How much larger than the pipe size should the drill bit being used to drill holes in the floor joist be?

Wrong Question... You first determine the hole size required for the mine plan and then based on the air capacity and pulldown capacity of the drill rig you can determine the optimal drill pipe diameter to achieve productivity from the drill. What size is your drill? Air Capacity in CFM, Pulldown Capacity. What size does your drilled hole (diameter and depth) need to be to suit the mine plan (for the drill & blast process)?