I need some M4 x 12mm countersunk plastic screws. The obvious easily
obtained material is nylon but I see that some other plastics are also
available - e.g. clear acrylic.

I'm not expecting metal strength but it would be good to know which
(reasonably priced) plastic is going to be stronger. I'm aming to use
the screws through a sheet of closed-cell plastic to pull things
'into' the plastic (rather like upholstery buttons).

--
Chris Green
·

Chris Green <cl@isbd.net> wrote:
> I need some M4 x 12mm countersunk plastic screws. The obvious easily
> obtained material is nylon but I see that some other plastics are also
> available - e.g. clear acrylic.
>
> I'm not expecting metal strength but it would be good to know which
> (reasonably priced) plastic is going to be stronger. I'm aming to use
> the screws through a sheet of closed-cell plastic to pull things
> 'into' the plastic (rather like upholstery buttons).

Acrylic is very brittle and propagates cracks easily - not what you want for
a screw.

Nylon (polyamide/PA) is pretty good as a mechanical element. There's also
various forms of fibre-reinforced nylon (GFR PA) which are stronger but not
sure you can make a sensible fibre lay-up for a small screw.

Don't overtighten, as I think that's a common cause of nylon failure - the
screw head shears off.

Theo

On 06/04/2024 12:11, Theo wrote:
> Chris Green <cl@isbd.net> wrote:
>> I need some M4 x 12mm countersunk plastic screws. The obvious easily
>> obtained material is nylon but I see that some other plastics are also
>> available - e.g. clear acrylic.
>>
>> I'm not expecting metal strength but it would be good to know which
>> (reasonably priced) plastic is going to be stronger. I'm aming to use
>> the screws through a sheet of closed-cell plastic to pull things
>> 'into' the plastic (rather like upholstery buttons).
>
> Acrylic is very brittle and propagates cracks easily - not what you want for
> a screw.
>
> Nylon (polyamide/PA) is pretty good as a mechanical element. There's also
> various forms of fibre-reinforced nylon (GFR PA) which are stronger but not
> sure you can make a sensible fibre lay-up for a small screw.
>
> Don't overtighten, as I think that's a common cause of nylon failure - the
> screw head shears off.
>
Pretty much all there. I found acrylic as will, but if it is a low
grade plastic screw nylon seems to be most used

In the model aircraft arena, the ability of nylon bolts to shear in a
crash is desirable

I actually found that at least with cross heads, the screwdriver could
not exert enough torque to shear them - the heads just mashed first.

> Theo

--
"Corbyn talks about equality, justice, opportunity, health care, peace,
community, compassion, investment, security, housing...."
"What kind of person is not interested in those things?"

"Jeremy Corbyn?"

On 06/04/2024 10:20, Chris Green wrote:
> I need some M4 x 12mm countersunk plastic screws. The obvious easily
> obtained material is nylon but I see that some other plastics are also
> available - e.g. clear acrylic.
>
> I'm not expecting metal strength but it would be good to know which
> (reasonably priced) plastic is going to be stronger. I'm aming to use
> the screws through a sheet of closed-cell plastic to pull things
> 'into' the plastic (rather like upholstery buttons).

I sometimes specify PEEK fasteners, mainly because of temperature.
They're pretty strong, though unreasonably priced.

https://highperformancepolymer.co.uk/products/countersunk-peek-flat-head-screws?variant=44169076539690

--
Cheers
Clive

On 06/04/2024 17:11, Clive Arthur wrote:
> On 06/04/2024 10:20, Chris Green wrote:
>> I need some M4 x 12mm countersunk plastic screws.  The obvious easily
>> obtained material is nylon but I see that some other plastics are also
>> available - e.g. clear acrylic.
>>
>> I'm not expecting metal strength but it would be good to know which
>> (reasonably priced) plastic is going to be stronger. I'm aming to use
>> the screws through a sheet of closed-cell plastic to pull things
>> 'into' the plastic (rather like upholstery buttons).
>
> I sometimes specify PEEK fasteners, mainly because of temperature.
> They're pretty strong, though unreasonably priced.
>
> https://highperformancepolymer.co.uk/products/countersunk-peek-flat-head-screws?variant=44169076539690
>

The good news is that the patent will expire pretty soon, assuming this
is the key one:

https://patents.google.com/patent/US8236919B2/en

Chris Green wrote:

> I need some M4 x 12mm countersunk plastic screws. The obvious easily
> obtained material is nylon

What about Delrin? aka Polyoxymethylene or POM

On 4/6/2024 4:02 PM, Andy Burns wrote:
> Chris Green wrote:
>
>> I need some M4 x 12mm countersunk plastic screws.  The obvious easily
>> obtained material is nylon
>
> What about Delrin? aka Polyoxymethylene or POM
>

https://bbs-industrie.com/materials/plastic/pom/

"not particularly UV resistant"

*******

This is advice from CoPilot.

Q: What is the best material to use to make a uV-resistant screw ?

A: The best materials for making a UV-resistant screw are plastics like
Acrylic (PMMA), Polycarbonate, PTFE, HDPE, Polyetherimide, Polyphenylene Sulfide,
and Polyvinylidene Fluoride. These materials are known for their
excellent UV resistance and are suitable for outdoor applications where
exposure to sunlight is a concern.

For instance, Acrylic and Polycarbonate are both strong and durable,
with Polycarbonate being particularly noted for its impact resistance.

If you’re considering metal screws, stainless steel screws are a
good option as they offer exceptional rust resistance and can
withstand outdoor conditions.

It’s important to choose the right material based on the specific
requirements of your application, such as strength, flexibility,
and environmental resistance.

https://www.mcmaster.com/products/polycarbonate-screws/?s=polycarbonate-screws

Paul

On 07/04/2024 05:46, Paul wrote:
> On 4/6/2024 4:02 PM, Andy Burns wrote:
>> Chris Green wrote:
>>
>>> I need some M4 x 12mm countersunk plastic screws.  The obvious easily
>>> obtained material is nylon
>>
>> What about Delrin? aka Polyoxymethylene or POM
>>
>
> https://bbs-industrie.com/materials/plastic/pom/
>
> "not particularly UV resistant"
>
> *******
>
> This is advice from CoPilot.
>
> Q: What is the best material to use to make a uV-resistant screw ?
>
> A: The best materials for making a UV-resistant screw are plastics like
> Acrylic (PMMA), Polycarbonate, PTFE, HDPE, Polyetherimide, Polyphenylene Sulfide,
> and Polyvinylidene Fluoride. These materials are known for their
> excellent UV resistance and are suitable for outdoor applications where
> exposure to sunlight is a concern.
>
> For instance, Acrylic and Polycarbonate are both strong and durable,
> with Polycarbonate being particularly noted for its impact resistance.
>
> If you’re considering metal screws, stainless steel screws are a
> good option as they offer exceptional rust resistance and can
> withstand outdoor conditions.
>
> It’s important to choose the right material based on the specific
> requirements of your application, such as strength, flexibility,
> and environmental resistance.
>
> https://www.mcmaster.com/products/polycarbonate-screws/?s=polycarbonate-screws
>

As that article mentions, it depends on the application and also
reliance on the material not being too malleable or brittle. If trying
to hold two pieces together that have a natural tendency to pull apart
you will not want to use a material that may stretch over time or when
fitting, nor when attempting to tighten that last quarter of a turn just
snaps.

It's much like the "plastic" back washers that come with many taps these
days. Great that they will not rust* but I've found when in an awkward
position and trying to tighten them the internal tread can deform and
jump back a tread effectively loosening the nut as you tighten. Once
this has happened once the chances of tightening are zero. I always
throw away the plastic back nuts and purchase the brass* versions.

*
I've encountered brass coloured steel versions that have rusted over 15
years :(

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 06/04/2024 21:02, Andy Burns wrote:
> Chris Green wrote:
>
>> I need some M4 x 12mm countersunk plastic screws.  The obvious easily
>> obtained material is nylon
>
> What about Delrin? aka Polyoxymethylene or POM
>
I could not find anyone making screws out of that.

--
“The fundamental cause of the trouble in the modern world today is that
the stupid are cocksure while the intelligent are full of doubt."

- Bertrand Russell

On 07/04/2024 07:47, alan_m wrote:
> It's much like the "plastic" back washers that come with many taps these
> days. Great that they will not rust* but I've found when in an awkward
> position and trying to tighten them the internal tread can deform and
> jump back a tread effectively loosening the nut as you tighten. Once
> this has happened once the chances of tightening are zero. I always
> throw away the plastic back nuts and purchase the brass* versions.

Yes 100%. I have a wobbly tap with an untightenable cracked plastic nut
that is in such an awkward place it been waiting around 6 years to be
replaced...
--
“The fundamental cause of the trouble in the modern world today is that
the stupid are cocksure while the intelligent are full of doubt."

- Bertrand Russell

The Natural Philosopher <tnp@invalid.invalid> wrote:
> On 06/04/2024 21:02, Andy Burns wrote:
> > Chris Green wrote:
> >
> >> I need some M4 x 12mm countersunk plastic screws.  The obvious easily
> >> obtained material is nylon
> >
> > What about Delrin? aka Polyoxymethylene or POM
> >
> I could not find anyone making screws out of that.
>
Quite! OP here, the basic choice for easily obtained (and not stupidly
expensive) screws seems to be between nylon and acrylic. Having found
a few sites with information I think nylon is almost certainly the way
to go for my application.

--
Chris Green
·

On 07/04/2024 10:00, The Natural Philosopher wrote:
> On 07/04/2024 07:47, alan_m wrote:
>> It's much like the "plastic" back washers that come with many taps
>> these days. Great that they will not rust* but I've found when in an
>> awkward position and trying to tighten them the internal tread can
>> deform and jump back a tread effectively loosening the nut as you
>> tighten. Once this has happened once the chances of tightening are
>> zero. I always throw away the plastic back nuts and purchase the
>> brass* versions.
>
> Yes 100%. I have a wobbly tap with an untightenable cracked plastic nut
> that is in such an awkward place it been waiting around 6 years to be
> replaced...
Is it wobbly enough to get a squirt of silicone under the flange to bond
it to the sink.

On 07/04/2024 17:17, GB wrote:
> On 07/04/2024 10:00, The Natural Philosopher wrote:
>> On 07/04/2024 07:47, alan_m wrote:
>>> It's much like the "plastic" back washers that come with many taps
>>> these days. Great that they will not rust* but I've found when in an
>>> awkward position and trying to tighten them the internal tread can
>>> deform and jump back a tread effectively loosening the nut as you
>>> tighten. Once this has happened once the chances of tightening are
>>> zero. I always throw away the plastic back nuts and purchase the
>>> brass* versions.
>>
>> Yes 100%. I have a wobbly tap with an untightenable cracked plastic
>> nut that is in such an awkward place it been waiting around 6 years to
>> be replaced...
> Is it wobbly enough to get a squirt of silicone under the flange to bond
> it to the sink.
BTDTGTTS

It just unscrewed even more

--
“It is not the truth of Marxism that explains the willingness of
intellectuals to believe it, but the power that it confers on
intellectuals, in their attempts to control the world. And since...it is
futile to reason someone out of a thing that he was not reasoned into,
we can conclude that Marxism owes its remarkable power to survive every
criticism to the fact that it is not a truth-directed but a
power-directed system of thought.”
Sir Roger Scruton

On 4/7/2024 11:39 AM, Chris Green wrote:
> The Natural Philosopher <tnp@invalid.invalid> wrote:
>> On 06/04/2024 21:02, Andy Burns wrote:
>>> Chris Green wrote:
>>>
>>>> I need some M4 x 12mm countersunk plastic screws.  The obvious easily
>>>> obtained material is nylon
>>>
>>> What about Delrin? aka Polyoxymethylene or POM
>>>
>> I could not find anyone making screws out of that.
>>
> Quite! OP here, the basic choice for easily obtained (and not stupidly
> expensive) screws seems to be between nylon and acrylic. Having found
> a few sites with information I think nylon is almost certainly the way
> to go for my application.
>

Is this an outdoor application ?

White nylon seems quite UV sensitive (a problem after one year).
Black nylon is better, but they don't make screws of it (at least 4 to 5 year life).

You may want to review thread design, in case what was tapped into the
steel, is different than how they cut the plastic ones.

https://en.wikipedia.org/wiki/Screw_thread

Paul

Paul <nospam@needed.invalid> wrote:
> On 4/7/2024 11:39 AM, Chris Green wrote:
> > The Natural Philosopher <tnp@invalid.invalid> wrote:
> >> On 06/04/2024 21:02, Andy Burns wrote:
> >>> Chris Green wrote:
> >>>
> >>>> I need some M4 x 12mm countersunk plastic screws.  The obvious easily
> >>>> obtained material is nylon
> >>>
> >>> What about Delrin? aka Polyoxymethylene or POM
> >>>
> >> I could not find anyone making screws out of that.
> >>
> > Quite! OP here, the basic choice for easily obtained (and not stupidly
> > expensive) screws seems to be between nylon and acrylic. Having found
> > a few sites with information I think nylon is almost certainly the way
> > to go for my application.
> >
>
> Is this an outdoor application ?
>
No, it's inside and hidden under panelling so will be kept in the
dark! :-)

--
Chris Green
·