My pin crimping tips -- what are yours?

Question

I am a self taught pin crimper. Sounds like a personal problem, I know.

I have a crimper tool that looks like this:

I use it to crimp pins for proto board soldered wire-to-board connectors that look like this:

At first, I was unhappy with the results due to the following results:

The wires would stab through the hole blocking the male end
I’d lose the pin from it falling off the cable before I could crimp it
the pins are hard to seat into the connector
the pins back out of the connector when connected to the male end
the wire breaks off at the base of the pin
the male pins would not want to stab into the female after everything was crimped and ready

<EDIT: See this post below for the crowd improved troubleshooting guide: https://www.element14.com/community/message/284233/l/re-my-pin-crimping-tips-what-are-yours#284233 >

Here's how I adjusted my approach:

Issue	Solution
Wires stabbing through the hole	I bend the wires back over the insulation
Dropping the pin	I’d pre crimp the bottom with just my fingers to hold it in place.
Hard to seat	After crimping the bottom of the crimp pin to the cable sheathing, I take a small plier to shape the female tip to remove any parts sticking out impeding entry into the plastic connector housing.
pins back out	After adjusting the pin shape in the previous step, I pull up the tab that will catch inside the connector to prevent it from backing out.
the wire breaks off	I stopped using jumper cables as the donor wire. Instead, I use ribbon cable.
Male pins not fitting	I use a single jumper male pin to pre stab in the female pins I just inserted into the connector to open it back up.

I now get reasonable results, but what bothers me is that I have to do all this. I would think I could just crimp and insert and be done.

So, my question is, what are the community members experiences, steps, and tricks for using crimp pins?

Thanks,

Sean

koudelad · Accepted Answer

I personally tried about 3 types of crimp tools (mentioned above and in the linked discussion) in addition to just small pliers. However, I don't always have original DuPont connectors and even small differences mean crimping might go wrong. Or the crimp looks OK, but the connector can't be inserted to the housing. I haven't seen anyone recommending Engineer's crimp tools: ENGINEER INC. - PRECISION CONNECTOR CRIMPING PLIERS FOR NARROW-PITCH AND UNIVERSAL CRIMPING It is a universal tool, have a look at the application guide: ENGINEER INC. - PRECISION CONNECTOR CRIMPING PLIERS FOR NARROW-PITCH AND UNIVERSAL CRIMPING It costs about €60. I use it for 2.54 mm connectors, but also made great crimps of JST 1.5 mm, 2.0 mm, 2.5 mm connectors. Specialized crimp tools for just one or two types were offered to us at work for about € 300. The downside is, you need to crimp every connector twice, the inner conductor first, the insulated part second. David

Sean_Miller · Answer

Thanks for linking that thread, Frank. All that shop talk was happening on my birthday. Funny thing was, I was probably trying to crimp pins and missed it.

Looks like the one twist I had from Shabaz's guide is how to use the second crimp zone. I had evolved to bend the bare wire back on the insulation and use both crimp zones to grab the insulation to prevent the wire from breaking and to get more copper surface area contacted. To see how they are mass produced, I just destroyed a store bought cable and did indeed find that the second crimp zone should be nothing but raw copper wire. So, I updated my troubleshooting chart below. Note, its not just for DuPont pins in mind, but variations.

Pin Crimping Troubleshooting Guide

Issue	Solution
Wires stabbing through the hole	Cut off enough insulation such that the cable insulation will sit at the base (outer) crimp zone and raw copper will be crimped in the next zone. If you have excess, "Double up" the excess to the raw copper zone or trim it to fit. See next issue to prevent it from slipping forward prior to crimping.
Dropping the pin	Paying close attention to orientation of the pin in the jaws (it's designed to fit only one way), squeeze the pin by itself until one ratchet click. Then, insert the wire. Make sure the copper isn't too long, then squeeze all the way.
Hard to seat in the housing	The standard crimping tool is designed to go one way. It has a recess on one so that the lower section of the pin crimps with a bigger diameter to accomodate for the insulation. The upper section of the crimper jaw has a smaller diameter to grab the bare wire. So, its imperative that you place the pin in the crimper such that each section is aligned with the tool correctly and no pin section overlap occurs in the center. If not, you'll deform the pin such that it will give unpredictable results when trying to slide in the housing. If the pin is so small that it fits inside the width of the crimper, then you need to switch to a different style crimper such as the PA-09. That style crimper doesn't have the offset and is designed to first squeeze the base of the pin at the insulation and then squeeze again at the next crimp section that is at the bare wire. After crimping, gently push the pin into its housing observing where any clearance issues may be. If needed, take a small plier to shape any parts sticking out impeding entry. This may be the case for the smaller pins or if your tool is slightly oversized than the pin your crimping.
pins back out when making final connection	Depending on the pin, there may or may not be a tab that will click into an opening visible of its connector housing. That needs pulled out a little if you did not get a confirmational click. Other problems could be you simply have not inserted it all the way in so that the catch mechanism has had a chance to click into place. Use a small flat tipped screwdriver to push the pin at its base into the housing further. You may need to put the pin under a microscope to fully understand the latching design. Note, most pins are designed to be oriented one way in the housing. Getting this backwards will definitely cause it to push back out.
the wire breaks off	Some cables are designed to be very flexible, but require pins that provide substantial crimp contact area as well as a connector housing that provides stress relief (example, DuPont pins on jumper cable). Such cables do poorly for pins that have tiny crimp contact area and no stress relief. For these, try ribbon cable instead or provide stress relief using heat shrink over the crimp zone of each pin and outward at least 1/2". In general, don't over squeeze or squeeze too quickly as it can snap the insulation section.
Male pins not fitting	For connectors used on 0.1" pitch headers, such as the Raspberry Pi, you may use a single jumper male pin to pre stab in the female pins prior to final assembly of the connector. This will correct any distortions that may have occurred in the crimping process. For other connectors, try a single male header pin to work each female pin individually.
All other	Practice, Practice, Practice!

After reading the other thread, coupled to my own experiences, I now feel confident I'm on the right track. I had a good project yesterday that gave me plenty of practice on an assortment of the cheap chinese pins. The results were custom sized, strong wire-to-board connectors that cleaned up the inside of the enclosure and are ready for the field. The project will measure vessel growth due to thermal expansion over a 30 hour operational cycle. This will allow me to locate vessel attachments without concern of clearance issues with its surroundings.

Thanks!

Sean

michaelkellett · Answer

That's a good link , Frank. @Sean As you'll see from Frank's link, bending the inner back over the insulation is wrong. It sounds to me as if you are using the wrong tool for the crimp, and stripping off too much insulation. The long stripped section is why you are poking the wire in too far. I suspect that backing out is caused by deforming the whole crimp, usually due to using the wrong tool. Having said all that, some crimps are just plain difficult, and unless you can afford a real tool (typically over £200 for once from the connector manufacturer) best left alone. I've had reasonable results with Molex KK types and Amp using cheapo tools. 08-50-0032 - Contact, KK 254, KK 254 4809 Series, Socket, Crimp, 22 AWG, Tin Plated Contacts Add to compare Image is for illustrative purposes only. Please refer to product description. Manufacturer: MOLEX Manufacturer Part No : 08-50-003 TE Connectivity AMPMODU MOD II Female Crimp Terminal Contact 22AWG 181270-2 181270-2 RS Stock No. 233-0038 Mfr. Part No. 181270-2 181270-2 Brand TE Connectivity MK

fmilburn · Answer

Hi Sean,

My experience is similar to yours. There is a good discussion here: https://www.element14.com/community/message/276825/l/re-creating-dupont-equivalent-crimp-terminal#276825. Several people give their experience including me. Andreas Spiess has a youtube channel and has quite a bit on them as well.

Andrew J · Answer

I use both the crimp pins Shabaz mentions in the other thread as well as he Molex KK pins mentioned above and get good results with both. The Molex pins requires specific KK series headers of course, which aren’t as cheap as the generic pin ones but shopping around helps. I’ve also found them just as easy to insert/extract as the generic pins. The tool I use for both is one also recommended by Shabaz on a different thread which I will try and dig out and post a link to (EDIT: don’t need to, I see Shabaz has already linked it!) My recommendation from discussions on this community is to: buy and use quality crimps - I.e. not cheap junk from eBay or Amazon, but name branded from somewhere like Farnell. Also, a decent tool, again not an el-cheapo ‘kit’ tool from eBay or Amazon. It doesn’t need to be a £250 manufacturer specific tool, just good quality with the right crimping die(s). I struggled at first with correct insertion depth and wiring falling out but it’s important to follow manufacturer recommendations from their datasheet - the Amphenol and Molex ones all stated the amount of wire to strip. To prevent falling-out, insert the crimp into the tool to the right depth then close one-click to grab it. You then have a hand to operate the tool and a hand to insert the wire. Observing from the other side of the tool to where you are inserting the wire you should be able to see the wire reach the right point and you can then ratchet it shut. I had to practice a few times to get this right and because I don’t do it every day and won’t build up muscle memory, will expect to get it wrong once or twice when I next get around to it.

Sean_Miller · Answer

I couldn't wait until Christmas. I got those PA-09 pair of crimpers. They were the missing link! Thanks, David. For my small pins pictured in my original post, they wouldn't fit into the ratcheting style crimper where they needed to. I was unknowingly cheating them to get it to somewhat work. The ratcheting style has a stepped die to crimp the insulated section wider than the bare wire. In turn, no matter how you try to fit a small pin there, it would deform the pin. The PA-09's allow you to crimp each section at a time without coming into contact with anything else. In turn, a perfect crimp. My learnings through this Discussion are: for bigger pins like DuPont pins, use the ratcheting style for speed, or get the PA-20 & PA-21. for small pins, get the PA-09. cheap bulk pins and connectors do work great with the right size crimper For both types, do the one-handed insertion method. Pre-squeeze the pin which frees up your hand to insert. So, for hobbyists, for about $100, you can get the two types of crimpers and a life time supply of connectors. Now that would be a good Christmas present! BeagleBone Fan with Shortened Cable -Sean

shabaz · Answer

Hi Sean, I've not found a universal tool, but I've got about three different ones, and between them I've so far got repeatable results for a good range of crimps. I'm sure there's other low-cost tools that are just as good or better, these are merely the ones I'm using: For the 0.1" pitch header pin sockets or pins, I'm at 100% repeatable results (unless I'm extremely careless) with the HT-225D HT-225D tool (some photos of how to use the tool, and the results on 0.1" crimps are in that other thread that Frank mentioned). It's also fine for other similarly-sized, and larger pins or sockets - it gives superb results with MATE'N'LOK crimps too (again 100% repeatable, with what looks to me like a great crimp and grip on the insulation; see photo below), which are intended for up to 19A. For smaller than 0.1" pitch, e.g. JST ZH (as used on the BeagleBone-AI serial connector) then I had to resort to a PA-09 tool. That's a fairly low-cost tool, which is useful for the extremely small crimps (like 2mm pitch). It can do 0.1" pitch too, but HT-225D HT-225D is better for those since that has a proper ratchet action and simultaneously does the insulation as well as the conductor. With the PA-09, they have to be done separately. Finally from Fry's I've got this crimp tool: https://www.frys.com/product/1922790 which is sometimes handy if there's some unusual connector. It is intended for D-sub connectors but works with other stuff. I prefer the HT-225D HT-225D overall though. Here's how I try to resolve the issues you mention: 1. Better accuracy with wire strip length, so that the wire doesn't go into the wrong area. Something like the Stripmaster Lite Stripmaster Lite is great for thinner wires, or the Knipex tool here: Knipex Precision Wire Insulation Strippers Review - Model 12 12 06 because they strip the insulation fairly square, and repeatably. The Knipex tool has a depth stop, and I think the Stripmaster Lite may have that as an optional extra (otherwise it should be easy to 3D-print an attachment for it). The photo above shows a wire that was stripped with the Knipex tool, and the insulation is cut very square. I didn't set the depth stop correctly since the wire is protruding by about 1mm into the space where it shouldn't, but I don't think that has an impact for this particular connector. If the wire is extremely thin, then I may fold back and double the wire, but not over the insulation. 2. I have no real solution to this, except either crimping the ratchet by one or two clicks so that the crimp is held in place and then I only need one hand on the tool and one hand guiding in the wire, or putting light pressure on the tool so that the crimp is held in place. In other words, the crimp is solely held by the tool, and that leaves me with one hand free to then insert the wire. With the HT-225D HT-225D , I can tell when the wire is inserted in to the correct depth, because I hold the tool at an angle and guide in the wire until I see a glint of the wire from the other side. Somehow that's quite repeatable, although it sounds like it shouldn't be : ) 3. I use your solution. It does sometimes happen, if the wire insulation is thicker than will easily fit into the plastic housing. 4. This doesn't happen much, but your solution seems good (or push the latching plastic on the shell in slightly, if the shell has that feature. 5. So far I don't see this issue too often, but for single jumper wires I like using heatshrink. 6. So far I've not encountered this much (usually the crimp tool won't affect the working end of the crimp) but the solutions you mention seem good.

michaelkellett · Answer

dougw wrote: Good crimpers are expensive Eeek - too true - I just decided that these were the optimum for a power supply I need to build 08-70-1031 - Contact, SPOX BMI, SPOX 5194 Series, Socket, Crimp, 18 AWG, Tin Plated Contacts https://uk.farnell.com/b/molex And this is the official crimp tool, at £347 63811-6500 63811-6500 - Crimp Tool, Ratchet, Molex SPOX 5194 Series 24-18AWG Contacts, 207129 Series Add to compare Image is for illustrative purposes only. Please refer to product description. Manufacturer: MOLEX Manufacturer Part No : 63811-6500 63811-6500 Order Code: 2668374 Product Range 207129 Series Needless to say I'll be using one out of the collection of oldies and cheapies ! MK

Sean_Miller · Answer

This is all great stuff. At some point in the future, I'll turn this to a guide/blog and put it under Connectors with proper acknowledgements. I'm eager to try the one handed, single click trick. Oddly, there's a satisfaction that comes with a well crafted, short board-to-board connector. Same feeling as tying flies for fishing. See ya', Sean

shabaz · Answer

Just noticed I'd had some KK contacts, so I tried that with the HT-225D HT-225D too. The result seems reasonable. (this is 22 AWG wire, quite thick insulation). I'll try to see what other crimp terminals I have, to see what works and what doesn't work (all 0.1" and upward, since smaller ones don't work with that tool). Unfortunately this data-point becomes less useful though if different wire thicknesses or insulation thicknesses are used, so I'll have to dig out some different wire types too.

IanJeffray · Answer

I bought these Engineers tools. I make just as much of a hash of crimping things with htese as with any other tools to be honest. My best tip for crimping is -- don't bother, buy pre-crimped wires. At least, specifically, I do a lot of work with Molex PicoBlade stuff and these pins are absolutely minute. The pre-crimped wires are eyewaterinly expensive, but worrk out efficient when I consider my time and annoyance level at trying to crimp these myself. Getting just the correct length of conductor exposed appears to be incredibly important too. With very much sub-millimetre precision. If the conductor is too long, it'll sit inside the crimp contact and cause issues when inserting the resultant crimped pin in to the mating connector. Getting the force correct is also incredibly difficult -- insufficient crimping forrce means the thing falls apart, obviously. Too much force can easily mangle the crimp pin and it either immediately breaks in half, or fails quckly in use. The whole crimping game is a total nightmare as far as I'm concerned. Buy pre-crimped leads.

dougw · Answer

Good crimpers are expensive and many pins require a specialized crimper to do an optimal job. It gets very expensive to acquire enough crimpers to cover all connectors. I have to make do with a low-cost crimper which covers numerous sizes and I use it for many different connectors: In order to achieve decent crimps for a variety of connectors, it is necessary to figure out a process for each type. For example on some connectors I have to crimp the wire first and the insulation in a second pass with a different jaw. It also requires close inspection of every crimp to ensure it is done well. I generally place the pin in the crimper jaw and hold it in position while closing the jaw until the pin is held securely. Then I slide the wire in to the proper depth before completing the crimp. Those small JST pins are particularly difficult with this crimper. In better crimpers, the pin fits the jaw with no ambiguity. Of course I would like better crimpers, but so far have not been able to justify their price. Needless to say, I only crimp when absolutely necessary. I use solder or insulation displacement whenever possible.

abrain · Answer

I know a chap who used to solder those Molex crimps.... I just bought the Molex crimp tool and it saved me both a ton of time making the connections in the first place, and the connections were reliable too! Those friction lock KK housings are pretty secure too, good enough for applications on the railway! A

dpenny · Answer

Hope I can figure how to add photo herein. First image comments.

A. shows good crimp and flaps folded otherwise I cannot insert pin.

B. shows flaps trimmed not yet folded. Tried 2 ways: without folding cannot insert pin, with folding pin pulls out of FRONT as I take apart male/female connectors.

C. shows pins as purchased.

shabaz · Answer

The crimp terminals are also available individually, and they have that flap portion sticking out by about 0.5mm. So, by looking at your photo A, you're doing the right thing by manually trimming that flap and if you cannot cut it so closely, then folding in any remainder so that it's not contributing to the width of the terminal any more than 0.5-1mm max overall. In my photo in my other comment, you can see that the flaps are just slightly wider than the rest of the crimp terminal (measured even after crimping to be about 3.6 mm according to my calipers) and it slid in fine into the housing, and I heard the click when it locked.

It looks like your photo A crimp should easily fully slide into the housing, and lock itself in permanently using the two side wings. If it comes back out, then examining the wings should reveal if the metal is buckling or not.

There's a chance the Amazon crimps or housings are not genuine Molex (there's plenty of clones of electronic parts and connectors on Amazon and eBay) and might not be made to the same tolerances or of the same materials as genuine Molex.

(By the way, you seem to have done a fine job with the crimp tool, just a small point is that the bare conductor length should be slightly longer than shown in the photo A, so that it's slightly visible egressing from the crimped portion, and also the wire insulation should be slightly visible from beyond the wire grip portion of the crimp terminal. But that's unrelated to the issue you're experiencing, it was just a minor comment).

My pin crimping tips -- what are yours?

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