Repair Services

This is a 1950s Martin 000-28. The owner brought it in because it was too difficult to play. The problem was the neck angle. Though the neck had been re-set before in this guitar, the action was uncomfortably high and my straight edge confirmed that the neck angle was not right and another neck re-set was needed.

In “the old days”, it was common practice to saw through the fingerboard at the fret slot where the neck joins the body of a guitar and remove the part of the fingerboard that extends over the body of the guitar. Unfortunately, that’s what had been done to this one.

I removed the sawn off part of the fingerboard using a heat lamp and a putty knife and steamed the dovetail joint to remove the neck from the guitar.

Whoever did the previous neck re-set used paper to shim the dovetail…

…so I used a chisel to clean up the paper and old glue in the head block and on the neck.

After cleaning up the  glue surfaces and correcting the neck angle by shaving wood from the heel of the neck I glued and clamped these mahogany shims to the neck dovetail so that I had plenty of material to  assure a good fit in the joint.

I’m going to chalk fit the dovetail. I’ll rub white chalk (pastel, from an art store) in the mortise of the head block and push the neck into place. Chalk will transfer from one surface to the other and show where there is contact between the pieces. Here’s my starting point. There’s only a little bit of transfer of the chalk to the tenon of the neck.

Removing wood from the tenon where the chalk transfers (indicating contact) improves the fit of the dovetail as the neck approaches it’s proper position in the head block. Here it is partially done.

Here’s what it looks like when it is properly fit. There is chalk transfer nearly everywhere on the tenon (the other side too) and the neck fits into the head block to the correct depth when the dovetail tightens.

Some hot hide glue on the dovetail, clamp the joint, and the neck re-set is done.

The frets on the guitar were badly worn, so I re-fretted the neck. That gave me a chance to plane the fingerboard, something that usually improves the playability after a neck re-set, and also gave me a better chance at getting the sawn off part of the fingerboard level with the rest of the ‘board. It was a pretty standard re-fret other than the sawn-off fingerboard extender. I took the opportunity to drive the frets into the extender while it was still off of the guitar so I could lay it on a solid surface while driving the frets, then glued it back into position. That left one empty fret slot; the one where the ‘board was sawn in two.

Since the fret slot is a saw kerf that goes all the way through the fingerboard, a driven fret might not hold well because it is essentially  pinched between two pieces of ebony rather than driven into a slot. To help assure that the fret will stay in position I put some glue in the slot…

…and drove the fret in with a snug but not tight fit.

After leveling and re-crowning the frets I moved on to setting the guitar up with a new bone nut and saddle. I prepared a bone nut blank and fit it to the nut slot, then used my half pencil…

…to mark the height of the frets on the “front” surface of the nut blank.

This line gives me a “target” for starting the string slots. If I file the slots almost to the line I know they’re close to final depth but not too deep.

To space the string slots I start by marking the position of the two outside strings with the nut blank in place… (These are usually about 1/8″ in from the edge of the fingerboard on the bass side and about 3/32″ on the treble side.)

…then, using this string spacing rule, mark the position of the other strings. Here, I’ve found the slots that line up with the marks on the nut blank. I’ll mark those two slots with a pencil. The space between these slots is graduated so that, by keeping the ruler correctly oriented with the bass end and treble end of the nut, I’ll have graduated spacing between the string centers. The bass strings will be wider and the treble strings will be narrower. Since the bass strings are larger, the spacing between strings will be more even by having the center spacing graduated.

Here, I’ve marked through the slots to locate the other strings on the nut. A drafting pencil will fit right in the slots in the rule, and by placing the rule over the top surface of the nut blank with with those two marked slots right over my two starting marks on the nut, I have my string spacing established.

I’ve learned that I can’t seem to file the nut slots straight down into the nut, so even when I start filing the slots right on my marks, there’s no guarantee that I’ll have even string spacing when I’m done because my slots can wander left or right as I file into the nut material. To keep my spacing correct I’ve learned to mark the face of the nut that contacts the end of the fingerboard too.

I use the same slots in the string spacing rule, lined up with my marks on the top surface of the nut, and simply continue the lines down the “front” face of the nut.

Here I am making a shallow notch at each pencil mark with a razor saw. These notches will help me start filing the string slots in the right place.

I’m using gauged nut files here. They cut round-bottomed slots the correct size for each string. I have a set of these so I can use a file that is a good size for each string.
I’m keeping track of three different things as I file the slots.
1. The angle of the slot is about halfway between the plane of the fingerboard and the plane of the peghead.

2. The angle of the slot is about halfway between the angle of the string going to the bridge and the string going to the tuner.

3. I’m keeping the slot on the lines that I’ve drawn on the “front” edge of the nut by angling the file if I need to.

It is, after all, the bottom of the slots that locates and correctly spaces the strings, so a slightly diagonal slot, like a couple of these, makes no difference to the string spacing. The diagonal slots are there because I saw that I was off the mark as the slot was starting so I angled the file to get the bottom of the slot on the line.

Now the nut slots are cut almost to the line that was drawn with the half pencil that indicates the level of the fret tops, and the nut is in place.

I’ll string the guitar and adjust the final depth of the slots for correct string height over the frets, so now we’ll move to the bridge saddle.

Someone has replaced the bridge on this guitar with one that has a saddle slot with “stops” at the ends. The original Martin bridge would have had a “through saddle”, meaning that the slot for the saddle would have been a flat-bottomed slot extending right through the center part of the bridge and out over the wings of the bridge rather than a slot, like this one, that stops right before it runs out of the wings of the bridge.  In some ways, this is a better design, and the bridge is of good quality and in good shape, so I’m leaving it there. This type of saddle slot makes the bridge look very much like an original “through saddle” bridge when the guitar is set up. I’ve prepared a bone saddle blank that fits snugly, but not tight, in the slot, and is the right length to just fit inside the stops in the ends of the slot.

I’ve crowned the top of the saddle blank lengthwise to match the radius of the fingerboard, and also rounded the top edge much like a fret so that the strings will have a definite, buzz-free, bearing surface where they leave the saddle.
Here’s the guitar strung up and ready for adjustments to the action height.

Back to the nut, for now. Although it really doesn’t make much difference if the string height is adjusted at the nut or saddle first, I usually do the nut first because it is unaffected by the saddle height.
Here are the strings sitting deep in their slots. I’m filing each slot, one at a time, to the correct string height determined by pressing the string down at the 3rd fret and essentially using the string as a straight edge between the nut and the second fret. When there is only minimal clearance over the first fret, the height is right.

With the string height adjusted at the nut, I can measure the height of the strings at the 12th fret to determine how much material I need to remove from the saddle. I’ll decide on a target string height, measure the actual height, and subtract the target height from the actual height for each E-string to get the amount the strings need to be lowered. Because the 12th fret is the halfway point of the strings, I need to remove twice that amount from the saddle to get to the target height. This one started out with the action 1/16″ too high all the way across the strings, so I measured 1/8″ from the bottom of the saddle at each end…

…drew a line connecting the two marks…

…and cut off the bottom of the saddle right to the mark.

I put the saddle back in the bridge and rechecked the height. I found the height to be just what I wanted.

Now the string height is correct at the nut and the saddle, it’s time to make the bone pieces look good.
I ground down the top of the nut until the string slots were a little deeper than half the diameter of the strings and filed away all the sharp corners…

…then sanded and buffed it for a nice polished appearance.

The saddle, I sanded smooth and cut the ends to sweep up gracefully from the wings of the bridge. The look is very much like the original bridge would have looked, the saddle height is 1/8″ (generally considered optimal) and the guitar’s action is low.
The bridge looks like this,…

the nut looks like this…

…and the guitar now has a good neck angle, low action, new frets, new bone nut and new bone saddle. It plays “like buttah”!