The typical "model engineering" steam engine doesn't push materials to the limits. Cylinders are typically cast iron or bored out of brass rod. Tolerances aren'

The typical "model engineering" steam engine doesn't push materials to the limits. Cylinders are typically cast iron or bored out of brass rod. Tolerances aren't too tight. It is a slow process because metal is kind of recalcitrant, and making one-off parts is a lot more time consuming than manufacturing in series. To be a model engineer you have to love the process and love spending time alone in the workshop. Another tedious/fascinating aspect is the jigs and fixtures that are often necessary to make even one example of a particular part. Model engineers have to devise ways of performing machining operations (often conceptually very simple operations) and it really has to be something you love. If you see the manufacturing process purely as a barrier to realizing what you designed on paper, it can be a real drag. So, rather than a high-tech thing, pushing limits, I think the task here (making a small steam engine) is an example of craftsmanship (with lathe, file etc.) and of doing something that is intellectually/conceptually/materially very simple and undemanding, but doing by hand using inherently slow traditional processes. It's an aesthetic choice (and CNC, aluminum extrusions etc. would be ruled out for aesthetic reasons).