Help with crimping

[pjo123]

Hi guys

Today after advice in the building section, I purchased a ratchet crimper.

As it's for DIY use, didn't want to spend a fortune, went with

http://www.screwfix.com/p/forge-steel-ratchet-crimping-tool/70036#

I went to CEF first, but theirs were way more expensive, but I did buy the blue crimps from there as being an electrical factors, I presumed they would be selling decent quality crimps.

I've got a bit of spare 2.5 T&E, had a lot of practice, but no matter how I try, I can always pull the cables out with very little force.

I've followed various instructions I've found on the web, I am crimping each side and I am crimping the middle metal bits rather than the plastic edge bits.

Any suggestions please?

EDIT: guide I followed is http://wiki.diyfaq.org.uk/index.php?title=Cable_crimping

 

[PrenticeBoyofDerry]

What they don't tell you is that solid conductors are a bastard to get a good contact when crimping, but the stranded cables are much better.

 

[pjo123]

Hmmm, Just tried the crappy hand crimpers, the ones you shouldn't use.

While not a perfect crimp and I would never use it, I am getting a much stronger crimp than with the ratchet one.

I presume this points to the ratchet being crap.

That being the case, is there one at Screwfix that's a reasonable price that looks better please?

Thanks

 

[pjo123]

What they don't tell you is that solid conductors are a b*****d to get a good contact when crimping, but the stranded cables are much better.

So would I be better off bending over/doubling the cable and using yellow crimps?

 

[holmslaw]

..

 

[holmslaw]

..

 

[JohnW2]

What they don't tell you is that solid conductors are a b*****d to get a good contact when crimping, but the stranded cables are much better.

I never cease to be amazed that crimped joints (as produced by the sort of ratchet crimpers most people use) of solid conductors are allowed at all by the regs, let alone in non-accessible places. I know I'm probably out on a limb, but I would certainly not allow any in my house.

Kind Regards, John.

 

[ban-all-sheds]

I've followed various instructions I've found on the web, I am crimping each side and I am crimping the middle metal bits rather than the plastic edge bits.

And you're using the crimper the right way round?

Any suggestions please?

Have you tried adjusting the tool?

 

[Paul_C]

I'm not convinced by the description of your crimper on that website. It says your crimper will crimp uninsulated and insulated crimps. Crimpers usually do one type or the other, not both.

If it is for insulated crimps the jaws should be marked with coloured spots to match the colour of the crimp. And you must keep squeezing until it self releases.

I'm not convinced by that description either, except that it's muddled and whoever wrote it doesn't seem to have done a very good job.

In the first general description it says it's for "yellow, blue and red electrical crimp connectors, interlocking connectors, cord end terminals, insulated and non-insulated terminals." But then under specification, it refers only to insulated terminals, and then has AWG and sq. mm mixed up!

If you enlarge the image though, it does appear to be intended for insulated terminals, as you can see the red/blue/yellow size spots.

Personally, I don't like the red/blue/yellow insulated crimp terminals of any description, and feel that much better results are obtained by using plain terminals, rings, etc. and applying sleeves separately as required.

 

[pjo123]

Thanks all.

I have tried adjusting them, still the same.

Have decided I'll take the crimper's back and get their CK ones as I've read various posts saying CK stuff should be good quality.

Then I'll see how I get on and will know whether it's me or the tool

Also, what is reasonable force when trying to pull apart the wires? A simple no force tug to check every-things tight or to use a bit of strength?

Thanks

 

[bernardgreen]

I know I'm probably out on a limb, but I would certainly not allow any in my house.

I am with you on the same limb. Crimped joints that have a cold weld between the two conductors are acceptable and in many cases better than soldered but cold weld requires the wires, the crimp tube and the tool to be correct and compatible and a very high pressure is required. I cannot see that the required pressure can be applied through a layer of plaster and have never seen any evidence of cold welding in an insulated crimp.

I am sure most crimped joints with prefitted insulation are just compression joints and would be prone to fail electrically if the pressure exerted by the tube was to weaken for any reason. ( heat and aging of the metal under stress being the prime causes of weakened pressure. )

This is how cold welds should be made

http://www.youtube.com/watch?v=suX-mCZ3j9c&NR

 

[JohnW2]

I know I'm probably out on a limb, but I would certainly not allow any in my house.

I am with you on the same limb. Crimped joints that have a cold weld between the two conductors are acceptable and in many cases better than soldered but cold weld requires the wires, the crimp tube and the tool to be correct and compatible and a very high pressure is required. I cannot see that the required pressure can be applied through a layer of plaster and have never seen any evidence of cold welding in an insulated crimp.

I agree totally and, like you, have never seen evidence of a cold weld. I'm not really surprised, particularly given that the 'crimpers' most people seem to use provide just single-plane 'squashing', rather than true concentric compresion. Apart from anything else, that leaves the scene set for sideways creep in the conductors. A lot is said, here and elsewhere, about the fact that one should use ratchet crimpers rather than the 'cheap and nasty'ones - but the usual ratchet crimper (for small sizes) is single-plane and incorporates no mechanical advantage - so probably offers little true advantage.

Of all the ways there are of joining copper conductors (screwed, soldered, brazed, cold-welded, crimped etc.), I have no doubt that the standard crimped joints are the ones I would least want in my house, particularly if non-accessible! In my personal (seemingly not widespread!) opinion, the allowance of crimped joints is one of the most surprising and potentially dangerous aspects of BS7671.

Kind Regards, John

 

[Paul_C]

In my personal (seemingly not widespread!) opinion, the allowance of crimped joints is one of the most surprising and potentially dangerous aspects of BS7671.

Certainly the allowing of such crimped joints to be inaccessible while other types of joint must remain accessible is something I don't like.

 

[mikhailfaradayski]

John/Bernard,

Do either of you have experience (real, not made up) of a failed crimped joint in a domestic setting?

 

[bernardgreen]

OOPS

I said "through a layer of plaster". it should have been "through a layer of plastic"

Looking at a crimp that does cold weld. The round tube is slit and during crimping the edges of the slit are forced inwards and pressed into the metal of the conductor.

Another type has ridges running along the inside of the tube and during crimping these are forced into the metal of the conductor.