Making a Tool

I need a long wrench--actually two long wrenches--to reach a bolt and nut that will join two pieces of tubing end to end. I'll have to reach inside the tubes from both ends. I was able to buy a set of wrench extenders. To make another, I bought the socket wrench, an adapter, and a long dowel. I filed the end of the dowel down to a square (roughly) to fit inside the wrench adapter. It'll at least work to get the nut in place. When I tighten it, it'll be with some thread locker applied. Maybe by then I'll have found a metal shaft that I will be able to turn harder.