Multi-Tool: Won't Hold Bit

If the thread on the end of the armature were stripped, you would not be able to tighten the collet nut to secure the bit in place. The would require you to replace the armature. To do so, remove the front cap, collet nut and then the collet. Remove the brush caps and the brushes. Take out all screws that secures the housing together. Open the housing and remove all the hold-downs on the motor assembly, and lift up. Slide the old armature out of the field and install a new armature into the field. Place the motor back down into the housing and secure it with the hold-down screws. Reassemble the housing back together. Reinstall the brushes and caps, followed by the collet and the collet nut.

The collet holds the bit in place. When the collet wears out, it will no longer be able to do this and will require a replacement. Remove the collet nut and remove the old collet. Install a new collet and reinstall the nut.

The collet nut tightens down on the collet, locking the bit in place. If the nut wears, or the thread becomes stripped, the collet nut will no longer be able to lock the collet on the bits. Remove and replace the collet nut.