Whilst you can buy pre-made heat shrink tee's, my general experience is that they are expensive and can be hard to find in small sizes.
I’ve used this method several times for most sizes of tubing and the only equipment required is:
- Standard heat shrink tubing,
- A heat source capable of shrinking said heat shrink tubing without melting it, like a hair drier, heat gun or even a cigarette lighter (please be careful with hot things, they can be burney).
- A craft knife, scalpel, exacto (I believe that’s what the Americans out there call it) or razor blade (please be careful with sharp things, they can be cuttey or stabby).
Step 1: Get Everything Together
I can’t stress enough how important it is to check you have all your equipment in one place and ready to go, there is nothing more annoying than noticing that you have forgotten to add a piece of heat shrink to a just soldered wire.
Start with two pieces of heat shrink tubing, the length is up to you really, but I find about 10 - 15mm or 1/2" is plenty, at the same time cut a piece around twice the length.
The longer piece is to become the branch of the tee, but does require some surgery to achieve its full potential.
You should just be able to make out the basic principal from the slightly fuzzy second pic, use your cutting implement of choice cut the longer piece of tubing along its length (down the middle) to about half way, then remove one of the halves being careful not to cut all the way through.
Then slightly taper the cut half towards the end, this makes life easier in a few steps time.
Next slide the pre cut pieces of tubing over the prepared wires before you solder / twist them together, making sure the cut piece of heat shrink is on the branch of the tee with the cut end towards the join.
Join the three wires together using your desired method, then butt the two equal pieces up together as close as possible and using your heat source shrink these tubes onto the wire as pics 2 & 3.
Now the easy bit, push the last piece of tubing down to the joint and wrap the flap of heat shrink around the joint and tuck it back into the unshrunk tube, this can be a pain if you’re using very small tubing, but I promise it can be done, I find just gently pinching the main body of the tube helps lift it away from the wire enough to push the flap in.
It’s like threading a needle, sometimes it goes in first time sometimes it takes a while.
Finally shrink the last bit of tubing and your tee piece is complete.
I am aware that the pics are not the best but my camera is not the best, in fact im suprised they came out this well.