Liutaio Mottola Stringed Instrument Design



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Installing the Frets in a Fretted
Stringed Musical Instrument

After the neck is built but before it is finished is usually the best time to install the frets in the fingerboard of a fretted stringed musical instrument. This page contains instructions for installing frets on a new instrument. The operation can be performed using very basic tools, but there are a variety of special purpose tools that can help.

This page does not contain fret dressing operations. Rounding of fret ends, leveling, re-crowning, and polishing are generally left until after finish is applied to the neck.

Initially appeared: August 30, 2007
Last updated: Sunday, June 01, 2014

About the Fret Wire

The wire used to make modern instrument frets comes on a roll from the manufacturer. When you buy fret wire in small quantities it is usually just snipped off a larger roll. Here is about 50 feet of fret wire:

Some suppliers cut the wire into 1 foot lengths and straighten them out. I generally don't recommend buying it like this. The short lengths are wasteful – you always end up with pieces that are just a bit too short to make a fret. The other thing is, with the exception of classical guitars and some old style steel string guitars and mandolins, the fingerboards of the kinds of fretted instruments I make generally have a cambered playing surface, and it is a lot easier to install fret wire that has a bit of a curve to it on a cambered fretboard.

The wire is generally made of nickel silver, an alloy that, oddly enough, contains no silver. Nowadays you can also get beautiful gold colored fret wire and also fret wire made of stainless steel. The latter is very hard and holds up very well but is a lot tougher to shape when you are installing it. I don't recommend it for those making their first instruments.

Pieces of wire are simply snipped off the roll for use as frets. Here's a pile of pieces:

And here's a close up of a single piece:

The little raised bumps you see along the tang are barbs. These help hold the fret into its slot in the fretboard. Here's a diagram of the end view of fret wire showing the names of the parts of the fret and also its critical dimensions:

The width of the tang is fixed by the manufacturer, and is either 0.022" or 0.023", although it is possible to get wire with a thicker tang for special purposes. For all practical purposes for new instruments you'll use one of these two sizes, though. As there is only 1/1000th of an inch difference and as whatever tool you use to cut the fret slots is unlikely to be built to such a fine tolerance, you can consider these both to be the same size. Speaking of sizes, when you buy fret wire you can select from a variety of widths and heights. Used to be, certain sizes were “for” certain instruments, but these days there is a trend toward wide fret wire for just about all instruments. The general theory is that narrow wire provides better intonation but wears quickly, but in fact there are no credible formal studies which show the intonation is any worse when using wide wire.

Tools for Fret Installation

The minimum tool set needed to install frets includes safety glasses, flush cutting wire nippers, a sand bag, a small mill file, and a small hammer with which to bang the frets into the slots in the fretboard. The safety glasses are a must – you'll be nipping off many sharp little pieces of metal, and they tend to fly all over the place. The flush cutting nippers are available from the lutherie supply places, or you can buy a pair of hardware store nippers and grind the tops of the blades flat so they make a flush cut yourself. My recommendation for a hammer is to get a 1" dead blow hammer with urethane faces. You can use any old plastic face hammer though, as I am using in these pictures. Some folks use steel hammers with polished faces, but I don't recommend them (even though I used one for years) as they easily mar both the fret tops and the fingerboard if the blows don't land just right. The sand bag is needed to support the neck while you bang in the frets. Mine is made of a piece of the leg of an old pair of blue jeans. And you'll need the mill file or a purchased fret leveler file to file the fret ends after they are installed.

There are some other tools that will help a lot. A tool blade that can be used to clean out the fret slots is very handy. You can buy one ready made from the lutherie supply places, or make one out of an old hobby knife blade, box cutter blade, feeler gauge, or hacksaw blade. There are specialty pliers that make it easy to grab fret wire in case you want to bend it, but you can get by with regular pliers. If your fretboard will be bound, then you'll have to undercut the ends of the fret tangs (more on this is a bit) and a special nipper to do this is really nice to have. You can do this operation with flush cut nippers, but the cut isn't that clean and will require a lot of tedious cleaning up with a file or deburring tool, so I highly recommend the nippers.

There are also a variety of tools that allow you to press in the frets rather than hammer them in. I use an arbor press to do most of the frets myself, as you'll see in the following pictures. Arbor presses are cheap and the cauls to press frets are readily available from lutherie supply houses. There are also fret pressing pliers and clamps. Do keep in mind if you are thinking of investing in tools like this that you pretty much can't get around having to learn how to hammer in some frets (some you just can't get to with a press or other tool). These tools can make the job faster and more consistent, but for one or two instruments you may just want to use the hammer.

Preparing the Fret Wire for Use

Again, I recommend you buy fret wire on the roll. It will usually be covered with congealed forming oil and adhesive where the roll was taped together, and all this should be cleaned off before you begin. It is just as easy to clean up the whole roll at one time, using a rag and some naphtha. Pay particular attention to the edges that will sit right against the fingerboard when the fret is inserted in its slot, as this is an area that is hard to clean up once the fret is installed.

The next step is to cut off about as much wire as you'll need to fret an instrument. For a typical guitar or bass you'll need about 6' of wire.

After the wire is cut off the roll it will still be curved from when it was rolled up. Now it will have to be either curved a bit tighter or straightened a bit, depending on the radius of the fingerboard surface. From looking at the fretting tools in the lutherie supply catalogs you could get the impression that the radius of the fret wire should exactly match that of the fingerboard. In my experience, the fret wire should have a slightly tighter curve to it than the radius of the fretboard for both ease of installation and to keep the frets well seated. Also in my experience, the actual radius of the wire is not critical at all – just make it a little tighter than that of the fingerboard. It is very easy to bend / un-bend the wire a bit while it is still in one piece. You can do this with your hands. While I'm on this subject, please note that for just about all steel string guitars and basses, I never have to do this. I use the wire just as it comes off the roll.

After the wire is clean and properly curved it can be chopped up into fret length pieces. Make each piece a little longer (about 1/2") than necessary. If you have more wire than you need for a single instrument it is probably good to just nip off the number of pieces you need right now. It is far easier to store the wire on the roll than in little pieces.

Different Fret End Treatments

There are basically three types of fret installation, each identified by the treatment of the fret ends. The most basic is used for an unbound fingerboard. Here, the fret slots are sawed across the fingerboard and the ends of the fret tangs show along the sides of the fingerboard, like this:

For unbound fingerboards the fret wire is cut into fret length pieces as described above and no other work is needed to prepare the frets for installation.

Bound fingerboards are a bit different, and they come in two variations. In the variation I use, the fingerboard binding goes on after the fret slots are cut. This results in the fret slots stopping before the sides of the binding:

But the fret ends must come right to the edges of the binding. This means that the ends of the tang must be nipped off so that only the bead of the fret covers the binding. A fret with undercut tang ends looks like this:

The tang is just a bit shorter than the fret slot:

There are two ways to nip off the ends of the tang. The hard way it to use the flush cut nippers to chop off a bit if the tang. This always leaves a bit of ragged edge that must be cleaned up with files or with a machinist's deburring tool. The easy way to nip the tang ends is to use a special fret tang nipper tool, available from lutherie supply houses. These make a really clean cut.

You just insert the end of the fret and pull the handle to nip the end off the tang.

The third type of fret end treatment is used for the second type of fingerboard binding. In this type, the fingerboard is slotted, fretted, and then bound, so the frets do not extend all the way to the side edges of the fingerboard. The binding is glued on high, so its top surface is level with the tops of the frets. Then the binding is scraped down between the frets to the level of the fingerboard playing surface, leaving little humps of binding at the ends of the frets. I never use this method. It it really difficult to do a good job with wood binding, plus the strings invariably end up getting pressed down into those binding bumps when the instrument is played. I think it is better to have metal fret material all the way to the edges of the fingerboard.

Installing the Frets

The text which follows explains how to install frets over a bound fingerboard. If your fingerboard is unbound, then just skip those steps that involve cutting the tang ends.

The first step is to thoroughly clean out the fret slots. Vacuum these carefully and then use a tool to physically poke any debris out of the slots. Do this from both sides of each slot. If the fingerboard is unbound and there is a lot of debris in the slots, you may find that as you push the debris out of the slot at the end that you also pick off a chunk of the side of the fingerboard. If you do, save that chunk and after the slot is thoroughly clean you can crazy glue it back on. If there is a lot of debris it is generally a good idea to stop short of the slot ends and use your cleaning tool to lift the debris up out of the slot rather than forcing it out the end. And if you can use the tool to just loosen the debris and then vacuum it out so much the better.

If the fingerboard is bound then you can't push debris out the end of the fret slots because the binding is in the way. For bound fingerboards it is a good idea to be meticulous about cleaning the debris out of the slot near the binding as it tends to collect there unseen. Any debris in the slots can keep the frets from seating correctly, so doing a good job here pays off.

Now is an excellent time to double check that the slots are deep enough to accept the fret tangs. All that sanding to surface the fingerboard may have resulted in slots that are now too shallow. It that turns out to be the case and the fingerboard is unbound you can easily saw the slots a bit deeper now. If the fingerboard is bound you can probably gouge out one or two shallow slots with whatever tool you used to clean the slots, but if a lot of slots are too shallow it is best to remove the binding, re-saw the slots and then re-bind the board. It is also possible to route the slots deeper with a small router and micro end mill, but do keep in mind that such end mills are really fragile and wicked expensive and you're likely to break some doing this.

After the slots are cleaned of debris you can slightly chamfer the top edges of the fret slots by running a triangular needle file along each slot. If you do this on a bound fingerboard be careful not to file a groove in the binding.

Now the fingerboard is ready for fret installation and you have a pile of pieces of fret wire. If the fingerboard is bound then you'll need to cut the tangs off the ends of each piece as discussed above. When you do this try to not cut off too much of the tang – make it as long as possible, but so it will still fit into the slot.

Inserting each fret involves providing some support for the neck directly under the fret slot to be filled. Some necks, like those for electric guitars that bolt-on, are easy to support. You can just use a sand bag and slide the neck along the bag so the slot you are currently working on is well supported. Things get a bit trickier for steel string guitar necks. When installing frets over the heel you'll need to support the end of the heel in such a way that it doesn't get damaged by the hammering. And when installing frets over the fingerboard extension you'll need to carefully support the underside of the extension to avoid breaking it right off when hammering. For these necks I generally use the sandbag under the neck shaft when installing those frets over the shaft.

For the frets over the heel I generally just sit the heel on top of a thin router pad on the workbench.

When installing the frets over the fingerboard extension I'll put two small pieces of MDF at the edge of the bench and place the fingerboard extension on top of them so that the heel is off the front of the bench. I use two pieces because on a lot of acoustics the adjustment for the trussrod sticks out of the heel. The space between the two pieces leaves room for the trussrod.

Perhaps the toughest instruments to install frets on are classical guitars, since the frets usually must be installed on the fully assembled instrument. This makes supporting the underside of the fingerboard extension difficult. There are two standard techniques for dealing with this. The first is to use a fret installation buck, which is a massive hunk of iron that you can slip into the instrument through the sound hole and hold under the fingerboard while you pound in the frets over it. I'm not a big fan of this solution. You can buy these but they are expensive and may have to be modified to deal with your instrument's neck block and transverse bracing arrangement. The other way to install these frets is to modify a bar clamp with an arbor and fret installation caul so that you can press the frets in. You can buy such fret installation clamps ready made from lutherie supply houses.

It is always best to figure out just how you are going to support the neck/fingerboard under each fret before installing any of them. If you only make one kind of instrument you will quickly assemble a collection of all the necessary cauls and supports. If you make different kinds of instruments you'll learn to be very clever about making temporary supports out of scrap pieces.

Now for the actual installation. It is pretty simple to hammer in the frets, but it is one of those operations that is a bit awkward at first. One tip about hammering. Most folks' only experience comes from hammering in nails, where the idea is to be able to pound the suckers in with as few macho whacks as possible. A bit more finesse is required here and in general a lot of small taps work better than trying to bludgeon the fret in with a couple of crushing blows.

To get the fret started, hold it in position with one hand and tap it down on one end to get the tang started in the slot. Once the tang is seated on one side you can get your fingers out of the way so you can drive the fret in all along its length.

I'm left handed so I start on the left side but start on whatever side is comfortable. Now start tapping and moving the hammer with each tap toward the other side of the fret. You should see the fret going deeper into the slot with each tap. If the end that you started with starts to pop out, go back and hammer it back down and start over again, tapping along the length of the fret. Once you get to the other end, reverse direction and tap back to the original end. Keeping going back and forth until the fret is firmly seated in the slot. If at any time an end pops out or starts to pop out, knock it back in and then proceed with hammering from that end. It doesn't take long to get the hang of this, and once you do you'll automatically start to increase the strength of your blows, so you'll be able to do a fret with less taps and in much less time. This is one of those mechanical skills where it doesn't take too long to become an expert.

Problems with frets not staying in are almost always caused by one of the following:

  1. The fret not being originally bent a little tighter than the radius of the fingerboard. If the fret is originally curved shallower than the fingerboard it is tough to get the ends to stay in;
  2. Lack of solid support under the neck, directly under where you are hammering;
  3. Junk in the slot;
  4. Pounding too hard;

Note that if you read other instructions for hammering in frets you'll probably find that not everyone suggests the same chasing back and forth method that I describe here. Some folks consider the technique used to hammer frets in to be absolutely critical to a good fret installation job. But lacking any real formal research into whether any one hammering method is better than any other I assume that they are all just as good, and describe here the method that seems to be the easiest for folks to pick up.

Frets should be pounded in one at a time. After you are done, take a good look at the fret along its length from both sides to be sure it is well seated and fully in contact with the surface of the fingerboard. Also take a look at the frets that have already been installed that are near the one you just put in. These sometimes pop up too, especially on the fingerboard extension, which is quite flexible. If a fret is not fully seated, pound some more. Pay particular attention to the ends of the frets. If a fret won't go in all the way, look at it carefully while you are hammering it at that spot. If the hammer blows seat it, but it springs back out, try chasing the hammer blows from side to side from that spot to attempt to straighten the length of the fret. If that doesn't work you can either remove the fret using flush ground nippers, cut a new piece of wire and try again; or you can glue down the offending spot with thin cyanoacrylate glue. The tiniest drop at the gap will wick under the fret and into the slot and a quick clamping will secure it for the minute it takes for the glue to dry.

Note that it is a lot harder to hammer frets into an ebony fingerboard than into one made of any other material. All the frustrations of learning how to hammer in frets are compounded when you have an ebony board, so learning your technique on a rosewood board may be a lot more satisfying.

If a fret won't go all the way in and hammer blows at that spot won't seat it at all, then there is debris in the slot or the slot is too shallow. In either case the fret will have to be removed and the problem corrected before you can try again, always using a new piece of fret wire.

Classical guitars and some others too have the end of the fingerboard cut to match the perimeter of the soundhole. This means the last fret is split. It is actually a bit tricky to cut the soundhole ends of these half frets. These have to be cut at a severe angle, and using fret nippers horizontally tends to mash up the tang. I usually prepare these pieces before the fingerboard is attached. The first step is cutting back the tang at one end of a length of fretwire.

Click to enlarge

Then the piece is positioned with the tang-less end over the soundhole. If the fingerboard is off the instrument as in the picture you can position the fret nippers right up against the fingerboard end and cut the fret end off.

Click to enlarge

If the fingerboard is attached to the guitar just mark the cut and then take the fretwire away to make the cut. The other fret half is done in the same manner. Note that if you are installing these pieces on an installed fretboard, you'll have to use a modified clamp and caul to clamp them into their slots. There is just no way to support the wood well enough to hammer these in without risk of damage to the top. Once the half frets are installed the soundhole ends are ground or sanded flush with the end of the fingerboard.

As mentioned earlier, I actually install all frets on electric guitar and bass necks and all but the frets directly over the heel on acoustic guitars using an arbor press. The rig looks like this:

The press has a shaped caul that presses the fret into the slot in one motion. The neck is supported under the shaft by a shaped, cork-lined tray (shown) and by a piece of MDF when pressing in the frets over the fingerboard extension. The technique here is pretty simple. Each fret is first started in its slot by tapping one end in with the hammer. Then the fret is positioned under the press and pressed in.

You can exert a lot of pressure with an arbor press, so care must be taken to keep from crushing the top surface of the fingerboard. You also need to be sure the tang is well started before you attempt to press it the rest of the way in. If it is not well started the press can tip the fret out of the slot and crush one of the sharp edges into the surface of the fingerboard, putting a gouge in it that will take some work to scrape out.

After each fret is installed (no matter how you install it) the fret ends should be nipped with flush cutting end nippers. You can certainly do this all at once, after all frets are installed, but it makes it a lot easier to handle the neck during fret installation if it doesn't have all of those sharp little fret ends sticking out all over the place.

Filing and Beveling Fret Ends

The ends of the frets are kind of sharp and jagged, so the next step is to file them flush with the sides of the fingerboard. You can use any flat mill file for this, or you can break the tang off a small mill file and glue a wood handle onto one face to make a fret end filing tool. You can buy such a thing from the lutherie supply places, too. Here's a picture of a regular mill file and a purchased fret end file:

Both work fine, but the file glued to the block is much easier to handle. Filing the fret ends is easy and quick. Just hold the file flat to the side of the fingerboard and start filing.

Now, you just want to file the fret ends flush with the fingerboard sides – you don't want to actually file the fingerboard. Luckily, mill files don't work too well when they are in broad contact with a flat surface like the side of the fingerboard so there is little chance of abrading the wood. But if you do, it can always be cleaned up with a little sandpapering. It's actually very easy to know when you are no longer filing fret wire and are in contact with the wood. While you are filing the fret ends you can feel the file chattering in your hand as it crosses over the fret ends, and it makes a kind of chirpy sound while it does it. Once the fret ends are flush with the fretboard sides both the chattering sensation and the chirpy sound stop.

After the ends are filed flush, they are filed again, this time to put a slight bevel on the fret ends. The operation is the same as filing the ends flush, only the file is held at a slight angle.

In this picture I am greatly exaggerating the angle to hold the file. I'm doing this just so it is clear when looking at the picture that the file is held at an angle. In reality, you'll want to hold the file at a very slight angle, about 15º. Beveling too steeply makes for an instrument that is difficult to play – it is too easy to bend the string right off the side of the fret if the bevel is too steep. Just a bit of bevel will do it.

Now, here you do have to be careful not to file the wood. The file is coming down on the edge of the fingerboard and you don't want to file a flat here. Again, feel the way the file feels and listen to the sound it makes as you file. When the chattering and chirping stop, stop filing.

Filling Fret Slot Ends

The fret slots in the fingerboard were sawed a little deeper than the depth of the tang of the fretwire. If the fingerboard is not bound, then you can see the holes under each fret end.

Click to enlarge

These holes need to be filled with some putty that matches the wood of the fingerboard. I use a putty made from fine sanding dust of the same species as the fingerboard, mixed with wood glue.

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I keep little cans of sanding dust for all the common wood species used in lutherie handy. These are useful for all sorts of wood filling applications.

The holes at the fret slot ends are filled with putty.

Click to enlarge

Most of the excess is wiped off now, but don't try to get it too neat. After the putty is dry the sides of the fingerboard can be sanded smooth with 150 grit sandpaper. This levels the putty fill and also smooths the ends of the frets in preparation for fret dressing.

That's basically it for fret installation. The frets still need to be dressed, but this step is best left until after there is finish on the neck.