Hamming’s concrete instance of Mechanization produces a different product: when fabrication moved from hand to machine, joining moved “from mainly screws and bolts to rivets and welding.”
Threaded fasteners are the hand-native join, a person with a wrench, working slowly, one at a time. Welding is the machine-native join, continuous, fast, cheap at volume, and dependent on fixturing and precision a human does not have.
Same structural function, different physics, different economics, and different consequences downstream: Welds trade serviceability for production cost.
He pairs it with a second instance: moving from hand accounting to machine accounting forced changes to the accounting system itself.
Source: The Art of Doing Science and Engineering: Learning to Learn