Thread form/type for plastic.

[Brian Reay]

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.

[Richard]

Post by Brian Reay
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.

Richard

[Brian Reay]

Post by Richard

Post by Brian Reay
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.
Richard

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.

[Clifford Coggin]

Post by Brian Reay

Post by Richard

Post by Brian Reay
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.
Richard

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.

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.

[Richard]

Post by Brian Reay

Post by Richard

Post by Brian Reay
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.
Richard

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.

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

[Brian Reay]

Post by Richard

Post by Brian Reay

Post by Richard

Post by Brian Reay
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.
Richard

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.

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

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.

[Peter Fairbrother]

Post by Brian Reay

Post by Richard

Post by Brian Reay

Post by Richard

Post by Brian Reay
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.
Richard

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.

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

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.

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