Abstract: The tool assembly includes a main body and a bypass assembly. The main body has an off-set through bore and a cavity to fit the bypass assembly. The cavity includes a cavity surface, a first fluid bypass port, a second fluid bypass port, and a pressure inlet port. There is also a flow restrictor in fluid connection with the pressure inlet port. The bypass assembly includes a bypass housing, a pressure chamber, a piston with a first piston position and a second piston position, and a spring assembly. A pressure differential created by fluid flow through the pressure chamber and flow restrictor actuates the piston between the first piston position and the second piston position. The proportional flow through the tool assembly and through the bypass ports can now be controlled to perform the downhole work, including drilling and hole cleaning.