Angela has a Kromski Polonaise spinning wheel, which looks like this.
One thing about them is the finials on the wheel uprights. They basically just sit there, having a poorly fitted joint. It’s fine if you never move the wheel but they’re easily knocked off if you need to move it much. Kromski suggest not using glue to keep them in place, though, so I came up with a different way using some thin cotton cord.
The first part is to cut the string to the appropriate length. About half an inch longer than the outside diameter of the upright worked great for hers. It’s probably fine if it’s a little shorter. What you want to avoid is it being so long that the ends of the string remain above the horizontal space of the joint (the next picture will make this more clear.)
With the piece of string centered over the opening, insert the finial. This will push the string down, causing the tail ends to set between the sides of the peg part of the finial and the cylinder walls inside the upright. It will take-up the extra space. If the string is too long, you can just remove the finial and trim the string a bit, repeating until you get the right length. If one string isn’t sufficient for a snug fit you can do a second, as I did on the other upright (it has a looser fit.)
The idea came from a woodworking technique known as hemp wrapping, as it uses thin hemp cord.