In this paper we revisited the effect of dither signal in servo-drives with dynamic friction. In opposition to existing results based on memoryless friction models, the average effect of friction can be qualified in terms of amplitude and frequency of the dither signal. This result is obtained by a new proposed modification of singular perturbation theory that, in particular. allows the stabilizing effect of the dither to be rigorously proved. Experimental results showing the stick-slip extinction are also presented.