DIAGNOSIS The jaws inside the keyless chuck are worn or contaminated with debris, preventing them from gripping the bit shank properly.
FIX Deep clean the chuck jaws.
- Open the chuck fully.
- Spray brake cleaner or isopropyl alcohol into the jaws to dissolve built-up grease and metal dust.
- Insert a bit and open/close the chuck repeatedly to work the cleaner in, then wipe excess away.
- Let it dry and test. This fixes it 80% of the time.
IF THAT DIDN'T WORK The chuck needs replacement. It's a standard 1/2" keyless chuck. The retaining screw inside is reverse-threaded (lefty-tighty). You'll need a large Allen key and an impact to break it loose.
HEADS UP Never use the drill to tighten the chuck by holding the outer sleeve and pulling the trigger—this damages the gear mechanism. Always tighten by hand.