The preface blogpost for this article tells general readers something about how my experience installing frets with epoxy began and what the advantages of this strategy are.  What follows are the technical details luthiers will need to install frets with epoxy the way I do it.

You will need—

• Dremel Rotary Tool-with-router base and a 1/16” collet.
• Carbide dental burs #FG556 and #FG557.
• Fretting saw, .025” kerf.
• Mold release agent: Meguiar’s Mirror Glaze #8 Mold Release Wax
• *Two infrared lamps, 250W.
• *Two adjustable lighting fixtures for the infrared lamps. The company that made mine years ago no longer makes the same model I have.  The main features needed are the ability to handle 250W safely and adjustability to put the lamps the right distance from the fingerboard. This dock light from Grainger could be a good alternative.
• *A mechanical one-hour timer for the infrared lamps, wired to a two-plug outlet. That’s a necessity so you don’t walk out of your workshop and forget to turn the lamps off.
• Epoxy & hardener: System Three epoxy and Fast hardener; plunger pump set for dispensing the ingredients; 12 oz. graduated paper cups for measuring & mixing.
• Hypodermic syringes: Exel 26218 Luer Lock Syringe & Needle, 5cc, 21G x 1 1/4″ (box 100). This needle size fits perfectly into the slot cut with the #FG557 dental bur.
• Fret Bender and/or Fret Bending Pliers. The fret bender is the fastest and most precise way to get a perfect radius in a piece of straightened fretwire but won’t straighten fretwire cut out of a coil. Of the two tools, the fret bending pliers are the indispensable one.
• Clamps: See this picture for the ones you will need.
• 6″ Stainless Steel Pocket Ruler,  You can probably find a similar tool locally.

*The infrared lamp setup is optional, and represents a substantial expense; the consequence of omitting it is that you will have to leave the clamps in place for 18-24 hours for complete curing to take place on its own.

Tools you will need to make (or may already have)—

• A stand for the loaded hypodermic syringe. This will help get the mixing bubbles to rise to the plunger end and provide a place to collect stray drips of epoxy from the syringe.
• Fret organizer: Once the epoxy is mixed and in the syringe, you will need to work quickly; there won’t be time to fuss around with measuring and cutting each fret.
• Retainer bars, spacer and caul for holding the frets in place while the epoxy cures. These pictures will show you what mine look like.
• Padded cauls for the neck for clamping the retainer bars to the fingerboard.
• Other cauls for clamping the retainer bars to the fingerboard area that passes over the soundboard. What you will need will depend on the inside soundboard structure in this area.

Let’s start with your fretless but slotted fingerboard, installed on the guitar. If you are doing a refret on an existing guitar, you will need to first clean the glue out of the empty fret slots.

So, we’ll get right into one of the crucial steps in epoxy fretting: using the Dremel router. (Your startup slots, less the glue, will probably be .025”-.028”, but they will eventually need to be larger to accept epoxy-installed frets.) You will need the carbide dental bur #FG556 to clean out the glue and enlarge the slot width to about 1/32” (.9mm).

Install the bur so that it extends >1/16” from the bottom of the Dremel base. Make a startup cut at the near end of the slot about ¼”, pushing the router into the slot. Then starting at the far end, rout the entire slot, pulling the router toward you. (The purpose of the startup cut is to avoid pulling an ebony chip from the slot end.) If you run into heavy resistance, slow down; it is possible to overheat and break one of these burs. Also, be careful to pull the router toward you in a straight line with the slot; carelessness here can result in the bur wandering outside the slot, especially if the bur is new and sharp. This step looks like this—

You’re now ready to true the fingerboard to the stage of rough-sanded. If you’re fretting a new guitar, you should be at this stage as well, with the neck carved and rough-sanded.

After truing the fingerboard, measure all the slots to see which ones are <1/16” deep. These will need to be deepened with a fret saw, and then re-routed with the #FG556 bur to even out the cut of the slot. Do not try to deepen the slot using the bur; this bur is much more effective removing fingerboard material from the slot sides than from the bottom.

After deepening the slots, you need to test the fit of the frets you will be installing. A fret tang should slip into the slot with no resistance from the barbs but with minimal excess slot width so that the final installation will be kept true to scale. If you’re fretting a guitar, it’s very likely that the slots cut with the #FG556 bur will be too small to meet that standard. If so, you will need to re-rout the slots using the carbide dental bur #FG557; this will enlarge the slot to about 1mm.  (Click here to read about an alternative to Dremel-cutting fret slots.)

At this point, you should final-sand the trued fingerboard and blow-clean the slots.

Taping the fingerboard for epoxy drooling—

• To tape the fingerboard edge frets 1-11—
  Use 1-3/8″ tape. Before applying the tape, fold the outer edge of the tape (ca 1/2″) sticky side back on itself .
  Apply the tape so its edge is exactly even with the bottoms of the slots.
  After the tape is applied to the fingerboard, bend the fold-back 90° in order to create a ledge to collect any epoxy that drools out of the fret slot end.
• To tape the fingerboard edge over the SB corner—
  Install a plastic full-coverage SB protector with open spaces at the SB/FB corners.
  Apply 1-3/8″ green tape up to ca 1/4″ away from the FB edge.
  Apply 3/4″ green tape to the FB edge. Apply the tape so its edge is exactly even with the bottoms of the slots.
  Apply a 3/4″x1-1/2″ strip of tape to the FB/soundhole edge to retain epoxy at the 19f.
  Make sure the tapes over the FB/SB corners are securely pressed onto the FB edge to prevent epoxy leaking behind the tape onto the SB.

Your finished result should look something like this—

Here the frets are already installed and the epoxy cured, so you can see how the tapes restrained the drool.

Preparing the fingerboard surface—

We want the frets to fasten hard into the fingerboard, but we sure do want to get rid of the excess epoxy when it’s all cured.  That’s where the mold release agent comes in.  This is a material that’s used widely in the fiberglass reinforced plastics industry, and it repels excess fretting epoxy very effectively.

Using a 2”x2” four-folded square of cloth, apply a small amount of it to the entire fingerboard surface, using strokes parallel to the slots to minimize the amount deposited in the slots themselves. Be sure to cover the fingerboard edges above the tape line, too. When you’re done, leave it alone; don’t polish away the excess with a clean cloth or towel. You will, however, need to remove the little bit of material that ended up in the edges of the slots. I find that the end of my pocket ruler works perfectly for this. Now is the time to install the piece of tape on the fingerboard/soundhole edge to restrain the epoxy from fret #19.

Preparing the frets—

As you know by now, my epoxy fretting strategy dispenses with hammering or any kind of pressure to force the fret into the slot. In fact, when the frets are in place and ready for epoxy curing, each fret is held against the fingerboard surface at only two points, each about 1/3 the distance from the end of the fret end, with just enough pressure to keep the entire fret flush with the fingerboard surface. To make this work, each fret should have a tiny bit more radius than the fingerboard. This will assure that the fret ends are all the way into the slots; the cured epoxy will assure that they stay that way.

If you’re starting with straightened fretwire, the fret bender can be a time saver. The job can be done with the fret bending pliers, but it requires some additional labor though a lot less than if you try to bend by hand. If your fretwire comes in a coil that has too much radius—likely if you’re fretting a classical guitar—your best bet is probably to use the fret bending pliers to reduce the radius unless you have enough production to make it worthwhile to make your own fretwire straightener. Matching the radius of the fingerboard is more critical if you’re using much stiffer stainless steel fretwire.

Never mix batches of fretwire on a guitar; you’re better off trashing a remnant of a batch that’s insufficient for an entire instrument.  I once mixed two batches where the crown height was a tiny bit different and ended up having to refret the whole fingerboard before it was all over.

The frets need to be coated with mold release agent, on the crowns only, to prevent epoxy adhesion. I prefer to do this to individual cut/bent frets to help avoid rubbing the material off.

Installing the frets—

Here are pictures of my syringe stand—

It’s easy to make and useful. When the job is done, remove the tape with the epoxy drippings and discard.

Here’s a picture of my fret organizer—

This picture of the fret installation showing the epoxy curing under the heat lamps also shows the assembly of clamps I use.

he black ones around the 12f area are 8″ Quick-Grip clamps.  It’s a good idea to have them assembled and close at hand to quickly apply them after the frets are in place.

The picture below shows the components of the clamping assembly I’m currently using: 1/4″ steel bars, the spacer for installing the bars and the caul for clamping.  The Ebony caul helps conduct curing heat to the fretwork.  It’s a good idea to treat the spacer with mold release agent in case you forget to remove it while the fretwork is curing.

Prepare a syringe by snipping the needle to 3/8″ long; grind the end to remove the crimping, and poke the end of the needle with a pin to clear the opening.

Mix 9ml epoxy (6ml resin/3ml hardener) in a paper cup; stir thoroughly.  Pour 5ml of the mix into the syringe, and invert the syringe to push out the air.  Put the syringe in the stand for 3-4 minutes to let the air bubbles rise toward the plunger.

There seem to be mixed opinions about epoxy shelf life.  The manufacturer of System Three epoxy claims that “[a]ll solvent-free epoxies have essentially unlimited shelf lives so long as they are stored in sealed containers. The resin may crystallize or the hardener may darken but this does not affect its performance” but then hastens to add, “[i]f the material is more than a year old do a test to satisfy yourself that it cures properly.”  I once used some System Three epoxy I could verify to be 3-1/2 years old and to have been kept sealed.  It hardened fully, finally, but it took many days even after the usual hour-long infrared exposure, and the initial setup was much slower which resulted in more than usual drooling.  So now I make it a practice to replace all epoxy more than a year old.

One characteristic of the epoxy/hardener mix that need always be kept in mind: the process of catalysis is exothermic.  That means that the process itself generates its own heat.  What’s more, this exothermia is indirectly proportional to the surface area and directly proportional to the bulk of the mix.  Practically speaking, our epoxy will cure most rapidly if left in the cup, less rapidly when in the syringe and most slowly when in the slots with the frets.  That’s why it’s crucial to get the mix into the syringe immediately after mixing.  Once it’s in the syringe, you can count on approximately 20 minutes working time to get the frets installed.

Using the syringe, inject epoxy into the slot from one end to the other; the slot should be brimming with epoxy plus a little more.  Immediately insert the fret, and push it all the way into the slot with a wood block applied to the center of the fret to wet out the full length of the fret tang.  Do this for each fret, one at a time.  Do not try to apply epoxy to all or even several slots and then install frets; this will allow some of the epoxy to drain out of the slots.  Here’s a picture of this operation.  (In the background you can see my workbench on wheels with all the clamps and related gear assembled and ready to go.)—

Once the frets are in place, install the bar assembly using masking tape to temporarily hold the bars in place while you apply the caul and clamps; the spacer, which was in place between the bars to hold them in position, should be slid out at the 19f end after the tape is applied.  When you’re done and ready to apply clamps, it should look something like this—

Now it’s time to apply the clamps.  Place the caul over the bars, leaving the spacing tapes in place.  I do this while the guitar is in a horizontal body vise.  When this is done, move the entire assemblage the table where the curing lamp setup is.  There’s no reason it couldn’t be left in the body vise or wherever you do your claimping, but whatever you do it’s crucial that the fingerboard be as level as possible to minimize running epoxy in the pre-cured state; shims, adjustments in the body vise, etc.  Also I like to give all the fret ends a little press with a wood block to make sure they’re all flush with the slot ends.

When epoxy cure is complete, remove all the epoxy drool tape.  This works best if you first snip and rough-bevel the fretends.

Now it’s time to remove the beads of excess epoxy on the side of each fret.   This is done with a chisel-tip tool, starting at one end of the fret to loosen the bead and moving the knife under the bead to the other end.  It should looks like this—

If your mold release agent is working like it should, each bead should flip right off in one piece with a single stroke of the knife.

There, you’re done.  The rest of the fretwork can be completed with the usual techniques except for one thing: when leveling the crowns, work lightly with your leveling tool, keeping an eye on progress under reflected light.  You’ll be amazed at how little material need be removed to get perfect leveling.

Update: Alternative to Dremel-cut Fret Slots—

Since this article was first posted, California luthier David Schramm has presented an alternative that dispenses with Dremel-re-cut fret slots.  His alternative entails the use of a Fret Barber to remove a small amount of the tang on the frets so they will fit easily into a standard-width slot.  The device looks like this image on the left.

I was a bit skeptical at first when David told me he was going to try this variation.  I was concerned that reducing the tangs might reduce the “grip” of the frets and make them unstable.  The more I thought about it, however, the better the idea seemed: the hardened epoxy forms a solid casting all around the tang of the fret; it would seem that it really shouldn’t take much barb extension for the fret to have a solid lock in the slot.  (For traditionally installed frets that rely on the tang gripping to fingerboard wood on the sides of the slot, I would still be skeptical of fret “barbering.”.)

Since then David has tried it on at least two guitars and avers that it works very well…presumably no evidence of fret instability.  I’m sufficiently convinced of the merit of his variation that I will probably try it myself on my next guitar.  For luthiers just starting to fret with epoxy, omitting a few steps and avoiding additional capital investment would certainly be a worthwhile benefit.

Update2: Eliminate Infra-red Cure—

In recent times, since I published this article, I have eliminated infra-red curing of the epoxy when installing frets with epoxy.  The System Three epoxy I have found most suitable in all other respects for this task tends to get very runny when warmed during cure, making it more difficult to control unwanted drooling.

System Three epoxy with Fast hardener will cure overnight to just the right hardness for removal of the epoxy beads from the frets; longer cure will make the epoxy even harder, but this can make the beads a little more difficult to remove.

Your epoxy should be fresh, not more than a year old.  (Not long ago I did a fret job with S3 epoxy that was 2+ years old; it cured to optimal hardness, but it took 3-4 days to get there.)