Abstract: A graphite target disk for a rotating anode x-ray tube is adapted for mounting it on a rotor stem in a manner which reduces the probability of the target cracking when it is subjected to high magnitude thermal and rotational shocks. The graphite disk has a counterbore in its front and rear faces which are connected with a smaller central bore so the counterbores define annular shoulders. A washer having a slot which serves as a keyway is brazed concentrically onto the shoulder of the front counterbore. The rotor stem has a threaded end which registers complementarily in the slot to effect a driving connection and the stem has a radially extending shoulder which interfaces with the shoulder in the rear counterbore. A nut on the threaded stem end secures the target to the stem.