Abstract: An internal mandrel is disclosed which is used for supporting the inner wall of a pipe during bending. A plurality of unique resilient discs is provided. The discs are dome shaped with a rim at the bottom of the dome. The dome has a concave side and a convex side. The discs nest together, i.e. convex side of one into the concave side of the adjacent disc to form a resilient plug. A hydraulic cylinder applies force on the convex side of the outermost disc and the concave side of the innermost disc to deflect the rims of the disc outwardly to contact the inner wall of the pipe being bent.