The chuck jaws are likely obstructed with debris. Clean it.
- Fully open the chuck by rotating the sleeve counter-clockwise.
- Use compressed air or a small brush to remove dust, metal shavings, or dirt from inside the chuck and the jaws.
- Apply a small drop of light machine oil (like 3-in-1 oil) to the chuck threads. Do not use grease.
- Insert a drill bit. Hand-tighten the chuck firmly clockwise until it's snug.
- Grip the chuck sleeve with one hand and give the trigger a short burst in the forward (driving) direction. This will finalize the tightening.
IF THAT DIDN'T WORK: The chuck might be worn or damaged. Check if the jaws move evenly. If one is stuck or misaligned, the chuck needs replacement. Also, ensure you're using bits with standard, undamaged 1/4" or 3/8" hex shanks (depending on your chuck type).
HEADS UP: Always secure the bit by holding the chuck sleeve, not the body of the drill, when tightening or loosening. This prevents damage to the gearbox. The 3-year European warranty covers defects in the chuck, but not damage from misuse.