Introduction: Make a Good Dupont Pin-Crimp EVERY TIME!

Picture of Make a Good Dupont Pin-Crimp EVERY TIME!

Anyone working with an Arduino, Raspberry PI, Beagle Bone, or any other multi-circuit-board project has become familiar with .025 X .025 in, square post pins and their mating connectors. The male pins are usually mounted to the circuit board with board to board wiring accomplished through mating connectors and wiring. These connectors usually consist of female pins that are individually crimped onto the wires which are then then inserted into multi-position connector shells.

These connector pins, also commonly called “Dupont Pins,” and are manufactured by AMP, Tyco, Molex, Samtec and a myriad of others.

Crimping Dupont female pins onto a wire requires a special crimping tool, precise techniques, and lots of time and patience! When I first started home-crimping these pins, I found that only about 1 in 10 came out right, with the rest defective in one way or another.

Thankfully, a few soles before me posted documentation, a few Instructables, and some YouTube videos that helped me get a started. Even at that, it took lots of trial and error and many crushed, damaged and unusable pins before I was able to get my failure rate under control.

Over time I studied my problems and came up with this guide and document to share some common crimp problems and solutions. In particular, you will see a very simple “Pin-Guide Tool” that you can make that will precisely position and hold the female Dupont pin inside of your hand crimping tool throughout the whole process. By using this Pin-Guide and a few other basic ideas, you too I can get a good crimp every time!

Step 1: Tools and Parts Needed

Picture of Tools and Parts Needed

Above you can see the items you will need. Although not shown, a good wire stripper is also required. Take care in selecting and using the stripper as you will see soon, consistent strip length, free of nicks, is crucial to good Dupont pin crimp results.

Step 2: What Goes Wrong?

Picture of What Goes Wrong?

I studied my many failed crimps in an effort to figure out what was going wrong. I came up with the DEFECT TABLE shown above. This table helped me determine the root cause(s) for each defect which in turn, led me towards solutions.

While I don’t claim this list to be a 100% comprehensive, it does represent a good summary of my most common reoccurring problems.

Step 3: Wire Strip Length

Picture of Wire Strip Length

The figure above shows the anatomy of a Dupont pin.It is seen that the total length of wire going into the pin should not exceed .2 in (5.0 mm). This means that when the wire is correctly and precisely positioned in the pin, the optimum wire-strip length is only 0.10 in (2.5 mm). A shorter strip length will compromise the conductor crimp while a longer strip length will either cause the wire to penetrate into the pin too deeply or lead to a degraded insulation crimp. For these reasons, I conclude that strip length is critical to achieving a good Dupont pin crimp.

  • While I’m sure there are precision wire strip tools out there, I don’t have one. Therefore, I check each strip length and carefully trim away any excess wire whenever my stripped length is too long.
  • As a reminder, take great care not to nick any of the conductors during the strip process as this will compromise the quality of the finished connection.

Tip: I found that recycled stranded-wire Ethernet cable is a good source for the interconnect wire.

Step 4: Pin Positioning Inside the Crimp-Tool

Improper pin-positioning within the crimp-tool tool was also a major reason for many of my crimp defects.

Perhaps I am just ‘all thumbs’, but once I thought I found the best spot to place the pin inside the crimper, I rarely seemed able to get it there. Furthermore, even when my pin placement was perfect, I frequently found that the pin would be pushed out of position or even rotated as a by-product of inserting the wire into the pin.

To solve this problem, I came up with a “PIN-GUIDE” tool. The Pin-Guide tool is nothing more than a strip of male pins onto to which the female pin to be crimped is placed. While simple, this Pin-Guide provides many benefits.

  1. The Pin-Guide provides a ‘handle’ for the pin so that placement into the crimper jaws is easier.
  2. The Pin-Guide precisely sets the position and depth of the pin relative to the crimper jaws. This serves to locate the CONDUCTOR-CRIMP zone and INSULATION-CRIMP zone in exactly the right spots within the crimp dies.
  3. Since the Pin-Guide ‘stays in place’ during the crimp cycle. it prevents the female pin from twisting, sliding, or moving while inserting the wire or performing the actual crimp cycle.
  4. The Pin-Guide also provides a ‘wire-stop’ that keeps the wire from going too far into the center of the female pin and obstructing the Mating-Pin Zone. Note that this fault only revealed when you find that you can’t plug the finished connector assembly onto the male PCB pins!

The Pin-Guide is easily fabricated from a 4-pin strip of male pins. The key to success however, is precisely setting the pin depth.

Step 5: Making the Pin-Guide

Picture of Making the Pin-Guide

It’s easy to use the Pin-Guide. Just cut the female Dupont pin from the carrier and place it onto the Pin-Guide.

Step 6: Loading the Pin-Guide

Picture of Loading the Pin-Guide

Step 7: Selecting a Crimp Port

Picture of Selecting a Crimp Port

The SN28-B crimp tool has three different crimp-ports. Each port has a slightly different die shape and will form the pin differently. As noted in the figure, I found that I get the best results using “port 1” with wire up to and including AWG 22 Ga; I do not get good crimps with 22 Ga wire in position 2. Your results may vary however, as each crimp tool is adjustable; your setup maybe different than mine.

While the tool markings implies larger gauge wire may be used, I suspect that anything much larger than 22 Ga may not fit into the 0.1 inch spaced shells used for most Dupont pin connector assemblies.

Step 8: Loading the Dupont Pin Using the Pin-Guide Tool

Picture of Loading the Dupont Pin Using the Pin-Guide Tool

As shown, with the female Dupont pin on PIN-GUIDE post #2, place the pin into the crimper jaws and close the jaws until they “click” and the pin is held in place. Be sure the pin is properly oriented and take care NOT to over compress the pin at this time as that will make wire insertion more difficult.

Step 9: Loading the Wire & Completing the Crimp

Picture of Loading the Wire & Completing the Crimp

Next, carefully insert the stripped wire into the pin. As shown, be sure the wire is fully inserted and is not ‘hung-up’ during placement. While holding the wire in place, compress the crimper-handles to complete the crimp. Release and remove the completed crimp and perform a QC inspection.

After each crimp, it is important to perform a VISUAL INSPECTION as well as a QC PULL TEST of the pin-wire combination. A few examples follows that show you what to look for. Since the pins are small, I recommend you use a magnifying lens for all visual QC checks.

Step 10: Inspecting Your Work: Example A

Picture of Inspecting Your Work: Example A

Step 11: Inspecting Your Work: Example B

Picture of Inspecting Your Work: Example B

Step 12: Inspecting Your Work: Example C

Picture of Inspecting Your Work: Example C

Step 13: Loading Connector Shells

Picture of Loading Connector Shells

When the crimped pins are completed, they are easily inserted into the connector shells as shown. Pay attention to the photo details as pin orientation is important. Note that the pins will only lock-into the shell when inserted with the proper orientation.

Step 14: Summary of Pin-Crimp Steps

Picture of Summary of Pin-Crimp Steps

Step 15: Troubleshooting

Picture of Troubleshooting

As another aid to diagnose and trouble shoot common crimping issues, I offer the expanded trouble shooting table above.


CLOSING COMMENTS

This Instructable aims at helping you get solid, consistent Dupont pin termination results. I have focused on female-pins but similar steps can be applied to help you achieve good results for male-pins as well. I invite you all to review and tweak these ideas as you see fit to get them to work well for you.

Take care and Happy-Crimping!

Comments

moonlight0551 (author)2017-12-06

Well done. I followed your guide and just did 4 perfect crimps after many previous failures. Using a pin guide makes all the difference. Nice clear instructions and the pictures are great.

ee_eng (author)moonlight05512017-12-07

Thanks for your followup. Glad to hear it worked for you.

dpeach (author)2017-12-06

This was great. Thanks for writing it. I had my first attempt at DuPont cable crimping a couple of months ago. Eventually I got it to work well and I actually enjoy creating wires of just the right length. This guide would have helped back then. I am sure it will be a help to others in the future.

bgreen3 (author)2017-12-05

Great guide. FWIW, I highly recommend using the "OK Industries" style wire stripper. It has a depth gauge that can be set for perfect strips every time. I've crimped thousands of dupont connectors and went through a similar journey to conclude that it starts with a perfect stripper and ends with a perfect crimper.


https://www.amazon.com/Industries-Wire-Stripper-Adjustable-20-30/dp/B0015A7DBI

ee_eng (author)bgreen32017-12-05

Thanks for your idea. Your stripper suggestion, while a little pricey, looks pretty cool!

bgreen3 (author)ee_eng2017-12-06

Search around for best price. I think I paid about $22 for mine. The OK Industries ones are very high quality and worth the money if you do this all the time.

ee_eng (author)bgreen32017-12-05

Thanks for your feedback. I will have to look into the OK model.

throbscottle (author)2017-12-05

Very informative piece, thank you.

I bought a very cheap crimping tool which looks a lot like yours, and found it has a peculiar problem - instead of curling the "conductor crimp" around into two neat humps, it pushes them down so I get a partial crimp with a gap in the middle and two little flanges on the the back. I made a quite a few of these before I realised there was a problem.

So I bought another very cheap crimping tool of different design, which also doesn't crimp properly but does form the "conductor crimp" into a better shape.

So now I start the crimp off with the second tool I bought, and finish it with the first one, the result being quite good looking crimps. Still not as good as the commercial ones, but far better than either tool on it's own (and still much cheaper than a decent tool which I simply can't afford)

It's a good job I don't do many...

ee_eng (author)throbscottle2017-12-05

Thanks for your feedback. If you regularly use Dupont pins, you will be well served to get a better tool. I think I paid less than $20 for the version I have and with some tender loving care (and a Pin Guide!) it works pretty well.

throbscottle (author)ee_eng2017-12-06

I confess the pin guide is a really good idea - I may have to make one. Nine times out of ten I get the terminal in the right place though, by being very careful!

JeromeS29 (author)2017-12-05

This has got to be the very best most technical without being too technical guide to crimping dupont pins in the universe. I wish you were in charge of the various guides and manuals that either exist or should exist!

ee_eng (author)JeromeS292017-12-05

Thanks for your comments. Sorry, don't know a think about the SN-48B; Hope someone else can give you some ideas.

pgs070947 (author)2017-12-05

If it's a genuine SN-28B crimper, you will need a small mortgage to buy one.

Really suspiciously cheap crimpers aren't worth buying, but there are some decent mid-quality crimpers that work really well.

I bought one of these for the smaller Molex 0.1" pitch friction lock female headers and can't fault it. Japanese, decent quality with a choice of crimp sizes.

https://www.amazon.co.uk/Universal-Micro-Crimping-Crimppins-Engineer/dp/B002AVVO7K/ref=pd_lpo_vtph_147_tr_t_2?_encoding=UTF8&psc=1&refRID=75A3K44F74HE2NVC6WKY

I don't know how these connector companies can justify charging 3-figure sums for a crimper, but if your firm is buying it, so what

ee_eng (author)pgs0709472017-12-05

Thanks for your comment. I agree that crimp tools from MOLEX or AMP are exceedingly expensive ($200-$400 or more). On the other hand, they do work well and tend to be more fool proof than the 'knock-off' varieties (like the one I have!) .

KenC7 (author)2017-12-05

Hate to suggest something that might be simpler, but I get perfect crimps on these without the guide part. The wire strip length is important, as noted. I put the pin into my tool, close the tool part way, so it's not crimping yet but the pin is held, then gently pull the pin so it sticks out of the tool more. The crimp end will be in the tool completely, and the insulation crimp will stop on the anvil for the wire crimp. The tool will hold the pin in that position (just enough friction.) Put in your wire, making sure the insulation travels in all the way (it too will stop on the wire crimp anvil), position the cable so that the wire rests on the base plane of the pin (you can see this), and crimp.

The only times this fails for me are when I didn't insert the cable fully, or didn't look to see the wire was laying flat on the base of the pin. If you get the wire strip length right, you can see - every time - that the insulation is far enough in and the wire is flat, because you won't see the wire going far enough or laying flat if you miss one of those two.

One additional note for #13 - You may find at times that the pin goes into the shell easily at first, and then is *really* hard to insert the rest of the way. When the crimp forms on the insulation, sometimes it becomes too horizontal (flattened). If you give it a small squeeze with a pair of needle-nosed pliers to make it slightly less flat, it will often solve this problem without compromising your crimp.

ee_eng (author)KenC72017-12-05

Thanks for your input. Good to hear that you've had good success with a simpler approach. I haven't had good success without the help of the Pin-Guide. Perhaps I just haven't terminated enough terminals to get good at it without some help from a simple fixture like the Pin-Guide..

JeromeS29 (author)2017-12-05

one question I hope someone knows the answer to: the SN-48B crimp tool, is its first slot equivalent to the SN-28B second slot? If so I would much rather buy the SN-48B as it can crimp larger things, which I have been known to need to do every so often, not so much with smaller gauge wires though. Thanks again!

ee_eng (author)JeromeS292017-12-05

Sorry, I am not familiar with the SN-48B,. Hopefully, someone else can help.

DurkVell (author)2017-12-05

Thank you very much for this brilliant explanation! I have all the tools and have tried a lot of times to make a working, neat Dupont crimp and have succeded only once!! I'll give you workflow a try! Once again thank you very much!

ee_eng (author)DurkVell2017-12-05

Thanks - Hope it works well for you!

medic265 (author)2017-12-04

This is one of the best written and documented Instructables I've seen. Great Job!!!!!!!!!!!!!!!!!

ee_eng (author)medic2652017-12-05

Thanks! Happy Crimping!

denaxasp (author)2017-12-05

Thank you!!

Andsetinn (author)2017-12-05

Very detailed. I like your pin guide. I might make a similar one.

warren.prints (author)2017-12-05

Wow. I did not know you could go so in depth on crimping. I loved it. Keep it up!

monguin (author)2017-12-05

This is the missing manual for that crimper tool. I have used mine enough that I have a "system" for getting the crimps right 95% of the time, but I wish I had seen this when I first got the crimper, it would have saved so much time and effort.

I love the defect table and the holder tool. Awesome writeup.

mbonifax (author)2017-12-05

THANK YOU.

I rarelly saw a so deep and, at the same time , easy and well done, syntesis.

remindMe (author)2017-12-05

Great example of "Why didn't I think of it". So cool and simple. Thanks!

TimothyJ999 (author)2017-12-04

Nice instructable!

Just a quick addition to your statement about using stranded Ethernet cable: the only Ethernet cable that’s stranded comes from interconnects (used between the wall and computer or other devices— the short pieces with a male jack at each end). Bulk Ethernet cable bought in 1000’ boxes or salvaged from inside the wall will NOT work. The wires inside are solid core and aren’t nearly flexible enough for use in short interconnects.

ee_eng (author)TimothyJ9992017-12-04

Thanks for your comment - You are right! The cable I was using and thinking of was indeed a dead male-male interconnect cable.

Good Catch!

lobo13 (author)2017-12-03

Man so simple but so useful, Thanks.

JorgD5 (author)2017-12-02

thanks for this.

i like the great detail it helped me a lot

ee_eng (author)JorgD52017-12-02

Great!
Happy Crimping

Eric Brouwer (author)2017-12-02

Well presented Instructable.

Thank you.

studleylee (author)2017-12-01

Nice!!!! I like the detail and great distance tips!! Thanks!

ee_eng (author)studleylee2017-12-01

Thanks for reading!
Take care.

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Bio: Electrical Engineer by training; Electronics Nerd before it was fashionable.
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