How to Join Wires Permanently (Create a Perfect Join)


Sometimes we run into a situation where a wire breaks or needs to be lengthened. So this is how to join two wires without tape, perfectly.

In any home with smart products, we ideally want less wiring, unless you are going all in with a very serious system.

Even aiming to go as wireless as possible, you will still need a cable here and there for certain products.

Sometimes the wires are not long enough. Sometimes you have to make your own.

Either way, this article will help you to join wires properly for any situation.

To prepare for joining wires:

The things you will need apart from the wires in question are:

  1. Soldering iron
  2. Solder
  3. Shrink tubing
  4. Wire strippers or cutters
  5. Hot air blower

These things are necessary if you plan to do a perfect and reliable join. Your local hardware store should have these items. If they don’t carry shrink tubing, try your local electrical supply outlet. 

Shrink tubing comes in different sizes and you ideally want a loose fit over the wire. This will allow you to easily slide it over any joined sections. 

For the solder, make sure it’s of good quality and has a flux core. This will allow the solder to flow and grip to the copper much easier.

Step by step procedure

Here are the steps you need in order to make a high quality, long lasting join.

Step 1: Prepare them

two wires ready

Start by cutting the ends off so you have a clean undamaged section of wires to work with.

This will prevent any other complications when trying to join or solder the wires. It can also aid in a good quality end result, both functionally and aesthetically.

Step 2: Strip off the insulation

wires with insulation removed

Using a pair of wire cutters or strippers, strip off a section on each one of insulation only.

Be sure that you aren’t damaging the copper strands of the cable itself. This will cause an unreliable cable that could break inside, after joining. It could even cause problems months or years later.

By having clean exposed copper, soldering will be easy. If you have a wire that cannot be soldered, you will not be able to get the solder to flow onto it and an alternative solution will have to be administered.

In this case, use a crimp tool with terminals. These terminals will be able to plug into each other and no solder will be required. You can also pick these up at a hardware store.

Once you have about a half an inch of insulation carefully stripped off the end of each wire, you are good to go for the next step.

Step 3: Twist them together

copper wire twisted together

While this is not an absolutely necessary step, it is, however, a step that makes the process easier for a beginner.

Before you twist the copper ends together, slip you shrink tubing over one of the wires. You can see from the image that a distance is kept from the tubing to the join.

This is important to avoid heat getting to the heat shrink tubing while soldering the wire. If the tubing receives too much heat, it will shrink in place and you won’t be able to slide it over the join.

Make sure you cut the tubing at least double the size of the join. You want the tubing to cover the join with plenty of overlap.

Now that you have twisted them together, it will keep everything in place to make soldering easier and eliminate the need for a vice. That being said, please make sure you have something under your work area to protect your table if need be.

Step 4: Solder the join

wires soldered together

Before using your soldering iron, make sure the tip is nice and clean and is coated with some solder. You can clean it easily enough by heating it up and poking it into a tip cleaner. It’s just some metal spirals bunched together. After that run some solder over it.

For the most part, if the iron is new, or has been used fairly regularly, simple run across a water soaked sponge is enough. Just run some solder over the tip first, before using it.

Just be aware, if your tip is not clean, the soldering process will be difficult. The end result will also be ugly.

Take your warm soldering iron and hold the tip under the twisted copper wires. Feed some solder directly onto the tip until it gets heated up and starts to flow against the bare copper.

This will apply enough heat onto the wire which will allow you to feed solder directly onto the wire itself. Do not keep the iron too long on the wire as you could end up damaging the insulation from all the heat.

As you feed solder onto the heated area, it will begin to flow through the strands of the copper wires and make a complete join. At this point stop feeding the solder and make sure it has flowed everywhere, just like in the image.

You can always apply more solder than necessary to ensure the solder has flowed everywhere.

Now you have a strong permanent connection. This type of join cannot suffer from poor contact or intermittent errors. It will last as long as the cable itself.

If you feel uncomfortable or feel that you haven’t done a good job of it, try again. It’s important you keep practicing. Before you know it, you will do this process without even thinking about it. It’s a valuable skill to have.

Step 5: Slide the shrink tubing over the join

wire join covered with heat shrink tubing

Now that they have been soldered together and the connection is strong, slide your shrink tubing over the join. Be mindful that you have your join nicely in the center of the tubing’s total length.

This will ensure the join is safe and nothing can be exposed. It also looks a lot nicer once you are finished to have equal lengths on either end of the shrunken tubing over the insulation areas.

If you feel like it’s difficult to move or tilt the wire without the tubing moving around, get someone to hold it for you for the next process, or simply use a vice. Another way is to take two objects that will give your joined area some height off the table that won’t be affected by heat.

Step 6: Apply heat to the tubing

applying heat to shrink tubing

Now that you have your wire and tubing prepared for some heat, take your hot air blower and on a fairly low setting blow the hot air over the tubing.

Be careful not to have the airspeed set too high, as you don’t want the tubing to move at all.

Also, be careful not to hold the hot air blower too close to the tubing. This can damage the wire and the tubing. Just bring it in range slowly and when you see the tubing starting to shrink, don’t go in any closer.

Allow the heat to gently do its work and apply heat all around the tubing, not just on one side. You want the whole piece of tubing shrunk everywhere it possibly can. This will give you a neat finish and a tighter seal.

You are done

completed join

That’s it, you now have a perfectly joined connection that will last just as long as the wire itself. I could argue that it might be even stronger than the original wire itself. 

Don’t believe me? Pull a joined piece of test wire until it breaks. I’d be very surprised if it broke on the join if you have done a good job of the join.

If you have more than one wire, you can simply repeat the process on them too. Once this is complete, take a larger sized shrink tubing to seal up all the joins, making your cable look more uniform. Don’t forget to slide the shrink tubing onto the cable first, before doing any joining.

Conclusion

I’ve used many joining products over the years. This is the one method that I stick to. It’s given me reliable joins that I still see working perfectly, even 15 years later.

Eliminating the electrical tape is another aspect to the longevity. It can’t unravel or lose adhesion in high-temperature weather.

So as far as perfection in joining wire, this is as good as it gets in my opinion.

Take it slow, keep practicing, and I have full confidence that you will master this skill. Best of luck. 

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