From Acoustic Guitar November/December 2021 | Martin Keith

Question: I have a Martin D-28 from 1958. When I removed the tuning button from one of the gears during the most recent re-pull process, I noticed that there were various black stickies inside the tuning gear (Grover Rotomatic 102C), which seemed to be overused. Life-span lubricant. I want to know if these gears may need to be cleaned, relubricated or repacked after 63 years of good service. I have read a bit about it and have been warned not to use Vaseline, and I have seen some people recommend Tri-Flo Superior Dry. What lubrication will you use to refurbish Rotomatic? --Bob Metzger

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A: First, let us quickly understand the main components of the mechanism: the "worm wheel" (the spiral part that connects the handle/button) and the pinion (the round part of the rotating string). Almost all guitar tuners use the same mechanism, with a few exceptions, the most famous being Ned Steinberger's linear drive "gearless" tuner and Bill Rickard's recent very innovative design, including a cycloid drive system.

Many old guitars and modern instruments that emulate them have open or exposed tuners. As the name suggests, these tuners can view the arrangement of worms and pinions without restriction. This also means that these gears tend to accumulate dust, shell fluff, and any other particles or fluff that may happen to appear. If debris accumulates in the gear teeth, it can cause stickiness and unreliable tuning, and may even cause gear failure. For this reason, I usually use dry lubricants on open tuners instead of pasty grease or other viscous lubricants that can collect contaminants. I have had some success with powdered graphite, but recently I used Tri-Flow for an open tuner on the advice of the great repairman and tuner connoisseur Frank Ford. Although it is distributed in the form of liquid oil, it is mainly used as a carrier for particulate PTFE (also known as Teflon). It adheres to the gear surface and continues to act as a lubricant even after the oil itself dries.

When lubricating an open tuner, I usually remove the strings so that I can turn the tuner freely in both directions. I put a small drop on the contact point between the worm and the pinion, and then use the winder to turn the tuner quite quickly. After the pinion rotates about 1/3 of a turn (usually the handle rotates three to five turns), I place another drop at the same contact point, and repeat after another four or five turns. Then, I continuously rotate to move the pinion through another complete rotation. This usually leaves a nice, uniform layer of lubricant around the gear without causing too much confusion. Keep a cotton swab handy to prevent dripping oil.

Modern cast or sealed tuners are another matter. In the past, cheap tuners were known for low-quality metals and poor manufacturing tolerances, and were often blamed on unstable tuning. Companies such as Grover, Schaller, and Gotoh have solved this problem by providing better gears, tighter tolerances, and tuner upgrades with a fully enclosed body, which allows the gears to rotate in a thick, paste-like grease bath. These tuners are designed to be permanently closed, and in many cases, after decades of maintenance-free service, they still perform well. However, the small discs or plates of the sealed back cover may fall and be lost, exposing the gears inside and allowing grease to accumulate contaminants. 

In these cases, I will try my best to disassemble and clean the tuner. A heated ultrasonic cleaner is the tool of choice in my shop, but the simpler solution is to soak it in boiling water for a short time and then scrub it with an old toothbrush. The next step is to reassemble and relubricate with medium weight grease. Blue or blue-green lithium grease usually works well for this, those with PTFE added are even better, but even the basic white lithium grease from a hardware store usually works. I will not overpack the gearbox-just a reasonable ball is enough. Then, replace the rear nameplate to close the gear set again. If you cannot replace the medal, please consider using Tri-Flo's dry lubrication method (as detailed in the open tuner).

The third common tuner series uses a stamped sheet metal back, covering the worm and pinion. Among the brands that produce these products, the most famous is Kluson, whose tuner has been used on Fender guitars and many acoustic guitars for decades. These tuners usually have a small hole in the back plate for lubrication at the key point where the worm and pinion intersect. This hole will also allow a lot of dust/dirt to enter, as I discovered when disassembling old equipment in some cases. If the tuner feels a bit rough or tight, a drop of oil through the hole is enough. If it feels worse than this, I usually do a thorough disassembly and cleaning.

Since we are discussing the maintenance of the tuner, I will also mention another very common problem with old tuners: rotten or cracked plastic buttons. Many old-fashioned tuners suffer from this problem. I have dealt with many guitars, and their buttons break when they are turned. This is due to the long-term degradation of the plastic used for the button. Apart from replacing the buttons, there is no real practical solution. Most vendors, such as StewMac, sell splice buttons for this purpose. After removing all the old plastic and oxide from the tuner shaft, the technician can use a flame or a soldering iron (I prefer an iron because the flame sometimes leaves black deposits) to heat it, and then press the button into place to form the tuner Plastic around the shaft. When everything cools down, the buttons will be firmly joined together.

One last point: most tuners have a bushing (metal sleeve) that is mounted on the surface of the guitar headpiece to support the string. This is just pressed into place on older tuners. On newer cast tuner, the bushing is threaded and screwed into the tuner housing through the head piece. Push-in strings are notorious for falling when it is inconvenient to change strings, and they can easily disappear under the table or in a gap. (Trust me that!) 

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When repairing the guitar, make sure the bushing fits snugly, or put a plastic bag on the headpiece to safely catch any missing parts. It is also a good idea to check the bushings on modern tuners regularly-they are often loose, and sometimes the gaskets under them can cause mysterious rattling and humming, which can be difficult to diagnose. Do not turn them too hard, as it will cause problems with the surrounding finishes. Just tighten them with an open-end wrench or socket. Almost every cast tuner uses a 10mm wrench. When lubricating the tuner, especially the old-fashioned open tuner with a press-in bushing, I also put a space between the string and the bushing at the 6 o'clock position where the bushing is closest to the nut. Small drops of oil.

Is there a problem? Not sure about the care and maintenance of your guitar? The ins and outs of guitar making? Or other topics related to your equipment? Send an email titled "Repair Expert" to Editors.AG@stringletter.com and ask Martin Keith, the repair expert on acoustic guitars, and we will forward it to Keith. If AG chooses to post your question, you will receive a free copy of the AG acoustic guitar user manual.

This article was originally published in the November/December 2021 issue of Acoustic Guitar magazine.

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