My vibratory tumblers have a simple wing nut, washer and 1/4"-20 threaded rod holding the lid against the bowl. That works OK, but I found it often loosens up while tumbling.
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Rather than over-tightening the lid and potentially stressing or warping the lid, I installed a stop using an upside down 1/4"-20 T-nut on top of a standard nut (I happened to use a square nut) and tightened them against each other. I positioned the nut assembly so that the lid was under slight tension when the wing nut is tightened down. Now I can tighten the wing nut as much as needed while not over-flexing the lid, and it doesn't vibrate loose even after running for hours.
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