Why does my drill chuck keep slipping or jamming?

A keyless chuck grips through three jaws driven by a threaded sleeve. Dust, worn jaw teeth and hexagonal driver bits used in a round chuck all reduce that grip, and once a bit has spun once, the marks it leaves make it slip more easily next time.

Step by step

1. Open the chuck fully and look inside.Three jaws should come together squarely and evenly. Rounded or chipped tips mean the chuck is worn out.
2. Blow the dust out.Masonry dust in the chuck body is the commonest cause of both slipping and stiff operation. Open fully, blow it out, work the sleeve a few times.
3. Push the bit fully in.Short-gripped bits pivot and slip. The shank should be well inside the jaws, not just nipped at the tip.
4. Tighten in two stages.Hand-tighten, run the drill briefly in a low gear to settle the bit, then tighten again firmly. Most keyless chucks need this second pull.
5. Hold the chuck and pulse the trigger to seat it.On drills with a spindle lock or a two-sleeve chuck, hold the rear collar and turn the front hard. A single-sleeve chuck usually needs the ratchet click.
6. Check what shank you are using.A hex driver bit held directly in a round chuck grips on three of its six flats and slips easily. Use a bit holder or an impact driver instead.
7. Look for damage on the bit shank.A shank that has already spun has a polished flat on it. It will keep slipping — grind a small flat properly or replace the bit.
8. Replace the chuck if the jaws are worn.Chucks unscrew from the spindle, usually with a left-hand-threaded retaining screw inside the jaws that must be turned clockwise to loosen, then the chuck itself anticlockwise. Replacements are inexpensive.

Tips

• The retaining screw inside a chuck is almost always reverse-threaded. Turning it the normal way tightens it.
• If a chuck jams shut with a bit in it, grip the bit in a vice and turn the chuck sleeve by hand — you get far more leverage than on the tool.
• For repeated screwdriving, an impact driver with a hex collet solves this problem permanently.

Common mistakes

• Tightening once and starting work — Keyless chucks settle under the first load. Without a second tighten the bit works loose within a few seconds and the shank starts to score.
• Holding hex driver bits directly in a keyless chuck — The jaws contact only three of the six flats, so grip is poor and the bit spins, damaging both the shank and the jaw tips.

If it doesn't work

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