A magnetic disc unit comprising motor means having a spindle rotatably mounted on a base for rotating a magnetic recording medium, a loading arm having one end swingably attached to the base and a center cone rotatably attached to the other end of the loading arm. The magnetic recording medium is interposed between the spindle and the center cone. A button lever having a control button projecting from one end is attached to the base and is movable with respect thereto. A clamping lever is also mounted to the base and linkage means interlocks the control button and the clamping lever. Depression of the control button translates the button lever so as to rotate the clamping lever to a first position in which the center cone engages the spindle with the magnetic recording medium interposed therebetween. Further depression of the control button translates the button lever to rotate the loading arm to a second position in which the center cone is released from the magnetic recording medium and the clamping lever presses the loading arm in the vicinity of the center cone.