If your drill chuck stops turning under load, the most common cause is a slipping spindle pulley, the pulley located directly above the chuck.

Over time, the connection between the spindle pulley and the drive sleeve can become worn or smooth, causing the pulley to lose grip. This results in the chuck stopping even though the motor continues to run.

🛠️ How to Fix a Slipping Spindle Pulley

1. Remove the (LH) Pulley Nut

   • This is a left-hand thread nut; turn it clockwise to loosen.

2. Remove the Spindle Pulley

   • Use a rubber mallet or dead blow hammer to gently tap the sides of the pulley while pulling it upward.

   • Once it pops loose, set it aside.

3. Access the Oscillating Mechanism (if needed)

   • With the pulley off, you'll also be able to reach the screws holding the oscillating mechanism.

4. Improve Surface Grip

   • Use fine-grit sandpaper or emery cloth to lightly roughen:

     • The inner diameter (I.D.) of the pulley

     • The outer diameter (O.D.) of the drive sleeve

   • This helps the pulley grip more securely when reinstalled.

5. Reinstall the Pulley

   • Press the pulley back onto the drive sleeve.

   • Tap gently with the mallet to seat it fully.

6. Reattach the (LH) Pulley Nut

   • Tighten it securely (left-hand thread, turn counterclockwise to tighten).

If the problem persists after this repair, there may be additional wear on the spindle or drive sleeve that requires inspection or replacement.