Thread form/type for plastic.

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.
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On 04/07/2018 21:50, Brian Reay wrote:


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.
Richard
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On 05/07/2018 18:10, Richard wrote:


Thank you.
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.
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On 05/07/18 20:05, Brian Reay wrote:


Holes in the rear of the TV are likely for a VESA mounting pate, to which is attached the bracket of your choice. As far as I recall they are a standard metric size.
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Clifford Coggin
Kent
England
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On 05/07/2018 20:05, Brian Reay wrote:


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
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On 06/07/2018 10:51, Richard wrote:


Thank you. I'm familiar with the VESA system. However, the position we want the TV doesn't lend itself to using a 'wall' bracket.
The holes I plan/want to use are for a foot/feet - I assume an alternative to the one supplied which uses another set of holes.
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On 08/07/18 00:02, Brian Reay wrote:

Well, you get self-tappers for sheet metal, and self-tappers for plastic.
Afaik the main differences are that the threads for the sheet metal ones go all the way to the head, and the minor diameter of the plastic ones is perhaps smaller.
Screw suppliers will sell you screws meant for plastic, if you pay them enough. But for me, in plastic, any self-tapper will do.
Peter Fairbrother
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