How did they made these ...in XVI century?

[Claudio HG]

I'm always mermerized when I see the machines made in the past, and I wonder how did they made them. In particular how did they made the parts that I've highlighted with red circles? Say the parts tagged A or B, did they made them with a hack saw and a file?? ...sooo precise?
And what about the parts tagged C and D?
(The machine in picture 2 and 3 were made by Vaucanson in 1783. I taken these pictures at the Musee des Art et Metiers in Paris, in 2019.)