A common shop repair is fixing spindles in a chair that have loosened up. When the end of the spindle is too small for the hole, a good fix is to simply wrap and glue thin veneer around it. To hold the veneer in place while the glue dries, use an automotive hose clamp. Once done, you can either rebore the hole or shave the spindle end for a snug fit.
Need to replace your trusty old level? You can check it for accuracy. Lay one working edge on a flat surface and check the bubble. Swap it end for end, then check the bubble again. It should be in the same position. Now try the opposite working edge. Take a reading, switch end for end, and take another reading. The bubble should be in the same position. Likewise check for plumb by holding it against a flat vertical surface.