GUN DRILL TROUBLESHOOTING GUIDE TROUBLESHOOTING GUIDE Drill Problems Hole Problems Excessive margin wear Rough surface finish Excessive flank wear Damaged wear pad Excessive corner wear Conical entrance Curved hole axis Flute bending Built-up edge Poor drill life Undersized Oversized Possible Cause Breakage Cratering Chipping Drill heat Runout Poor clamping + + + + + Insufficient coolant flow + + + + + + Low coolant pressure + + + + Incorrect coolant type + + + + + + + + Feed fluctuations + + + + + + + + Feed too high + + + + + + + + + + + + Feed too low + + + + Spindle speed too high + + + + + + + + Spindle speed too low + + + Material structure + + + + + + + + + Material shrinking due to heat + + + + + + + + Thin wall section of workpiece + + + + Misalignment + + + + + + + + + Undersized hole + + + + + + + Rough cutting edge finish + + + + + + + + Built-up edge + + + + + Worn out edge + + + + + + + + + + Interrupted chip flow + + + + + + + + + + Flute clearance too small + + + + + + + + Incorrect drill profile + + + + + + + + + + + + + Incorrect head angles + + + + + + + + + + + + + Vibrations + + + + + + + + + + + + + Oversized bushing + + + + + + Gap between bushing & workpiece + + + + + + + + + Undersized bushing + + + + + + + + Loss of coolant pressure + + + + + + + + + High coolant pressure + + Overheating coolant + + + + + + + + Insufficient coolant + + + + + + + + + + + Head inside angle excessive wear + + + + + + Head outside angle excessive wear + + + + + + + Carbide head too short + + + + + + + + + + + + + + + + Tool heel drag + + + + + + + + + + + Worn supporting pads + + + + + + + + + Tool whip - reverse tool rotation + + + + + + + + + + + 707