September 10, 2011 - ModGuitar Senior Editor
Mandolin Fret Dress and New Nut
I acquired this Fullerton “A” style mandolin a few years ago when one of the big retailers was closing out the brand. It’s a nice instrument overall, well constructed and for the price was a great way to learn some mandolin. What I’ve found lacking was the fret-work. So here we go, getting down to brass-tacks and doing a pretty thorough fret dress. What got me going on this was the nut developing a crack which made it necessary to craft a replacement.
Here you can see the nut, like a broken tooth, removed from the mandolin neck. Removing the nut makes an ideal situation for doing fret work, as the leveling files can go over the full length of the neck.
By sighting down the neck with the strings slackened and pulled aside, and the nut removed it’s pretty clear that there are some high frets which directly affect how low the action can be set. This becomes a major issue with a mandolin, as the frets are the smallest available, so that great care must be taken to only level them as much as necessary.
After an initial brush over with my leveling plane (an industrial diamond coated steel plate), it became clear that these frets had some very uneven tops. This was no quick fret dress.
Using my rocker file up and down and across the neck confirms this with the clear clacking sound as the file rocks back and forth when balanced over a high fret.
Using a sharpie I mark the tops of each fret, allowing the ink to dry before proceeding. Careful not to stain the binding or fret board with the ink. Another sweep across the whole fretting surface with a fine leveling plane reveals the high and low frets and the ink is worn off. This is work, observe and continue sort of process. Observing how the plane is removing material from the top of the frets guides me where to apply firmer pressure.
Unfortunately, a few frets were very high, and I had to move to a medium leveling file to get the frets leveled down evenly. This instrument is made in China and typically with this level of quality the frets are not made of the hardest form nickel-silver.
A soft paint brush is excellent for brushing the fret dust off. With a high quality instrument, (or a customer’s for that matter), greater care would be taken to mask off the instrument body to prevent the chance of scratches.
A triangular file with a single rounded edge is used to put a taper on the fret edges. These frets are pretty soft, so the final rounding is done with graduated grades of sandpaper.
An issue that came up as I worked through my various leveling files working down to the finest grade was that the frets are so small that none of my crowning files will work to give the frets the necessary angled side profiling after the tops are leveled. Ideally, the tops will be leveled, slightly rounded over, and the side tapered to create a finer point of contact for the strings. These keeps the notes accurate, and the tone clean without buzzes.
I put some extra pressure on the highest frets from the point where neck meets the body. This keeps the action low for the final set-up. There’s usually some slight rise in the fret board where the neck is glued in verses the part of the neck that is clear of the body. This mandolin doesn’t have an adjustable truss rod. Most likely there’s a plain steel rod set into the neck under the fingerboard to provide the rigidity to offset the pressure of the string tension.
Filing done, I move onto using sandpaper (grades 400, 800, and 1200) to put a bit of roundness on the top of the frets and polish them up to a bright gloss. Using finer and finer grades removes the scratches left by the former grade of paper. It’s important to work the frets over evenly, avoiding upsetting the delicate leveled state made during filing.
Once the sanding is done I use denatured alcohol to clean the fret board. You can see the kind of grime that comes off on the rag in the photo. I keep going back over it using the solvent until the rag comes away clean.
Denatured Alcohol is pretty safe to use, and not nearly as harmful (potentially) as harsher solvents, like naptha or benzine. Still, care should be taken to avoid using any solvents near open flames, smoking, pilot lights, etc. I follow the manufacture’s warnings on the solvent packaging, including working in a well ventilated area.
The denatured alcohol dries the fretboard surface, a well as removing any traces of waxes or other conditioners. To offset this I use either lemon oil or simply mineral oil to condition the board. This gives it a nice luster and protects the fret board from drying out too much.
Next the nut is cut from a scrap piece. And formed and fitted using files and sandpaper. It’s a back and forth process getting the shape just right.
Once the basic shape is formed, I use a feeler gauge with a grooved edge to very carefully cut the start of the new nut slots. While luthiers with busy shops might have a pattern for this, I do not, so the process takes some care to get it just right.
After cutting the nut slots using fine files to make them deeper the nut is then reshaped a bit and polished up before being fitted to the end of the neck permanently.
This mandolin is starting to shape up, the frets leveled, new nut, and now the bridge leveled and cutting fresh slots to space the strings evenly.
I use a soft faced hammer to tap the string grooves into the bridge. A few turns of the bridge adjustment nuts and the bridge height is set.
The bridge is set so that the feet are at the mid-points of the two cut-out F-holes. That’s it, ready to tune it up and try my hand at playing some mandolin.
This is the kind of work you can do yourself if you’re handy. This article glosses over the key steps in performing a fret-dress.