What is the basic process of manufacturing metal parts of a machine?

Update:21-01-2020
Summary:

To do casting, milling and turning, and do some drillin […]

To do casting, milling and turning, and do some drilling and welding.

Precision parts are machined from raw metal blocks (gearboxes, lifters, valves).

Large pieces such as chassis are usually welded to small pieces (frames).

They can be finished with plating or paint.

Molten metal is cast and then machined (bulk engine block, header and transmission, and differential case).

Draw, stamp, cut and bend thin pieces from sheet metal parts (brackets, trim strips, electrical parts, body parts (hoods, fenders, etc.)) of various thicknesses.