Introduction: Master a Perfect Inline Wire Splice Everytime

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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


AlexandreS90 (author)2017-05-24


DocR (author)2016-07-31

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.

mosmond (author)DocR2016-11-30

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

fred_ (author)DocR2016-07-31

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?

DocR (author)fred_2016-07-31

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

Braindead63 (author)DocR2016-08-01

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.

wb7ptr (author)fred_2016-07-31

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.

nic.bryan.73 (author)fred_2016-07-31

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.

Heyup (author)DocR2016-07-31

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

asitnik (author)2016-08-08

Good instructable. You may want to check NASA's standards:



VladM3 (author)2016-08-04

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).

cv66seabear (author)2016-08-04

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!

ericfrankel (author)2015-11-06

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.

Homee2010 (author)ericfrankel2016-07-31

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


steveastrouk (author)Homee20102016-07-31

From the wiki

This type of splice is more suited to solid, rather than stranded conductors, and is fairly difficult to complete.

Homee2010 (author)steveastrouk2016-08-03


arvevans (author)2016-08-02

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.

phaedrus.1 (author)2016-08-02

Back in the 60s we called that a lineman's splice because it was first used to splice heavy transmission lines and the splice needed to be very strong.

JohnK241 (author)2016-08-02

Rather than cutting to the exact length and fighting with the 'sharp' ends, you can leave them long [oversize] until the insulation is reached and then trim off the excess.

Scott_1224 (author)2016-08-01

Love this tutorial! I work a lot with spliced USB wires so I can make Steampunk LED light fixtures. It's annoying how most USB wires are so tiny, so I end up splicing them with a thicker wire which helps a lot.

jerry.ericsson2 (author)2016-08-01

Way back when Christ was a Corporal, I attended the Field Wire-man course in Fort Leonard Wood. (1970). We were dealing with a bit different wire back then, the old field wire consisted of two conductors, twisted as a pair. Inside the water proof nylon cover were (I believe) five steel wire strands, and six copper. We were taught to strip back the wire, after striping back each conductor the length of the pliers, and tie a square knot, then cut the steel wires leaving enough to reach the cover. Then we wrapped the copper wires over the steel conductors till it met the insulation, then tape it with two coats of rubber tape, going first up then down the splice. In order to pass the course, the entire splice on one side must fit under a dime. There was no solder, of course since this was done in the field and there was no heat source.

As far as hard drive destruction, I have a nice collection of magnets as well, I am regularly given computers to destroy, as the folk here abouts don't much trust the 5 buck an hour bums that the city puts out at the dump to direct depositing of garbage in the proper pile. Being a disable police officer/paralegal/vietnam vet, I am respected and trusted in my home town. I also make some nice wind chimes using the platters as wind catchers after drilling holes in them to nuke data.

CBTman99 (author)2016-08-01

Electrical connections are just that: they allow electricity to go through. Subjecting a cable splice to tensions or vibrations is a recipe for disaster. Regardless of whether a splice uses twisted wires, soldered wires, crimped terminals, etc., a mechanical device should always protect the splice from vibrations and tensions. Soldered splices have less losses, but they become brittle. The same happens with soldered terminals. Crimped terminals are the gold standard in most applications, even at high currents. I remember using crimping devices powered by hydraulic pumps or even shotgun shells to drive the piston into the terminal or splicing tube. Even then, there was always some kind of clamp or bracing device to transfer all mechanical loads away from the terminal or splice. Nowadays, we have plenty of splicing accessories that allow us to make efficient and safe splices.

LawrenceH8 (author)2016-08-01

100 YEARS prove the WESTERN UNION SPLICE (no solder, no parts needed) works best - no tape needed, AIR TIGHT clean, strong, and lasts forever (as long as the wire). Those "connectors" are for "lowest common denominator": as a way to get and "OK" fitting, Verses trying to train someone to do it RIGHT.

Daral3 (author)2016-08-01

This will work great, but not acceptable for military application. We must use the western union method of the wire shaped into 2 hooks and soldered. One reason for this is if we ever need to take it apart.

KISELIN (author)2016-08-01

Actually... don't mind what it looks like :) the absolutely MAIN thing is that it works right. Me 64+ to age worked all my life with elec. In the industrial works we used heatshrink of that having "glue" inside the shrinktube that melted whilst heating, thus giving an execellent isolation for water oxy ++ , to them ends of the shrink

IkeB2 (author)2016-07-31

Interesting how-to even though I've used in-line spices for longer than I care to remember. One aspect you didn't touch on is whether to do or not do strand twisting after stripping the wire. Doing it is less prone to stray strands but not doing it results in a less lumpy joint.

One point about soldering I'll mention about this technique that I haven't seen mentioned in the article nor in the comments, that is to do with mechanical stresses. A friend of mine, a race car mechanic, swears by the in-line joint but skips the soldering. He pointed out to me that where ever the solder ends, the strands are prone to breaking since they flex much more at that point. I've taken to using his no-solder approach and instead spreading some anti-oxidant paste over the joint before applying the heat-shrink tubing.

Now I hadn't heard of the Western Union joint until now but I'm thinking that perhaps it's a way of soldering the middle so as to extend into the wraps but not allowing time for wicking to the ends, thereby not stressing the strands beyond the end of the twisted wire segments. Thoughts?

throbscottle (author)IkeB22016-08-01

You can twist the strands one way and then twist the wires together the other way, so that when you twist the wires together the strands tend to untwist a bit so it stays pliable instead of locking up, and it's smoother. That's how ropes are made I believe...

If you are very patient you can also splay out the strands, interleave them from each wire, and twist the whole thing together. I've tried it with limited success.

I just had to look up the Western Union joint. It's designed for solid core and to not be soldered as tension in the wire makes it tighter.

I would have thought your friend would use crimp connectors? Open barrel connectors have strain relief built in, and coloured crimp connectors with head shrink attached (to provide strain relief) are cheap enough.

ac-dc (author)IkeB22016-07-31

Flexing is not an issue, or rather it shouldn't be. Any areas that significantly flexes should have the solder joint moved, two joints at areas outside the area that flexes and a continuous piece of high strand count wire added, put in the flex area, wire designed for flexibility used in that area.

"Usually" each wire end should be twisted together before the splice, at least at the very ends so the individual strands do not fray out as they are difficult to keep tight against the spice if they are not twisted there. It does not need to be a tight twist, only enough to keep the strands tidy.

A no solder approach is a bad practice, actually quite terrible if the wire is flexing. I wonder if this is just imagination on your friends' part as there are only two types of situations, where a wire is expected to flex and a continuous high strand piece is used in the flex area, and situations where the wire would only flex if it is not fastened down properly.

Neither the solder joints nor the ends of them are supposed to be mechanical connections.

IkeB2 (author)ac-dc2016-07-31

My buddy has been building and repairing cars for a long time so I figure he knows a thing or two about his work. Sure there are other ways to avoid excessive flexing but the no-solder joint has been working for him ... and me since I started to use his technique. The anti-oxidant coating I use keeps any possible joint corrosion from happening and the shrink wrap locks the joint down tight. I might experiment a bit soldering the middle of the Western Union joint, putting heat sinks on the end wraps.

gm280 (author)2016-07-29

The twisted inline splice you shown is both a good splice and mechanically strong as well. But even with shrink tube, it looks bumpy. But it will work and be a very electrically good splice. Another inline splice is called a lap joint or splice. That is where you basically lay one wire parallel with the second wire from the opposite direction and solder. It also is a great electrical connection but not as mechanically good as the twisted. but it looks nice and clean. When I splice multiple wires in a bundle, I stagger the splices to there isn't a bulge in one place with all the splices. It keeps the bundle small and smooth. One other thing you may consider when making splice joints or connections, Use a thermal shunt to keep solder from wicking up under the insulation. That way corrosion with not start under the insulation and cause future problems. And clean the soldered connection with an acid brush and alcohol before heat shrinking to remove any flux. Thumbs Up!

photon1116 (author)gm2802016-07-31

IMHO 'acid' anything should not be used on an electrical connection as it will degrade very quickly. Do NOT use acid core solder. Use resin core only.

gthompson20 (author)photon11162016-07-31

Acid should NEVER be used with wiring. Gm280 was on the right track with the thermal shunt, the problem is not the solder but the flux that causes the corrosion. Even resin flux will break down over time and cause corrosion. Therefore any traces must be removed for a perfect job, Also for a perfect joint the wires should be chemically cleaned prior to soldering to remove finger oils. Isopropyl alcohol is good for both of these.

Heyup (author)gthompson202016-07-31

Hi, Exactly what type of alcohol should I be asking for on ebay etc?

Obviously its not beer lol.... Thanks john Doncaster :)

gthompson20 (author)Heyup2016-07-31

Isopropyl alcohol, available on ebay, plus if your interested there are some very good (and some absolutely horrid ones) videos on Youtube that show the requirements for perfect soldering, do a search "High reliability hand soldering" It was originally an eighty course when I did it 35 years ago.

CheesesOfNazereth made it! (author)photon11162016-07-31

He said acid brush. Not acid. An acid brush is a very common tool for electronics soldering. It does not have acid in it. Here is a picture.

Both gm280 and CheesesOfNazereth are correct about using an acid brush. These are called acid brushes because they are acid resistant so they can be used to brush acid. I've seen them in many shapes from tooth-brush shaped to the picture provided by CheesesOfNazereth.

One trick that I've found with the type shown above is the bristles are too long for scrubbing. I've used cable cutters (the type with the two curved blades) to cut the bristles down to 0.5 to 1cm long. Then they work really well for scrubbing flux deposit off splices and PCBs (along with generous helpings of alcohol).

What he said.

The correct name of that brush when used in electronics is 'Flux Brush'. I'm a retired electronic tech and have used them all my career, so when the word 'acid' was used in the same conversation as electronics soldering, I replied as I did. They are called 'acid brushes' when used in the context of using them for soldering metal pipes such as in plumbing.

Flux Brush:

Acid Brush:

And yes, it is Rosin not Resin.

If I had known this was going to turn into a war of semantics I would never and will never reply to one of these instructables again. I was only trying to be helpful.

wb7ptr (author)photon11162016-07-31

I think your comments were very helpful and I have the same understanding is you with me use of acid core solder and electronics. I also have background and electronics and am ham radio operator and home brewer. Please don't hesitate to comment in the future because people can learn from your knowledge.

KenS74 (author)photon11162016-07-31

Don't be discouraged. Your opinions are are valid as anyone's, but it is in the nature of commenters to want preciseness. Sometimes things seem a little nitpicky, but as long as people to not get personal and profane, comments are just striving for accuracy and completeness. All to make the rest of us a little better informed. Even if there is disagreement or controversy it's good to know that it exists and what the issues are.

wb7ptr (author)photon11162016-07-31

It's actually a rosin core solder that's used. Acid core will cause corrosion of the material being soldered which is not good. Acid core solder is a project such as Plumbing not for electronics. It can also damage electronic components other than the wire beats other day.

EdS85 (author)photon11162016-07-31

I think you mean rosin core solder, don't you?

billbillt (author)photon11162016-07-31

This is very true.. Resin core ONLY on electrical... Acid core is for metal soldering...

geopro (author)gm2802016-07-31

And I say this in the nicest possible way, so don't get upset, but MY GOD, talk about anal. ha ha ha

pinheadBE (author)2016-07-31

Such "simple" tricks are often the most ingenious and the most useful of all. I will definitely give this a try and will take some time to practice.

Big thumbs up, and thanks for having shared this.

inventor2 (author)2016-07-31

An additional hint.

Where more than one wire is being spliced from the same enclosed insulation, make each wire to same standard but different lenghts. This will prevent a bulge, but more importantly prevent shorting even when shrint rap degrades.

Regards Stephen Fitton

richg99 (author)2016-07-31

My only suggestion on this project is....Don't forget to slip the heat shrink tube on FIRST. Can't believe how many times I've forgotten that little step.

deswiger (author)2016-07-31

There are many ideas of what is the best way to do this and yes I prefer to not solder as it makes wire hard and brittle. (there are many things to do to make it work, so please, no arguing who's right or wrong).

This not my first choice but it works in many cases. Nice job, thanks for the share. Semper Fi

toothpick5 (author)2016-07-31

Nooo!! You left out the most important secret if all! : DONT twist the strands on each side before joining them! Leave them lose and straight just as they are after stripping. maybe even spread them apart a bit needed. then join the wires with strands intertwined . Then continue twisting as you instructed. This results in an interlock between each strand instead of just the one twisted wire. It makes for a MUCH tighter contact with every strand and will never come lose over time. Also, it allows for better solder flow and much better contact without that coating of finger oil on the wires! My job involves near constant soldering of all sorts of wire. That technique improved my wiring jobs better than anything I have ever learned! And it is actually easier to skip the twisting (which is what eats your fingers up) assuming you are careful to not mess up the strands. They must be perfect before sliding them into each other. otherwise, they will never mesh. In that case, i cut and start over

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