Here's a picture of between the 2 pieces that spin. There's a nut in there with a washer on the one side of it and a thin plate on the other side which has 2 small hex head screws holding it tight. I'm trying to figure out how to accomplish this. Here's what I was thinking: If I get a bearing and a bolt that fits inside it (snug). Recess the one piece of lumber to accept the bearing so it's flush. Drill a smaller hole inside that to accept the head of the bolt. Install in that piece of wood. Than slip a washer (that has a diameter bigger than the bearing) over the bolt and use small screws to fasten it to the wood (to keep bearing assembly from companies no out). Than thread on a nut to act as a spacer, and another washer after that. Drill a hole in the other piece of wood so the bolt slips through and on the other side recess the hole to accept a washer and nut. It sounds complicated but when you think about it, it could be how this one is done. I can't take it apart to check so I thought I'd ask your take on it.