Help with crimping

[JohnW2]

Does it mean all the strands of a stranded conductor, or what.

That's what I would take it to mean.

I certainly can't think of what else it clould mean - but it's dreadful wording for a technical Standard!

I just cross-checked the same regulation in the revised 14th edition (the 1970 metric revision), and the wording had changed to allow limited inaccessibility under certain conditions:

Maybe 'limited' but seemingly allowing the burying a crimped joint in plaster or concrete! It sounds as if they weren't too concerned about the joint overheating, provided it did not set fire to the building!

Kind regards,John.

 

[Paul_C]

I certainly can't think of what else it clould mean - but it's dreadful wording for a technical Standard!

I don't know how far back that particular wording goes, but it was certainly carried forward as "all the wires of the conductors" from the 13th edition, since the same phrase was used there in the equivalent regulation.

Although I tend to hold these older editions of the Wiring Regs. in higher esteem than the more modern versions which followed, I have to admit that they too have some bad phrasing in places. Just look at the long-standing definition of a neutral conductor in the Regs. as an example: Aside from the technical inexactitude that you can't really have a neutral conductor in a simple 2-wire system, the definition was very poor in reference to a 3-phase system by defining a neutral conductor as....... A neutral conductor!

 

[JohnW2]

I I don't know how far back that particular wording goes, but it was certainly carried forward as "all the wires of the conductors" from the 13th edition, since the same phrase was used there in the equivalent regulation. Although I tend to hold these older editions of the Wiring Regs. in higher esteem than the more modern versions which followed, I have to admit that they too have some bad phrasing in places.

Once they've appeared, these things are very likely to propogate and persist - and it's not just 'bad wording',since it can also apply to plain errors ....

...an academic Chemist was recently telling me that it has just been discovered that some alleged chemical reaction that had been described in most textbooks for the past 100 years simply does not happen. It apparently first appeared in a book in the early 1900s, and has been 'copied into' the great majority of books ever since then!

Kind Regards, John.

 

[pjo123]

I just looked at crimpers in a professional tool catalogue. The price range was from £11-odd to £473!

Indeed, the three I have range from £11 to about £70, but I have looked at more expensive ones.

The good ones seem to start around £50, and are similar to the AMP one I was describing.

I can't say that I've seen £473 ones, but I can but repeat that I haven't personally yet seen any which appear to correspond with what you've described. There is virtually no difference between my £11 and £70 ones and both look remarkably like the ones that BAS is always advocating, and which I suspect many electricians are using.


Kind Regards, John

The first ones I brought had a completely different jaw layout to the CK ones. Both sides were exactly the same.

If you zoom into the jaws http://www.screwfix.com/p/forge-steel-ratchet-crimping-tool/70036#


what you see is exactly the same if you look at it from the other side.

The CK ones have different depths both sides, which I suspect is like all the ones you have seen.

 

[EFLImpudence]

Why would you want one side to be crimped less tightly than the other?

 

[JohnW2]

Why would you want one side to be crimped less tightly than the other?

I'm not sure, but I think their idea is that the bit with the wider gap goes over the expanded end bit of an insulated crimp. ... I'm pretty sure I've seen some 'advice' about doing that on some website in my time.

Kind Regards, John.

 

[stillp]

The good news is that I now have a copy of BS 7609 "Code of practice for Installation and inspection of uninsulated compression and mechanical connectors for power cables with copper or aluminium conductors". Catchy title eh!
The bad news is that it is limited to conductors having a cross-sectional area equal to or greater than 10 mm2 for copper and equal to or greater than 16 mm2 for aluminium, so it doesn't help us much with domestic installations. However it is clear that it applies to both stranded and solid conductors.
It refers to hexagonal or circumferential crimping, which seems self-explanatory, and indent crimping, which is what I was trying to describe earlier. It also points out that the connector, die-set and tooling should be as specified by the manufacturer, which is likely to be difficult to achieve in practise given that most people will buy the connectors and tooling separately.
There are some examples of unsatisfactory crimps, which include compression too far from the end of the connector, or too close to the end, as well as over-compression due to incorrect tooling.
Another bit of wishful thinking is the following statement "At suitable intervals not exceeding 12 months and, depending upon tool types, usage and manufacturer’s recommendations, the tools should be submitted to a suitably qualified maintenance, test and inspection authority". Anyone had their crimping tool recalibrated recently?

I'll keep on trying to find a more appropriate standard.

 

[JohnW2]

The good news is that I now have a copy of BS 7609 "Code of practice for Installation and inspection of uninsulated compression and mechanical connectors for power cables with copper or aluminium conductors". Catchy title eh!
The bad news is that it is limited to conductors having a cross-sectional area equal to or greater than 10 mm2 for copper and equal to or greater than 16 mm2 for aluminium, so it doesn't help us much with domestic installations. However it is clear that it applies to both stranded and solid conductors.

Thanks for the update. As you say, this is unfortunately not very relevant to the domestic situation.

The It refers to hexagonal or circumferential crimping, which seems self-explanatory, and indent crimping, which is what I was trying to describe earlier.

Quite. As you presumably realise, it was the first two of those I was talking of as 'proper crimping' and the latter (which seems to be what most electricians use) which I rather rudely described as 'single-plane squashing'! Does the Standard say anything about limitations of the latter, and is there any mention of using split crimps with that technique?

I'll keep on trying to find a more appropriate standard.

Thanks. It will be very interesting (and may avoid the need for lost of future threads like this one!) if you can find an appropriate one.

Kind Regards, John.

 

[stillp]

it was the first two of those I was talking of as 'proper crimping' and the latter (which seems to be what most electricians use) which I rather rudely described as 'single-plane squashing'

John, I should perhaps have explained that "indent crimping" supports the connector and conductor in a U-shaped die and forces a blunt spike into it, which was the style I used in my college experiments. This is not the same as the 'notched pair of plier jaws' that I understood from your use of the term 'single-plane squashing'.

 

[JohnW2]

John, I should perhaps have explained that "indent crimping" supports the connector and conductor in a U-shaped die and forces a blunt spike into it, which was the style I used in my college experiments. This is not the same as the 'notched pair of plier jaws' that I understood from your use of the term 'single-plane squashing'.

Sorry, I wasn't at all clear, either - in fact, actually failed to say what I meant to say! Yes, I understand what you mean by 'indent crimping', and have seen plenty of pictures of sections through joints crimped in such a fashion. Even though it still only essentially involves 'single-plane squashing' the indent crimp is likely to be much better than the 'only single-plane squashing' that most electricians seem to use, because of the presence of the indent.

Kind Regards, John

 

[JohnW2]

John, I should perhaps have explained that "indent crimping" supports the connector and conductor in a U-shaped die and forces a blunt spike into it, which was the style I used in my college experiments.

Do I take it that you are talking about a crimp something like this:

Untitled

• JohnW2
• 20 Jun 2011
• 1

?

Kind Regards, John.

 

[stillp]

No, that's something different, and shows signs of a failed crimp. Imagine one jaw of the tool is a simple U shape into which the barrel of the connector fits snugly. The other jaw is a shallower U, with a peg in the centre that is driven into the connector. The conductor material and the connector barrel are compressed by being displaced by the 'peg' towards the sides of the U-shaped die. Sorry I can't find a picture that I can post.

 

[EFLImpudence]

I think this must be what I have seen referred to as a 'B' type crimper for obvious reasons.

 

[JohnW2]

No, that's something different, and shows signs of a failed crimp. Imagine one jaw of the tool is a simple U shape into which the barrel of the connector fits snugly. The other jaw is a shallower U, with a peg in the centre that is driven into the connector. The conductor material and the connector barrel are compressed by being displaced by the 'peg' towards the sides of the U-shaped die. Sorry I can't find a picture that I can post.

Ah, OK, I understand. The pic I posted was of a split crimp applied with an appropriate tool, not a failed one.

Kind Regards, John.

 

[JohnW2]

No, that's something different...

Any closer (all the pics I can find are pretty awful!):

Untitled

• JohnW2
• 20 Jun 2011
• 1

Kind Regards, John.