The machining device is for machining the material of a pipe system that has a joint area between a pipe that has a smaller inner diameter and a pipe that has a larger inner diameter. The device has protruding parts that have been adapted to position the device inside the pipe that has the smaller diameter. A steerable actuator is adapted for removing material from the joint area and steering device for controlling the direction of the machining device in relation to the longitudinal axis of the pipe that has the smaller inner diameter while removing material from the joint area. The method is for machining material of the joint area that has a thinner and a thicker pipe.