NOVELTY - A bore within a tubular portion has a central axis and receives drilling fluid with particulate matter (205). A fin (305) creates a rotary motion within drilling fluid when drilling fluid flows through tubular portion and forces a denser portion of drilling fluid with an increased concentration of particulate matter away from central axis. A lighter portion of drilling fluid that comprises a reduced concentration of particulate matter continues to flow throughout bore and out of drill bit (104) into a wellbore annulus where denser and lighter portions coalesce.    USE - Downhole centrifugal drilling fluid separator for use with drill bit during drilling of wellbore for oil, gas and geothermal exploration.    ADVANTAGE - The lighter portion of drilling fluid can cake the bottom of the wellbore with less particulate matter without the separation, so that the cutting elements are provided with the ability to cut fresh formation and to interfere minimally. Since a significant amount of particulate matter is removed from the lighter portion, the lighter portion exerts a lower pressure against the well bores floor. Thus, in only selected regions of the wellbore, a controlled under balance drilling situation can be created. This result in the formations pressure contributing to breaking the well bores floor, thus enabling more efficient drilling. The under balanced condition requires less effort to penetrate into the formation, thus, increasing the rate of penetration and durability of the drill bit. The drilling fluid remove cuttings from the well, control formation pressures, seal permeable formations, maintain wellbore stability, and minimize formation damage. The denser portion is combined with the lighter portion, so that the drilling fluids weight is more appropriately matched to push against the well bores wall and prevent cave-ins. Each fin in a leading row is spaced around the circumference of the central hub and has the same angle of attack, thus the succeeding trailing rows are progressively increased in angle and the centrifugal effect is enhanced on the drilling mud. Lighter drilling fluid may flow through the turbine and into the porting mechanism and the hammering action of the center indenting element provides increased efficiency in the drilling process. Thus the lighter drilling fluid reduces the wear on both the porting mechanism and a turbine, while reducing the buildup of particulate matter in the piston chamber. The denser drilling fluid is expelled out of the tool string above the bottom-hole assembly, preventing the drilling fluids caking effect to plug up the downhole tools equipment or wear down their components. The heavier weight drilling mud can be routed from the periphery of the tubular portion towards the center through a narrowing diameter of the barrier and a downhole tool operates more efficiently within a central portion of the alternate pathway.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for method for separating mixed drilling mud downhole.    DESCRIPTION OF DRAWING(S) - The drawing shows the cross-sectional view of the downhole centrifugal drilling fluid separator connected with drill bit.    Drill bit (104)    Formation (105)    Particulate matter (205)    Fin (305)    Hub (311)