When you are confident that you have the knack, fill all the remaining slots with veneer, glue, cut and sand. Brush off and inspect your work. There are probably a number of little holes you missed. Fill these with wood dust and super glue. Remove the old position markers by drilling them out, being careful to go no deeper than necessary (you need that truss rod!). Place a little glue in the bottom of the hole and cover it with wood dust. Fill the hole to the top with wood dust and tamp in, leaving only the slightest crown. Wick super glue into the dust and let set. This will take a few minutes, and the fillet may even smoke a little as the glue sets up.

When everything has hardened, sand the whole neck with the long sanding block with 120 grit sandpaper. Sand straight along the neck with even pressure, with the grain of the fingerboard, taking care to follow the radius of the neck. You will want to sand all the way across the width of the neck, angling the sanding block to conform to the curvature of the neck. Take care to stay away from the edges. The are certain to get sanded as a result of sanding near the edges. Inspect the fingerboard again and make any necessary repairs.

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FRETLESS INSTRUCTIONS

If you are making a fretless guitar, you are almost done. Once you have the fret slots filled and level sanded, you must sand with increasingly fine grits. Sand with 220, 320, 400 and 600 grit, then brush off with an old toothbrush. Inspect the side of the neck and carefully trim any protruding veneer or glue with a single edge razor bleade or x-acto knife. If you have been extremely careful, you won’t need any touch-up. Wax the fingerboard, remove the tape and polish the entire guitar with a soft cloth.

You will need to sand the nut down since the distance between the strings and the neck is now less by the height of the frets. Mark off a little less than the height of a fret along the bottom of the nut with a sharp pencil. Glue a piece of 80 grit sandpaper to a flat piece of wood and sand the nut by rubbing the bottom of the nut over the sanding block, sanding almost to the line. Put the strings on and try the guitar. Play it for a while and adjust the height of the nut until it is just right.

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Calculating the fret positions

Now you have a smooth, filled fingerboard and are ready to mark the positions for fret slots. To calculate the length of your fret scale, measure the distance from the nut to the octave fret and multiply by two. Measuring from the nut to the bridge is not reliable. The general formula for the distance from the nut to the kth fret is

f(k)=length(1-1/r)

where f(k) is the distance to the kth fret from the nut, length is the total scale length and r is the ratio you want from the fret. Let’s say, for example, you measured a 12″ from the nut to the 12th fret and that you want frets placed so as to give a scale of

1/1, 9/8, 5/4, 4/3, 3/2, 5/3, 15/8, 2/1.

This is an example of a just major scale. The nut is at 1/1, the first fret is calculated by

f(1)=24(1-1/(9/8))=24(1-8/9)=24(1/9)=2.67″,

the second fret is calculated by

f(2)=24(1-1/(5/4))=24(1-4/5)=24(1/5)=4.8″.

The remaining calculations are similar. The octave is 2/1, so the fret calculation is

f(8)=24(1-1/(2/1))=24(1-1/2)=24(1/2)=12″,

just as it should be.

The formula for equal tempered fret spacing is the same, but now instead of ratios, we use powers of two (unless you are using a non-octave scale).

The formula

f(k)=length(1-1/r)

is better written as

f(k)=length(1-2^(-k/n))

where the carat is the power sign and n is the number of equal tempered steps to the octave. As an example, let’s calculate a few fret measurements for 19tet with a 35″ bass guitar scale. The 0th fret is the nut, and the distance to the first fret is given by

f(1)=35(1-2^(-1/19))=35(1-.9642)=35(.0358)=1.25″.

The distance to the 8th fret is

f(8)=35(1-2^(-8/19))=35(1-.7469)=35(.2531)=8.86″.

Keep your figures accurate to four places and your final measurement should be accurate to 1/100″. Notice that .2531 is very close to 1/4. This is as it should be, since the 8th fret in 19 approximates the perfect fourth (4/3) very well, but is a little sharp. Plug 4/3 into the equation for just frets and you will get

length(1-3/4)=length(1/4)=length(.25).

It is a good idea to test the algorithm a couple of times in this way before you cut to make sure you are using it correctly.

The general procedure for measuring for fret slots is the same whether you are using just intonation or equal temperament. Draw a pencil line down the centerline of the neck. Tape your ruler against this line with two sided tape with the end exactly against the end of the fretboard, and make a mark where the first fret will be. Be sure you do this very precisely. Use a very sharp pencil or a mechanical pencil with .5mm lead. Mark each fret position until you reach the octave. The last mark should line up exactly with the former 12th fret. Retape the ruler at the octave, and mark at 1/2 the distance calculated for the first octave. Now, depending on the type of ruler you have, either flip it over and tape it on the other side of the center mark, or slide it over and tape it parallel to the center mark. In either case you want a new set of marks parallel to the first and on the other side of the neck. Repeat the process until you have two sets of parallel marks. Connect the marks and you have a set of lines marking where all the frets will be placed. It is very important to do the measuring and cutting precisely. Check your work and redo the process if you have any doubt about the accuracy.

Cutting the new fret slots

It is time to cut the fret slots. If you are cutting the slots by hand, you will need a guide to clamp or tape on the neck to assure that the saw cuts the slots accurately. I use a straight piece of wood that has a little cup cut out so as to fit snug against the face of the fingerboard. It is possible to cut fret slots by hand without a guide, but you increase the possibility that the saw will slip and mar the fingerboard. Tape or clamp the guide to the neck using a leather or cork jawed clamp, being careful to line it up about 1/2 the width of the fret saw behind the pencilled in fret mark. Making sure the saw is parallel to the neck, take one light swipe over the neck from side to side to make sure the block is properly placed. If the saw has cut out the line you are OK. Realign the guide if necessary. Cut into the fingerboard to a depth of about 1/40th of an inch deeper than the fret tang. You don’t have to be anal about this–you just don’t want to cut the slot too deep or too shallow. The same depth as the old slots is usually about right. Continue up the neck until you have all the slots cut. You may want to cut the top fret slots first so that your technique improves as you get closer to the lower frets, which, in general, will be the most used. If you nick the fingerboard during this process, wait until after the position markers are laid in to fix the nicks.

Laying in the position markers

We will now lay in the position markers. Decide where you want the position dots (if any) and mark them by connecting with pencil the left and right ends of the fret slots between which the markers will be placed. You now have an “X” whose center marks the dot’s position. Punch the center and drill the hole to the depth of the marker. Place the position dot in the hole and wick in super glue. When the dots are set, sand the fingerboard with the long sanding block using 120, 220, 320 and 400 grit paper until the neck is smooth and blemish free. If there is any touch up you need to do, now is the time to do it, as once the frets are laid in this chore will be extremely difficult.

Placing the frets

Re-wax the fingerboard, being careful not to get any in the slots. If you do, drag the fret saw lightly through the slot a couple times to remove it. The wax will help keep the super glue leaks from sticking to the fingerboard. To lay in the frets, cut off a piece of fret wire with the end nippers (or fret puller or toenail clipper), making sure there is enough straight tang to span the entire slot. The fret should be a little longer than the slot so that the deformed end where is was cut does not have to be pounded into the slot. The protruding ends will be cut off later with the end nipper. Lay the neck in a padded cradle made from a 4″x4″x4″ piece of wood with a cup cut out about the same radius as the back of the neck. I use a piece of sheepskin to line the cradle. This cradle insures that the back of the neck is protected while the fret is being hammered in and also that there is a good coupling from the table to the neck to transfer the energy of the hammer into the fret. For a classical guitar, the cradle may have to be taller. Plase the fret over the slot and tap the fret in lightly on one side of the fingerboard using the fret hammer. Once the fret is seated on one side, tap across the fret to seat it all the way across. Check to make sure it is seated against the fingerboard by eye and by trying to run you fingernail under it. If it needs to be tapped in harder, tap from the center to the outside in both directions. Be especially careful when doing this on a classical guitar. I prefer not to fret a classical above the 12th fret using a hammer since the risk of cracking the top or loosening braces is so great with this method. If you want to get fancy, there are a number of products available to press in frets. Again, you might want to practice on the higher frets first until you get a hang of the method.

Take the end nipper and start from the lower frets, nipping off the protruding frets flush with the edge of the fingerboard. With care, you will not mar the surface. Carefully apply a coat of wax with a Q-tip to the edge of the fingerboard, avoiding the fret slots. Apply one drop of super glue at a time to the fret ends, allowing it to wick in. About 3 drops is enough for each side is enough. Make sure glue is not oozing out the other side of the fret slot. If there are any frets whose ends just wouldn’t stay down when you tapped them in, clamp them down before you apply the glue. A little baking soda on the glue will help it set up faster (though super glue accelerator is better). When the frets are all glued in, you may find that a little glue has seeped out between the fret and the fingerboard. Carefully cut the glue off with a single edge razor blade. You can score the glue next to the fret so it will come off easily. Here is where the fingerboard waxing is so important. With enough wax, the glue actually just peels off.

Dressing the frets

Your frets are laid and it is time to dress them. Polish the wax on the fingerboard until it shines, then lay masking tape between all the frets to protect the fingerboard. This time, you may need to use painter’s masking tape so it will stick better to the waxed surface. Run a magic marker across the top of each fret so you can tell what has been cut. Run the flat file lightly over the surface of the frets along the length of the neck, taking care to avoid making the same stroke twice. You should make a sort of criss-cross pattern along the length of the neck, trying to cover the length of the neck from several different angles. This way the file will tend to average the height of the frets over the whole surface.

As you file, the marker is cut from the highest portion of the frets. You are finished when there is at least a thin line cut through the magic marker all the way across every fret. Some of the lines of visible fret material will be wider than others, and that is all right. Brush off the filings and re-ink the frets. If you have a fret crowning file, run it across the top of each fret until there is a thin continuous line of fret material showing.

If you don’t have a fret crowning file, run the long sanding block lightly over the fret surfaces using 320 grit sandpaper until a thin line of fret material shows through every inked fret. Now is a good time to lay in side position dots if you want them. The procedure for removal of the old and laying in the new is the same as that for dots on the surface of the fingerboard. Use the flat file to smooth the sides of the fingerboard where the frets end and the dots have been laid in. With care, you can do this without marring the finish much.

You may want to refinish the fingerboard edges, or you may want to wax them after a light touchup sanding. Never use silicone wax, as it will make refinishing impossible should you decide to do so in the future. With a jeweler’s file or a file with a flat, noncutting edge (place the non cutting edge in contact with the fingerboard), using one or two light strokes only, file the tips of the fret at the edge of the fingerboard where the fret meets the fingerboard surface. The file should start at 45 degree angles to both the plane of the fingerboad and a parallel to the length of the fret. The file remains at a 45 degree angle with the plane of the fingerboard, but during the stroke its angle relative to the length of the fret changes from 45 degrees to 90 degrees. This action takes a little practice, but the end result is a fret with a smooth edge where the hand is likely to contact it.

To finish the frets, start with 220 paper (or 320 if you used a crowning file) and vigorously hand sand (no block, fingers gripping a small piece of sandpaper) each fret along its length to smooth the crown and remove nicks. When you are done with one grit, move up to the next finer, taking care to brush the fingerboard free of grit from the previous coarser sandpaper. This insures that a finer sandpaper will not drag a piece of detached coarse grit across the fret and mar the surface. Following the 600 grit paper, use 00 or 000 steel wool for the final finish. Brush off the neck, remove the tape and admire your handiwork.

Final steps

Apply a fresh coat of wax or polish, re-attach the neck and replace the nut. Since you have new frets you may have to adjust the height of the nut. You can remove material from the bottom of the nut or from the slots, or if you need to raise the height of the nut (more likely) you can shim it with slips of brass strip (to be found at hobby stores), or with drops of super glue on the bottom of the nut hardened and filled by dropping baking soda on it. File the baking-soda-super-glue filler with a jeweler’s file of an X-acto saw to get the right string height at the nut. You will probably have to adjust the bridge height too. Open a new set of strings, string it up and play!!

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Where to get Supplies

A fret saw, fret puller, weighted plastic or brass faced hammer, ruler marked off in hundredths of an inch, and fretwire can be obtained from Luthier’s Mercantile, Stewart McDonald, GHS, or any number of luthiers’s supply companies. A hand fret saw may be made by purchasing a good quality miter saw of approximately 0.023″ blade width and flattening the kerf (the waviness of the set of the teeth) carefully with a light hammer on an anvil or other flat surface.

The ruler in hundredths of an inch can usually be obtained at an art supply store or sometimes at a college book store (drafting classes!).

Jewelers files can be obtained from jewelry supply stores or good hardware stores.

Instead of a fret puller, you can grind the face of an end nipper (availableat a good hardware store) until the bevel of the cutting edges is ground away and the face is smooth and rounded. I have also heard of people using toenail clippers. The main thing is to have a flat or convex clipping face.