Jonathan Edwards’ Martin D12-35
The guitar in the post was brought to us by American Singer/Songwriter Jonathan Edwards, who you may know from such hits as “Sunshine” and “Shanty”, both from his 1971 debut album. In regards to this repair, Edwards stated:
“…it’s the first one I pick up at home and on-stage. It plays as smooth and as easy as any of my six-strings and sounds big and bright and better than it ever has.”
His full take can be found on our reviews page. Read on to see the repair process!
A few months ago, we were brought this lovely early '60's Martin D12-35 by the singer/songwriter Jonathan Edwards. This guitar needed a lot of work to get it back into good working condition.
For our acoustic setup specs, we like to see a clearance at the 12th fret of 6/64" between the fret and the bottom of the lowest string. Here you can see that when the guitar came to us, it was twice this distance!
As mentioned in previous posts about acoustic setups, when a straight edge is placed on top of the frets and extended to the bridge, it should sit just above the top of the bridge but, here you can see that it is much lower than where it should be. Both this and the previous measurements are evidence that guitar is desperate need of a neck reset.
This guitar also does not have an adjustable truss rod so, one of the things we have to work out is the neck relief. We start by placing a notched straight edge on the fretboard which gives us an idea of how level the playing surfaces is from headstock to body, while not ignoring the frets themselves.
Without an adjustable truss rod, we like to plan for 0.007-0.010" of relief. Here you can see that we are measuring 0.024" which is far too much and will need to be corrected.
In addition to the issues with the neck, the bridge has begun lifting away from the body, evidenced here by a piece of paper sliding underneath, even without the tension of the strings on it.
The first thing we do is apply heat to the bridge. This will loosen the glue to allow us to remove the old bridge, which is being replaced.
Since the guitar is also getting a full refret, we then pull all of the old frets from the board.
After we have done this, we put the guitar into our neck jig. In this stage we will be using the jig to reintroduce the effects of string tension on the neck to correct the relief issue mentioned previously.
We reduce the pressure on the neck to get a relief measurement of 0.016" before sanding.
By sanding the board flat at this pressure, once the guitar has strings back on it, the relief should be 0.008", which is within the parameters we mentioned earlier.
Once the prep work is done on the fretboard, small holes are then drilled at the 13th fret which we use to inject steam into the neck joint. This will heat and loosen the glue while the jig pictured here is used to apply pressure to the neck heel to separate it from the body.
Here you can see how the neck is being pushed up and away from the body by the jig.
Now that the two parts have been separated, we can clean them of any debris and glue residue and begin the process of tapering the neck back to compensate for the years of string tension. We will be making some mahogany shims to place in the joint to assist in this process.
Once we have everything in place, we go through the process of fitting the neck to the body. This is done by masking off the body and placing a piece of sand paper on it. When the neck is then placed in the joint, we pull the sandpaper out which contours the heel into the body.
While we have been working on the neck, we have also been creating a new bridge for the guitar. Once it has been finished, we glue it in place with these bridge clamps.
Now that we have made adjustments to the neck joint, we can glue it back to the body.
We then move on to refretting the instrument. Something we haven't really covered before that we thought would be cool to share is how the dust from freshly leveled frets can help to show any low spots in the neck and frets. When frets have been leveled, there should be a relatively even amount of dust on either side of the fret. Any spots that have no dust (like near the nut for example) would indicate a section that has not been touched by the leveling beam. If a spot like this is seen around a fret, you would know that it is sitting lower than the frets surrounding it.
Now that all of the repairs have been done to the instrument we can move on to the last thing. We had been asked to install a K&K pickup into the guitar. Here, we are reaming out a hole for the endpin jack. Once that is completed, we did a setup on the guitar and recorded the following clip while testing it out. Special thanks to Jonathan Edwards for trusting us with your guitar and for the kind words!