Questions about screws.

[alphacat]

Hey,

I'd like to thank first for everyone who helped me out before with the screws.
I learned alot.

I got 2 questions please:

1. In my product, there are 3 metals - Live, Netural, Earth - that are screwed into the product's plastic enclosure.
These metals (which are inserted into the mains) can carry up to 16Arms current.
Should the screw's head (the screws which fix the metals to the plastics) be not flat, so they could conduct the current better? (larger surface area means more space for electrons to flow)
Or can their heads be flat?

2. I'm sorry if you find this question stupid.
In general, is there a difference between the prices of black screws silver screws?

Thank you very much.

 

[Boncuk]

Hi,

there are different kinds of screw head terminals, the cheap ones making contact directly between the cable (wire) and the screw. Those screws are normally slightly cone-shaped for two reasons:

Firstly, produding into the copper wire they provide a larger contact area and secondly the mechanical stablility increases (hard to pull out a "bolted" wire). If the screw heads were flat there would be the possibility to cut the cable when applying much force to the screw.

Good quality screw head terminals have a wire protection device, a small metal strip being driven by the screw in order to neither poke nor cut the inserted cable.

The top quality screw head terminals are fitted with a lift for the wire protection device.

Boncuk

 

[alphacat]

Hey,
thank you very much for your detailed answer.

What about when screwing the screws into metallic pins (Live, Neutral, Earth)?
Is there any significance for non-flat (con-shaped as you said) screws head in such case?

Thanks again.

 

[Boncuk]

Hi,

sorry, I don't understand your question.

Please specify.

Boncuk

 

[alphacat]

Hey,

In the following configuration, what would be better?
A flat head or A pan had screw?

 

[Boncuk]

Hi alphacat,

for a connection like illustrated you best use any screw (not lentil shaped), a tooth lock washer and a soldering eyelet.

The tooth lock washer keeps the mechanical construction tight and the soldering eyelet ensures best conductivity.

For extra good conductivity you might also solder the eyelet to the metal.

Sequence of parts is shown in the attached sketch. (Plastic part omitted)

Boncuk

 

[Mr RB]

??????

I remember the other thread where you asked about using 16 amps with screws into plastic, and everyone telling you it's not safe as the plasic will "give" and you will get a bad connection and overheating etc. You need non-compressable material to clamp the connection, ie metal screws into metal posts with no squishy plastic in there anywhere.

Now you're telling us not only is it 16 amps, but it is 16 amps AT MAINS VOLTAGE???

And you still have screws supported only by plastic!!