I'm trying to determine if the screws used in plastic -metal screws into 'hard' plastic, typically found on things like TV cases etc. I'm thinking of the screws that don't go into metal bushes- have a special thread form.
They look very like 'self-taping' screws or even screws intended for chipboard - a near parallel spiral, except near the tip.
I am not really sure what your question is , but ... IMHO the best screws for plastic are those with an extremely course thread pitch. Often the pitch is half the major diameter or more. Thread profile steep sided and sharp, minor diameter same as, or smaller than the pilot hole in the plastic. Point tapered. Not sure if there is a standard or if manufacturers design their own.
Perhaps I should explain. I need to mount a TV. It has 4 pre-drilled holes which look to be 'tapped' (ie have signs of a thread in the plastic) for (I assume) an alternative stand/feet to that supplied. (Perhaps for a different market etc). No screws for these holes are provides and, for the task at hand, none of the supplied ones would be long enough (even if they fit otherwise).
Therefore, I need to find/source 4 suitable screws. When in place, the TV will be subject to vibration etc (it is for a motorhome) and the holes are along the lower edge. They will, hopefully, provide the only mounting.
At the moment, we pack the TV away. This will allow us to save on 'set up/tear down' time. Obviously, the TV isn't used while in motion.
As Cliff said there are normally 4 tapped holes on the back of the TV for a VESA mount. I would assume that holes near the lower edge would be for a foot mount only. Are you sure there is not a VESA mount on the back? Which TV is it? I have a Cello in my MH. Richard