problems crimping with yellow crimps, 6mm.

[HappyHippyDad]

This is only the second time I have had to crimp 6mm cable. I remember the first time a couple of years ago I had problems. Again this time the connection just pulled apart in my hands.

After looking through the forum I can see that others have had the same problem specifically with yellow crimps. 1mm and 2.5mm seem to crimp perfectly well (again seen in other threads), but with 6mm there is a problem.

The reason for this thread is because other threads point to the crimp or the crimping tool being the problem. I have a CK crimping tool which has good reviews and crimps 1mm and 2.5mm very well (I have tested these in a vice), so I believed the crimp to be the problem. I was about to buy some SWA crimps as other threads point to these being good quality. However, my red and blue crimps were bought from the same manufacturer as the yellow so it didn't really make sense that it was the crimp at fault.

I've just been in the shed crimping 6mm in a number of different ways and think I have found the problem. With red and blue crimps you have the crimp flush with the crimping tool when you crimp. I assumed it would be the same with yellow, however the crimping tool is wider for the yellow crimps meaning that when you crimp you are crimping the entire half of the crimp (perhaps even slightly over), meaning that you are crimping down on the piece of metal that sticks out in the middle of the crimp and I think this must be stopping the crimping tool from crimping properly.

The top crimp (see picture) was crimped with the yellow crimp (outer part) flush with the crimping tool and just pulled out easily. With the other two I slightly pushed the crimp into the crimping tool so that the central piece of metal would not be disturbed (you can see that the bottom 2 crimps have a bit in the middle still raised whereas the top one doesn't). I could not pull either of these out when placed in a vice.

Correct crimping is so important I thought I'd mention my little test. I tested the 2 ways each with 5 crimps and it was the same with all of them.

 

[Aindowsimon]

Good shout ! I have the ck crimper and I do wot you have explained for a while , I reckon that maybe our crimper is designed for lugs in regard of keeping insulated cover flush to end of crimper

 

[joehat]

What's the max size cable yellow crimps do?

 

[Aindowsimon]

4-6mm as far as I know

 

[davesparks]

For 6mm it is better to use an uninsulated crimp with a hex crimper than those plastic jobbies.

 

[Simonslimline]

I just tried with my cembre crimpstars and it is totally solid. No getting it off.

 

[Aindowsimon]

I've seen butt crimps spoken about on this forum , quite a bit dearer but with adhesive lined heat shrink can see it being a superior crimp with it slightly translucent, wholesalers around me don't stick em

 

[Marvo]

Anything above 2.5mm I'd use an uninsulated ferrule or lug with an indent crimper or if it's a larger size like 16mm or above a hex type crimper then use heat shrink to finish. I'm not a big fan of insulated lugs TBH, they're not very consistent and they're not visually checkable in the same way an uninsulated crimp is.

 

[HappyHippyDad]

I just tried with my cembre crimpstars and it is totally solid. No getting it off.

I've just looked at that crimping tool Simon and there seem to be a few different varieties. Most seem to have the yellow part of the crimping tool flush with the red and blue, but the tipo HP3 has the yellow part sticking out just like the CK crimping tool.

 

[HappyHippyDad]

Anything above 2.5mm I'd use an uninsulated ferrule or lug with an indent crimper or if it's a larger size like 16mm or above a hex type crimper then use heat shrink to finish. I'm not a big fan of insulated lugs TBH, they're not very consistent and they're not visually checkable in the same way an uninsulated crimp is.

Do you mean this in relation to uninsulated butt crimps Marvo? I'm guessing you must mean the outside of the crimp is visually checkable rather than anything going on inside?

 

[HappyHippyDad]

For 6mm it is better to use an uninsulated crimp with a hex crimper than those plastic jobbies.

Anything above 2.5mm I'd use an uninsulated ferrule or lug with an indent crimper or if it's a larger size like 16mm or above a hex type crimper then use heat shrink to finish. I'm not a big fan of insulated lugs TBH, they're not very consistent and they're not visually checkable in the same way an uninsulated crimp is.

Why do you feel it is a better crimp when uninsulated (crimping tool is making direct contact with metal rather than PVC?)? Also, why a Hex crimping tool when the conductors get larger? Is this from experience or just known better practise?

 

[Simonslimline]

I've just looked at that crimping tool Simon and there seem to be a few different varieties. Most seem to have the yellow part of the crimping tool flush with the red and blue, but the tipo HP3 has the yellow part sticking out just like the CK crimping tool.

Yep thats the ones i have.

A silly question perhaps but which side are you putting the cable in to?

 

[davesparks]

Why do you feel it is a better crimp when uninsulated (crimping tool is making direct contact with metal rather than PVC?)? Also, why a Hex crimping tool when the conductors get larger? Is this from experience or just known better practise?

Because you can see when the conductor is properly inserted and can see that the crimp is properly located in the crimp die. Plus the standard uninsulated crimps have a thicker copper tube than the metal of the insulated.
I've stripped the insulation off of a few insulated crimps to have a look inside and they don't inspire confidence.

 

[HappyHippyDad]

Yep thats the ones i have.

A silly question perhaps but which side are you putting the cable in to?

View attachment 31875

The correct side

You should have been able to tell that Simon from the position of the indented number on the crimp

 

[Simonslimline]

The correct side

You should have been able to tell that Simon from the position of the indented number on the crimp

Just checking lol.

 

[HappyHippyDad]

Because you can see when the conductor is properly inserted and can see that the crimp is properly located in the crimp die. Plus the standard uninsulated crimps have a thicker copper tube than the metal of the insulated.
I've stripped the insulation off of a few insulated crimps to have a look inside and they don't inspire confidence.

How can you see? You cannot see inside so I'm guessing you mean where the conductor enters the crimp, but that would be the same as an insulated crimp? I'm talking in relation to butt crimps.

 

[Marvo]

I just think that compression crimping with the insulation in the crimper is just going to inherently give inconsistent results. I was taught as an apprentice that indent crimps were never to be used on MV terminations, only hex. I can't specifically remember why but they were considered more reliable. Also I have a small hand operated hydraulic hex crimper that has crimping dies going down to 16mm and up to 185mm so it's just easier for me to use it on any crimps in that size range, for 16mm and under I have a ratchet type indent crimper that is regularly calibrated, we pull-test lugs or ferrules as well and they pass with good results.

I think technology, materials and techniques have probably evolved somewhat since I was taught so I guess if they sell insulated crimps for 6mm then it should be okay to use them but with uninsulated lugs especially you can better visually check the result of crimping.

 

[davesparks]

How can you see? You cannot see inside so I'm guessing you mean where the conductor enters the crimp, but that would be the same as an insulated crimp? I'm talking in relation to butt crimps.

You can see by looking at it, you can see that all strands of the conductor have entered the tube and you can see that the conductor has gone all of the way in to the tube. Plus you can see that the crimp die is correctly positioned on the tube.
With an insulated crimp you cannot see the metal tube to know that the crimp die is correctly located, or see if there are any imperfections in the tube.

Plus, as you have noticed, the length of the insulating tube isn't quite standardised between manufacturers. So if you have crimps from the same manufacturer as your crimpers then you probably won't come across the issue you highlighted in your OP, however using crimps from another brand could be part of your issue.

With an uninsulated crimp and a hex crimper it is much simpler to do a test crimp and see if it is all ok before making the connection. Cutting through the test crimp to view the cross section of the crimped joint allows you to see if it has been made correctly or if there is a problem, a good crimp will compress the conductor fully, a bad crimp will leave gaps between the strands of the conductor.

 

[rich.250]

In my opinion those CK crimpers are a load of junk! My new one went in the bin and out came the old draper expert one I brought 12 years ago lol.
Never had a bad connection with that one.

 

[Andy78]

In my opinion those CK crimpers are a load of junk! My new one went in the bin and out came the old draper expert one I brought 12 years ago lol.
Never had a bad connection with that one.

I have to say that my daily ratchet crimp tool is CK and I have never had a problem with it. Still tight and makes a good compression every time. It is nearly 10 years old however and I do feel that CK tools in general were of a better quality some years back now. I had a set of CK drivers that lasted for years with daily abuse. I also had a newer batch that all shattered under normal use.