Hi all, it's not meant to be a silly question.

What's the best way of wiring a screw-terminal plug with flex?

I don't think solid-core flex exists - in any case all the flex I've
come across has conductors composed of multiple small strands of
copper wire. How best should they be used in a plug with the standard
hole in the pin with a grub screw to screw down?

Some commercially supplied equipment has plugs where the end of the
conductors is tinned, which makes it easy to insert in the hole in the
pins, then seems* to provide a good connection when the grub screw is
tightened up.

(* I say seems, as there is some debate about the dissimilar metal
interface providing a good, long-lasting contact)

If I don't tin the conductors, then what is the best way?

1) Stuff the stranded core into the hole in the pin, and tighten up
the grubscrew?
2) Twist the stranded core, put in the hole and tighten up the
grubscrew?
3) Twist the stranded core, fold back on itself and re-twist, place in
hole and tighten up grubscrew?
4) Use some other method?

I ask because I'll be wiring up a lot of screw terminals in the near
future and I'd like to do a good job that I don't have to come back
to.

I did know an American at university, now a high power lawyer, who
approached the unfamiliar English electrical system in an interesting
way. Having bared the conductors, the flex was stuffed into the plug
and wiggled about until 'it worked', then left alone. I was
speechless, but then spent a brief period rewiring all the plugs in
the said lawyer's rooms.

Many thanks,

Sid

Hi Sid

On Mon, 23 Jul 2007 07:28:35 -0700, wrote:

Hi all, it's not meant to be a silly question.

What's the best way of wiring a screw-terminal plug with flex?

I don't think solid-core flex exists - in any case all the flex I've
come across has conductors composed of multiple small strands of
copper wire. How best should they be used in a plug with the standard
hole in the pin with a grub screw to screw down?

Some commercially supplied equipment has plugs where the end of the
conductors is tinned, which makes it easy to insert in the hole in the
pins, then seems* to provide a good connection when the grub screw is
tightened up.


I'd advise against tinning the flex ends.

One company I worked for did this on some equipment that was drawing
reasonably high currents at 110V - and then had to send an engineer to
the States (all the way from Washington to the Mexican border) to
replace these leads - as the tinned conductors had a tendency to
deform over time. As they deformed, they heated up - which made them
deform further.... and so on....

Narrowly avoided getting sued over it !

So - don't tin the flex ends...

I've always twisted the ends and then tightened the screw down -
doubling it over on itself if it's particularly thin flex...

Not sure what the 'official' way might be though

Regards
Adrian

In article .com,
writes:
Hi all, it's not meant to be a silly question.

What's the best way of wiring a screw-terminal plug with flex?

I don't think solid-core flex exists - in any case all the flex I've
come across has conductors composed of multiple small strands of
copper wire. How best should they be used in a plug with the standard
hole in the pin with a grub screw to screw down?

Some commercially supplied equipment has plugs where the end of the
conductors is tinned, which makes it easy to insert in the hole in the
pins, then seems* to provide a good connection when the grub screw is
tightened up.

(* I say seems, as there is some debate about the dissimilar metal
interface providing a good, long-lasting contact)

You mustn't do this. Back in the days when appliances were
supplied like this, the instructions always said to cut the
tinned part off. It was there for easy connection for testing
on the production line. Using it in a screw terminal results
in the solder creeping, loss of contact pressure, and a poor
contact forms over time.

The right way to do this is to crimp a bootlace ferrule onto
the strands -- if that's already been done, leave it on if
the cable has been stripped the right length for the plug.

If I don't tin the conductors, then what is the best way?

1) Stuff the stranded core into the hole in the pin, and tighten up
the grubscrew?
2) Twist the stranded core, put in the hole and tighten up the
grubscrew?
3) Twist the stranded core, fold back on itself and re-twist, place in
hole and tighten up grubscrew?

2 or 3, depending on the size of the conductor relative to the hole.

4) Use some other method?

Consider buying bootlace ferrules and an crimping tool for it
(sadly the tool is very expensive).

I ask because I'll be wiring up a lot of screw terminals in the near
future and I'd like to do a good job that I don't have to come back
to.

Can you change the lead? You can buy leads with molded plugs
very cheaply in quantities.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 23 Jul, 17:05, (Andrew Gabriel) wrote:
In article .com,
writes:



Hi all, it's not meant to be a silly question.

What's the best way of wiring a screw-terminal plug with flex?

I don't think solid-core flex exists - in any case all the flex I've
come across has conductors composed of multiple small strands of
copper wire. How best should they be used in a plug with the standard
hole in the pin with a grub screw to screw down?

Some commercially supplied equipment has plugs where the end of the
conductors is tinned, which makes it easy to insert in the hole in the
pins, then seems* to provide a good connection when the grub screw is
tightened up.

(* I say seems, as there is some debate about the dissimilar metal
interface providing a good, long-lasting contact)

You mustn't do this. Back in the days when appliances were
supplied like this, the instructions always said to cut the
tinned part off. It was there for easy connection for testing
on the production line. Using it in a screw terminal results
in the solder creeping, loss of contact pressure, and a poor
contact forms over time.

The right way to do this is to crimp a bootlace ferrule onto
the strands -- if that's already been done, leave it on if
the cable has been stripped the right length for the plug.

If I don't tin the conductors, then what is the best way?

1) Stuff the stranded core into the hole in the pin, and tighten up
the grubscrew?
2) Twist the stranded core, put in the hole and tighten up the
grubscrew?
3) Twist the stranded core, fold back on itself and re-twist, place in
hole and tighten up grubscrew?

2 or 3, depending on the size of the conductor relative to the hole.

4) Use some other method?

Consider buying bootlace ferrules and an crimping tool for it
(sadly the tool is very expensive).

I ask because I'll be wiring up a lot of screw terminals in the near
future and I'd like to do a good job that I don't have to come back
to.

Can you change the lead? You can buy leads with molded plugs
very cheaply in quantities.


Thanks all for the replies.

The strip, twist, fold over (if necessary), insert in hole and screw
looks like the way to go. As you say, the bootlace ferrule crimp tools
are expensive, which is a pity. The cheapest are the plier style
ones, which I know from experience don't give a good crimp - I can't
justify a proper tool for the one-off occasion. Unfortunately, it's
not just a case of buying another set of IEC flexes with moulded
plugs, which I'd prefer.

Some of the terminal connections are likely to be the screw with
washer type as well, where you loop the conductor round a screw under
a washer, then screw down tight. I hate doing those. At most it's 54
of them, so I guess I'll be a dab hand by the end of it. I'd be
tempted (if I had the appropriate tools) to use an uninsulated ring
crimped onto the conductors for those because they are so fiddly
otherwise, but I suspect the crimped connection wouldn't be secure
enough unless it were made with the proper (horrifically expensive)
tools.

Cheers,

Sid

On Mon, 23 Jul 2007 10:19:24 -0700, mused:

Unfortunately, it's
not just a case of buying another set of IEC flexes with moulded
plugs, which I'd prefer.

What is the lead you're making going to be then OOI?
--
Regards,
Stuart.

On 23 Jul, 18:21, Lurch wrote:
On Mon, 23 Jul 2007 10:19:24 -0700, mused:

Unfortunately, it's
not just a case of buying another set of IEC flexes with moulded
plugs, which I'd prefer.

What is the lead you're making going to be then OOI?
--
Regards,
Stuart.

It's a host of BS 546 2A plugs and a smaller number of standard (BS
1363) plugs that are hard-wired (not IEC connectors/sockets) to bits
of lighting and kit that are being moved in a friend's room
rearrangement exercise. I just wanted to make sure we do things
properly. I suppose that in an ideal world, every corner of the room
would have enough sockets for the hi-fi, video, dvd, satellite, X-box,
and latest toy-du-jour, but his house was built before the explosion
in consumer electronics.

Cheers,

Sid

You will probably cringe at this confession Andrew,
but sometimes, if I am making a connection to something
like an in-line switch or connector I fold the conductor strands
over the PVC insulation and tighten the screw hard down
on the insulation. My thinking is it gives more mechanical
strength than just the copper alone should the outer sheath
slip through the main clamp.

I suppose I developed this technique years ago when there
was a lot of imported crap fittings with fibre cable clamps
that were not up to the job.

--

Graham.
%Profound_observation%

On Mon, 23 Jul 2007 21:22:53 +0100, "Graham" mused:

You will probably cringe at this confession Andrew,
but sometimes, if I am making a connection to something
like an in-line switch or connector I fold the conductor strands
over the PVC insulation and tighten the screw hard down
on the insulation. My thinking is it gives more mechanical
strength than just the copper alone should the outer sheath
slip through the main clamp.

I have found a few CE marked items with terminals wired like this.
--
Regards,
Stuart.

In article .com,
wrote:
Some commercially supplied equipment has plugs where the end of the
conductors is tinned, which makes it easy to insert in the hole in the
pins, then seems* to provide a good connection when the grub screw is
tightened up.

They are tinned to allow quick and easy testing at the factory. The tinned
ends should be cut off before fitting a screw connection plug - the tinned
end has no 'spring' to it and is more likely to work loose.

(* I say seems, as there is some debate about the dissimilar metal
interface providing a good, long-lasting contact)

If I don't tin the conductors, then what is the best way?

1) Stuff the stranded core into the hole in the pin, and tighten up
the grubscrew?
2) Twist the stranded core, put in the hole and tighten up the
grubscrew?
3) Twist the stranded core, fold back on itself and re-twist, place in
hole and tighten up grubscrew?
4) Use some other method?

Twist the strands reasonable tightly with your fingers. If the hole is
large enough double over.

--
*I feel like I'm diagonally parked in a parallel universe*

Dave Plowman London SW
To e-mail, change noise into sound.

On 23 Jul., 19:19, wrote:
On 23 Jul, 17:05, (Andrew Gabriel) wrote:



In article .com,
writes:

Hi all, it's not meant to be a silly question.

What's the best way of wiring a screw-terminal plug with flex?

I don't think solid-core flex exists - in any case all the flex I've
come across has conductors composed of multiple small strands of
copper wire. How best should they be used in a plug with the standard
hole in the pin with a grub screw to screw down?

Some commercially supplied equipment has plugs where the end of the
conductors is tinned, which makes it easy to insert in the hole in the
pins, then seems* to provide a good connection when the grub screw is
tightened up.

(* I say seems, as there is some debate about the dissimilar metal
interface providing a good, long-lasting contact)

You mustn't do this. Back in the days when appliances were
supplied like this, the instructions always said to cut the
tinned part off. It was there for easy connection for testing
on the production line. Using it in a screw terminal results
in the solder creeping, loss of contact pressure, and a poor
contact forms over time.

The right way to do this is to crimp a bootlace ferrule onto
the strands -- if that's already been done, leave it on if
the cable has been stripped the right length for the plug.

If I don't tin the conductors, then what is the best way?

1) Stuff the stranded core into the hole in the pin, and tighten up
the grubscrew?
2) Twist the stranded core, put in the hole and tighten up the
grubscrew?
3) Twist the stranded core, fold back on itself and re-twist, place in
hole and tighten up grubscrew?

2 or 3, depending on the size of the conductor relative to the hole.

4) Use some other method?

Consider buying bootlace ferrules and an crimping tool for it
(sadly the tool is very expensive).

I ask because I'll be wiring up a lot of screw terminals in the near
future and I'd like to do a good job that I don't have to come back
to.

Can you change the lead? You can buy leads with molded plugs
very cheaply in quantities.

Thanks all for the replies.

The strip, twist, fold over (if necessary), insert in hole and screw
looks like the way to go. As you say, the bootlace ferrule crimp tools
are expensive, which is a pity. The cheapest are the plier style
ones, which I know from experience don't give a good crimp - I can't
justify a proper tool for the one-off occasion. Unfortunately, it's
not just a case of buying another set of IEC flexes with moulded
plugs, which I'd prefer.

Not really - I found a nice crimp tool along with a set of different
ferrules for less than 10 Euros. I don't think screwfix or any other
UK store doesn't carry those for a similar reasonable price.

Tinning was done for ages in many European countries... and was the
origin of several fires as I was told.

greetings Ranger

"Lurch" wrote in message
news
On Mon, 23 Jul 2007 21:22:53 +0100, "Graham" mused:

You will probably cringe at this confession Andrew,
but sometimes, if I am making a connection to something
like an in-line switch or connector I fold the conductor strands
over the PVC insulation and tighten the screw hard down
on the insulation. My thinking is it gives more mechanical
strength than just the copper alone should the outer sheath
slip through the main clamp.

I have found a few CE marked items with terminals wired like this.

Best example is lampholders that dangle from a flex.

--

Graham.
%Profound_observation%