It is something of a commonplace in Heidegger interpretation that the famous example of the broken hammer provides us access to the present-at-hand (as opposed to ready-at-hand) and hence to the scientific stance toward things. When my class read the relevant section in Being and Time, therefore, I expected them to see this in the text — and yet they obstinately refused to do so. In fact, I think my insistence on this common interpretation hobbled our understanding of Heidegger’s actual account of the scientific attitude through the rest of the semester.
The actual point of the broken hammer example is to give us access to the world as such. When I confront a broken hammer, I don’t immediately reflect on the raw materials (except insofar as they might account for its brokenness, its unsuitability for its purpose) — instead, I reflect explicitly on the network of purposes to which the hammer belongs. Our ordinary absorption into our tasks does not allow for such reflection; only when the world “stops working” do we have the necessary distance. (Heidegger’s account of animal life in Fundamental Concepts of Metaphysics helps to clarify this aspect of our relationship to the world by contrast. The animal’s disinhibitor ring never “stops working” in such a way as to allow room for explicit reflection.)
This distance from the world might lead one to reflect further that the world of human products and purposes is not infallibly effective, hence that the beings we encounter do not exist solely for us. This gives us access to the present-at-hand (beings in their brute existence abstracted from any human purpose), but merely viewing things as present-at-hand is not yet the scientific attitude. (Basic Problems of Phenomenology has an interesting section that traces the origin of the Greek ontology to the experience human production, which accounts for the ontological privilege of the present-at-hand as what something “really” is, before receiving a human-imposed form.)
As he clarifies in chapter 4 of division 2, the shift to science takes place when we project upon beings in a new way — above all, when we project the present-at-hand as belonging to a total system called “nature,” which is defined by its mathematizable laws. This projection leads to a “project” in the normal sense of the word, which requires considerable practical labor and technical apparatuses (i.e., science is not about abstracting from the practical in order to get at the theoretical). And this aspect of projection is why Heidegger needs to wait until this late in division 2, because he needs to have the “future-first” temporality structure in order to account for the unique scientific form of projection.
When I brought this interpretation up with my handful of Heidegger tutorial students (who spent the spring semester following up on Being and Time by reading several of his seminars from that period), they all seemed to think it made a lot more sense. I apologize to the other students for misleading them and promise that I’ll do better next time. I also apologize to any readers for whom this was always painfully obvious.