Weekend Mod Project: D-28 Open-Gear Tuner Upgrade

I’ve made an effort to play more acoustic guitar in 2014, which has partly entailed overhauling my Martin D-28. Now a decade old, the spruce and rosewood dreadnought has matured both acoustically and aesthetically; it has also endured some normal wear and tear. Several months ago, I performed overdue maintenance on a worn mammoth ivory saddle. More recently, I set out to replace the stock Gotoh tuners (right) — at least one of which was showing symptoms of a stripped gear. The Martin-labeled enclosed machines are unfortunately not available through retailers (either singly or as a set), which means owners must navigate the myriad aftermarket options.

A generic, Gotoh labeled drop-in replacement is available, but for several years I had been eyeing vintage-inspired, open-gear tuners. Open-gear tuners are stock on most high-end Martin vintage reproductions, and boutique manufacturers like Collings and Bourgeois also opt for the classic look. The problem is that open-gear tuners have a very different overall design footprint (including set screws and and peghead bushings) than most enclosed tuners — which is to say this is no trivial mod.

After extensive research, I opted for a well-reviewed and reasonably priced set of Gotoh open-gear tuners available from Luthiers Mercantile International. Acoustic Guitar and Martin Guitar Forum users routinely compare these favorably to pricier, American-made models by Waverly. Installation can be daunting for the uninitiated, especially if it entails drilling and reaming holes in an expensive instrument. Needless to say, it’s a job worth taking to your luthier if you feel the least bit uncomfortable with the mod. For those who take the DIY route, I hope this post can serve as a helpful guide (this page and this page are also extremely helpful).

Step 1: Stock Tuner Removal and Peghead Preparation

The first and easiest step is to remove the stock tuners. For enclosed tuners, this usually involves removing a single set screw and loosening the hex nuts on the bushings. On my instrument, the tuners and bushings easily fell away. Some owners have a little more trouble with the bushings, which are occasionally pressed into their holes and require careful loosening.

If the stock tuners have been on the instrument for years (as mine were), it’s not uncommon for the removed bushings to leave behind polished depressions commonly referred to as “raccoon eyes” (see left). It’s challenging (if not almost impossible) to remove the eyes entirely. However, it is possible to polish and buff the peghead to a glossy enough sheen that the eyes are rendered largely invisible from a distance. I used a mix of Stewart MacDonald Swirl Remover, Preservation Polish, and no small amount of elbow grease — I probably buffed and re-polished the rosewood peghead veneer at least ten times (take care not to overdo it by inadvertently buffing through the nitro finish). On a standard series Martin, the gold foil logo looks especially sharp against the polished peghead (see final product below).

Step 2: Reaming the Peghead Holes and Installing the Bushings

If the instrument previously sported inclosed tuners, there’s a good chance the original peghead holes are too small to accept the open-gear tuner bushings. This requires careful reaming to expand the hole just large enough that the new bushings can be pressed in with only a gentle amount of force. There are various improvised methods for reaming the holes, but I highly recommend spending $15 on an actual reamer (like this one, or this premium version from StewMac), which ensures even and circular expansion. Gently (but firmly) press the reamer in the hole, twisting one full turn at a time and testing with the bushing to see if the hole is big enough.

As noted, the bushing should press in with a small amount of force — too much force (implying a too-tight fit) might crack the peghead, while too little will ultimately result in loose (and possibly rattly) bushings. I used a hand-operated bar clamp (with rubber clamp protectors), available at most hardware stores, for the final fitting of each bushing.

Step 3: Drilling New Set Screw Holes

This was the diciest part of the job, from my perspective. Each tuner required two new set screw holes; drilling a misaligned hole means correcting with an unsightly fill/re-drill, or just accepting the bad alignment (which may or may not affect the actual operation of the tuner). That said, it’s easy to drive yourself insane trying for precision; it’s worth noting that the tuner alignment of factory guitars is often a little off (mine was). Perfection can be the enemy of the good; you’re dealing with a musical instrument, not a space rocket that might explode if tolerances are off at the micrometer level.

As with all aspects of lutherie, it’s important to take your time, measure, re-measure, and re-re-measure before metal meets wood. I used the imprint from the stock tuners as a guide, laying down a piece of masking tape to mark the sideways alignment of the first and third tuner on each side. The middle tuner on most Martins is actually inwardly offset from the other two, requiring separate alignment. After marking the alignment, I put the tuner in the hole and marked the position of the set screws with a sharp awl, serving as a guide for the electric drill bit (which was carefully marked for depth with masking tape; you don’t want to drill through the peghead!). I slowly drilled each hole, making it through all 12 without incident.

Step 4: Final Installation

Once the set screw holes have been drilled, final installation is simple. At that point it’s worth giving the peghead another quick dust and polish to get rid of fingerprints and debris. Put in the set screws for each tuner, and string up the beast. In the end, I was very satisfied with the alignment and fit of the Gotohs (and this was my first time doing such an installation). The new tuners largely cover the footprint of the originals, with only the slightest edge of one of the original set screw holes visible (at some point in the future, I’ll probably fill the original holes for the sake of neatness). Most importantly, the Gotohs operate smoothly and hold a tune quite well; I heartily recommend them to anyone seeking a reasonably priced, vintage-inspired tuner upgrade for their acoustic.

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