Well, I have not tried it on boiled eggs but raw. So for this reason I recommend to leave the egg in the egg box by putting a paper towel folded several times below and above simply fired the spring above the weight, since it is much too steep, and that it blew the egg. Instead I toque 5 times the egg weight going up to the top and dropping it. Thus the top of the egg goes alone or sometimes I use my little nails ...
PS: To remove the spring, remove the black plastic cover, remove the nut with a wrench, remove the spring then do the reverse procedure to reassemble the (without calling the spring course ;-))