How to make acoustic guitar tuners move smoothly

Extract from the November / December 2021 issue of Acoustic guitar | By Martin Keith

Q: I have one 1958 Martin D-28. During a recent readjustment, I noticed that the tuning gears (Grover Rotomatic 102C) had all kinds of black sludge inside, looking like lubricant after its life, when I pulled the knob out. adjustment of one of the gears. I wonder if, after 63 years of good service, these gears might need a cleaning, relubrication, or repacking. I read a bit about it and was warned to use petroleum jelly and saw that Tri-Flo Superior Dry is recommended by some. What would you use as lubrication to renovate a Rotomatic? – Bob Metzger

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A: To get started, let’s take a look at the main components of the mechanism: the ‘worm’ gear (the spiral shaped section that connects to the handle / knob) and the pinion (the round part that is turn the rod of the rope). Almost all guitar tuners operate on this same mechanism, with a few exceptions, notably Ned Steinberger’s linear drive “gearless” tuners and Bill Rickard’s recent and highly innovative design involving a cycloidal drive system.

Many vintage guitars, and the modern instruments that emulate them, will have open-back or exposed gear tuners. As the name suggests, these tuners give an unlimited view of the worm and pinion arrangement. It also means that these gears are susceptible to collecting dust, case lint, and any other particles or lint that may come in. If debris builds up in the gear teeth, it can cause a sticky and unreliable setting and potentially even gear failure. For this reason, I usually use a dry lubricant on open back tuners, rather than a paste grease or other sticky lubricant that might collect contaminants. I have had moderate success with powdered graphite, but lately I have been using Tri-Flow for open back tuners, on the advice of great repairman and tuner connoisseur Frank Ford. Although it distributes as a liquid oil, it primarily functions as a carrier for microparticulate PTFE (aka Teflon), which adheres to gear surfaces and continues to act as a lubricant even after the oil itself. even has dried.

When lubricating open back tuners, I usually remove the strings, allowing me to freely turn the tuner back and forth. I apply a small drop to the point of contact between the worm and the pinion, then use a string winder to spin the tuner pretty quickly. After about 1/3 turn of the pinion (usually three to five turns of the crank), I apply another drop to the same contact point and start again after four or five more turns. Then I turn continuously to move the pinion another full rotation. This usually leaves a nice, even layer of lubricant around the perimeter of the gear, without doing too much damage. Keep a cotton swab handy for any dripping stray oil.

Modern molded or sealed body tuners are another story. In the past, inexpensive tuners were known for their shoddy metal and tight manufacturing tolerances, and were frequently to blame for unstable tuning. Companies such as Grover, Schaller and Gotoh have solved this problem by offering tuner upgrades with better gears, tighter tolerances and fully enclosed bodies, which allowed the gears to spin in a grease bath in thick paste. These tuners were designed to be permanently closed and in many cases still perform admirably after decades of maintenance free service. However, the small disc or plate that seals the back cover can fall off and get lost, exposing the gears inside and allowing grease to collect contaminants.

In these cases, I will disassemble and clean the tuner as best I can. A heated ultrasonic cleaner is the preferred tool for this in my shop, but a simpler solution is a brief dip in boiling water followed by a scrub with an old toothbrush. Then comes the reassembly and relubrication with a medium weight grease. Blue or blue-green lithium based greases generally work well for this, and those with added PTFE are even better, but even basic white lithium grease from the hardware store will generally do. I don’t race gearboxes, a reasonable dollop is enough. Then replace the rear medallion to enclose the gear train again. If you can’t replace the medallion, instead consider the dry lubrication approach (as detailed for open-back tuners) using Tri-Flo.

The third common family of tuners uses a stamped sheet metal back that covers the worm and pinion. Among the brands that produced them, the best known was Kluson, whose tuners have been found on Fender guitars for decades, as well as many acoustics. These tuners often have a small hole in the backplate, which is meant to allow lubrication at the strategic point where the worm and pinion intersect. This hole can also let in a surprising amount of dust / dirt, as I have discovered in some cases when taking older sets apart. If the tuner feels a bit rough or tight, a drop of oil through the hole should be enough. If it’s worse than that, I usually do a disassembly and deep cleaning.

Since we are discussing tuner maintenance, I will also mention another very common problem that arises with vintage tuners: rotten or cracked plastic knobs. Many vintage tuners suffer from this problem, and I have handled a number of guitars whose knobs simply cracked when turned. This is due to the long term degradation of the plastic used for the buttons. There is no real practical solution for this other than replacing the buttons. Most vendors, such as StewMac, sell fusion buttons for this purpose. Once the tuner shaft has been cleaned of all the old plastic and oxidation, the technician can heat it using a flame or a soldering iron (I prefer the iron, because the flame can sometimes leave a black deposit) and push the button in place, molding the plastic around the stem of the tuner. When everything cools, the button is securely together.

One final note: most tuners have a ring (metal sleeve) that fits over the front of the guitar headset to support the string post. It just falls into place on older tuners. On newer cast body tuners, the ring is threaded and screws through the headset into the tuner housing. Snap-in ones are known to fall off at inconvenient times when changing strings and can disappear very easily under tables or in crevices. (Trust me on that one!)

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When working on your guitar, make sure the bushings are snug, or place a plastic bag over the headphones so that any lost parts are safely collected. It’s also a good idea to periodically check the bushings of modern tuners – they are very often loose, and sometimes the washers underneath can cause mysterious rattles and buzzes which are infuriating to diagnose. Do not push them too hard as this can cause problems in the surrounding finish. Simply secure them with an open-end wrench or socket. Almost all cast iron tuners use a 10mm wrench. When lubricating the tuners, especially older open back models with tight fit bushings, I also put a small drop of oil between the string shank and the bush, at the location of 6 times when the ring is closest to the nut.

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