Acoustic Guitar Neck Reset
Step 1: Loosening The Fingerboard Extension
Before removal of the neck begins the portion of the fingerboard which glues to the top must be loosened.
Heat is applied to soften glue beneath the small
area of fingerboard that overhangs the top.
I personally use a specially designed heating "blanket" which is similar in size to the fingerboard's extension. This allows me to heat only this part of the fingerboard without heating the surrounding finish.
Before the days of handy sized heating blankets I used a traditional clothes iron. This required shielding the instrument's top from the heat to avoid blistering lacquer and other vulnerable finishes.
With the glue soft from heating I use a smooth spatula to slide between the fingerboard and top. Using a smooth, even polished spatula insures the finish around the fingerboard is not scratched. When the finish is fragile I use low tack, paper tape to protect it. (Think Post-It® sticky) On vintage instruments with flakey finishes it can really come in handy.
Step 2: Steaming The Neck Loose
With the fingerboard still hot I remove the fret which lies directly above the dovetail pocket. On nearly all instruments this is one fret up from where the neck meets the body, this is usually the 15th fret.
With this fret removed I can now drill a hole straight thru the fret slot which will lead directly into the pocket. This serves to avoid any visible signs or changes to the fingerboard that would indicate a repair had been done.
Drilling a hole thru the fret slot helps to avoid any obvious change to the instrument.
Steam is injected into the neck block to soften the glue. Instruments with loose necks may permit steam to escape around the heel of the neck. When this is an issue I use an air hose to blow steam away from the area, keeping it dry and cool.
Some truss rod nuts are accessible beneath the fingerboard extension, as a result steam will also find it's way out thru the truss rod hole and care must be taken to plug the hole and protect the interior of the instrument.
Steaming usually takes only a few moments. In all but a few instruments water soluble glue is used. Because a well fit dovetail is relatively tight, very little glue is between the dovetail and sides of the neck block.
Step 3: Removing The Neck
Pushing the neck free from the body.
As the glue is softened the neck begins to move with effort.As separation becomes apparent I apply pressure to the heel cap to press the neck out of the block. When the fit is very tight I use what I call my "sissy jig". It's a real life saver when my bionic thumb can't do the job.
Step 4:Changing The Necks Angle
Once the neck and joint have dried and old glue is removed the neck's angle is changed by shaving material from the heel.
I use chisels to remove the majority of wood, followed by sanding sticks when necessary.
A new taper of the heel's sides will increase the neck angle.
When string height has risen due to an increase in the top's arch (belly) material is removed from the bottom portion of the heel, tapering gently to the top of the heel (below the fingerboard). With the instrument lying on it's back this adjustment would pitch the neck back, placing the peghead closer to the bench.
Wood is removed in very small increments, the neck placed back in the pocket to recheck it's angle, rinse and repeat...
As detailed in my article on neck angle we are adjusting the necks angle to insure it's plane passes over the bridge.
While shaving wood from each side of the heel, the side to side pitch of the neck is also closely watched. Removing more wood from one side than the other would place the outer E strings unequally from the edge of the fingerboard.
Ideally the center of the fingerboard should run right between the D and G bridge pin holes. When dealing with vintage instruments it is not uncommon to find that the bridge is not dead center on the top, so to avoid an issue the neck is centered using the bridge, not the top's center glue seam.
Step 5: Shimming The Neck Block
After adjusting the neck's side to side angle and it's pitch, shims are used to lock the dovetail in place.
I glue mahogany shims to the sides of the neck block and start the process of fitting the actual dovetail, that which "locks" the neck in place. The shims are sanded to insure an even fit from top to bottom of the heel.
A well fit dovetail will hold a neck in place before glue is even applied.
At this point all angles are re-checked to insure nothing has been overlooked.
Step 6: Re-gluing The Neck
The easiest part of the job ...gluing the neck back in place. Titebond Regular is applied to the sides of the dovetail joint and beneath the fingerboard extension.
Clamps are used above the dovetail and over the fingerboard to insure complete seating of the joint.
Gluing the neck back on a Martin guitar.
The Grand Finale
Titebond (and other aliphatic glues) are water soluble. This permitted the neck to be removed with steam. It also makes clean up relatively easy as well. Warm water will clean up dried glue that has squeezed out during clamping.
Now that the angle of the neck has changed the fingerboard is now bending slightly downward to make contact with the top. For a truly professional job the fingerboard is planed straight and re-fretted. The tiny holes drilled beneath the 15th fret filled and now a distant memory.
Neck resets are not often performed on inexpensive instruments for the simple reason that they can actually be replaced cheaper than they cost to repair.
Neck resetting a dovetail joint like the one detailed above start at $650.
Acoustic Guitar Repairs
- Action / Set Up
- Bridge Plate
- Bridge Pins
- Buzzing - Noise
- Care / Maintenance
- Convert Rt. to Lt.
- Fret Replacement
- Fret Types
- Neck Damage / Issues
- Neck Angle
- Neck Resets
- Part Glossary
- Strap Buttons
- String Changing
- String Choices / Effects
- Truss Rod
- Tuning Machines
- Tuning Troubles