I just got a 3956-02 for christmas and I removed the shipped collet nut to put on the chuck and I was shocked that it would not screw on at all. Not even one turn.
I tried putting the collet nut back on and it too does not screw down at all on the shaft. In fact nothing will screw down on the shaft now. I have no idea how the collet nut was able to be put on there when it shipped but the tool is now useless and I am getting really dissaointed here.