1. Check the drills that precede the final drill to be sure they are the correct size.
2. Be sure the final drill is not dull or damaged.
3. Be sure the coolant is reaching into the hole or consider using a coolant hole drill.
4. Check the drill to be sure it is not bent.
5. Check the Drill Collet to be sure it is not damaged, is clean, and firmly holds the drill.
6. If chips are not breaking into small sizes that are easily removed from the hole, consider a chip-breaking drill.