Like a fine wine, some musical instruments get better with age. Sometimes, due to age, neglect and abuse, older guitars needs some work and TLC to be returned to playable condition. This blog documents some of the work I have performed on musical instruments for myself and others over the years.
But since we're on our way down
We might as well enjoy the ride.
After waiting two days, the hide glue holding the fretboard to the neck had dried. I removed the clamps and cleaned off the excess glue with a razor blade. With the difficult parts of the repairs behind me, what was left to be done on This Old Guitar would be easy. I was looking forward to some reassembly and hearing what this one sounded like again. Good timing, it was the beginning of the weekend.
I reattached the neck to the body with some turns of a screwdriver, and grabbed a long ruler for checking her centerline and neck set angle.
The centerline and set angle looked good so far, so I moved on to reinstalling her nut and tuners.
After the glue holding on the nut had dried, it was finally time for a new set of strings. I grabbed a fresh set, her bridge pins and a peg winder.
After playing her unplugged for a few minutes, I borrowed my sons amp and checked out the variety of sounds she produced as an acoustic electric. The controls on her preamp were smooth and easy to use. After a half hour of playing, I noticed no difference in playability, and she kept in tune rather well for having a new set of strings. So far, it was a lovely ride.
The centerline was off by about 1/32inch at the 12th fret, and the12th fret action was a
tad high for my taste. Those are both easy enough to adjust with a
little shimming and sanding in the neck joint. Her neck was showing a slight amount of relief with zero torque on her truss rod, just where I wanted it to be. Satisfied for the time being, I left off her truss rod cover and neck heel finish plate until I could get back to shimming the action and set angle. I set her aside to see how she held up after a few hours with full string tension.
Before gluing the fingerboard back to the neck, the width of the end of the neck needed some filing and sanding to get a snug fit into the neck block.
It was finally time to prepare for reassembling the fingerboard to the neck. With the neck sitting in the body, I taped the fingerboard to the neck in three places, and used a bar clamp in the sound hole. Then came a final check of the center line alignment and the neck scale length, comparing the measurements from the head stock end of the fretboard to the 12th fret and from the 12th fret to the bridge.
Satisfied, I removed the neck and added a piece of tape to mark the fretboard and neck alignment at the dovetail end.
Before detaching the fingerboard and applying the glue, I taped and clamped a metal ruler to the head stock to provide a mechanical stop. Then I did a dry run without glue, to figure out how I would use clamps to secure the assembly as well as to make sure that the fretboard would end up as planned while using the mechanical stop.
Feeling confident I had this one figured out, I removed the clamps, applied hide glue to the neck side of the joint, and started putting the clamps back on from the headstock end. While attaching the third clamp, I could feel that the edges of the binding and the neck were getting out of alignment. Releasing the second clamp, I reversed it to the bass side of the neck, and continued with the staggered clamping pattern. It worked, and made it much easier to get my hands inbetween adjacent clamps for tightening.
After wiping down the squeeze-out glue, I removed the ruler from the head stock and set the assembly aside to dry. Then I moved on to the acetone bowl repairs.
A popsicle stick worked well for scooping the partially dissolved binding strip out of the jar. The excess acetone evaporates slowly, so it has a good, long working time. Like applying nail polish, it can be tricky to get a smooth, even coat, but its always possible to do it over again.
Slowly building up and working the area with a few applications of material, I used a well-worn piece of sandpaper held firmly against the repair to apply a similar texture to the patch.
I had enough material left to do some reconstruction to the edges of the dovetail opening.
Having had my fill of glue on my hands and fumes from home made black nail polish for the evening, it was time to call it a night.
Well I got nothing against the press.
They wouldn't print it if it wasn't true.
After skimming a few articles and columns in the newspaper, I realized there were much better things I could be doing with my time on a rainy Sunday. The last thing I needed to do before reattaching the fretboard to the neck was to add another pair of shims. This pair increases the width at the end of the neck to match the neck block slot, providing a way to align the centerline of the neck with the bridge.
Like the neck set angle, I cut these scabs thick enough to allow for some trimming. After attaching these scabs with a pair of cauls, glue and three bar clamps, I left the assembly to dry overnight.
Melting down celluloid binding with acetone to a workable, paste-like consistency takes a few days. There were a few places on the ivory fretboard binding that needed some touch up, and I needed some black material for repairs at the rear of the bowl at that hole repair along with a few other places. Not having any unused mason jars on hand, I made a run to the store for some jars of baby food. After stirring the mixtures of binding bits and acetone, I sealed the jars tightly and left them to sit for a few days.
Having done all I could on this Sunday, I settled down with the comics to see what my son found so funny in Rhymes With Orange.
This turned into a busy week at home as well as at the office. Tuesday and Wednesday came and went without any time for this project. It was Thursday by the time I got back to the shed to work on This Old Guitar. It was good timing, as a package was waiting for me on the doorstep that evening.
The new rotary tool I bought online the previous week had arrived, and I already had the perfect task in mind to break it in.
After a dozen or so years of use, the rechargeable battery on my Dremel was close to the end of its life. The flexible shaft extension and variable speed control on this 120VAC Wen made easy work of trimming of the excess binding material with this hole-in-the-bowl repair.
I left touching up the exterior repair with some melted-down binding for another time. It was time to start level the neck block of This Old Guitar. After unclamping the caul, I taped off the surrounding area. Using a rasp and rough files, I got as far as removing just enough wood from the three recently scabbed-on pieces to make a matching surface before calling it a night.
It was Saturday afternoon when I got back to working on the neck block. Starting with an even surface, I used a chisel, followed by files and a sanding block, to get the block and neck surfaces in the pocket to match up
I removed enough material for the dovetail joint to go together again and provide approximately the right neck set angle. Then, being careful to provide the correct centerline alignment, I clamped the neck in place so I could locate and drill a set of pilot holes.
Drilling through the end of the neck and just barely into the neck block with a 1/16-inch bit provided an accurate way to transfer the marks I needed onto the flat surface of the neck block.
After drilling through the block with a 7/64-inch bit, I clamped the neck back into the body. This time, I drill through the neck block and just 1/8-inch into the end of the neck with a 3/32-inch bit. With all four holes drilled, I removed the clamps and installed the four screws with matching ferrules just far enough for the tips to show at the neck block side.
After double checking the screw hole alignment, I turned the crews in the rest of the way into the neck heel.
I decided some black paint on the hardware at final assembly was in order. Checking the neck angle was the important task at hand. I temporarily reattached the fretboard with some tape and a clamp and set up a straight edge across the frets to check the clearance at the saddle.
In the following picture, the straight edge is projecting the plane of the frets to a point slightly higher than the current bridge saddle height. As this saddle had been trimmed for a shallower neck set angle, this projection at the saddle is right where I wanted it to be for now. This alignment makes it possible to trim out the angle and saddle height after some final shimming of the dovetail joint.
Before final shimming of the dovetail joint, I still needed to shim out the width of the neck block pocket to match up with the end of the neck. It was already getting late, so I decided to leave that for next time. Before closing up shop for the night, I made one last piece of infill for the end of the neck and glued it in place.
By the time I got out to the shed this Monday evening, it was already late. I didn't have enough time to level out the neck block pocket, so I left that for another evening this week, and used Monday evening to take care of a few minor repairs.
Sometime before or after the neck heel of This Old Guitar was damaged by a previous owner, her pickup and preamp were removed, and her busted neck and body were used as wall hangings at a musical instrument store repair desk. Although I'm all for displaying non-working musical instruments for art's sake, there was an extra hole in the rear of the bowl that needed to be repaired. Celluloid binding strip, as well as the plastic Jay Turser used to make their bowls, can be melted down easily with pure acetone.
I masked off the area to help contain the reaction at the outside of
the bowl, and poured some acetone into the bottle cap.
The OSHA guideline for acetone describes its appearance and odor as a colorless liquid with a fragrant, mintlike odor. It's the main ingredient in nail polish remover, and full-strength acetone doesn't smell at all like incense or peppermint to me. The effect of inhaling too much acetone can be a light-headed "psychedelic experience" at best, and a "bad trip" at worst, including nauesea and depressed respiration. If you've ever spent a long time in a beauty parlor or nail salon with poor ventilation, some of these symptoms might sound familiar.
The exhaust fan
in the This Old Guitar workshop is on the weak side, so I was careful to work up wind of the acetone and worked quickly. A couple of narrow pieces of black binding sandwiched together filled the
hole, to be trimmed down from the outside with a knife and sand paper.
The hole was through the label on the inside of the bowl. This side of the repair to the bowl will also get trimmed, but I'll leave the label as-is and let the repair be purely functional.
Despite my efforts to be careful, I made a few new dents and deep scratches in the neck while working on the heel repairs. I used a hobby knife to widen and deepen these damages slightly past the finish, so that I could fill them in with some very small slices of scrap mahogany. After pushing some carpenters glue into the damaged areas with a finger, I used a hobby-grade metal probe and the side of the hobby knife to push in and compress the mahogany splinters.
Strips of painters tape around the neck acted as clamps until the glue dried.
I'm taking the time for a number of things
That weren't important yesterday.
And I still go.
I managed to put in a few hours on this project over the weekend. After another half hour or so with a file and a rotary sanding drum on my Dremel, I had the dovetail joint fitting up nicely.
Before drilling pilot holes through the neck block, that groove of a hole I had made needed to be fixed. My preference would have been to route out the groove and make the bottom of it flat, but I don't have a good way to clamp her body down or a drill press to do it with enough accuracy. Instead, I decided to shape a piece that would match the u-shaped opening. I started with a piece of oak that had the grain running in the long direction and of dimensions slightly larger than that of the groove. After a few minutes with a coping saw and a belt sander, I had this in-fill piece ready to be glued-up and clamped in place.
Since the slot would still need to be shimmed to set the neck angle, I left the infill piece proud of the existing outer surfaces of the groove. This would also allow me to fill in the rest of the slot and then sand that entire surface to the correct angle at one time.
When the glue on the first piece had dried, I moved on to the two other pieces needed to level the plane of the neck block pocket. A pair of popsicle sticks and some scrap furring strips wrapped in painters tape served well as clamping cauls.
While running errands and shopping over the weekend, I worked in a trip to Lowes and Home Depot for hardware. Neither store carried the right-sized parts I was looking for in the color black, but what I found is plenty strong enough to do the job. Still considering two repair options, I picked out and bought the bits and pieces for both methods of attachment.
The four plain wood screws and ferrules in the next picture are for the first repair option. The wood screws are to go through the body and neck block from the rear, and go directly into the neck to hold it in place while the glue dries. The screws are to remain, and would be removed to allow the neck to be steamed out for future set angle adjustments.
In this last picture are the machine bolts for the second repair option. The four inserts are to be installed into the heel. No glue is to be used in this option, the neck can be easily removed with the turn of a screwdriver on four bolts, and the neck set angle can be easily adjusted by shimming the neck heel and block.
Ain't so hard to recognize - These things are clear to all from
time to time.
After removing the clamps, I checked the newly attached pieces to be sure that they had not shifted before the glue had dried.
It all looked good, so I cleared off the few drops of glue squeeze out I was unable to reach until now. Then, I moved on to getting the planes of the new shims to match the rest of the heel.
I clearly had added enough wood at the widest part of the heel for the next few tasks. After an initial fitting, I took some measurements to be sure that I had also added enough wood at the narrowest part of the heel. With that condition confirmed, it was finally time to fully reshape the width of her neck's dovetail and make a snug fit into her body block.
After about an hour with a chisel, a flat file, a Dremel with a rotary cutting tool and a
sanding block with 60-grit paper, the heel was about 1/8-inch away from being fully seated in the block. It was starting to look like a dovetail joint again.
Before continuing with the remaining work on the heel, my Dremel and I needed to be recharged. I put my tools away for the night, and got to thinking about the way the neck joint might have failed before I
bought This Old Guitar. This was a mystery to the previous owner as much as it was to me. It was time to apply some forensic science to the situation.
The epoxy joint was clearly stronger than the wood. I
thought a little bit about the physics of what could have caused the heel to split
near the truss rod and through the heel without leaving any other obvious signs of
damage to the neck or body. A force against the rear of the neck or excessive string tension would likely have caused some stress where the fingerboard meets the top plate, or some separation of the fingerboard from the neck near the body, or some damage to the bridge or top plate, so I decided those were most unlikely scenarios by the evidence.
A force against the front of the neck, midway or close to the headstock, could have produced enough bending in the neck to result in a crack through
the flat part of the heel and traveled all the way through through the other end of the heel, splitting the heel wood through the dovetail joint. Or, there could have been a
defect in the neck wood, caused or aggravated by excessive tightening of the truss rod.
Either way, I was determined to make the
neck joint stronger than before, as well as to make it possible to make future adjustments to the neck angle. Thinking about how to take advantage of the geometry of the heel and neck block, I came up with three repair options. With a little more thought, I ruled out the first option, and a repair strategy appeared.
Option One:
Count on the strength of hide glue in the dovetail joint and the
surface area between the flat part of the heel and block to hold things
together. Fill in the groove in the neck block and glue in shims to set the neck angle. Shim out the width of the neck block to close the gaps at the neck and block closest to the high and low E strings, and drill some small pilot holes beneath the 15th and 18th
frets to provide a way to steam out the neck for future resets. The
only problem was that there might not be enough surface area to develop
enough strength in the joint, and there would be no way to test the joint and neck angle with actual string tension, as the majority of the strength and in the joint would be provided after the glue between the flat parts of the heel and the block was allowed to dry. Hmmm...
Better yet was Option Two:
Fill in the neck block groove and gaps, and use hide glue for the joint as in the first scenario. Install wood screws through the back of the bowl, through the neck block and into the flat part of the neck heel. These screws would also provide the clamping strength needed to hold the joint in place while allowing the glue to dry. Some ferrules would help distribute the load through the back of the bowl into the neck block, and the screws would be left in place after the repairs. Removal of the screws would provide ample access holes to steam out the neck for future resets, so I would not need to provide pilot holes beneath any of the frets.
Then there was Option Three:
If Option Two fails, install two pairs of black bolts, located within the 16th and 18th frets, through the back of the bowl, through the neck block, and into the flat part of the neck heel. Again, the four black ferrules would make this presentable, and I would install four metal inserts into the neck to receive the bolts. Use shims to make the angle adjustments, just like on the old-style Fender necks. I researched this repair method and found a bolt neck insert kit offered by Onyx Forge for this type of repair to bolt-on necks with worn wood screws.
Just like Page and Plant once wrote:
Ain't so hard to recognize - These things are clear to all from
time to time.
