Soldering Tutorial: Inline Splicing





Introduction: Soldering Tutorial: Inline Splicing

Soldering is an essential skill for hobbyists and anyone interested in DIY electronics projects. This article will provide step-by-step instructions for inline splicing, a widely used procedure in electronic assemblies. Inline splicing involves joining two stranded wires in a straight line. The instruction is tailored for both first time solderers and intermediately skilled individuals looking to improve their technique.

Soldering iron
Solder filler wire
Stranded copper wire
Wire stripping / snipping tool

Tips and Precautions
Always exercise caution to avoid burns and electrical shock.
Use gloves and protective eyewear to minimize risk of bodily harm.
Always work in an adequately ventilated environment and avoid inhalation of vapors.
Soldering products often contain lead and may be harmful if inhaled.

Step 1: Step 1

Strip both wires approximately 1” from ends. Do not twist strands after stripping.
Note: You may choose to later insulate the splice with heat shrink tubing. If so, remember to slip on the shrink tubing before soldering the splice.

Step 2: Step 2

Align and evenly interweave the strands of both wires.

Step 3: Step 3

Carefully twist the intertwined portion of the two wires.

Step 4: Step 4

Place the spliced section on a flat surface and anchor both wires, as it is preferred to have both hands free for the next step.

Step 5: Step 5

Press the soldering iron onto the center of the splicing area.

Feed solder directly into the stranded wire adjacent to the contact point of the soldering iron.

Step 6: Step 6

Apply heat generously to evenly distribute the solder along the length of the splicing area. Next, flip the splice over and repeat for the underside.

Step 7: Done!

Your inline splice is now finished! Allow it to cool for 30 seconds before handling. The result should look similar to the picture. At this point, you may insulate the splice with shrink tubing or electrical tape. Insulation is recommended when the wire will be connected to high voltages or exposed to outdoor environmental conditions.



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    24 Discussions

    How would you twist the wires (step 3) if they are part of a 2-wire cable?

    3 replies

    I would be happy to write another instructable for a two-wire cable! Good idea--thank you!

    I would be happy to write an article for 2 wire cables! thank you for the idea.

    If it's a jacketed pair of insulated cables, remove the jacketing a bit farther back, strip both pairs of wires as indicated, then do one pair of wires. Then pre-twist the second pair well behind the splice point, mesh them together, put a clamp of some kind in the middle of the spot you're joining, and remove the twist on the wires. The un-twisting of your pre-twist will put the twist on as in the instructable. I'd use vise grips or something similar to hold the wires pre-twisted, and a third one to put a clamp on the middle, then remove the outer two and the wire should start the twist on its own.

    Wow, thanks for the instructables. Never thought of not twisting the splice and interweave them together. I did the old fashioned phone cable twist, where you place them about halfway from eachother and bend them around to prevent the bind from sticking all out and looking ugly.

    1 reply

    You're welcome!

    I made this years ago for a work/school related project and would be happy to write more articles if anyone has suggestions.

    Definitely a reliable connection mate, but one that will NOT like to be moved about. If there IS going to be a moving connection, after step 3 I would leave the connection UNSOLDERED, & wrap a few turns of electrical tape around the joint, as neatly as possible, then tighten up a cable tie in the centre.

    I have never had a failure when leaving it unsoldered, & it works anywhere but out in the weather or underwater! However, my method could be used underwater by using heatshrink that is pre-lined with a sort of hot-melt glue.

    1 reply

    Yes, it is true that the splice will not like to be moved about, as the joint can be prone to wear and tear. I usually use this with heat shrink tubing for added strength and use an adhesive to bind the wire to a solid substrate so its does not move around.

    Love this tut! Twisting 2 wires together and then soldering them may be a better connection, but it looks like hammered dog doo :/ This is a much cleaner look :D

    1 reply

    I agree with your feedback. Twisting two wires together and using a wire nut or solder joint is preferred in many applications.

    This method is mainly used to achieve an aesthetically sound splice when wires are visible in the end-product.


    Thank you for the positive feedback. I used to work in LED lighting manufacturing and came up with this method for clean looking splices for wires that are visible to consumers.

    I am happy that this helped out!

    Nice and simple ible.
    One thing. The sentence " At this point, you may insulate the splice with shrink tubing or electrical tape. " should be at step 1, as it is always infuriating to forget the shrinking tube.

    3 replies

    Thank you for the comment! you are absolutely correct. Nothing is worse than forgetting to slide on your heat shrink tubing before soldering!

    Thanks for the feedback!

    I will change the part about shrink tubing to step 1. Forgetting to put it on beforehand can definitely be frustrating.

    Great system. I used this method with 1 addition at step 3. After interweaving the strands I used a single strand of wire from spare wire of the same size to wrap the joint prior to soldering. This held in the ends of the spliced strands to make an even solder joint.

    You may have to clean this solder joint properly! Whatever flux you are using (liquid flux or flux core solder) can be extremely corrosive if not cleaned. There are water soluble fluxes that are easily cleaned with hot water and there are "no-clean" fluxes that do not require cleaning. There are also rosin core or RMA flux that need chemicals to clean properly. Review the solder/flux you are using to see what kind you have.

    Most roll solder has a flux core that provides the required flux to solder the joint. Check the roll and or datasheet for the solder to see what the cleaning requirements may be.

    This is critical. I think that many have been turned off by soldering having tried to solder only to see a green corroded solder joint a year later because they did not clean it properly or did not use a no-clean solder/flux.

    I tend to use water soluble flux and clean with hot water.

    1 reply

    I have things that were soldered 30 years ago with rosin core solder and never cleaned, and there is no corrosion. Rosin is basically tree sap, and while it's sticky and not very pretty, it's not corrosive. That's the whole idea.