Technical Crimping Tutorial

Ok, after a discussion about soldering, crimping, etc I was asked to do a tutorial on proper crimping methods... so here's the start.

Let's start with tools. Now, I don't care for 'open' crimp terminals (I'll describe them below) and use them only when I have to. I much prefer 'barrel' terminals, and my focus will be on those. For those who may be wondering, this is a barrel terminal...


Note this is uninsulated. That's all I'll use and I'll show why.

So, what tools to use? I see this type a lot as it's sold in most auto parts stores...


Now these are actually 'name brand' crimpers, made by Thomas & Betts, but there's bunches of varying quality copies out there. Designed to crimp both insulated and uninsulated crimps, as well as stripping/cutting. About all I use these for is cutting 6/32 through 10/24 screws to length, they work great for that. As crimpers, not so much. Terrible strippers...

Here's my crimper...



Now, these are older than I am, I'm pretty sure they're WW2 vintage. Made by T&B, long discontinued but they do turn up on Ebay or garage sales. What's special about them is they have three sizes; A, B, and C, covering from 22 to 10 gauge wire. All this does is crimp. But there are current replacements; Klein, Ideal, and T&B all make nearly identical crimpers with two sizes that will do the job. Parts numbers are Klein 1006, Ideal 35-5431, and T&B WT111M. The T&B is the most expensive, Klein next, then Ideal. I see prices from as low as $13 (new Ideal on Ebay) to $45 for the T&B. List is about $30 for the Klein and Ideal pliers. Shopping will pay off..

Need to crimp larger sizes? These are all over Ebay and Amazon....


Prices are in the $30 to $50 range for a ten ton unit like this, I gave $33 including shipping for this one. Do watch how many dies you get, not all come with all dies. This one does up to 2/0 wire and works great.

There's also sixteen ton units if going even bigger on wire size for about another $20. Yeah, they're both Chinese but for the hobby guy they'll do the job. You don't even want to know what the 'name brand' ones cost....

Last, strippers. I do see guys with those big clumsy strippers that cut/remove the insulation in one handle squeeze and I'd see them once in a while in the trade but nobody really used 'em. Here's what the pros use...


These are made by Ideal, but any name brand (Klein, T&B, Gardner Bender) will do. I've found the HF and other cheap copies don't hold up quite as well. Strips 18 to 10 gauge, and you can do larger once you get used to them. This style will be about $12 at the box stores. Fancier ones will be more, but I prefer these because of their smaller size; you can get them in almost anywhere. Replacement was usually due to cutting a wire that wasn't dead... LOL.

So lets do some crimping....

 

So there's basically two types of crimping; what I call the 'mash it flat' type, and indent crimps. Indent crimps are far superior, but if you're using insulated crimps you're pretty much stuck with 'mash it flat' unless you're willing to severely damage the plastic sleeve. So lets look at what you get....


Here's a typical insulated crimp done with a 'parts house' type crimper. To see what it looks like, I'll cut off the plastic sleeve...


The barrel seam split a bit, so there's room for corrosion to get in there, plus it's not a 100% crimp. Here's another one done with the same crimper, minus the plastic sleeve before crimping...


Better, less barrel seam separation but still not 100%. But no matter which crimper you're using, if it's not a indent type it's going to look pretty much like these and is an inferior crimp. These can fail, either by either fully or partially pulling out, or corrosion getting inside the barrel. If you think about it, this is the same as sticking the wire between two flat pieces of metal then bolting the metal together. You can get pretty much the same results by just squeezing the connector with ordinary pliers. Used as intended and according to the NEC, they're pretty reliable connectors but remember, they weren't designed for automotive applications. This type of crimp in automotive use is what gave these their bad reputation. Fancy ratchet crimpers may mitigate this, but won't eliminate the issue.

The other big issue with insulated crimps is they offer very little strain relief. The plastic sleeve does give some protection against bending strain, but virtually none against vibration. You could put a shrink sleeve over the whole thing for that, but finding a shrink big enough to go over the sleeve will probably mean it won't shrink enough to grip the wire.

I will not use insulated crimps in any permanent installation on a vehicle.

 

So lets look at the best method; indent crimps. These have to be done on uninsulated connectors, but it is superior in every way to the 'mash it flat' method.


Here's a close-up of the business end of my crimper partially open. When closed, the opening looks like a 'U'. The bottom jaw supports the crimp, the upper jaw does the indent. One thing I like about this crimper is the lower jaw is a bit wider than the newer ones which gives less distortion in the crimp.


Here's a crimp in place in the jaws. Note that the barrel seam is on the support half of the jaws away from the indent; this makes a difference...


This what you get if the seam is on the indent side... not good. Do it right and you get this...


… With the indent opposite the seam...


This WILL NOT pull out; the connector or wire will break first. This gives a 100% crimp and achieves what the techs call a 'cold weld'; the metal is so compressed, there's virtually no free space left within the crimp. This also prevents any corrosion from penetrating into the crimp. I have NEVER seen a properly-done indent crimp fail for ANY reason, and that includes 30+ years of doing electrical for a living. The flag end or the wire may burn off, but the crimp will still be there. Note that you still have a round barrel, the shrink tube will fit and look better.

So simple to do, I can't understand why you would want to do anything more complicated. Put the crimp in the crimper with the seam on the support jaw using the smallest opening it will fit into, insert the wire, and squeeze the handles as tight as you can or until the jaws close all the way. You're done!

Of course, don't forget the shrink tube before crimping... LOL.

 

So where’s the tutorial ??

 

So lets look at 'open' crimps.... Here's one type... Did I mention that I don't like these?



There's literally dozens if not hundreds variations of these, but all share the same basic crimp design, just the connection end changes. The worlds most-used small wire crimp design...

The OEMs and manufacturers love these, for basically two reasons. First and foremost, they're cheaper to make compared to a barrel crimp. While barrel crimps are almost always made using tinned copper, these are typically brass or even tinned steel. When you're building a million harnesses a year with a hundred or more connectors in each one, even penny savings add up quickly. Second, these have built-in strain relief. You have a crimp for the wire, and one to grip the wire insulation. Where the problems enter for us is these need multiple operations to correctly crimp them. If you look at the top pic, the arrow is pointing at the strain relief crimp. The bottom pic shows that it's larger than the wire crimp, so you now need at least two different dies. Watch the American Autowire video link in the post below; crimping just one wire needs three separate operations with two separate dies. What a PITA....

These have been around on vehicles at least since the '50s. But before the advent of shrink tube or plastic plug connectors, the OEMs would typically mold a large 'sleeve' around each crimp out of heavy vinyl or rubber anyplace it would be exposed to vibration and/or contamination. Not even the OEMs fully trusted these.

I was asked on another thread just what did the OEMs use to crimp these? They're not using hand-held crimpers; between the labor costs and the probable carpel tunnel claims they'd go broke. Nope, they use special 'production' crimpers that can perform both crimps in one shot. Information on these is scarce, but I did find a Molex page at Digikey that gave prices and parts available. How about $900 for the bare crimper in a pneumatic version with no dies? A bench mount for the crimper with foot control, over $1K! Over 50 different dies sets covering multiple combinations, starting at about $700 each! If you're building a million harnesses a year, a sound investment; but I don't think anybody here is in that market...

So as hobbyists, we're stuck with hand-held crimpers for these. But there's more obstacles; while the basic design is the same across these types, each manufacturer introduces variations. As an example, go to the first pic I posted again and look carefully at where the arrow is pointing. Notice that there's 'barbs' sticking up on the relief crimp. These are designed to fold, then stick into the wire insulation for a positive mechanical connection. Then take a close look at the crimp done in the video; this one has just simple 'flaps' that's folded over the wire. Even if the wire is the same size, the same die isn't going to do one of them right. In addition to major manufacturer variations, you can run into issues with 'generic replacement' crimps due to slight changes in manufacturing or issues with patents.

Your tool options are limited. For best results, using a crimper specifically designed for your brand/type of crimp will give the best results. Usually not cheap though. Next best is a quality 'generic' crimper with interchangeable dies, but still not cheap. Last choice is the inexpensive 'copies' available, but you need to watch these. I've used a number of specialty crimpers over the years and one quality constant was they all had machined dies for precision. The cheapies I've seen use die-cast dies, I'm very suspicious of these being able to give a quality, repeatable crimp. YMMV...

Like I said at the beginning, I don't like these for all of the above issues. But keep in mind that barrel connectors come in a lot of types that will be functionally the same except for the wire crimp style. You may need to hunt for them a bit though. Because I use the open type so rarely, I haven't invested in multiple crimpers for these, so I do occasionally solder these (OH! The Horror! LOLOL...) if the crimp looks a bit dodgy.

To those of you that like AMP/Tyco or GM weatherpak plug assemblies with their small, fragile crimps (or if you just want a better plug connector than whatever the OEM one is), I'll suggest looking at Deutsch connectors. Expensive, but much easier to work with as they use a barrel-type crimp. Their connector is also easy to install/remove wires and is fully sealed. All kinds of configurations are available including bulkhead connectors. You do need a special crimp tool, but a good quality 'generic' version is available for about $35. Look here:
https://www.wirecare.com/category/connectors-terminals/wirecare-deutsch-assembler

Lastly, I was asked where to get uninsulated connector/splices. One source will be your local industrial electrical/electronics outlet. In a lot of cases you'll have to order them in quantities larger than you want. I'll just cut the plastic sleeves off the insulated ones in most cases, it's the same part without the sleeve. But the big box stores are now offering these in name brands, some by online sales only, but in smaller quantities like we need. Somebody mentioned the HF crimps and how cheesy they are. Yes, they're not as heavy a gauge metal but in lighter-duty places will work fine if crimped properly. I wouldn't use them under the car or in the engine compartment, but under a dash
for lighting or gauges or in the interior they should be fine.

 

Check this one out... Maybe it will help

American Autowire - How To Properly Use A Crimp Tool

 

He's saving posts so he can try and get it all posted in order without a bunch of useless crap splitting it up but it looks like he wasn't fast enough to avoid that.

Sent from my SM-G950W using The H.A.M.B. mobile app

 

I had a real crappy crimper, about as cheap and nasty as you get.
It failed me numerous times, so I got a pair of those ratchet wire crimpers with the inter changeable jaws which I have found to be great.
I also purchased a decent Chinese wire stripper which also makes life much easier for a rank amateur like me...

 

I use the one hand wire stripper thing under dash or in tight corners, works good for me.

 

Subscribed.

 

Wish I had a set of those AMP crimping tools we used in the USAF. They popped open after the crimp was made. Never saw them for sale anywhere. Probably extremely exspensive anyway. Lots better then the pliers type crimpers you find now a days that causes failed crimps.

Gary

 

Perfect timing for me and I've learned something useful and worthwhile already, so thankyou for that Steve. Subscribed.

Chris

 

Super comprehensive description, Steve.
This is the adjustable Burndy crimper I use on cable up to 250Kcm cu. great for welding cable and battery terminals.

 

Great information. Thanks guys.

 

Thanks for your time and effort.

 

What is the consensus on soldered joints?Yay or Nay?

 

Thank you

 

Thank You.Much good information.

 

Thanks Crazy.

 

Thanks for the info, now time to get new terminals. I never liked the plastic coated ones but used them, not going to use them any more.
Tony

 

Thanks for sharing,good stuff.

 

Well done. Early on you mentioned cutting screws, how about showing how that is done. Most people don't know what those little holes are for in the strippers and you've got the right set to show them.

 

Got the same ones for doing battery cables and motor cables picked them up for $50 bucks at a swap meet, asked the guy if he would do less.... he looked at me and said “ you know what these are and what they cost new right?”
Quickly handed him his 50 bucks and left with a smile on my face!!

 

Thanks Steve.

 

Thanks--great writeup

 

It takes more than a pair of side cutters?

 

@VANDENPLAS ,
Yes, new its a $600 tool.

 

As an aside, I had always had problems crimping spark plug terminals until a bought a crimper specially designed to do them. As pointed out here, the proper tool makes a big difference.

 

I took a pair of dies that came with a 'universal' set and welded them to an old crappy pair of vice-grip style pliers. Works great!