I needs crimps

[Dave-sparks]

I’ve used RS pro crimps for years, never had a problem. They’re not bargain basement so while I’m sure others like cembre might be “better” I’m really not sure how you could quantify that?

There's a few things that can be done to quantify the quality of a crimp and the crimping tool.

The most obvious are visual inspection, longevity, signs of wear, ease of use, number of unsuccessful crimps.

Then there's calibration and accurate measurement of crimping force, crimp profile etc.

There are go/no go gauges for some types of crimper.

A good, and relatively easy test, is to accurately measure the resistance of a length of cable at its rated current. Then cut the cable and join it with a through crimp, then accurately measure the resistance of it again, at its rated current.
Compare the two measurements and the greater the increase in resistance from the crimp, the worse it is.

When I say accurately measure I mean down to the milliohms at least

 

[daleyd]

There's a few things that can be done to quantify the quality of a crimp and the crimping tool.

The most obvious are visual inspection, longevity, signs of wear, ease of use, number of unsuccessful crimps.

Then there's calibration and accurate measurement of crimping force, crimp profile etc.

There are go/no go gauges for some types of crimper.

A good, and relatively easy test, is to accurately measure the resistance of a length of cable at its rated current. Then cut the cable and join it with a through crimp, then accurately measure the resistance of it again, at its rated current.
Compare the two measurements and the greater the increase in resistance from the crimp, the worse it is.

When I say accurately measure I mean down to the milliohms at least

I meant for the average person using a crimper, not for someone working to aerospace/military specifications with access to a lab- the RS ones will meet and exceed a minimum standard, and are great value in my experience. I’d say they are a good compromise between cheap no name and likely no quality control items and high end ones.
As i said I have used them in my line of work (instrumentation and electrical with many used for low milliamp/millivolt range signals) for many years with no failures, or bad connections, except where there has maybe been operator error and I’ve missed the crimp. If I’ve never noticed any ill effects from a crimp in a 4-20 ma circuit then it’s unlikely to be an issue for someone using them for more general use.

I don’t really know how you would measure a resistance of a cable “at it’s rated current” unless you mean measure it’s volt drop across the cable when “at it’s rated current”? Again, not something I’ve ever felt the need to do in probably 30 years of working with instrumentation, let alone for something like general panel wiring.

 

[Dave-sparks]

I meant for the average person using a crimper, not for someone working to aerospace/military specifications with access to a lab- the RS ones will meet and exceed a minimum standard, and are great value in my experience. I’d say they are a good compromise between cheap no name and likely no quality control items and high end ones.

I'm an electrician and I've come across a fair amount of failed crimp connections made by the 'average person using a crimper'.

Obviously I don't know why they have failed, it could be failing to clean the conductor, using crimps from one manufacturer with tooling from another, or a crimp tool not quite doing its job properly.

But from my point of view I want to minimise the possibility that the connections I make could fail in a few years time.

 

[Dave-sparks]

I don’t really know how you would measure a resistance of a cable “at it’s rated current” unless you mean measure it’s volt drop across the cable when “at it’s rated current”? Again, not something I’ve ever felt the need to do in probably 30 years of working with instrumentation, let alone for something like general panel wiring.

You can use a 'ductor' tester or it's modern equivalent. They can't necessarily be set to a particular current but do measure very low resistances at high current. These type of testers are used routinely for testing busbars and their joints, busbar trunking etc etc.

Or as you say, and the method I have used, is to pass a current through the conductor and measure the voltage drop. A simple constant current supply, a variac and known load in series or even something like an old Oxford welder can be used for the source.

 

[daleyd]

I'm an electrician and I've come across a fair amount of failed crimp connections made by the 'average person using a crimper'.

Obviously I don't know why they have failed, it could be failing to clean the conductor, using crimps from one manufacturer with tooling from another, or a crimp tool not quite doing its job properly.

But from my point of view I want to minimise the possibility that the connections I make could fail in a few years time.

So do I but I don’t measure joints to “milli-ohm” ranges or have a set of go-no go gauges, or exclusively use crimps made by the same manufacturer as my crimping pliers - so I think we need to be realistic and say that if the crimp looks ok and it doesn’t fall out when given a tug then it’s likely going to be just fine - so I stand by my statement that it’s going to be hard to quantify for the average guy between RS pro and some more expensive brands.

I’m sure what you say is perfectly true but absolutely no one would go to those lengths in the real world unless you were working on something of a very very high spec (eg military/aerospace) in which case I doubt you would be asking for advice on here about crimps, as you would use what you were told to use.

 

[Arc Tourist]

I'm an electrician and I've come across a fair amount of failed crimp connections made by the 'average person using a crimper'.

Obviously I don't know why they have failed, it could be failing to clean the conductor, using crimps from one manufacturer with tooling from another, or a crimp tool not quite doing its job properly.

But from my point of view I want to minimise the possibility that the connections I make could fail in a few years time.

I'm not an electrician, but have done a quite a bit of wiring in my time, and always have at least tinned the ends of stranded wire with solder before crimping connectors on, and never had a fail issue.

 

[mike os]

As long as the user is half competent using this type of crimp there is really no need to get pissy over it

If we were talking precision connectors.. circular, milspec etc then you need the right tools, crimps and all the other kit, and know how to use and test etc.

The ones that go wrong are generally the ones incorrectly used and fitted...

 

[Dave-sparks]

I'm not an electrician, but have done a quite a bit of wiring in my time, and always have at least tinned the ends of stranded wire with solder before crimping connectors on, and never had a fail issue.

But that is specifically prohibited by the wiring regulations due to the 'cold flow' of solder causing weakening of the joint over time.

 

[Dave-sparks]

The ones that go wrong are generally the ones incorrectly used and fitted...

This is very true, incorrect use and fitting is generally the reason for most failed connections.

A good electrician is able to make a reliable connection using any of the available connection methods.

 

[Maker]

I'm not an electrician, but have done a quite a bit of wiring in my time, and always have at least tinned the ends of stranded wire with solder before crimping connectors on, and never had a fail issue.

I'm pretty sure you're not ever supposed to solder stranded cable as it'll work harden and break with vibrations.

Anyway, I'm off to hunt for a Keithley 2001 to check the resistance of my joints.

 

[Memmeddu]

I'm an electrician and I've come across a fair amount of failed crimp connections made by the 'average person using a crimper'.

Obviously I don't know why they have failed, it could be failing to clean the conductor, using crimps from one manufacturer with tooling from another, or a crimp tool not quite doing its job properly.

But from my point of view I want to minimise the possibility that the connections I make could fail in a few years time.

That's why I do prefer non insulated terminals

 

[Kayos]

I'm pretty sure you're not ever supposed to solder stranded cable as it'll work harden and break with vibrations.

Anyway, I'm off to hunt for a Keithley 2001 to check the resistance of my joints.

I have soldered many hundreds, if not thousands, of wires in cars and engine bays, even on engine looms.

Not had one failure due to vibration

 

[ukracer]

I'm pretty sure you're not ever supposed to solder stranded cable as it'll work harden and break with vibrations.

Anyway, I'm off to hunt for a Keithley 2001 to check the resistance of my joints.

Is that not what solder is for?

 

[8ob]

This is very true, incorrect use and fitting is generally the reason for most failed connections.

A good electrician is able to make a reliable connection using any of the available connection methods.

Finding one around here is hard work which is why I do most of my own, they rock up with a fist full of qualifications quoting rules and regs but produce some very shoddy work. I have taken plug sockets off the wall and discovered loose wires in the terminals and where stuff cant be seen wires draped over sharp edges of steel work, I could write a book on it. My biggest gripe is they wont fix anything back with a screw longer than 25mm and half a red rawlplug.

Bob

 

[mtt.tr]

This went down a rabbit hole, I just want something that's reliable and consistent.


The ducter test is just Kelvin method or 4 wire testing. Just need a stable power supply and a multimeter.

 

[MetalMonkey]

I have soldered many hundreds, if not thousands, of wires in cars and engine bays, even on engine looms.

Not had one failure due to vibration

If the joint is inside a taped loom and not subject to movement, the chances are it will be fine. Cars are not really subject to vey much use in the grand scheme of things.

I've encounter broken soldered joints at connector ends on vehicles where they have been repaired, but seen a lot more issues on plant, which is obviously subject to a lot more use and abuse.
The key thing with solder joints is to ensure that any flex takes place at the unwicked part of the cable, which can be quite a way back from the joint. The joint must be supported and strain relieved.

On critical applications crimps are the accepted standard because of the improved resilience to vibration and flexing and less variable quality when terminated (a calibrated crimp will give a very repeatable result).

 

[Dave-sparks]

Finding one around here is hard work which is why I do most of my own, they rock up with a fist full of qualifications quoting rules and regs but produce some very shoddy work. I have taken plug sockets off the wall and discovered loose wires in the terminals and where stuff cant be seen wires draped over sharp edges of steel work, I could write a book on it. My biggest gripe is they wont fix anything back with a screw longer than 25mm and half a red rawlplug.

Bob

Yes there are a lot of sub-standard electricians out there. But they are cheap and fast, and a lot of customers value price and speed over quality.

 

[Kayos]

I used my crimper again today, not failed (yet)

 

[daleyd]

I used my crimper again today, not failed (yet)

Yes but have you checked it with a milli-ohm meter?

 

[Kayos]

Yes but have you checked it with a milli-ohm meter?

Not yet, top of my list in the morning though.....