Tubing Connections With String




About: I'm a retired mechanical engineer, woodworker, boater, and inventor. Now I'm getting into wood turning, and have found that all my wood projects need not be flat and square.

I was going to call this Instructable emergency tubing connections with string. But I now use this method often, even when not an emergency situation. It works when you need to connect any small flexible hose to copper tubing or metal pipe, and do not have hose clamps or barbed fittings.

Step 1: Materials

Assuming that you already have a rubber or vinyl hose, and a metal tube you need to connect it to, you will need:
  • String.  Best is fine nylon cord, but it just needs to be strong. Several feet (a meter or so) long.
  • Tools: A knife or scissors.

Step 2: Optional Step - If Using Copper Tube, Flare the End Just a Bit.

Copper is soft, you can flare the end out slightly with needle nose pliers, a nail set, or a center punch.

Step 3: Make the First Wrap

Wrap the string around twice, make a simple knot , and pull it tight.

Step 4: Make Second Wrap

Making sure the first wrap stays tight, take another wrap and a half with the two ends and tie a knot (it will be at the bottom this time) and again pull tight. It helps to grasp the ends with a tool to get a good grip.

Step 5: Third Wrap

Now take another wrap and a half, pull tight, and make a final double knot. This knot will be on top.

Step 6: This Won't Come Apart

Each successive wrap increases compression considerably. If you later cut the string loose, you will see the the deep imprint of the string and it will be obvious how tight the connection was.



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    9 Discussions

    Bill WWapplemilkshake

    Reply 6 years ago on Introduction

    I agree, and should have thought of it earlier.
    Others have mentioned this same knot. I added an image of the knot, see below.
    Thanks for commenting.


    6 years ago on Introduction

    The only thing I would recommend to improve this is to wax the nylon. It can be slippery and a bit of wax can help out a lot to keep it from slipping. Spearfishers use the constrictor knot all the time when tying up bands and they use a waxed thread to prevent slipping in a wet environment.

    3 replies
    Bill WWCaseyCase

    Reply 6 years ago on Introduction

    The constrictor knot would be great here.
    There are plenty of images of this knot, here is one of the most clear.


    6 years ago on Introduction

    Interesting idea! I use iron wire, two turns, no more,, no less. But it has an ugly look.