Loose plug on back of older American-made Grover Rotomatic tuners

As you may remember, in these worm & gear assemblies, the string post and gear are a single piece that is inserted through the big hole, and a round plug covers the hole. For some reason, although never removed, some plugs no longer fit very tightly, and downward pressure on the string post (for example while changing a string) pushes the gear against the round plug, popping it out into free fall.
What can be done to tighten up the fit so the plug stays in place?
(photos from Frank Ford's "Tune up your Gears" maintenance page in

Tags: Grover, Rotomatic, tuner

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I have used a drop of thin superglue wicked around the cap. Since nobody has brought one back saying "This fell off again" I assume the fix is successful. Be sure to clean off any grease from the cap and ledge it sits in with solvent for best adhesion.

Greg Mirken
Thanks, Greg, I'll try that! You know, this turners were always touted as "permanently lubricated, never needs lubrication, etc.," but the fact is, these are bone-dry inside, with a few dry dark-gray crumbs. Any idea approximately how full and with what lubricant I should refill them?
Clean out the old dried-up grease and smear some white lithium grease in the gear threads. No need to pack the thing full or anything, these aren't going to spin so fast as to fling the grease off!

You can back the button shaft out of the housing on the other tuners and do the same thing to them without removing the cap.

Greg Mirken
Good ideas, Greg. Thank you for your help.


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