head thus improving overall nozzle efficiency as the oil reaches the head assembly it passes from the housing wall onto the facing surface of the main body portion and spreads over the surface of the passageway grooves continuing to be driven forward along the passageways by the carrier gas as the passageways exit onto the tapered exit portion 36 of the head the oil film travels to its needle point 22 it collects there forming a droplet of growing diameter until the force exerted upon the droplet by the exiting carrier gas is sufficient to remove it from the point carrying the droplet with the carrier gas flow to the target to be lubricated the passageway grooves have an uneven cross sectional area the cross section of the groove lessening towards the exit edge 50 of the housing 18 this causes any lubricant that remains in that portion of the groove when gas flow is interrupted to be drawn back towards the wider entranceway portion 44 of the groove by surface tension thus nozzle dripping is minimized the head construction depicted in fig4 can be machined with a cnc lathe milling head a construction in which the entranceway is more offset with respect to the central exit portion of the groove as generally depicted in fig1 with a pair of opposed helical wall portions requires more complicated milling procedures but may have a marginally higher efficiency while the.