Making Custom Tube Fittings and Connectors

by Melvyn Wright

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Making Custom Tube Fittings and Connectors
I got fed up of trying to obtain suitable tube adapters and connectors of the exact size to fit the various sizes of tubing and sizes of hole that I could drill, so I decided to make my own. Being made out of wood, they are easy to glue onto wooden surfaces, giving an airtight fit.

I use flat bits to make large holes in wood and MDF, and these can only be obtained in a limited range of sizes.  For instance 13mm, 16mm, 20mm, 22mm, 25mm, 28mm 30mm, and so on. I found that these didn't always exactly fit the sizes of plastic tube available to give an airtight fit.  Also, the flexible pond-type tubing is corrugated externally, so it has to fit over a tube, and not into a hole!  So some sort of method is needed to add a tube to a wooden surface, giving a proper airtight fit.

Unfortunately, you will need a lathe to make these adaptors, but only a cheap Chinese one. Or you can make a lathe with a springy pole and a piece of string!

I make the tube adaptors from hardwood dowel.  Broomsticks are a good source.  These are usually just over 1" in diameter and are ideal for making 1" adaptors.  This procedure might seem obvious, but it's not so straightforward as it might seem, because the walls of the adaptors are too thin to be gripped in the chuck without being crushed.  

Cut a piece of dowel to the length required (usually around 1.5").

Chuck it up and face off each end.

Mark the centre of the length of the dowel and turn one end to the exact diameter required to fit your tubing, or hole, or whatever. Do not turn it right down to the centre line, leave about 2mm unturned to form a shoulder.  Do not take heavy cuts.

Reverse the dowel and lightly tighten the chuck. Now turn the other end down to exactly fit the other tube, or the hole in the wood. Again do not turn it right down to the centre line, leave about 2mm unturned. This will leave a shoulder between the two diameters.

Now fit a flat bit in the tailstock and slowly bore out the centre of the dowel. The flat bit must be no bigger than the diameter of the dowel minus 4mm, to leave walls no thinner than 2mm thick.  So if you want to make a 1" adaptor (25mm) you mustn't bore it out more than 21mm.

Watch for the flat bit coming out of the other end of the dowel and stop advancing before it hits the chuck!  You should see a wooden plug being pushed out.  Stop when this happens. Remove from the lathe and push the plug out by hand.

Not only does the shoulder serve a useful purpose in use, it also prevents the dowel from being pushed into the chuck during boring out, meaning that only a light chuck pressure is required.

Finish off with a light sanding with sandpaper.

Stage 1

Stage 2

Stage 3


Here are some examples I made earlier!

Simple tube connector for coupling different size tubes, or as an input connector

Flanged connector. Plenty of glue oozes out around the shoulder to provide an airtight joint

Flanged connector used to provide an input connection to a windchest


Simple right-angled connectors
The right-angled connectors are made with a block of wood large enough to accomodate the tubes.  If you do not have a block of wood large enough, then glue several layers together until you do!

First make the block by boring a hole all the way through with a flat bit (bore from each end towards the middle to avoid splintering). Next bore the second hole until it breaks into the first one.  This is the neatest way of boring holes at right angles without having to spend ages chiselling away the corners. Warning, the bit may snatch the wood when breaking through to the first hole. So use a hand vice if possible.

Next glue on a small piece of MDF to blank off the unused hole.

Then make the tube on the lathe so that one end exactly fits into the hole, and the other end exactly fits the tubing you are using.

You can use worm-drive clips on these connections as long as you don't go mad when tightening them!  But if you have made the tubes the correct size you will find that they fit so tightly that clips are generally not necessary.

Right-angled connections

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