Stealth Pilot wrote:
... coca cola PET bottles ... melting this down to a rod of
machinable plastic. ...

are there techniques that work well enough in the workshop?
...

From my very limited experience, I would say NO! "Melting down" is not
something that PET does. It is so viscous that it doesn't flow to fill
a container except under pressure. Under heat it becomes soft globs,
not what you'd call liquid.

To repeat: from my very limited experience,
Bob


--
Nota for President