I have used this tool for years, but when I took it out to use it this weekend, I couldn't get the collet nut to lock down on the bit. The shaft of the bit just falls out no matter how much I tighten the collet nut. I bought a new collet nut set, but that didn't help. None of the bits I have lock into the device. The motor runs fine, the bits just fall out and won't spin if I can't lock them in place. What's going on? I'm using the tool the same way I always have.

Tools & Hardware - Others - Dremel - Variable - Speed Multipro Rotary Tool 395