Also other ways to calculate moment of inertia are
1: to take the disk off, place it on a rotational pendulum and calculate the difference in period.
2: place the disc and axle on two bars at a slight decline. By timing the disc rolling measured distance at a measured angle you can calculate the MOI. If anyone wants a full explanation of these method please feel free to e-mail me and I will dig out my 2nd year lab books.

Joe Townsend