Measure the gap in the tiles with a standard ruler or millimeter ruler to be more precise. You need to measure to acquire the right drill bit. A drill bit too big will overflow onto the tiles and damage them.
Purchase a drill bit that matches the gap. Attach the drill bit to the drill and secure with your drill bit tightener. Put on your protective eye goggles.
Plug in the drill, using a grounded extension cord if necessary. Place the drill in the center of the tile grout gap. Power the drill and slowly drill out the tile grout, working in small sections.
Brush away the loosened tile grout before moving to another section. Tile grout can easily scratch ceramic tiles. Continue slowly drilling the rest of the grout by again working in small sections.