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DIY: How to Convert a Flattop to Nashville Tuning

Turn your spare acoustic into a sparkling wonder that transforms songs from mundane to magical.

It’s a safe bet that every Nashville session player owns a high-strung guitar. Flattops configured this way are essentially half of a 12-string guitar, with strings 6–4 tuned up an octave. When you strum a guitar in this “Nashville tuning,” you get shimmering chords with lots of deliciously close intervals that are impossible to finger in standard tuning. But the high-strung guitar isn’t limited to Nashville studios—many guitarists bring a high-strung flattop onstage to add glistening tones to their live shows. While Nashville tuning simulates a 12-string, it’s much easier to tune and play, and it takes up considerably less space in a mix.

Fortunately, it’s easy—and cheap—to explore these jangly sounds. Switching a guitar from traditional to high-strung tuning requires only a basic knowledge of stringing and setup, and it only takes a few minutes, too. If you fall in love with the ringing timbres after trying it out on your axe, you can optimize the guitar for Nashville tuning by installing a new nut. Best of all, you can always return the guitar to its original state by simply reinstalling the old nut. Because it’s reversible, this is the perfect mod for acoustic guitarists.

Let's hear it first, then see how it's done:

The clip includes a number of short passages that illustrate the sound of simple open chords, basic strumming, more elaborate fingerpicking, natural harmonics, and even dropped-D riffage. In each case, the left-hand fingering and right-hand picking are straightforward—the ear-grabbing, close-interval voicings, octave jumps, and jangly timbres are all automatically generated by the Nashville tuning.

Step 1:

1. Before restringing for Nashville tuning, measure the action in standard tuning with normal strings. This dial caliper provides precise readings in thousandths of an inch. 2. A close-up of the dial caliper used to measure action.

Take Preliminary Measurements
Before you start any guitar project, first analyze the instrument’s general setup. Write these measurements down, so you can refer to them later if you decide to return your guitar to its original configuration.

1. Tune the guitar to concert pitch. To measure the string action—the height of the strings from the frets—I like to use my trusty old dial caliper, though alternatively you can use a precision metal ruler or string-action gauge. I typically measure from the top of the 12th fret to the top of the low E string (Photos 1 and 2), and then record the measurement. I do the same for the high E string.

2. Note the amount of relief in the neck, and then measure the string height at the nut. (For a detailed explanation of how to measure neck relief and string height at the nut, see “DIY: How to Intonate a Flattop Guitar,” April 2012, or go to YouTube to view the companion video for that PG article. YouTube search term: DIY: How to Set Up and Intonate an Acoustic Guitar.)

Step 2:

Restring the Guitar
Now you’re ready to remove the old strings and install the new ones.

1. Be sure the new strings are the correct gauge. The easiest and most popular way to do this is to string your guitar with the four octave strings from a light-gauge 12-string set, as well as one each of the set’s doubled 1st and 2nd strings. From 1st to 6th string, these high-strung gauges are typically .010, .014, .008, .012, .018, and .027. Simply install the strings as you would normally.

2. Tune to pitch as follows: High E (1st string) and B (2nd) are tuned to standard guitar pitch. Next, tune G, D, A and E (3rd–6th) one octave higher than normal. Strum the chords to a favorite song and dig the jangly, soprano-like sound.

Step 3:

3. After removing the standard strings and restringing with high-strung gauges, check that all open strings vibrate freely when seated in the original nut. 4. With Nashville tuning, strings 4–6 are replaced with thinner gauges and tuned one octave higher. Only one string is wound—the 6th. In most cases, these thinner strings can actually be played in the wider, original nut slots (shown here), in which case you’d stop at this point. But for optimum sound and playing comfort—string spacing is noticeably affected when using these thinner strings in the original nut—savvy guitarists equip their instrument with a new nut that’s cut for the specialized high-strung gauges.

Check Playability

1. Check action. If it needs to be altered, either adjust the truss rod for the proper relief (it should have a slight forward bow) or adjust the saddle height, or both.

Tip: If you have any doubts about how to adjust a truss rod, get a guitar repair book or study the manual that came with your instrument. Many manufacturers offer free online instructions for adjusting the truss rods on their guitars.

2. Examine how the strings sit in the nut slots. Even though the new strings have much smaller diameters and look out of place in the large nut slots, it’s only the slots’ depths that matters in relation to the frets, and that remains unchanged. To check string height at the 1st fret, hold each string at the 2nd fret and tap the string down onto the 1st fret to determine if there’s a small gap between string and fret (Photo 3). If so, you’ll be able to play the guitar as it is and bask in the sound of Nashville tuning.

Even if all the open strings clear the 1st fret and vibrate freely, the string spacing will be noticeably affected, and the new low strings may look and feel considerably spread out (Photo 4).

You have two choices here: One is to do nothing further—if the guitar plays and sounds great, then you are ready to roll (and rock). But on our particular guitar, the strings no longer lined up perfectly along the neck, so we opted for the second choice: Make a new nut.

Step 4: (Optional)

5. To loosen the original nut, use a small hammer to gently tap a wood block against the front and back of the nut. 6. Carefully pry out the original nut.

Remove the Original Nut
Before you remove the old nut, take a moment to look at the distance between the low E (6th) and high E (1st) strings, and also notice how each one lines up along the edge of the neck.

Now you are ready to remove the old nut.

1. If there is a build-up of lacquer around the nut ends, use a razorblade to score along the nut edges. This prevents the lacquer from chipping when you remove the nut.

Tip: It’s a good idea to measure and record the distance between the two outside strings, as well as their individual distances from the fretboard edge at the 1st fret. These three measurements will allow you to calculate string spacing on the new nut.

2. Next, using a piece of scrap wood (approximately 6" x 2" x 1/2") and a small hammer (I use my fret hammer), gently tap on the front and back edges of the nut until it is loose enough to remove (Photo 5).

Tip: The wood block needs to be wide enough to span the whole front or back of the nut, so there will be equal pressure along the nut surface when you tap the block.

3. A jeweler’s flathead screwdriver works well for prying out the loose nut (Photo 6).

Step 5:

7. Don’t be surprised if a small amount of wood sticks to the original nut when you remove it from the guitar. 8. The dried glue that held the original nut in place. Using a razorblade or scraping tool, carefully remove the old glue from the nut slot. 9. The nut slot after being scraped and blown clean.

Clean out the Nut Slot
The nut is usually lightly glued into the slot. A small amount of wood may lift up with the nut when you remove it (Photo 7). Don’t panic, that’s normal. Once you’ve removed the nut, you need to scrape out any residual glue from the slot.

1. Identify any spots of dried glue and scrape them out using a shop razor blade or scraping tool (Photo 8).

2. After scraping out the glue, brush or blow out all the debris from the nut slot, so it’s clean and ready for the new nut (Photo 9).

Step 6:

10. Sand the thickness of the bone nut blank so it fits snugly in the nut slot. 11. Check the blank thickness during the initial sizing process. 12. The nut blank is ready to be trimmed for length. 13. Pencil marks indicate the fretboard edges. 14. Sand off the blank’s excess length. You can also do this with a small hobby saw. 15. Check the blank’s edges against the fretboard.

Install a New Nut
Once you have a clean slot, you are ready to fit and install the new nut. At our shop, we use a Plek machine—a computer-controlled fret-dressing and cutting device—to set the string spacing and cut the nut slots. That said, you can do everything by hand—the way luthiers have for centuries. (For a complete explanation of how to measure, cut, slot, and install a nut, see “DIY: How to Convert Your Axe to a Baritone,” March 2012.)

1. Carefully measure the nut slot and then shape the bone nut blank to fit into the slot, starting with the blank’s thickness. Go slowly and measure frequently. (Photos 10 and 11).

2. Once the blank fits into the slot (Photo 12), it’s time to trim off the excess length. With the nut in the slot, mark where it reaches each edge of the fretboard. These marks indicate how much bone you need to remove (Photo 13).

3. Trim the nut’s length. You can sand it down to the pencil marks (Photo 14) or use a small hobby saw to cut the blank to size. Take your time and check your progress frequently (Photo 15).

16. The blank’s edges are now flush with the fretboard. 17. Mark the nut to trim its height by sliding a pencil sideways along the frets. The top line results from placing the pencil flat on the frets. Draw the lower line by tipping the pencil down and sliding it along the 1st fret. You’ll remove material from the top of the blank down to the upper line. The lower line roughly indicates where the nut slots will bottom out. 18. Sand the blank down to the upper line. 19. Sized to its rough height, the nut begins to take shape. 20. Use the original nut to determine the location of the 1st and 6th strings. 21. A hobby saw that has been ground to a thin blade for cutting nut slots.

4. When the blank’s edges are flush with the fretboard (Photo 16), the next step is to trim the nut height. Lay a pencil on the frets and move its point up against the nut. While resting the pencil on the frets, slide it sideways, moving back and forth with the tip marking the nut. The resulting line marks the top of the nut—you’ll remove material from the blank to this line.

Next, repeat the marking process, but this time tilt the pencil tip down and slide along the 1st fret (Photo 17). This second line roughly indicates where the bottom of the nut slots will ultimately be, once they’re cut.

5. Sand or file the top of the nut blank down to the upper line (Photo 18). Once you’ve sanded down to the top line, insert the blank into the slot and admire your work: Now it’s beginning to look like a nut (Photo 19).

6. If you liked how the original nut positioned the 1st and 6th strings relative to the fretboard edges, simply transfer this distance to the new nut. Place the original nut at a right angle to the blank and mark the center of the 1st and 6th string slots onto the blank (Photo 20). The spacing of the remaining four string slots is calculated from these two points.

7. Calculate the interior string spacing. At Glaser Instruments, we use our Plek machine to space and cut the string slots. The easiest way to set the string spacing manually is to use the String Spacing Rule, a handy metal ruler from that automatically determines the proportional treble-to-bass string spacing. It comes with simple instructions that guide you through the procedure, which is quick and easy.

Tip: Again, for detailed instructions on how to cut a nut manually, see “DIY: How to Convert Your Axe to a Baritone,” March 2012.

To take its measurements, the Plek machine requires that all six strings are on the guitar. To cut shallow guide slots that hold the strings in place during the initial measuring phase, we use a hobby saw that has been ground to a fine edge (Photo 21). Ultimately, we remove the strings from the nut and the Plek cuts new slots, after its software calculates the optimal string spacing, splay, and slot depth for a particular fretboard.

22. Cut the shallow guide slots for strings 6 and 1. The spacing of the four interior strings is calculated from these two points. 23. With the exterior strings in their guide slots, position strings 2–5 using the String Spacing Rule.

String spacing—whether done by hand or machine—is always based on subdividing the distance between the 1st and 6th strings. Using the marks transferred from the original nut, cut shallow guide slots for strings 6 and 1 (Photo 22).

From these two points, calculate the string spacing for strings 2–5 using the String Spacing Rule. Once the strings are spaced to your satisfaction (Photo 23), it’s time to cut the slots.

24. The Plek performs computer-controlled fret leveling and several other operations, including cutting string nut slots. 25. Filing sharp edges from the nut. 26. Polishing the nut with abrasive paper. 27. The finished bone nut after being filed and polished. 29. Burnishing the nut slots. 29. Before gluing the nut in place, check the string height at the 1st fret. When you depress each string at the 2nd fret, you want a small gap between the 1st fret and that string. This gaps allows the open strings to vibrate freely.

8. Cut the nut slots. Our Plek holds the guitar inside a chamber that houses sophisticated measuring devices and a computer-guided cutting tool (Photo 24).

After securing the guitar in the Plek, we take several measurements to program into the software that controls the cutting. This software plots a nut’s many specifications, including string spacing, string splay, slot depth, nut top height, nut top radius, and string break angle.

Once the initial measurements are done and the software is programmed, we close up the Plek with the guitar inside. The Plek then takes its own detailed measurements of the fretboard and action, before shaping the nut and cutting the slots with a precision bit.

It only takes a few minutes for the Plek to cut the slots and rough-shape the nut height an radius.

After the Plek has done its magic, we put the nut back into its slot to confirm that everything looks right.

9. Now it’s time to polish the nut and burnish the slots. Begin by filing off any sharp edges (Photo 25) and then sand the nut smooth, first with 80-grit, then 400-grit, and then finally 600- or even ultra-fine 800-grit paper (Photo 26).

When you’ve finished filing and polishing the bone nut, it should look shiny and feel completely smooth (Photo 27).

Next, burnish the nut slots with a very fine nut file (Photo 28). Be careful here—you don’t want to change the depth of the slot, but simply make sure there aren’t burrs or file marks in the slot that might catch a string. Some luthiers gently rub an old string through the slots to burnish them. If you do this, pick a gauge that drops easily into the slot and slides through it without resistance.

10. The final step is to glue in the nut. But before you do, string up the guitar, tune it to concert pitch, and recheck the string height at the 1st fret, using the tapping technique described earlier (Photo 29).

30. Getting ready to glue the nut into the slot. 31. A small drop of super glue at each end of the nut secures it to the fretboard. 32. In Nashville tuning, the highest open string is no longer the 1st, but the 3rd.

Put a small drop of super glue on the end of an old string or jeweler’s flathead screwdriver (Photo 30) and carefully let it seep into the tiny space between the fretboard and the nut (Photo 31). You don’t need to do this all along the nut, just at each end. The goal is simply to keep the nut from falling out when you change strings, and prevent it from shifting sideways due to string tension or string bending.

Have Fun Being High Strung!
And now you’re done! Your flattop is reborn as a high-strung guitar. Typically, the saddle that worked for you in standard tuning will accommodate the four new octave strings just fine and offer intonation that’s basically as good as it was before—sometimes even better. That was the case with our 512c, which, once we strung it up with the new nut, took to its high-strung configuration like a duck to water.

Look closely at this guitar, and you’ll see that the highest string is now G—the 3rd string (Photo 32). On a high-strung axe, every chord form you know is automatically revoiced in new—and sometimes startling—ways. Octave displacement, an advanced composing and improvising technique, is built into Nashville tuning, and the resulting riffs, melodies, and chords should offer many years of creative inspiration.