Determine the output RPM of a driven pulley based on diameters and input speed. Fundamental for belt-driven machinery like drill presses and compressors.
For speed ratio, no. Only the diameter where the belt rides (pitch diameter) affects the speed ratio.
Use a smaller pulley on the motor and a larger pulley on the machine. This slows down the machine but gives it more cutting/driving force.
D1*N1 = D2*N2