On 6 Feb, 17:48, 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.

Or if you can get a rough surface on the plastic, which one pretty
much always can/does with thermosets, fill the holes with araldite,
redrill pilot and screw.

You might also be successful using plastic sleeving. Put a little in
the hole, hold it on the outside as you screw, cut off excess.

Or use those press-in fasteners insteaad of screws.


New bigger ss screws is usually the easiest way.


NT