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Martin Dovetail Neck Reset

7/28/11 – This article was featured in the July, 2011 Finger Lakes Guitar Repair Newsletter. Sign up for the free newsletter today! Just type in your email in the sidebar to the left and press Go.

1.0 Martin D-35 Brazilian Rosewood Neck Reset high action.JPG 1.1 Martin D-35 Neck Reset low saddle.JPG
1. A Martin D-35. Built in 1966, this guitar is really hard to play because it has high action. The neck is pretty straight so I’ll look at the saddle to see if I can lower the action there. 2. A Low Saddle. This saddle can’t be lowered any further without completely disappearing into the bridge. The symptom is high action but the problem is that this Martin’s geometry has changed as a result of exposure to over 45 years of string tension. This guitar needs a neck reset to reestablish an ideal relationship between the plane of the fretboard and the bridge.
1.2 Martin D-35 Brazilian Rosewood Neck Reset score heel cap.JPG 1.3 Martin D-35 1966 Neck Reset heat fretboard tongue.JPG
3. Scoring the Heel Cap to establish my final cut line. Using some simple math, I’ve determined that .053” must be removed at the heel cap. I’ve stacked up a couple of feeler gauges against the binding to correctly locate my marking knife scribe. 4. Heating Things Up. A heat lamp softens the glue between the fretboard and the top of the guitar.
1.4 Martin D-35 Neck Reset remove fretboard extension.JPG 1.5 Martin D-35 Neck Reset steam dovetail neck joint.JPG
5. Removing the Fret- board Tongue with a thin spatula. I’ve also removed the 15th fret and drilled two small holes through the fret slot in order to inject steam into the neck joint. 6. Steaming the Neck Joint softens the glue. A cappuccino maker pushes steam through an inflating needle attached to the end of a radiator hose. The needle is inside one of the holes that I drilled. The majority of the steam circulates out through the neck joint via the 2nd hole in the 15th fret slot.
1.6 Martin D-35 Brazilian Rosewood Neck Reset clean up old glue.JPG 1.7 Martin D-35 Neck Reset sand heel cap.JPG
7. Cleaning Up the Old Glue. This neck took less than 3 minutes to remove but I’ll still set this guitar aside for a few days to reacclimate to the shop’s climate before resuming the neck reset. 8. Sanding the Heel Cap to my scribed line will determine my maximum depth of cut on the heel.
1.8 Martin D-35 Neck Reset back cut heel.JPG 1.9 1966 Martin D-35 Neck Reset cut heel.JPG
9. Back-Cutting the Heel will make it easier for me to fine tune the neck angle as I cut the outer edge of the heel. 10. Establishing the New Neck Angle is done by cutting the heel of the neck. I’m removing .053 of the neck’s heel at the heel cap. I’ll taper my cut to zero where the heel meets the bottom of the fretboard. I have two angles to control: the pitch and the yaw.
2.0 Martin D-35 Neck Reset sand heel.JPG 2.1 Martin D-35 Brazilian Rosewood Neck Reset determine rough thickness of shims.JPG
11. Final Fitting of the Heel is done with sandpaper. The sand- paper precisely translates the contour of the sides to the heel. 12. Determining the Rough- Thickness of the Shims. Since I changed the neck angle, the dovetail joint that holds the neck and body together is now too loose. I’ll make a couple of mahogany shims to fill that gap in the dovetail joint.
2.2 Martin D-35  Brazilian RosewoodNeck Reset.JPG 2.3 Martin D-35 Neck Reset establish taper of shim with thickness sander.JPG
13. Dry Fitting the Joint with Neck-Set feeler gauge tells me how thick I need to make the top and the bottom of the shims. First I’ll establish how thick the gap at the bottom of the dovetail joint is, I’ll then measure the gap at the top of the dovetail joint. When the neck won’t quite sit all the way down into the body, I know that I’ve established the correct thick- ness and taper of my shim. 14. Establishing Shim Taper. During a standard dovetail neck reset, the shim will always be wedged shape. My two shims will taper from .030” thick to .018” thick. I’ll thickness sand both shims to .040” thick. Then I’ll sand the very end of the top of each shim to .028” thick.
2.4 Martin D-35 Neck Reset hand plane shim.JPG 2.5 Martin D-35 Neck Reset glue and clamp shims.JPG
15. Hand Planing the Shims to their finished taper and thickness. On the workbench, I plane across the grain against a scrap of maple clamped in my end-vise. 16. Neck-Set Go-Bars clamp the shims in place while the glue cures. I’ll put aside the project for 24 hours.
2.6 Martin D-35 Neck Reset dry fit neck with carbon paper.JPG 2.7 Martin D-35 Neck Reset trim tenon to fit.JPG
17. Dry Fitting the Neck with carbon paper in the joint helps me determine where I need to remove material from the tenon. 18. Paring the Neck’s Tenon with a chisel will remove the high spots marked by the carbon. I’ll repeat the carbon paper dry fit and paring steps until the neck fits tightly and all the way down in the neck block.
2.8 Martin D-35 Neck Reset glue and clamp neck.JPG 2.9 Martin D-35 Brazilian Rosewood Neck Reset no damage to finish.JPG
19. Gluing the Neck with 2 c-clamps and 3 clamping cauls ensures good clamping pressure without damaging the guitar. 20. No Sign of Repair. The repair is undetectable.
3.1 Martin D-35 Neck Reset low action.JPG 3.2 Martin D-35 Neck Reset proper saddle protrusion.JPG
21. Low Action. With the 6th string capoed at the first fret, the action measures 3/32” at the 12th fret. 22. Plenty of Saddle protrusion above the bridge. In most cases, the saddle protrusion above the bridge at the 6th string should be twice that of the 12th fret action.