Flat bottom drills are an excellent solution for counterbores or when you need to remove the angle left from a typical drill and a flat floor is required. Flat bottom drills are also used to drill into curved or angled surfaces that a typical drill would walk. Flat bottom drills are also an excellent choice when a burr-free hole is require when parts have crossholes or intersecting geometry. If you need to drill a partial hole that does not make 360 degrees contact around the drill, flat bottom drills are the best choice when the drill is partially off the part. The longer a drill is, the higher the chance that it will walk. Start a hole with the shorter length flat bottom drill first before using the long length drill.