An abrasive fluid jet cutting device is disclosed comprising a rotating joint that includes a first path for abrasive and a second path for fluid, a mixing chamber where the first and second paths meet, a first expanding volume arranged above the first path to accumulate abrasive, and a second expanding volume arranged below the first path to accumulate abrasive between the first volume and the mixing chamber, in which the second volume forms a barrier against the return flow of humidity along the first path.