What are the risks of reusing a thread cutting screw in a plastic subsrate?
I have a service operation that is disassembling a small appliance PC housing that was originally assembled with a thread forming/cutting screw (tri-lobe). Is there an issue of resuing the disassembled screws if they are extracting a very small amount of the plastic?
No. As long as the amounts of plastic being removed does not exceed the structural/strength limits. If it poses no risk of breaking if you try and bend it slightly, or apply the same weight it would normaly carry, then it is fine.
If you reuse a plastic screw enough times though, it will need to be replaced.