Formula for screw conveyor

1. I need the formula for finding the volume of a screw conveyor.

Flight diameter : 10.5 inches ,Length of the screw : 8ft, Shaft dia : 1.5 inches.

Distance b/w flight : 7 inches.

2. Secondly to have distance b/w flight say 10 inches for a shaft dia of 1.5inches what should be the bore to be drilled of the flight.