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.