These are named "mechanical pencils" in English, but some other languages use the term "lead holder" (eg. French : portemine). What word in esperanto would be the most understood?
By coincidence, we were discussing this very question on Facebook in the Lingva Konsultejo just a few days ago. While PIV lists ĉukkrajono and puŝkrajono several people commented that these terms were not clear (especially before it was clear that I was quoting PIV and not simply making them up.)
The only alternative which was made was "reŝargebla krajono" - which seems OK to me. It seems you could also call it "reuzebla". In spite of what it says in PIV, it doesn't seem like there is a single stable term for mechanical pencil.
According to PIV: ĉukkrajono. Puŝkrajono, kies grafitaĵo estas tenata per ĉuketo.