Ian Stirling wrote:
robgraham wrote:
I've a plastic cold water filter that is some 150mm in diameter and is
assembled using eight 4mm dia self tap screws. Five of the screw
holes have partially or totally stripped their thread, not so much due
to abuse - possibly in the original assembly though (!) - but I think
due to an over large hole existing in the manufacture for the pilot
hole.

The plastic is hard but I is I think thermoplastic rather than
thermosetting - what suggestions are there for a solution ?

Obtain a shaving of the plastic, and a soldering iron.
While the iron is heating up, try melting the shaving with it.
If it does, then scrape off more, and smear it into the hole, using the
soldering iron, with a block of wood or something behind it.
Do this outside, or in a well-ventilated place.
Until you build it back up to flat plastic.
Now, screw it up.

Or more likely, repair using a nut and bolt, with the bolt screwed
through the other way from what the screws were, and then tightened.


Another option is a thread tapping bit..forget what they are called -
that self taps into something and has an internal machine screw thread.

If its a thermoset plastic just chars without melting) use car body
filler and redrill teh holes later.