These enclosed tuners, whether made by Grover, Schaller, Gotoh or others, typically have a central screw holding the button. This screw usually adjusts the feel of the tuners by increasing or decreasing the friction between the button and the cast housing of the tuner body. It's a common misconception that making the buttons tighter will make the tuners stay in tune better. It hardly ever works that way, because the worm gear system really can't run backwards. Not a bad idea to check the tuner button screw, especially on older Grover Rotomatic tuners such as those found on Martin guitars:
Here's why:
First, let me show you what's inside the gearbox. It's a regular worm and gear assembly just like the open tuners, but it's held together differently. The string post and gear are inserted through the big hole in the back. Later a round plug covers the hole. Then the worm is slipped into the housing and it is retained by the button screwed on at the other end:
Mostly on older American made Grover Rotomatics, the button screw has a tendency to work loose. (Modern Grover Rotomatics are made in Korea, and don't have this problem.) Then the string tension takes over, forcing the worm back out of the housing the way it was originally assembled. Look at the tuner on the left. The worm has inched out about 1/8" so far. You can actually see the first full turn of the spiral gear:
This is bad news. And insidious. Since the string tension forces the button back toward the housing, the guitar player isn't even able to feel or see the difference from the front of the guitar. Eventually, the worm advances so far that it runs out of teeth to engage the round gear. When that happens, it's very likely the worm will break off one of the gear's teeth, and then the entire mechanism is dead. Moral of the story: If you have older American made Grover Rotomatics, keep a close watch on those dang buttons!
How to tell the difference, you ask. Well, it's very easy. Check out the photo below.
On the left we have an American Grover. It has a SLOTTED screw in the button. The gold one in the center is also says "Grover" but it is Korean, with a PHILLIPS screw. Some years ago Grover quit making a lot of products in Cleveland and started importing them from Korea. Just for kicks I threw in the Schaller (German) on the right, which also has a slotted screw.
Should you care, here's a good rule of thumb. American and German gears tend to have slotted screws, and Asian ones have Phillips. In the case of Grover, all American ones have slotted screws and all Asian ones have Phillips.
If you'd like to be prejudicial about it: The real ones have slotted screws in their buttons, the copies have Phillips. Schaller still makes all their own gears in Germany (note the straight edges on the buttons.) There are probably more copies of Schaller tuners than any other. To the best of my knowledge, Schaller copies are not made by or for Schaller.
If a tuner carries the guitar's name, like Martin, Ovation or what, it means that the guitar company simply ordered enough from the gear maker to have their name stamped. None of the guitar makers actually manufactures tuners.
Are the "real" ones better? In my opinion, not necessarily. It's just an opinion, but I see good and bad examples of all these things. . .
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