[piva00]

Honest question: what makes it a hobby and not just a collection?

I think of pens as tools for a hobby but not as a hobby itself, collecting pens I can consider a collection hobby though.

I get confused because I've seen this stated a few times and it does not make sense to me, there's no "power drill hobby" but one can have a hobby of collecting power drills.

[iancmceachern]

It's a hobby if you go to "shows" and talk to other hobbiests about it. A pile of stamps in a shoebox in someone's attic is a collection.

A well presented book of stamps that is taken to shows, shown, discussed, etc. That person is a hobbiest.

[copperx]

Not the OP, but learning and practicing calligraphy is a hobby and is often associated with pen collecting. A pen hobby might also include maintainace, repair, and restoration of an often large collection of pens.

[OJFord]

I suppose if you spend time researching, reading about, talking about (online fora etc.) the thing you collect then it starts to look more like a hobby.