rubber layer is set to be higher than the bottom end face of the metal sleeve.

Abstract: A rust-resistant cylindrical metal sleeve for preventing rust and corrosion from developing around the wall of a branch hole when the sleeve is rigidly fitted into a branch hole that is drilled through the wall of a metal conduit such as a water pipeline. The sleeve has a projecting portion on its outer circumference and an inner flange portion inwardly projecting at its lower end. The metal sleeve on its outer circumference is coated with a water-absorbing swelling rubber into which a synthetic resin rubber and a water-absorbing polymer are blended. Preferably, 100 parts by weight of styrene-butadiene rubber or ethylene-propylene-dienemetylene linkage rubber is blended with 10 to 40 parts by weight of the water-absorbing polymer. Since the water-absorbing swelling rubber increases its volume as it absorbs water, pressure in the rubber increases, preventing water ingress through between the metal sleeve and the wall of the branch hole.