The situation may be different now - in that it is possible to make accurate metal prototypes, DIY if a person has the required expertise. ie I sometimes causa

The situation may be different now - in that it is possible to make accurate metal prototypes, DIY if a person has the required expertise. ie I sometimes causally read a English magazine named "Model Engineer" that means projects with tight tolerances. I observe there are also small scale "Milling Machines " advertised