I've run into this interpretation (a pdf) in a few different places: that the word translated as "carpenter" was often used to describe a scholar, a person who was good at sorting out complicated ideas and fitting concepts together cleverly.

From that paper:

In Hebrew, the term for skilled craftsman or carpenter is commonly used euphemistically or idiomatically in reference to a Torah scholar. In the Jerusalem Talmud it is written, “This is something that no carpenter nor a son of a carpenter can explain.” The word for carpenter in this passage is נַגָּר (nagar), and is a reference to those individuals who were well known for being skilled in sorting out conflicting information, especially with respect to religious issues. This same concept is also expressed in the Babylonian Talmud.

In Greek (the language of the gospels), the word is tekton, τέκτων a skilled craftsman.

So, it might be that he wasn't working with wood at all, but with books.