« Reply #1 on: April 08, 2017, 08:26:20 AM »
I've seen that same 'warning' issued with every tuner I've ever bought -- which is a grand total of three: two Korg and one Snark. As a rule I don't leave any of the tuners on my guitars on a permanent basis -- mainly because I have three tuners and, well, far more than three guitars... And like you, I've not seen any damage to the finish on any of my guitars. With the Korg tuners, I have noticed a tendency for them to leave some kind of residue on the headstock where the rubber clamp pads touch the guitar (looking something like a fingerprint); I imagine the rubber pad has been treated with something to keep it soft, and I would speculate that other manufacturers similarly treat the rubber pads on their tuners. The residue wipes off easily and had not seemed to cause any damage, but I don't know what (if anything) would occur if I left the residue on the finish indefinitely...
In the end, I'm pretty certain the warnings about finish damage are largely the result of product lawyers being product lawyers; most modern guitar finishes are pretty durable, in particular, Taylor's. But I'm sure it's possible for the rubber compound or the softening agent on the clamps of these tuners to react with someone's guitar finish somewhere out there -- more than likely a valuable vintage guitar that the tuner manufacturer doesn't want to pay to restore. Hence, the warning to use the tuner at your own risk...

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