Formation / improper bit selection • Formation too abrasive for bit type selected. • For abrasive formations, select bits with smaller cutters and/or greater blade count. • Use premium PDC cutters. Excessive RPM for application and specific bit type • Optimize RPM for formation. • For abrasive formations, select bits with smaller cutters and/or greater blade count. Inadequate hydraulics • Increased hydraulic energy is needed to address this condition.