Repair Services

Most mandolins have traditionally had flat fingerboards as opposed to the arched or “radiused” fingerboards common on steel string guitars. Many modern players prefer an arched fingerboard on a mandolin too, so many new ones are made that way, and players sometimes have the flat fingerboards of their mandolins arched. That was the case with this one. When the current owner was buying the mandolin used, it was in need of some neck work that required a complete fret job. While the work was being done, he decided to have the fingerboard arched.
After playing the mandolin for a while, he concluded that he did not like the arched ‘board, and decided to have it restored to a flat ‘board.

While converting a flat ‘board to an arch is more common, here is the opposite job; converting an arched ‘board to flat.

Click on the thumbnail images to see larger ones.

Here’s the mandolin stripped down and ready for the work to begin.

Here’s the arch in the fingerboard. It must have been a very thick ‘board to start with because it is still thick enough to mill flat without becoming too thin. The fingerboard bindings are plenty wide, and I’ll try to mill the fingerboard down until it is flat and level across from the existing corners of the bindings. That way, I’ll have removed the minimal amount of material from the neck needed to accomplish the job.

To get started, I’ll pull out all the frets…

…and find my first “surprise”. The fret slots are very wide, with the frets glued into them. The slots are so wide that whoever put the frets in crimped the fret tangs to make them fit more tightly into the slots.
Notice also that the tangs are “nipped”, or cut back from the ends so that the fret beads can overhang the binding and extend the full width of the playing surface. I’ll be doing the same thing to the frets I’ll install.

I’ll have to glue these frets in the slots. The slots are too wide for driven of pressed frets to hold no matter how wavy I make the tangs, so I’ll just clean out the slots with a couple of home made tools…

…and check the fit of the fret stock that I plan to use. The tang is wide enough that the fret slips into the slot with finger pressure, but is tight enough to stay in place when I let go.  (You can see my slot cleaning tools in this picture.)

The slip fit of the fret wire into the slots is just about right for the epoxy method of installing frets, so that’s the method I’ll use.

Now begins the work of milling the fingerboard flat. If there were no pearl inlays, I would like to start with a block plane, but I don’t want to damage a plane iron on the pearl, so I’ll start with 60 grit sandpaper on a straight-milled sanding block.

I’m starting by sanding right in the center of the ‘board with long sanding strokes to maintain the straightness of the fingerboard surface.

I suspected from the beginning that I might loose some inlays by the time I got the center milled all the way down to the binding level. As you can see, the fingerboard is milled almost to the bindings in the area of the 12th fret, and the 15th fret inlay is sanding through.

Now I’ve milled the ‘board flat nearly to the binding level from the nut end to the 12th fret area, but the flat part doesn’t span to the bindings beyond that, and the sandpaper hasn’t even hit the surface past the 22nd fret. I’m glad to see that, actually. I want a little bit of “drop off” past the 12th fret to compensate for the upward deflection of the neck shaft caused by the pull of the strings.

Here at the other end of the neck there is still a little corner of wood that was rounded over a little too much when the ‘board was arched. I’m not worried about that. It won’t affect the frets, and furthermore, I’ve only sanded with 60 grit sandpaper so far, and I’ll be sanding with enough subsequent grits of paper that the little corner drop off will probably sand level. That’s also the reason you can still see the impression of the old frets in the binding. I’ve still got some sanding to go and I expect that to clean up before I’m done.

Here I’ve sanded the extender nearly flat using a method that I’ll explain later. There is a low corner here too, left from the arching procedure, but as I said above, there’s still plenty of sanding to do.
Notice the “bulls eye” look of the place where the inlay sanded away. The hole was drilled with a brad point drill bit; a type that cuts a clean edge on the hole, and has a center spur.

The hole left from their center spur will center my brad point bit when I drill a new hole to replace the inlay.

The inlay was a little closer to the 11th fret than the 12th, so my re-drilling chipped out a little bit or ebony into the fret slot. Here’s the new pearl dot lying in the drilled hole.

I plan to glue the dot into the hole with black superglue (cyanoacrylate), but I don’t want the glue to run into the fret slot through the chipped place. I found that a piece of plastic the thickness of a “pre-approved” credit card fits into the slot. It’s a little loose, but it will keep the slot open. It’s about the best use I’ve come up with for a credit card, but to be honest, this is a piece of an electronic hotel room key that I found, still in my wallet, after a trip. I throw those things in a drawer and use them for spreaders, scrapers, shims, and various other things around the shop.

The superglue is thin enough that I can just drool it around the edge of the dot and it will wick all the way under and fill the cavity.

I had my fingers crossed while I was replacing that inlay hoping the others would survive the remaining sanding without getting too thin but all the center ones ended up needing to be replaced.

I plucked the pearl out of the holes with a graver…

…drilled new holes and superglued new pearl dots into them.

Here is the method I used to sand the “drop off” of the extender. I put as many layers of masking tape as I needed across the fingerboard to tilt my sanding block to the right angle to mill the extender level from the end to about the 12th fret. I have sandpaper over half of the sanding block, and I’ll lay the bare end of the block on the masking tape “shim”.

To check my progress, I’ll draw some  cross-hatched pencil lines on the fingerboard…

…and sand with the masking tape shim in place.

When I see that the pencil lines have sanded away to about the area of the 12th fret, I know that things are shaping up about right.

When I get to about 220 grit sandpaper, I usually chamfer the edges of the fret slots slightly for a few reasons, some of which don’t really apply to this epoxy fret job. The chamfer allows room for the inside corner of the fret bead and tang where there is not a sharp 90 degree corner. That helps allow the frets to go in the slot completely. The chamfer helps frets start into the slot when being driven or pressed in a more “normal” fret job, and the chamfer may help avoid excessive chipping when frets that were driven or pressed are later removed.
Though it’s not really important on this job, I’ll go ahead and chamfer the slots slightly.

My tool of preference for the job is this checkering tool. It’s made for checkering gun stocks, but it works great for chamfering fret slots.

It has a replaceable, attachable burr that does the cutting. It can be mounted in the handle in either direction so it can cut on the push stroke or on the pull stroke. I prefer the pull stroke because it feels more controllable to me.

Here’s the size of the tool.

Now the ‘board is milled flat and sanded to 320 grit, the inlays are replaced, the slots are cleaned out and chamfered, and everything is ready for the new frets. I’ll be using epoxy to set the frets so I need to keep any excess from sticking to the surface of the board. I’ll coat the surface with wax. Notice the label says “pure carnauba wax in turpentine”. No mention of silicone. I wouldn’t use a silicone containing product because the residue can cause all manner of problems for repair people in the future.

I don’t want excess epoxy to stick to the fingerboard surface, but I do want the epoxy to stick to the ebony inside the fret slots, so I have to apply the wax to the fingerboard surface and keep it out of the slots.

This is wood dust, collected from under the table saw, rubbed and packed into the fret slots. Now I can rub wax on the surface with a rag with no worries.

Now the wax is dry and I need to get the dust back out of the slots. A shot of compressed air and the slots are clean.

I’ve mixed 24 hour cure epoxy (System Three) by weight rather than volume, and put some in a syringe so that I can “inject” the fret slots with epoxy. I’m wearing latex gloves because epoxy is a skin sensitizer and keeping it off of the skin is a good idea.

I’ve “injected” epoxy into all the fret slots and slipped all the frets into their slots.

In order to be sure that the frets are fully in the slots and as level as possible I’ll leave them clamped over night with a flat wooden caul. I put a piece of waxed tissue under the caul to make sure that it doesn’t get glued to the frets if it contacts any of the epoxy.

The following day I removed the clamps and caul.

Now I need to remove all the excess cured epoxy from the fingerboard. Because of the coat of wax, I can run the point of a slightly dull graver down the corner at the edge of each fret and “peel” the epoxy right off.

If I got sloppy and got a drop of epoxy on the waxed surface, a tool like this X-acto blade will lift it right off.

From here on out, the job is about like any normal fret job. I’ll clip off all the fret ends flush with the edge of the fingerboard…

..and file them to an angle a little steeper than 45 degrees right to the binding edge.

This is just a “formality” on this job, but if I had driven or pressed the frets in, I would use this little tool to check for high frets. It is part of a yard sale adjustable square with one edge shortened and the surfaces ground straight. There are three straight edges of three different lengths on the tool so that I can span three frets at a time from one end of the ‘board to the other. If the tool “rocks” anywhere, there is a high fret. Normally, I would drive it down level, but that is not an option with these glued frets. These turned out pretty level, with just a little bit of “rocking” on the frets on the extender.

With everything looking good and relatively level, I’m back to my sanding block and  some 320 grit paper to level the tops of the frets.

The frets were level enough that I had contact with all the frets from 1 to 12 with very little sanding, but remember the slight rocking I had with the straight edge tool on the extender? It was this fret right here. That’s why is shows a wider flat, reflective top surface than the others after sanding the tops level.

Now I’ve milled the tops of all the frets level. Actually, I have two planes of level frets; one from fret 1 to 12, and one from fret 12 to 24. (Remember the drop off I wanted at the extender to compensate for the neck pulling up?) My straight edge will rock slightly on the 12th fret, but nowhere else, so all is level, but I can’t just leave those flat fret tops. I have to re-crown the frets.

This re-crowning file is one of my favorites. It has replaceable burrs, and the one that is in it now fits this fret wire very well so I can quickly re-establish the nice round contour of the fret wire. Alternately, I could do this with a safe edge triangular file, (safe edge meaning the edge is ground smooth so it will not cut, and it can be run right against the instrument safely) but I know I have a good fit with this wire and this file, so I’ll use it.

I put a piece of masking tape at each side of the fret I’m filing so I won’t scratch the fingerboard if I slip off of the fret with the file.

Another thing I like about this file is the fact that I can “back drag” it, or pull it backwards over the fret in the direction that it doesn’t cut, and burnish the frets to a shiny surface. The frets to the right in the picture have been re-crowned and the frets to the left still show their white, reflective flat tops in this light.  That’s how I know when I’m done re-crowning the frets. I put a lamp on the other side of the neck so that the light reflects off of the flats making them easily visible, then I file until the flat just goes away, burnish the fret a little, and move on to the next one.

In order for the mandolin to feel smooth and comfortable to play, the ends of the frets have to be finished without any sharp edges or burrs. To finish the fret ends I start with a small safe edge flat file and round the corners where the fret meets the binding…

…so that they look like this.

That’s a “bondo” spreader I’m using to protect the top from any slips with the file. It’s meant for spreading body filler when repairing damaged car bodies, It’s tough and flexible, and I just tape it in place.

These are safe edge triangular files.

One of these is what I will use to finish rounding the fret ends…

… into sort of a bullet shape.

A good rub with 0000 steel wool, and the frets are clean and shiny, the remaining epoxy “fuzz” is gone, the wax is gone, and the fret ends are fairly smooth and bullet shaped with a small facet of the original filed angle on each one.

It’s ready for a new bone nut, a new bridge saddle, all the parts put back on, new strings and a set up.

I was going to show a picture or two of the completed instrument, strung up and ready to play, but the customer came and got it before I got around to taking the pictures! He was much happier with the flat fingerboard.