Covington Large Sphere Machine 1''1/4 x 9'' Spheres. Rough cut 80 grit only. 80 grit is classified to size. Or finer grit. To speed up surface cut I grind dime size flat spot all over the surface of the sphere. and i use cup size of 1/2 2/3rds the length of spheres diameter, for rough cutting the surface grind with 80 grit.