Understanding Guitar Intonation

Tools Tips and Tricks

Simple Tools For Nut and Saddle

Calculating Needed Compensation Offsets

Pre-test Measure Compensation Offsets

Using Shims for Nut and Saddle

Locating Fret Buzz

Hollow Grind

String Spacing At The Nut


Simple Tools For Nut and Saddle

This topic is directed at DIY-ers; luthiers and pro techs know what they need, and already have the tools.

Though professional tools can greatly improve your speed, and perhaps the resulting quality, they are by no means essential.  For instance, you would expect a professional luthier to have a good set of nut slot files, but that may be too expensive for an owner of one or two guitars.  You can do the job, if you are careful, with a set of mini needle files from a local hardware or a luthier supply.  keep in mind, though, that, in the case of the nut slot files, there is a huge difference in the ease and accuracy of the real thing vs the substitutes.

There is more than one way to do most setup processes, even among professionals, so use your imagination to find a good way to accomplish what you need to do.


For rough nut shaping, you can use 80 grit sandpaper. It works best to get stiff-backed sandpaper. Lay it on a flat surface, or fasten it to a flat board and move the nut material rapidly across the sandpaper. You can utilize a wood squaring block against the nut material. Follow up with 100 grit.

I don't have shop space for a table-top sander, so I made a simple wood base to support my belt sander on its side, and I use that, along with my thickness sander, for speedy shaping.

For other work and for final shaping, just get an assortment of various grits. 1 sheet each goes a long way. Small files can also be used for final shaping.

Nut Slot Files. 

For working on nut slots you will need something to create or deepen the slots.  There is a wide variety of tools available for slotting and shaping, with a wide variety of cost.

Quality nut file sets from Japanese Uo-Chinkyu and Hosco range from about $60 to $120, depending the number of files included.  (These are also sold under labels: Stemac, Grizzly, Ibanez, and Allparts.)


There are two main types of these files.  The flat ones cut only on the edges, not on the sides; both edges are abrasive and they are of the same cutting width (you can widen a nut slot by slightly tilting the file).  The files are hard and brittle - the thinner ones requiring care to keep from breaking.

The other type of files are tapered on both edges.  There are usually 3 files in a set and each edge is of a different cut size, giving you 6 sizes.  Along the tips of the large tapers on each side are tiny rounded ridges that do the cutting.  (You cant really see the ridges in the photos.)  These files can cut sideways. The files do not include small sizes below about .020"(.5mm), so you would probably use a hobby saw for the first and second guitar string. 

The cheap tapered files are not accurately sized, in fact they may likely vary wildly from the labeled sizes, and may vary from one end of an edge to the other.  They still can be useful in combination with other items - I made test cuts with each edge on an ice cream stick, measured the cuts with a feeler guage, and then applied sticker labels.

Needle files are designed for general purpose, not for musical instruments, but with care and patience, you can  make effective nut slots with needle files. The slots will be V-shaped, rounded at the bottom. The sets are all super cheap (about $3 & up).  There are about 6 different file shapes, and a set usually contains 2 of each shape. 

Another super cheap option is a set of thin abrasive rods that come in ether a key-ring or small metal box holder. These are actually made (and sized) for cleaning gas pipe nozzles! While they work, they are very slow. I have found them to work well for the base strings, but the ones for the treble strings flex too much, so you could cut a negative curvature if not careful. 

Other Popular Tools.

1.  A string winder - to tighten or loosen strings more quickly.  It almost always includes a bridge-pin puller.  There are many choices available starting at about $2. 

2.  A neck rest (or cradle) - it secures the neck and headstock for work on the strings, nut, and frets.  You can buy one of make your own; I did with a little scrap wood, and padding on top.  If you need more height to get your string winder in place, you can attach a piece of 2"x4" lumber to the bottom of your neck rest to make it stand higher.

3.  A string action ruler - an aid and guide for setting string action height at the 12th or 14th fret and for other uses.  Alternatively you could use a 6" stainless precision rule.

4. A set of thickness feeler guages - they are needed for measuring string thicknesses, string action height at nut, neck relief, and many other things. Thicknesses from .002 to .030 are most popular.  Professionals often do setup work by eye (without measurement) but I don't recommend that - it saves time, but does not produce the best result.

5. A steel ruler - For measuring, and for checking the level of fret tops on the fretboard. You may already have something that will work.  You also need a short (2-3") scale for isolating and adjusting individual high frets by rocking across 3 or 4 frets at a time. 

6. A 6"/150mm caliper - for accurate measurements for fitting nut and saddle, for measuring string diameter, and for many other things. (If you are into DIY, you will wonder how you ever got along without one before.)  There are three types - digital, dial, and vernier.  All are good - I prefer digital - vernier will require a bit of a learning curve. 

7. Hobby saws and miter box - for cutting nut material and for nut slots for thin strings, etc.

8. Fret crowning file - to dress fret tops after fret leveling.

9. Miscellaneous - 

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Calculating Needed Nut Compensation Offsets

After accurately tuning the selected string while fretting behind fret 2, release your finger and then measure the cents-off-pitch of the open string.  Then multiply the number of cents off by an amount related to your scale length below.  It's as easy as that!

The compensation amount (length) per cent-off-pitch:

for 25.5" scale is .01472"    (This is more accuracy than you need.)

for 24.875" scale is .01436"

for any other scale length, multiply the 25.5" compensation amount by your scale length divided by 25.5".

Example: 25.5" scale, open Low E is 6¢ flat.  Compensation amount is 6 x .01472 = .08832", round to .088" of compensation of the nut toward the first fret.  

Note: As the cents-off increases, the compensation amount per cent decreases, as does the width between frets as you go up the fretboard, however, the decrease is so tiny for the first 10 or 15 cents of the first fret, the difference can be ignored.

Note: Please stand by for a little more detail and exposition of the logic behind this topic.

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Pre-test Measure Nut Compensation Offsets

Offset estimating toolWhile the offset length can be calculated, many would like a quick, easy way to get an estimate of offset length. (In either case, the final adjustment of the nut offset will need to be done with pitch measurements.)

Here is a simple tool that you can make!  With it, you can do a temporary string compensation, and then, somewhat accurately, measure the offset. It took me about 10 minutes to make this tool from a regular paper clip!

To use it, find a gauge of the right thickness, that will allow you to slide the tool under a string, almost to the nut, putting just a tiny bit of upward pressure on the string. Then, using your strobe tuner or program, slide the tool to where the open string is in tune with the 2nd or 3rd fret. Then measure the distance from the nut to the approximate centerline of the tool wire. Since this is an estimate, add a little more length, so you won't come up short.

With this information, you can do most of your offset filing prior to installing the shelf nut on the guitar.

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Using Shims For Nut and Saddle

Guitar techs take pride in making new nuts fairly quickly in preference to using shims. For me, that all changed when working with compensated nuts, and more accurately compensated saddles. If you have substantial time invested, you wouldn’t want to throw your work out just because the slots are a bit low. For other than thin shims, the shim should be glued to the nut or saddle. My rule is to not stack more than 2 unglued thin shims.

I have used shims since my very first $20 guitar (my older sister brought it from Mexico) and I have done setup work on all the instruments I have owned since then. As long as you use materials that are reasonably firm and you maintain good contacting surfaces, you will not damage the sound of the guitar. Don’t use tape or anything with adhesive.

Wood and bone are very desirable for shims, and they are natural to put between the bone nut or saddle and the wood guitar neck. For wood shims, I suggest (don’t laugh) popsicle sticks, tongue depressors, and coffee stirrers. (These are also sold as craft sticks.) They are made of birch, usually Baltic Birch, which is cheap, but also strong and stiff, somewhat comparable to maple. Look for them in your local dollar store.

Trim the stick to approximate width and length and then super-glue it to the bottom of the nut or saddle. Trim off any excess width, and then, as a unit sand the bottom of the wood to the needed height with flat sandpaper, starting with course, or on a table sander.

For bone, if you have a band saw, mini or precision saw, cut of a strip of material from a new nut or saddle blank, and then proceed the same as with wood, gluing the smooth surface of the shim to the nut or saddle.

Metal is also desirable for a thin shim. (Don’t use metal so thick that the weight is significant – it could change the tone of the guitar.) I bought a 1/3 sq ft piece of .003” bronze shim stock at a local bearing supply. (You could also try an electric motor shop.) (.003” is a good thickness to compensate for a few years of fret wear on the string slots.) It is easily cut with strong scissors.

You can also find scraps of aluminum. I saved a piece of a throw-away aluminum pie tin, and, even though it’s crimped for strength, there is still plenty of flat materiel that measures .0045” thick. I saved another scrap of .006” aluminum from a food container.

Re-filling Nut and String Slots

I have a good solution for re-filling nut slots. When the nut slots on my 2 steel string acoustic guitars became too low, I cut out a .003" bronze shim to raise the nut action and then I reset the action. After 3 years of playing they were low again.

Instead of another shim, I used Marine-Tex white epoxy putty to fill the nut slots. Now 3 more years have gone by and the action is still fine on both guitars!

The product is slow drying – it took 3 days to fully harden. The color is very white. You can tint it to match the bone, but the color difference doesn’t really show when the strings are on. The hardened product is very strong. (I patched a large hole in my camping trailer with it more than 10 years ago, and the patch is still secure.)

To prepare for filling, clean the slots with alcohol or comparable, lightly file all the inside of the slots, then clean again.

Products You Can Buy:

Stewmac veneers (Use to shim nut or saddle.


Has anyone experimented with light-curing dental material?

If so, I would like to know about it.

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Locating Fret Buzz

Buzz got you baffled? You can find which frets are buzzing with your volt-ohmmeter.   Set in resistance mode, connect one probe to the test string between the nut and the tuning machine.  Hold the other probe on the end of a suspect fret, and pick the string firmly.  The VOM will register Open Line for no buzz, less resistance for a bad buzz, and more resistance for a weak buzz.

My pocket-sized digital multimeter works really well for this, but here’s an inexpensive tool that’s a little more specialized, from Schrammguitars.Com.

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Hollow Grind

When making a partial shelf nut, I need to file back the nut a little for the stings that are already over-compensated.  In order to keep the top front of the nut as vertical as possible, rather than file a sloped surface, I use a small Dremel grinding stone to make a hollow grind.

You probably notice that my shelf nuts have a smoother, continuous appearance, especially compared to Delft's.  That's partly because the cut-backs don't show up well in the (not so sharp) photos.

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String Spacing at the Nut

If you are making a new nut, it's a good time to consider string spacing.  The most common recommendation for string spacing on steel-stringed guitars is equal distance between the strings. That would give you more distance, center to center, the thicker the strings.

I prefer to space the strings equal distance center-to-center.  This is a matter of personal preference, so I'll just give my reasons my preference.  

My theoretical reason is that the thickness of the strings doesn't matter; the fingers are reaching for a position where the center of the string will be.  (The thickness of the fingers might make a difference, though.)

My practical reason is that I like to cover two bass strings with one finger, such as an Em 022000 chord fretted by the first or second finger, leaving the third and forth fingers available to play notes on the higher strings.  I couldn't do that on a classic style guitar with equal distance between strings. 

I also like adequate space between the treble strings.  I would think that players with fat fingers would prefer equal center-to-center spacing.

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