I have built an insulated box for the filter and pump for our spa pool.
There are 4 ball valves, and I have extended the shaft using a 20mm aluminum tube so that the handles can be on the outside of the box.
Now to the simple part, to connect the handle and the aluminum tube I thought of using a dowel.
The inner measurement of the tube and the handle is 18mm.
The closest I found is an 18mm copper tube, but I would prefer a solid rod, I only need 4 pieces of 5cm each.
I personally had bought a 20 mm rod which I placed in the wood lathe and turned down to 18 mm, but that's probably not an option for you... Go to a specialty woodworking shop, there are plenty of those in your area, and ask them to do the same thing. The alternative is to use a sharp knife and sandpaper. I think it will be difficult to find a pre-turned round rod with an 18 mm diameter.
It is easy to whittle a piece of wood from a length of square dowel. It doesn't have to be completely round but should preferably fit with a press fit.
I myself would have taken an 18 Cu tube any day of the week.
