I mad up my first extended length QB tube on a drill pres. I only needed to do small slots.The chuck came out of the taper, I stopped immediately. Next trick was to apply some LocTite 222 to the taper shaft left it for 24hrs and it held to finish the slots doing cuts of about .005" until I went through. I couple of words of caution, don't use carbide as a drill press is not nearly rigid enough, if it splinters you'll be in trouble. If the chuck drops out that end mill is super sharp and you won't want it catching up to you while it's spinning.
You should not need to put loctite on the quill taper.Clean the socket, clean the taper, drive the chuck into the socket with wood block on Chuck face with Chuck jaws retracted and clear of Chuck face.I will stay in unless it's dirty or has mating surfaces damaged