Crimping two wires together on the same crimp-connector it's criminal?

bwilliams60

Joined Nov 18, 2012
1,417
I have skimmed over this 80 post thread and it sounds like it comes down to solder vs. crimp. I for one am a big believer in solder, however when it comes to "crimp" connectors, if they are done properly with the proper tool, it is just as effective. Vehicle manufacturers have been using crimp connectors for years and as pointed out earlier, aerospace as well. Deutsch, Weatherpack, Metripak, Framatone, AMP, Delphi, and Molex just to name a few, are all crimp connectors used on some of the most rigourous equipment this planet has to offer. I don't think they can all be wrong.
What it really boils down to is installers choice. Crimping can't be wrong. I would have never said that ten years ago. But...it has to be good!
 

AnalogKid

Joined Aug 1, 2013
9,351
Also, solder wicking onto the spring or press fit connector can prevent the full range of movement on the connector and, again, change the current rating (resistance) of the connection.
It also makes the connector impossible to replace without destroying the hole plating.

ak
 

AnalogKid

Joined Aug 1, 2013
9,351
How do they make it completely oxygen free? I get that the interface is under pressure in that area but I would assume there is always some conductor that is in contact with the atmosphere unless it is potted or really good shrink.
The tonnage of force applied to the crimp area is far greater than most people realize. It squeezes out *everything*. Everything up to the nanometer before the crimp area can be exposed to air, water, corrosives, and whatever else the wire is rated to handle - don't care. Wire integrity is someone else's problem. The contact between the touching parts of the barrel and the wire is pretty much perfect.

Solder isn't the best conductor you're right but I can't help but think the intrinsic resistance of a soldered joint would be less than the contact resistance of a crimp. Maybe this is a misconception on my part I'm not sure.
Copper is the 2nd best conducting metal on this planet. An unsoldered joint is copper-copper. A soldered joint is copper-tin/lead-copper. Anything else except silver is worse, which means that tin, lead, antimony, rosin, and whatever else is in there can only make the connection worse. Note that we're talking milli-ohms here, but in this discussion, "better" and "worse" have a bit of concreteness to them. The ultimate would be bare, raw, unplated, untinned copper wire and barrel walls, but the packaging and handling necessary to prevent oxidation before assembly is too expensive.

To prevent oxidation, most lead wire is plated with something, usually solder. MIL grade hookup wire is silver plated for all of the reasons above. If a spool has been sitting around for a while, you can see that the cut end of the wire is black. Also, MIL and other high-grade solders are called silver-bearing solder because they have a few percent silver to improve conductivity.


ak
 

#12

Joined Nov 30, 2010
18,223
An unsoldered joint is copper-copper. A soldered joint is copper-tin/lead-copper.
And a crimped joint with solder added after crimping is copper-copper in electrical parallel with copper-tin/lead-copper.
Except all the crimp terminals I can buy are coated with some white metal. Some look like chrome and some look dull. That seems to eliminate the copper to copper interface for my crimp jobs.:(
 

mcgyvr

Joined Oct 15, 2009
5,394
And a crimped joint with solder added after crimping is copper-copper in electrical parallel with copper-tin/lead-copper.
Except all the crimp terminals I can buy are coated with some white metal. Some look like chrome and some look dull. That seems to eliminate the copper to copper interface for my crimp jobs.:(
Its always tin or silver plating..
 

mcgyvr

Joined Oct 15, 2009
5,394
The tonnage of force applied to the crimp area is far greater than most people realize.
One of our 8 to 2 AWG pneumatic crimper press is 6 tons.. the other is 7.5 tons..
Our 24 to 10 AWG mechanical crimping press is 5 tons...
The hydraulic crimp unit for up to 750 kcmil is 14 tons

All will EASILY crush a finger paper thin in an instant..

Even old "wire-wrap" connections are considered "gas tight"
 

RichardO

Joined May 4, 2013
2,271
Oh and one more thing.. Almost all "professional/listed" hand tooling is "controlled cycle" in that it must fully close before its allowed to open again.. This guarantees that the crimp is fully "crimped".. Hardware store hand tools don't have that and hence are prone to allow a "user" to under crimp a connection..
Unfortunately, a proper tool can cost $1000 -- if you are lucky. A friend needed a crimper for a specialized connector. The price he saw was over $5000. That was for a _hand_ crimper. :eek: His "needed" quickly changed to "wanted".
 

tcmtech

Joined Nov 4, 2013
2,867
Vehicle manufacturers have been using crimp connectors for years and as pointed out earlier, aerospace as well. Deutsch, Weatherpack, Metripak, Framatone, AMP, Delphi, and Molex just to name a few, are all crimp connectors used on some of the most rigourous equipment this planet has to offer. I don't think they can all be wrong.
You would think so yet as someone who has spent their working life in the service and repair part of industry I can assure you that even with all those companies high end precision crimping machines and quality control routines that crappy crimps are a constant problem in pretty much everything built. :mad:

Automotive, farm and commercial equipment are notorious for having crimped joint failures in wiring harness that cause anywhere from those off 'come and go intermittent electrical issues' to all out connector burndown and occasional entire machine burndowns.

My last major job was in the oil fields as an electronics service tech and dealing with failed electrical connections due to failed factory crimp joints in the wiring done wrong was a literally daily routine for our department.

Our fix, where possible, was to replace the bad connectors with crimp and soldered ones followed by one or two layer shrink wrap seal and strain relief followed by proper cable support within as short of distance and possible to prevent vibration from working wires loose.
Unfortunately a lot of the failures we saw were in wiring harness and comms cables with one piece molded connectors on the ends so we had to replace entire wiring harnesses and cables in those instances.

As for what we found to work best in the high vibration harsh environment application of fracc work our follow up reworks with the combination crimp, solder and support had very low failure rates and those that did were primarily due to non electrical damage like having wire harnesses pulled out of boxes or severe moisture/electrolytic breakdown at the terminal blocks. Actual connector to wire joint failures were almost unheard of.

Thanks to that job I have at least a miles worth of 200' foot long 6 lead commercial grade outdoor application rated ethernet cabling with nothing wrong but one of the molded one piece connectors being bad which in every one we ever dissected was found to be due to one of the wires having either pulled out of crimp or having corroded in the crimp.

I am saying that crimp only joints fail everywhere and they fail a lot. Solder joints between wiring and cable end connectors on the other hand if they were not physically broken off or damaged by heavy external corrosion rarely ever fail. They do but my experience is they are a good 20:1 or lower than crimp only joint failures.

BTW I have worked with military surplus electronics for most of my life and I have seen them use crimp only solder only and both combined in many instances.
I have a 1950's military AC power genset that is all original and that uses crimp and solder on every wire end connection. I also have a mid 80's 24 VDC military geneset that has both as well so at least in genset application it must have been a very common thing for many years.
The newest military surplus item I have is a 36 volt 150 amp battery charger and that uses crimp only on the lighter gauge control circuits and crimp/solder on the high current connections. It's got a control system issue and I suspect that when I find it it will be a bad crimp joint some place. :p
 

ian field

Joined Oct 27, 2012
6,539
Stuff in as many as will fit, crimp, and solder.
Solder cures many evils!
Solder basically turns all those strands into a solid conductor which is more liable to fatigue and break.

You can get snap lock connectors for splicing onto automotive wiring harness.

They work on the same principle as IDC connectors on computer ribbon cables.
 

#12

Joined Nov 30, 2010
18,223
Solder basically turns all those strands into a solid conductor which is more liable to fatigue and break.
Yes. As already stated in this Thread a dozen times, a solid core wire will fatigue worse than a stranded wire IF THERE IS CHRONIC MOVEMENT.
You can get snap lock connectors for splicing onto automotive wiring harness.
Yes, two little blade edges make a much better connection than crimp or crimp and solder. That's why I have replaced dozens of wall recepticals that failed where the licensed electrician used the, "Stab-loc" connector instead of the screw provided. I have also replaced a few snap-lock connectors in cars, but I have never found a bad connector that was crimped and soldered.
 
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shortbus

Joined Sep 30, 2009
8,797
Our 24 to 10 AWG mechanical crimping press is 5 tons...
Worked at Delphi/Packard Electric and the terminal presses we used were 5ton rated for those gauges. The critical crimp presses also had a strain gauge under the die set, to certify the proper crimp force also.
 
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Thread Starter

gimpo

Joined Jan 27, 2016
124
Today I made 8 crimped connectors. I was not satisfied with 1 one of them so I had to make a new one.
Crimping is not easy. What is more disturbing me is that I have no sensation of control, I mean... there is no direct feeling between the action and the result. Seems like a russian roulette, you press and you have a prefixed probability that the crimp will be ok. Bad feeling...

I heard you talking about tools costing hundreds or thousands dollar ( :eek: ). Honestly speaking, what probabilities I have to make good crimps using the pololu tool below?
Selection_022.jpg
0J3281.1200.jpg

It has 3 slots for different wire diameters: 26-28 / 22-26 / 16-20 AWG

By examinating the connectors with a magnifier they seems not so bad... but here again, it's not easy to establish when a crimp is good or bad only by using your eyes. Should I start to be worry?
 

ian field

Joined Oct 27, 2012
6,539
I have skimmed over this 80 post thread and it sounds like it comes down to solder vs. crimp. I for one am a big believer in solder, however when it comes to "crimp" connectors, if they are done properly with the proper tool, it is just as effective. Vehicle manufacturers have been using crimp connectors for years and as pointed out earlier, aerospace as well. Deutsch, Weatherpack, Metripak, Framatone, AMP, Delphi, and Molex just to name a few, are all crimp connectors used on some of the most rigourous equipment this planet has to offer. I don't think they can all be wrong.
What it really boils down to is installers choice. Crimping can't be wrong. I would have never said that ten years ago. But...it has to be good!
It makes all the difference whether you use high quality brazed join crimp connectors, the ones that aren't brazed can overlap or go sideways when the crimp tool closes on it. With the brazed join type, the more wire you fit into it - the more secure the crimp will be. The unbrazed type can sort of burst and some of the strands escape.

I only ever solder in cases where it couldn't make things any worse - I try to only solder the wire that protrudes through the crimp, any solder that wicks through makes a short bit of solid wire that's prone to fatigue fracture.
 

BReeves

Joined Nov 24, 2012
410
Gimbo, I have made hundreds of crimps with a tool like you pictured, it works great. Won't release until the crimp is complete which insures you have a proper crimp.
 

mcgyvr

Joined Oct 15, 2009
5,394
what probabilities I have to make good crimps using the pololu tool below?
View attachment 102573
Assuming it works for your terminal.. Wire AWG isn't the only thing.. But a nice pull test after crimping will be sufficient..
Thats actually a "decent" crimper as its controlled cycle too..
In general most "OEM" hand crimpers run from about $300 to $1000 dollars each..

Today I actually had to buy a new die set for our manual crimper and it was $550
 

Thread Starter

gimpo

Joined Jan 27, 2016
124
Thanks for your replies, BRreeves and mcgyvr. :)

Now I'm curious to see a photo (or a link) to a manual crimper costing 500 bucks or more. Somebody can post something? (I will show it to my wife! :D )
 

Thread Starter

gimpo

Joined Jan 27, 2016
124
It makes all the difference whether you use high quality brazed join crimp connectors, the ones that aren't brazed can overlap or go sideways when the crimp tool closes on it. With the brazed join type, the more wire you fit into it - the more secure the crimp will be. The unbrazed type can sort of burst and some of the strands escape.
Brazed? Do you mean those connectors where the part grabbing the wire insulation has a cylindrical shape? If so, they are usually not available on the market for connectors (and housings) for electronics purposes (e.g. TE-Connectivity and other mfgs) :(
 
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