A shaft for rotationally coupling a main device to a tubular device includes a first free end that is configured to be introduced into the tubular device, and a second end configured to be secured to the main device. The shaft also defines at least a first bearing region along an outer circumference that is configured to form a contact in a hollow accommodating region of the tubular device, and further includes at least one torque-transmitting section configured to engage with a torque-transmitting section of the tubular device. A securing device of the shaft includes a locking device that, in a locked state, is configured to prevent the securing device from being dismounted, and that, in an unlocked state, is configured to enable the tubular device to be dismounted. The securing device further includes an interlocking device that is arranged on the first end of the shaft, and that enables locking and unlocking the locking device.