A drive mechanism for a drug delivery device, preferably for a pen-type injector, the mechanism comprises a spindle (6) movable in a first direction during a delivery step, a splined portion (5, 11) operatively coupled to the spindle (6), and retraction means (12, 15, 16, 17, 20) acting on the splined portion (5, 11) at least at the end of the delivery step. Thereby, that after the delivery step the spindle (6) and/or the splined portion (5, 11) is moved in a second direction contrary to the first direction, such that the whole drive mechanism is relieved from stresses.