My dremel tool runs fine (the motor)but the

there is a tubing connector between the collet and the motor, they hot glue these together. i just go to the auto parts store and get a new piece of tubing and glue it the same way.you will have to partially disassemble it to replace the coupling. if you disassemble it the collet just lays in the housing on the motor side cut the tubing to the right length. a slightly smaller size won't need the glue.