Plug Dryer Problem

[Swimmer]

Maybe the Professor can help with this. The el cheapo dryer setup I bought has a shaft that is 5/16's square. It comes in three pieces and when it turns I have the ugly feeling it wants to come apart. Is there such a thing as 5/16"s square stock that can be bought. Or barring that, is there 5/16 round stock that the end can be squared to 5/16's, so it fits in the dryer motor. The shaft now turns inside of sleeves that have set-screws in them, which I tighten against the 5/16's square stock. I like the overall job I did, and this has popped up as a lose end and is bugging me. I am going to PALCO plastics to buy some clear plastic to make the door with now, which is the last thing I need.