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Rate my crimps

Which crimp is better?

  • Crimp A

    Votes: 4 16.0%
  • Crimp B

    Votes: 8 32.0%
  • Either is acceptable

    Votes: 9 36.0%
  • Neither is acceptable

    Votes: 4 16.0%

  • Total voters
    25

rv12is

Active Member
I'm getting ready to crimp some d-sub pins and have two crimpers to choose from. I'm not sure which crimper is the better option. So I crimped two test pins and examined them under the microscope. Despite the two crimpers looking very similar, the resulting crimps are definitely different.

crimp.jpg

Which crimper would you choose? A or B? Is either acceptable? Or neither?
Crimp A:
crimp A.jpg

Crimp B:
crimp B.jpg
 
Either one looks good. I would strip the wire so the end of the insulation would press firmly against the barrel for support.
 
Crimp B looks like it may have bent the barrel which may cause some difficulty in getting it seated into the connector body. My vote goes to A.

BYW, too much insulation has been stripped from both samples.

Bevan
 
Insulation

Both style of crimpers are OK (single of dual indentation)
Both have a tight wire bundle with no birdcaging of the wire.

But:

A has too much insulation exposed. Ideally you want just enough exposed so that one can see that no insulation shards are inside the barrel. B looks better in terms of insulation exposed. Too much can cause shorting either from adjacent wire or debris. And wire will birdcage easier during assembly or removal.

As others have mentioned, the barrel needs to be straight, if bent something went wrong.

Every barrel and every different wire size ( wire AWG) will need to have the crimper reset. The holder should have a chart with the tool setting based on wire guage.

I would not put the insulation up against the barrel; if this is done, then any flexing of the wire may tend to pull the stands out of the crimp.

The best source of information is the Garmin G3x installation manual. Free to all with an internet connection.

My rule is that all crimped pins must have the wire supported within a few inches of the crimp. This is usually accomplished with the back shell. When tying the crimped wires together, with no back shell, extra care must be taken so that one wire doesnt take all the stress from the bundle. I dont advise this in vehicles with vibration.
 
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Crimp A looks very good - I like the double crimps on it. Can you share with us what kind it is? All mine are like your B photos, but with a bit more insulation. :)
 
Both crimpers are relatively cheap crimpers. This is why I wanted to do some test crimps to see how well they performed. I wasn't really paying attention to the insulation clearance, as my goal was to evaluate the performance of the crimper tool itself.

But since multiple comments were made on the insulation clearance, (and I had no idea what was appropriate) I looked into this some more. It appears that NASA specs (NASA-STD-8739.4A) specify a minimum insulation clearance of 0.01" and a maximum of 0.03".
Screen Shot 2022-09-07 at 6.37.29 AM.png
Is this an appropriate spec to be working to? If so, I measure the insulation clearance of A to be 0.035". So as many have suggested that distance is too far and should be reduced. On the other hand, crimp B would appear to be well within the specified range.
 
I'll vote for A. The double spread will put less stress in a single area, look at it as a back up. Also work on the stripping lengths so you have very little wire showing between the barrel and the insulation. Also crimping too tight is almost as bad as not crimping tight enough. This should be set on the crimper to ensure repetitive shrimps.
 
But - the pull test is the real test of a crimp after the visual inspection.

I'm not sure of the proper way to perform a pull test. However just based off of the name, I did perform a couple of tests.

Test #1: I crimped identical pins onto each end of the same 22 AWG wire. One side crimped with tool A, the other tool B. I then grabbed each pin with pliers and pulled until failure. The source of the failure was the wire pulling out of crimp A.

Test #2: I crimped a pin onto a 22 AWG wire. Using vice grips I secured the terminal to the bench vice. I then attached the wire to a fish scale and slowly pulled until failure. Crimp A failed at around 19 lbs, while crimp B failed at 17-18 lbs.

No wires were damaged or broken. They simply pulled out of the crimp. While my sample size is way too small to conclude anything, it appears the crimp retention force (or whatever the proper term would be) would be similar between the two tools.

So now the remaining question from my testing is, what's the proper minimum force for an acceptable crimp connection on a 22 AWG wire?
 
Send 'em both back and buy a used Daniels AFM8!

I like your thought process. If I was building any RV other than a 12iS that's likely the approach I would take. However, with the 12iS the wiring harness comes mostly assembled. There are probably less than a couple dozen pins that will need to be crimped with this tool.

The SteinAir crimpers were free and the Greenlee crimpers are some that I've had for a while. If either of these produce acceptable crimps, I don't think I can justify the expense of a tool that I would use so few times.
 
Down the rabbit hole we go

I don’t think you will find any manufacturer of Mil-DTL-24308 type connectors that will list those tools as acceptable. What you are after is a oxygen free connection between the connector and wire. That is dependent on the wire size. Looking at the outside doesn’t show that. It also has to make a crimp that doesn’t distort the connector. You could smash it with a vise and pass a pull test maybe even get it to insert but good luck getting it out. If you want it done right you have to buy an approved adjustable crimper and it’s going to cost 5 times more than you want to spend.
 
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No wires were damaged or broken. They simply pulled out of the crimp. While my sample size is way too small to conclude anything, it appears the crimp retention force (or whatever the proper term would be) would be similar between the two tools.

So now the remaining question from my testing is, what's the proper minimum force for an acceptable crimp connection on a 22 AWG wire?

The wires should break and not pull out.

Edit: for aircraft use, I think there is a pull spec minimum. I will update my answer to say that for aircraft use, as long as you meet the pull spec, they will be good enough. your plane, your decision.
 
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If this is the case, then neither crimp is acceptable. Maybe I should stop being so cheap and just buy the proper tool...

Bob Nuckolls - wiring and aircraft electrical system expert - says you should be able to pull about 8 lbs on an AWG 22 connection - so your crimps were fine.
 
Several people noticed Connector B appeared bent. That would be a bust for most aerospace QA inspectors. Just for kicks try putting both in a connector body and then try extracting them.
 
Several people noticed Connector B appeared bent. That would be a bust for most aerospace QA inspectors. Just for kicks try putting both in a connector body and then try extracting them.

There is a very slight bend to connector B. It's easily visible under the microscope, but not apparent without magnification. I did test it in a connector body, and (from what I could tell) there was no change in insertion, locking, or removal.

Just for testing purposes, I did crimp a few more terminals with crimp tool B. All of them exhibited a nearly identical bend.

Even though the bend is slight, and it didn't appear to cause a problem in my one off test, I think this is reason enough to prefer crimp tool A over crimp tool B.
 
Pull Test

Attached is a pull test table. Use the Mil spec chart. The numbers are a minimum for not failing. There are other publications and standards that have the pull test within but IMO not worth having. Your test was good, as was the value. The DMC tool will precisely restrict the deformation of the crimp according to the specific pin and wire dimensions, that is what the tools you have don't do.

FYI, the DMC (Daniels) is the gold standard, and depending on military funding cycles you can find many or none on ebay. Get a pretty one for the best price you can find. Also, there is a maker of a clone, China of course, named JR Ready. Also on eBay. While it is still expensive, I would prefer a used DMC before buying a new clone for $375. The positioners are another matter. They simply hold the pin in the center and axially correct. I got 5 of the popular positioners for 1/2 the price of a new DMC. They were perfect.

Crimp Pull Table.png
 
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