Nibs and feeds (Lamy's at least) are not designed to be constantly removed! They rely on friction to stay in place. Constant removal of the pieces causes wear and looseness.
I second that.
I never remove any of my Lamy nibs from their feeds.
I buy my pens with my preferred nib size and leave each nib on its feed, all the time, even when it is time for cleaning or, before an ink change.
If one wants to experiment with different nib sizes, one can buy standard colors Safari, Al Star and Vista in each nib size then switch the feeds from one pen to another for line variation.
Lamy Joy can be bought as sets with different calligraphy nibs.
Edited by Anne-Sophie, 25 June 2020 - 21:57.