Master a Perfect Inline Wire Splice Everytime




In this instructable i will teach you how to make a perfect inline wire splice, every time

What is an inline splice?

Well, if you work with any type of electrical wiring, and need to join 2 pieces of wire you have 2 choices, pigtail or inline

Pigtail splices are when you hold the 2 pieces of wire, one end going up, the other going down, and twist their stripped ends together.

The issue with pigtails are...

1) They are ugly

2) They redirect the wire 180 degrees, so going from point A to B requires a sharp bend

3) After making that sharp bend you have this chunk of pigtailed wire flopping about, usually with a nice wad of gooey black tape, and sometimes a zip tie to act as a strain control

4) Since the connection is 180 degrees (or going the totally opposite direction) without some form of strain control, all it takes is a stout yank to sheer the connection (even with solder), altho honestly this is an extreme con

The pro's of pigtail's are
1) they are "easy"

Inline splices is where you take two pieces of wire, and join them in a nearly seamless extension of wire

Inline the issues with inline splices are ...
1) the are "hard" (and I claim shenanigans!)

The pro's of inline splices are
1) They are almost invisible, and look professional

2) They do not redirect the wires natural flow, going from point A to point B is just as simple as if you had the chance to place a wire from point A to point B

3) Since there is no bends in the wire, there is no chunks to manage, which is especially handy in tight situations or where you do not have a lot of wire to waste (ie: repairing wires in a vehicle)

4) they are really strong, even without solder bonding them (keeping in mind that they are not permanent, stress and vibration will eventually disconnect them without solder)

Step 1: Supplies

Something to splice
1 thumb and 1 finger per hand
Hemostats or needle nose pliers and maybe some gloves (see below)
Wire stripping utensil
Soldering Iron
Insulating material (heat shrink tubing recommended)

let me go off on a green note for a moment, my wire was scavenged from an old computer power supply, if you see anyone throwing away an old pc, snag it, its LOADED with wire thats good for jumper wires on your veroboard , or ribbon cable witch is also good for jumping, but since its tiny it works well with smd devices ect ...

your standard "still working but junk" power supply will net you a fiist full of wire, some voltage regulators, a heat sink, at least 1 good fan, a couple big caps, some other random electronic components, a handful of molex connectors for fans, or a nice +- 5v, +-12v and 3.3 volt bench power supply that can handle 10+ amps!

scrap the motherboard and you end up with MORE voltage regulators, connectors and swag, and if the case is at least ATX, well there you have a perfect platform for your pimping case mods, all for the cost of stopping the diptards at work from tossing that Pentium II thats been in the closet for over a decade, which equates to "hey let me have that!", as its headed to the dumpster

OK, about the hemostats and or needle nose pliers. you can do this technique with any gage wire, solid or stranded, but a brief word of warning!

even small gage solid core wire has a habit of screwing your hands up, ive had 24 gage stuff go deep into my thumb with little effort, and one time it went in to my thumb, to the side of my bone and thumbnail, and poke out the other end quite a bit (felt like a paper cut, until i pulled it out)

same with thick stranded wire, get some thick stranded wire and those strands become stray needles

if your working with these types of wire, pigtailed or inline, i recommend the use of metallic objects when you get to a point where twisting the wire

You should be able to start, and nearly finish the twist with your hands, but once it gets tough for your fingers, go for the tools, rather than a gash / piercing, and some nasty words spoken out loud around your loved ones

In this instructable I was using 20 gage stranded wire, which is quite soft, and wont poke my tough old work fingers at all

Step 2: Stripping Your Wire

One of the major keys to making a perfect inline splice is stripping your wire to about the same length on both ends

In a perfect world it would be exactly the same length

In my world its regulated down to the Centimeter marking i drew out with a sharpie on my work surface, based on a hot pink ruler i got tired of looking for

I aimed to strip 2cm off the insulation, as long as its pretty even you should be just fine, you could even eyeball it (and most of the time i do)

my stripping utensil of choice tonight was a hobby knife / xacto / scalpel, I like these when dealing with stranded wire in a workbench situation, but you can accidentally cut it clean off when using thin wire, and with thin solid core wire you really risk the chance of nicking the wire, once that happens it will break clean off, so use whatever suits you best for whatever application (same applies for "automatic strippers")

Step 3: Starting the Splice

Now that your wires are stripped to basically the same length. you need to cross them in a X form, where the center of the x is about midpoint of the 2 stripped sections of wire

Step 4: Start of the Splice

Whichever wire is on top (closest to you) bend away (or back) and then down, the wire will make a upside down L shape around the back wire

Step 5: Start of the Splice Part Two

Now take the other wire, bend it towards you (or forward) and then down, twisting it around the first wire, making a M shape

Step 6: Continue Twisting

There are two directions to twist, you do not want to twist the entire wire, just the splice.

I recommend using your thumb and forefinger of each hand, 1 will go clockwise (or towards you) the other will go counter clockwise (or away from you), pinching hard, twisting only the spliced section, slowly moving towards the insulation with both hands

if your using solid core wire, or thick gage wire once you get near the ends I strongly recommend you wear gloves or use hemostats / needle nose pliers to finish up the twist

if you got close enough to the same length of stripped wire, and made your X close enough to the center of the 2 wires you should end up with both ends of the wire running out just at, or before the start of the insulation

And a super strong splice ready for service

Step 7: Wrapping Up

Solder the splice, but be warned once its soldered properly its quite a struggle to get it back apart, its actually easier to cut the splice out and start over, so make sure you have your heat shrink and whatever other accessories (ie parts to a fuse holder) in place before

Once you have done this a few times, it will become just as fast, as a simple pigtail

Your electronics enabled buddies will nod to you, and your other friends will be amazed at the clean nearly invisible splice, and how fast you managed to do it

Thanks for your time, and please if you have any questions or comments post them

-- Osgeld

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207 Discussions


2 years ago

Okay seems my initial response created some issues.

First let me say that before I retired, I was a certified NASA Micro Miniature Solderer, with yearly updates/certifications 'til I was out of the circuit building and repair department years later.

So when I stated the different wire splices, I am going off the proper military and NASA methods. And yes thermal-shunts are used when tinning any wire before any type connection is made. because such a thermal shunt keeps solder, and of course rosin, from wicking up under the insulation.

That keeps the soldered connection from corrosion and down the road and failures. And that can happen with any type flux, be it liquid rosin, or paste or any other type as well.

However, after all the soldering is finished, you still have to use an Acid Brush (that is a type of brush and has no acid on it what so ever) and Alcohol and thoroughly clean any flux residue off the soldered connection regardless what type flux or solder was used.

Then after cleaning, you use heat shrink tubing to insulate the connection again. That is how it is done. Hope that clears things up better.

And for the record osgeld's post is a good one to show some concepts for splicing wires together. And all this may seem anal, as "geopro" so eloquently stated it, but if your life depends on how such things are connected and cleaned when you are in outer space, it doesn't seem anal then.

1 reply

Reply 9 months ago

30+ years tech and I fully agree and support GM280s statements. I doubt very much any indivdual organizations have put more testing and resources into electrical connections especially in harsh enviorments than NASA and the US Mil. Think of the duration and large varation in enviroements and conidtions they must survive in for these orgnazations. There are Sats up in orbit still functioning from the 60s many decomminsioneed gear up in the salvage orbit still function. Mil, think of the abuse and wildly differing enviornemnts they are required to survive in say in avaiation nautical etc.

To add to his comments, the heat shrink insulation sleeve always exteneded 3x largest wire diamenter past core wires manf insulation. This will always exceed past any solder even if it incorrectly butted up to the wires parent insulation. This would as support and ridgity to those areas and unless forceed the wire would bend prior to the sleeve. If properly done it would also seal out contaniments.

IMO 99% of all crimp connectors used by hobbist or home users are done incorrectly and almost without exception are either loose or have damaged the wire strands. Add to this the constant vibrations in a automotive enviroment will lead to at the very least some reduction of strands from damage. You look on some of the extreme off road comp tech and you will see they almost all recommend soldered joints not crimped solderless mechinical joints. Whatever you do never ever use the blade connectors that slice thru the insulation to make contact with the conductor core. They always damage the core strands and eventually cause breakage leading to gremlin shorts etc.. They are a nightmare and also look like poo.

If a splice was not going to have to survive any tension or abuse a simple lap splice is easy and puts no strain on the wires. Strip ends, tin, hold even overlap 3-6 daimenter in length touching, solder filling the valley where the wires meet. Acid bruch clean connection. Shrink wrap or best a combo insulation solder sleeve that overlaps factory wire insulation by 2-3x diameter.

As far as I know there is no standard/auth splice that allows open wire wraps around the connecting wire such as done in this article. As others have said this is a loose Western Union/Linemans Splice but would fail any inspection becasue of the loose wraps. For those that have some basic knot tying experince. Think about a Uni-knot and how the wraps sit. Would you ever leave one with the wraps gapped between each other? No of course not. These are very similar and actually there are some of the same reasons for each in the way the wraps are positions.

When comparing them to some factory connections such as used in automotbiles harnesses etc do not forget that cost is a HUGE factor in the choices made. Its always a balance over all what is going to cost the least and make the most profit. Not always the best choice to follow when looking for a gold standard.

All of this said the splice done will hold just fine and have no noticable (in this scope) resistance increase and will hold just fine short of being yanked on to levels far beyond what anyone would expect a splice to typically hold for. But in automotive a trailer connection is one area this might not be true given the level of abuse these connections deal with. People forgetting to disconnect after the ttrailer has been unhooked and driving off etc.. In these cases IMO the only splice to use if you must have one is a linemans soldered with a water proof sleeve. I prefer to use delectric grease in the actual connector to connector as well. Using typcial commerical multimeters not lab quailty resolution meters I have not measured a increase in resistance or drop in voltage using even copious amounts of this grease. Not advocating doing the later of course just a case in point of any real world negative effects on the electrical pathway.


2 years ago

That pentium that's been sitting in the closet for a decade, eh? OK ,, you say "lemme have that, as it's going to the dumpster".

"Um.. no can do "Sorry.. 'Company policy. They've got hard drives in them so we can't give them away'"


Same with thrift shops here. I used to love buying old PCs and especially retired Macs.. at one time I even had a coupkle of really collectiuble SE/30s scoered from thrift shops. Not anymore .

"Company policy. They've got hard drives in them so we can't sell them"

Nowadays sourcing a used computer here in western Canada is harder than finding a gold bar in a thrift shop. And I'm not exaggerating, Recently someone DID donate a handful of GOLD BARS! They of course priced them at 20% over spot. They don't price things in these shops within the reach of poor people. Because they need to make as mnuch profit as possible to pay all the "volunteers" and fund their "poor outreach" programs.

So here we have to get our wire the old fashioned way. New. At the hardware store.

Great aricle though, I hate pigtails. They're always coming undone.

7 replies

Reply 2 years ago

DocR, I lived on the "left coast" for a while. It really is a dysfunctional farce of a society.


Reply 2 years ago

It's possible to pull company data off the hard drive even if it's been formatted or even over written. There are free programs to wipe a drive and over write it enough times to prevent hardware methods of extracting data. Or just crush the drive platters. Why scrap a puter that still has worth to somebody?


Reply 2 years ago

Well, you know that, and I know that and of course I've *tried* to explain that to the thrift shops, it's always the same routine over again. "Sorry. Company policy" I think they just don't want to be bothered, or perhaps they're just deferring to head office rules. Freebee donations is big business, after all, here in Canada


Reply 2 years ago

I am also in western Canada, and what DocR says about the hard drive policies here is true. I am a hobbyist recycler, and in the past I had deals with several corporations, travel agencies, and colleges to remove the old tech. And I even got paid to take most of it, but even ten years ago, I had to physically remove and "destroy" the hard drives on site. For most drilling a 1/2" hole into the disc area was enough, at other locations where there was a safe place to get "therapeutic" I always carried an implement of destruction I named "Dr Damage" (a 30-40 lb. wrecking/pry bar of unknown origin). Either way, I always ended up with some awesome magnets. Now if I need an old computer, it means checking my email for the Craigslist search alert emails.


Reply 2 years ago

They can remove the hard drives from there and sell you the rest of the computer with no problems at all. That's what the Goodwill here does now.


Reply 2 years ago

My school sells their old pentium IIs, no drives included. Works for them, and it makes them back some of the money those things cost.


Reply 2 years ago

You could use insulation tape to stop your pigtails coming undone :) :)


2 years ago

Western-Union or Lineman splice are all names for this type of splice, though I would call this one the lazy-lineman. A true lineman or WU splice would be done thus:

Make the first 3 twists at a 30-45 degree angle, then make at least 3 very tight twists with each wire on either side.After you solder this splice it should be stronger than the wire itself. You can test it by pulling it apart. If the splice breaks first you did it wrong. In the picture you will find a few variations. This type of splice held together long spans of heavy wire back in the day (or so I'm told).


2 years ago

Nice instructable! A simple process, but sometimes a very hard one to accomplish neatly, and without shedding some blood! :)

Thanks for sharing, love your humor as well!


3 years ago

My father taught me another inline splice in the 60's. He called it a Western Union Splice. He had worked for Western Union while he was in high school. Here is a link to that technique. It handles longitudinal stress well and can also be soldered.

4 replies

Reply 2 years ago

I havent used this Western Union splice. But I shall. next project. Do you usually solder this splice, or just leave it as is?



2 years ago

Seems that every new generation has to re-invent or rediscover the ancient telephone and telegraph "lineman's splice" that was routinely taught and used in the 1920's era, and probably before that. Still, it is good information for the newbies.