For a 1/8 inch rivet, the appropriate drill bit size to use is a #30 drill bit. The #30 drill bit has a diameter of approximately 0.1285 inches, which is slightly larger than the 1/8 inch (0.125 inch) diameter of the rivet, providing the correct hole size for the rivet to fit properly.
This size ensures a proper fit for the rivet in the drilled hole.