How do I remove and replace a drill chuck?

A chuck is a consumable that outlasts the tool on good drills and does not on cheap ones. Worn jaws that no longer grip, a chuck that will not run true, or one seized solid are all replaceable for a fraction of a new drill. The job is straightforward, and almost every failure of it comes from one detail: the reverse-threaded retaining screw.

Safety

What you'll need

• Replacement chuck of the correct thread or taper
• Large hex key
• Screwdriver that properly fits the retaining screw
• Mallet or hammer
• Penetrating oil (optional)

Step by step

1. Identify how the chuck is attached.Three ways. A threaded spindle with a left-hand retaining screw inside the jaws, which covers most cordless drills. A plain threaded spindle with no screw. Or a Jacobs taper, a friction fit found on older corded drills and drill presses, with no thread at all.
2. Note the size stamped on the chuck.Threaded chucks are marked with a thread size, commonly a half-inch UNF or a metric equivalent. A taper chuck is marked with a taper number. Buy the replacement to match — this is where the job goes wrong before it starts.
3. Open the jaws fully and look inside.Shine a torch down the middle. A screw head at the bottom means a retaining screw. No screw means threaded or tapered attachment.
4. Remove the retaining screw the wrong way.It is left-hand threaded so that the drill's own rotation does not undo it. Turn it clockwise. Use a screwdriver that fills the head completely, because these are usually tight and frequently rounded by the first person who tried.
5. Break the thread with a hex key and a shock.Fit the short arm of a large hex key into the jaws and tighten them onto it hard. Then strike the long arm sharply with a mallet in the anticlockwise direction. A single firm shock beats steady pressure.
6. Use the motor if that fails.With the hex key clamped and the long arm resting against the bench or a solid block, set the drill to reverse and blip the trigger. The impact when the key hits the block breaks the thread. Keep hands clear and use very short bursts.
7. Clean the spindle before fitting the new chuck.Wire brush the thread, wipe the taper if it is a taper fit, and check the spindle is not bent by rolling the drill on a flat surface with a long bit fitted.
8. Fit the new chuck and remember the screw.Screw the chuck on hand tight, then tighten it fully by reversing the hex key trick. Refit the retaining screw anticlockwise. Forgetting it means the chuck unscrews itself the first time you use reverse.
9. Seat a taper chuck by shock, not by thread.A Jacobs taper chuck is driven on. Support the spindle, offer the chuck up square and drive it home with a soft mallet on a block of wood across the face of the jaws with them closed.

Tips

• Photograph the assembly before you start. Screw, washer if fitted, chuck orientation — five seconds now saves a puzzle later.
• A keyless chuck can usually be replaced with a keyed one and vice versa, as long as the thread or taper matches. It is a reasonable upgrade if bits keep slipping in demanding work.
• On a very cheap drill, a replacement chuck can cost a meaningful fraction of the tool. Price both before committing to the job.

Common mistakes

• Turning the retaining screw anticlockwise — It is a left-hand thread, so that tightens it. People shear the head off, and drilling out a hardened screw inside a chuck is a genuinely miserable job.
• Using steady force instead of a shock — Threads and tapers that have been running under load for years release to impact, not to leverage. Steady force just rounds the hex key.
• Buying a chuck by capacity rather than by fitting — 10mm and 13mm describe the biggest shank it takes. What matters for fitting is the thread or the taper on the spindle.

Questions people ask