Thanks to everybody who gave me a lot of good suggestions. I rejected the idea of wood because I wasn't confident that I would be able to build it well enough. I then explored making one out of steel
Clearly, you need a better steel supplier. There are such things as DOM and HRS (hot rolled seamless) square tubes. Neither is allowed to have evidence of an inside seam. They cost more than stuff th
My steel suppliers don't stock tubing that provide slip fits, either. It's not the weld, it's the selection of ID/OD that's generally available. It's the standard dimensions of seamed, seamless, DOM,
Here's my rambling story of mixed success... I did get some tubing that was a sliding fit. It was square mild steel, with a visible seam in the middle of one seam. I used it to make a pair of "safety