Abstract: A volumetric machine comprises a screw rotatable inside a casing and cooperating with at least one pinion-wheel. The screw has a low pressure end adjacent a low pressure port and a high pressure end adjacent a high pressure port, the high pressure end being provided with an annular sealing device substantially preventing axial leakage towards a cavity maintained at the low pressure to reduce axial thrusts on the screw. The profile of the screw corresponds to that of the casing with a very small clearance, except in an area adjacent the sealing device where the clearance increases from the low pressure side towards the sealing device.