Inside The Secret World Of Crimping

At some point in your electrical pursuits, you’ll need to make a connector. Maybe you’re designing something that will connect to another device, or maybe the spaghetti mess of wires coming out of your Raspberry Pi has become a pain to deal with. Whatever the reason, a proper connector can solve a lot of headaches in electronics projects.

Your first thought might be to run to your favorite component distributor and order the connectors, terminals, and crimping tool. Unfortunately, those tools can cost thousands of dollars. Maybe you’ll just solder the connectors instead? Don’t! It makes for easily damaged connections.

Fortunately, [Matt Millman] has a great guide on wire-to-board connectors. This guide will explain why you should never solder crimp terminals and then get into working with some of the most common wire-to-board connector families.

For example, the Mini-PV series (which often get called “Dupont”) are one of the most ubiquitous connectors in hobbyist electronics. They’re the connector on those rainbow colored jumper wire sets, and connect perfectly to 0.1″ pin headers. The connectors and terminals are cheap, but the official HT-0095 crimp tool costs over $1500. Most crimp tools make a mess of these terminals since they require a cylindrical jaw to crimp correctly. By using a combination of two unofficial tools, you can crimp these connectors properly for under $60.

If you want to learn more about the art of wiring, the NASA Workmanship Standards are an interesting read.

[Thanks to MarkMLl for the tip!]

34 thoughts on “Inside The Secret World Of Crimping

  1. Knipex. I forget the model number, but, these are best ones I have used. Precision dies; these are important for the smaller DuPont connectors. Forget those chinesium imports, the dies are cast and not formed properly and just don’t work. You end up mangling more connectors than you make. Spend the extra cash and get one that works. Those who buy cheap, buy twice! I’ll post the model number if no one else does. (Couple of days when I’m home again)

      1. +1 It’s not about force, it’s about properly applied force. I would put any of my hand crimps (done with the proper tool) up against any machine crimp any day. Also, measuring the finished crimp height will verify the quality of most crimps. Nearly all crimp datasheets or product family datasheets will specify crimp height and other non-destructive inspection criteria.

      1. The really useful thing about that article is the information on the connector designations, e.g. the correct names for the DuPont and slightly larger/older Molex 0.1″ families. I think it complements the JST article nicely, and admit that I’d not spotted the link in the earlier comments.

        Obviously these small connectors shouldn’t be confused with the 0.25″ receptacles etc. (red/blue/yellow sleeve depending on wire size). The better tools for those actually emboss the size designation onto the crimp to make inspection easier.

        MarkMLl

    1. Had a really cheap one (well “cheap when Ali was not yet around”) before and got one with changeable (seemingly ground/milled) inserts (model SN-28B with SN-2 jaws) and it makes things WAY simpler. €8,– well spent :-)

      1. Same here, got the same model few years ago, never regreted this SN-28B / SN-2 model, the best 10€ ever spent!
        Used with crimps connector from AE, gold plated, they are a must for prototyping

    2. I crimp professionally every day for motorsports applications and we have a Hozan P-706 (~50€) as our universal tool for anything that doesn’t fit the original ratcheting crimping tools and for repairs on the tracks. I highly recommend it for anyone doing less than a few thousand crimps, before buying any of the more expensive handtools (+500€).

    1. It really depends on your needs. Having worked with some aerospace companies who had engineers and qa people who specialize in crimping I can tell you it’s a science. If you crimp things properly the connection can be very strong and resilient, you probably won’t get that with needle nose pliers unless you’re really good. A crimping tool, preferably ratchet style, will definitely improve your connections,

  2. I’ve recently ordered a PA-09 from Japan (55 euros from ebay). It takes a bit of practice to crimp small connectors but at least the die is formed well for crimping. I also have a few chinesium/local hardware store crimp tools for larger connectors and a ferrule crimping tool from Velleman for about 50 euros which works well.

    Finding the right kind of wires to use with the connectors is equally important in my experience. If the wire is too thin you can fold it over but it’s not recommended. Too big you can crop off some strands to make it fit but it can be hard to get the connector to clamp on the insulation and into the plastic part.

    1. I picked up the PA-09 and PA-20 for about 90euros in japan. I’ve never looked back nor have i not found a connector i cannot crimp (within the size range). Of course, these are for just a few crimps here and there, if your going for short runs or thousands of crimps then the cost of a semi automatic crimp is worth it

  3. “Dont solder ever!”

    =

    Be careful when soldering, here are some of tehe pitfalls.

    Gvien a choice of even a $60 crimper verses solder guess what.
    Unless it’s high vibration / high motion on the wire it’s solder very time. The problem with wicking and be over come with holding the cable. tie downs etc.

    When I’m not working on the Space Shuttle I’ll use solder happily.
    If solder not hand then it’s long nose pliers and some skilful bending.
    YMMV, as may your skills and ability to crush a walhut lefft handed.

      1. Ah well I have a confession. I will happily reuse crimp terminals and theri connectors for that very reason: connectability / unconnectability

        But I begrudge paying for them when they litter disposable electronics. So in true recycling I’ll chop both sides out and hang on to them.
        When I need a connector I’ll solder the wires inline with heat shrink, or I’ll decrimp/recrimp.
        Being aware of the pitfalls.

        Behaviour learned long ago when things were 5-10 times the cost that they are now and before easy parts ordering. But old habits…
        I mostly do this with cars. Transplanting engines between years, modding, upgrading, carb to FI, etc.

        But also your comment about desoldering (cutting the wires really) for unplugging.
        How mean connectors in their lifespan were designed to be plugged in for the life of the product and never disconnected?
        But for ease of assembly. Yet their make/break rating will be in the 10,000 range.
        Isn’t that wasteful?

        1. I used to do the same. It wasn’t that I was unwilling to buy them. It was that I didn’t know what the things were called and couldn’t find them to buy! Back in those days I used to buy old way-outdated computers to salvage certain parts from. I often wouldn’t know what usable parts might be inside until I got them home and opened them up. For some of them those connectors were the only thing I managed to use! That was more wasteful than buying new. I buy those things in bulk on Ebay or Amazon now!

    1. The thing about crimping with a proper tool is that it can produce consistent results. It could be good or bad depending on the tool and whether you are using it correctly. Not the same can be said about your soldering unless you are a full time solder god on a production line.

      Then there is the wicking, melting of wire insulation etc. Some of the connectors e.g. JST are so tiny and have almost no space between the contact, crimps for the wire and insulation that you can’t solder anyways.

  4. I struggled with Dupont connectors for a long time. I just didn’t want to spend that kind of money on a crimper!

    First I used needle-nose pliers. Sometimes with solder, sometimes without. I probably developed about a 50% success rate. All my wiring has been a bit extra long and sloppy and few wires have matching lengths. This was because I could never sure just how many times I was going to have to cut off the ends and redo them so I had to start with extra length. What a bother!

    Then I decided to finally break down and by a purpose made tool. At the time I was buying my connectors from futerlec.com so I bought their tool. Of course I was still being cheap so I went with their lowend, non-ratcheting tool. I think it was an HT-202B. That thing is worthless. I’m not sure it’s due to it’s lack of ratcheting though. Better crimpers, if you look at the die there is a ledge in there. One side is getting squeezed a bit tighter than the other. This cheap crimper is all flat. I found that using this crimping tool the wire would seat much more secure than I had been getting it with the pliers but it would also bend the connector making it nearly impossible to fit into it’s jacket.

    For the next few years I kind of 50/50 went between those crimpers and the pliers.

    Finally I gave up and just started ordering tons of ready-made jumpers and just cutting off one end if I only wanted a connector on one side.

    Then I got a set of Trinamic drivers for my 3d printer. For those I needed to daisy chain a bunch of SPI wires. That’s three wires that needed 6 connectors on each one, 4 of which are doubled up with 2 wire ends going into the same connector.

    I thought about just cutting up a bunch of pre-made jumpers and splicing them with 3m butt connectors. (I don’t like soldering wires directly, they become too brittle at the bending point) I didn’t have any 3-way butt connectors of the propper size plus my 3d printer is my main pet project. I don’t like being so messy with it.

    I finally broke down and bought a better crimper. I read a lot of forum posts and reviews. In my still somewhat cheap price-range I found a lot of recommendations for the SN-28B. This seems to be a common model number for something that has been cloned by a lot of Chinesium shops. Researching that though I also found the SN-2549. It seems to be the same thing with an extended die with slots for one more kind of connector. I’d like to not need to buy 1000 more crimp tools so I liked that idea and went with that one. An SN-2549 from IWISS off of Amazon. It was only $23!

    So far my Trinamic harness is the only thing I have crimped with it but it was great! This is the best experience I have ever had with Dupont connectors that is for sure! My only complaint was the lack of detailed instructions. I had to find a Youtube video to determine which way, how far to slide the connector in.

    When I was reading reviews I did see some people recommended against ratcheting crimpers. I think they had more control with non-ratcheting. Perhaps a non-ratcheting set but with a much better die than my first set would have been good to also try. I only wanted to buy one tool though and with my first project requiring all that double-stuffing I thought the extra torque would be a good thing.

    Now, checking Amazon to refresh my mind on model numbers I see this IWISS Crimping Tool Kit. It’s a zipper case with a ratcheting crimper, a non-ratcheting wire stripper, and 5 interchangable dies. It’s still under $30! I wish I had seen this much sooner. Dupont connectors aren’t the only things I have bought crimpers for. They are kind of multiplying on me and cluttering my workbench. This could have saved me some valuable space!

  5. Yes, soldering makes your connection more brittle in some cases, but there are also cases where nothing but solder helps. Consider attaching 0/2 AWG (9.266 mm) 1024-strand copper welding cable to a terminal with a hydraulic crimper. Although your connection is tight with literally tons of force, the strands will tend to migrate out of the crimp. Dropping the cable end into some rosin and a solder pot before crimping mitigates that.

    1. If the strands migrate, they didn’t reach high enough pressure during the crimp. A proper crimp should consolidate the strands so tightly they cold-weld to each other and to the barrel. A lot of cheap hydraulic crimpers don’t have a pressure indicator nor enough mechanical advantage on the ram, so when the user goes “I guess that’s tight enough”, it isn’t.

    2. Industry experience (as well as the NASA workmanship document etc.) mandates against tinning. However, I suspect that the bottom line is that it’s harmful if it leaves sufficient soft alloy between the strands that they can creep, while a layer which bonded the strands but had negligible residual thickness would be OK.

      The correct term for a well-crimped joint is “gas tight”. In other words, sufficient pressure has been applied to force the sleeve strands into intimately packed contact, while still leaving the sleeve with sufficient spring to maintain long-term pressure. If a crimped joint creeps then either the tool or working method is wrong, or the wrong crimp has been selected for the cable type (including the case where the crimp manufacturer doesn’t know what he’s doing).

  6. Oddly enough about eleven or so years previously I bought from RS the cramping tool who will work for practically all of the connectors that we are talking about, it was 30 dollars then. Oddly enough Jameco wants a preposterous 100 dollars for the thing. And does sell the Dupont connectors. I bought a batch of the individual male and female connectors and sleeves from a shop here in Manhattan. That tool works. And I just bought the regular assortment from Micro Center in Brooklyn several weeks ago, and as it happens the same week this computer arrived. Oh and here’s a giggle the connectors used by sound card cables are part of the same family.

  7. As someone who has managed, specified, and procured crimp tooling for a wide variety of crimp tools and applicators for the past 19 years, I can say that the write up is done fairly decently. It covers many aspects that most in the DIY segment can value.
    There are some comments made that are not quite true. For example, there are many more tools for the Molex KK series than he implies to cover the ~1500 terminals in that family. Also, it is not too hard to find specified tooling for proper terminals from the manufacturer’s site. I look them up routinely. However, for knockoff terminals, you get what you pay for so tooling is usually questionable.
    At my current employer, an electronics contract manufacturer, we have over 150 hand crimp tools. Some are specific to just a few part numbers of crimp terminals from a manufacturer and others cover entire families of crimp terminals. We have all the standards: Molex, TE, JST, DMC, Panduit, Hirose, etc.

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