Abstract: A crust breaking machine includes a self-propelled carriage having front wheels and rear wheels, a crust-breaking tool of the continuously breaking type mounted on the carriage, and an arm provided on the carriage and adapted to support the tool. This arm is mounted for swinging movement in the vertical plane and in the horizontal plane, with a mounting located between the front and rear wheels and in front of the driver's seat seen in the normal driving direction of the machine during crust-breaking. Thus the tool can be brought into a working position on each side of the carriage and into a rest position in front of the carriage.