A mobile flanging machine for pipes has a portable frame on which a drive is mounted, which drives a roller via a transmission, and an adjustment mechanism fixed to the frame, on which a counter-pressure roller is movably held, wherein a bent flange can be produced on the pipe end by inserting a pipe end into a gap between the roller and the counterpressure roller. A method for assembling the mobile flanging machine involves transporting and setting up a frame with a rotatably mounted roller and an adjustment mechanism on which a counterpressure roller is movably held, transporting a drive with a first coupling part to the frame, connecting the first coupling part to a second coupling part for driving the roller, and fixing the drive to the frame.