1977 Gibson Les Paul Special: Neck Reset and Body Cracks

Related Topics: | Refret | Truss Rod Adjustment | Body Cracks |


1. A Failed Neck Joint and Cracked Body. When the neck joint began to fail, the string tension was unevenly distributed causing the body to crack. I can actually wiggle this section of the body freely. This is an indication that this chunk of the body is completely severed from the rest of the body, while still attached to the tenon (hidden part of the neck that is glued into the body).	2. A Failed Neck Joint and Cracked Body Cont. The body on the treble side of the neck is also damaged, though not as severely as the bass side.


3. An Open Neck Joint. The heel is open. The strap button is likely helping to keep the neck attached.	4. Evidence of Previous Repairs. It looks as though this guitar got dropped on its head. The "touch- up" work done to the headstock is an indication of past damage and repairs.


5. More Evidence of Previous Repairs. If you look really close at the binding over the body you'll see some red stuff that's similar in color to this guitar's lacquer finish. This material is not as brittle as 30 year old lacquer so I'm guessing this neck joint was repaired with epoxy that was dyed red. The tinted epoxy squeeze out filled any gaps in the finish resulting from the previous damage. Hopefully the neck was not glued in with epoxy. We'll soon find out...	6. Removing the Pickups will give me access to the back of the neck joint. This guitar sports two P-90 pickups. Here's a look of one without it's black, plastic pickup cover.


7. The Back of the Neck Joint is now freely accessible. Close in- spection reveals that the neck was joined to the body before the elec- tronics cavities were rouded, the fingerboard affixed and the cherry- red lacquer applied. At the bottom of the cavity some of the tenon remains. The body crack on the bass side of the fretboard has gone all the way through the instrument and is visible in the pickup cavity.	8. With the Strap Button Re- moved I can tell that the failed neck joint was indeed pulling on the strap button. The deep compression mark left by the strap button is con- sistent with the angle in which the neck was pulling free: the joint failure was more severe on the bass side of the neck joint as seen in photo #1.


9. Loosening the Truss Rod Nut is necessary since I'll be removing this neck with steam. Since my intent is to salvage the original neck, rather than replace it, I don't want the steam to further damage the neck. An en- gaged truss rod adds compression to the back of the neck. This could result in a cracked neck if the steam gets into the truss rod cavity.	10. Scoring the Finish around the neck will prevent unnecessary damage to the finish as the neck is removed. The Gibson factory sprayed the finish on this guitar after the neck was set. This resulted in the buildup of lacquer around the neck joint.


11. Scoring the Finish Cont. It's tough to make out, but upon close inspecion there is more dyed epoxy masquerading as finish at the heel.	12. Drilling into the Joint. The technical term for this neck joint is a "mortise and tenon" joint. The tenon is the end of the neck and the mortise is the cavity in the body into which the neck was glued.


13. Softening the Glue at the Fretboard Extension will make separating the fretboard from the body easier with little to no chance of splintering. A custom made heat shield protects the binding and the lacquer from the heat lamp.	14. Separating the Fretboard Extenion from the Body. Now that the glue is soft from the heat lamp an artist's pallette knife slides under the fretboard with relative ease, effectively severing the glue joint.


15. Removing the 21st Fret. I'm pulling the fret while the rose- wood fretbaord is still hot. This prevents the fretboard from chipping.	16. Drilling into the Neck Joint Cont. I'm drilling two more holes into the neck joint. The holes are through the fret slot so they will be easy to hide after the neck is reglued.


17. Steaming the Neck Joint. The steam goes in through the holes in the back of the joint and comes out through the holes in the fret- board. Steam weakens glue, making it possible to disassemble instru- ments. The Gibson factory uses a type of wood glued for Les Paul neck joints. Alaphatic resin glue (as this type of wood glue is called) is readily weakened by steam. Many epoxies will weaken after enough exposure to steam. However, if this neck was epoxied in things could get complicated. Hopefully though, the past repair person only used epoxy to touchup the finish...	18. The Removed Neck. Clearly, this instrument was once cracked, the neck removed and reglued with tinted epoxy. The previously severed portion of the body (bass side mortise cheek) still remains attached to the tenon, despite the steam, as does a smaller portion of the treble side mortise cheek.


19. Removing the Bass Side Mortise Cheek is pretty easy as the epoxy was weakened by the steam.	20. A Tenon Previously Repaired with Epoxy. Clearly, the neck broke accross the tenon years ago. The previous repair person made no attempt to employ advanced joinery repair techniques. Rather, they simply glued the neck back in with epoxy.


21. Cleaning out the Severed Tenon from the mortise is a quick affair with a chisel and a mallet. I'll imitate the factories original depth of the mortise by extending the bottom of the mortise into the neck- pickup cavity.	22. Regluing the Mortise Cheek with Hot Hide Glue. Since the break is a half-moon shape I had to apply clamping pressure from two directions. A cam clamp provides quick action, downward pressure, with the help of a rubberized-cork lined, padded caul to protect the finish and distribute the clamping force through- out the affected workpiece. Two small go-bars clamp from within the mortise itself. The gobars are simply thinned out spruce stock that are slightly longer than the mortise is wide. The force of the spruce attempting to straighten itself out acts as a simple spreader. I had to clamp this up fast since full strength, hot hide glue begins to set in 10 - 15 seconds.


23. After Gluing in the Bass Side Mortise Cheek. Now for the treble side...	24. Preparing the Mortise Cheek for a Graft. I'm cutting away the cheek to just below the epoxy glue line. This type of fine work requires a woodworking tech- nique called "parring" (pronounced "pear-ing" this simply means cutting with a chisel without the assistance of a mallet).


25. Ready for a Graft. Note the epoxy-free portion of the mortise cheek near the bottom of the mortise. This is further evidence that the neck broke accross the tenon and was simply glued back into the mortise with epoxy.	26. Fabricating a Graft for the mortise cheek from some scrap Honduran mahogany (the same species of mahogany this guitar's body and neck were constructed from).


27. Fabricating a Graft Cont. I'm splitting the graft along the grain to get the rough stock down to a more manageable size.	28. Laying out the Graft's Gluing Surface.


29. Beveling the Graft's Gluing Surface with a chisel. Again, I'm making parring cuts.	30. Truing the Graft's Gluing Surface with a dead-flat-soled, razor-sharp, block plane ensures that I'll have a well matched gluing surface.


31. Laying Out the Graft's Rough Height.	32. Gluing the Graft. Again, I'm using the same clamping "system" I used to repair the bass side mortise cheek. I'll leave this clamped for 24 hours.


33. Trimming the Graft Flush is necessary because I left the graft a bit proud in order to ensure that I would have enough material to properly shape the graft after the glue cured.	34. Trimming the Graft Flush Cont.


35. Epoxy is all over the place. Close inspection reveals that a significant amount of the mahogany spintered during the original break/repair and the previous repair person simply filled these voids with epoxy (which is a good gap filler, though far from ideal in a repair like this).	36. Cleaning Things Up with a chisel. I'm cutting away the epoxy impreg- nated, splintered up treble side mort- ise cheek that's still attached to the tenon. Since this part of the body is hidden beneath the fretboard exten- sion, no one will see the grafted section of the mortise cheek (unless they remove the neck pickup).


37. Cleaning Things Up Cont. I'm cutting away the damaged, epoxy impregnated, cheeks of the tenon.	38. Creating a Scarf Joint. I'm trimming away the bottom of the tenon to get below the glue line. Next, I'll fabricate another graft, this time for the tenon. A flat, angled, glue joint like the one I'm creating is called a "scarf joint".


39. Laying Out the Tenon Graft. I squared a piece of scrap mahogany. Now I'm laying out my rough cuts to make the wedge that I will eventually glue to the existing tenon.	40. Rough Cutting the Tenon Graft. A Japanese dovetail saw does a great job of quickly and cleanly cutting off much of the excess mater- ial. Next, I'll clean up the graft and plane to rough shape.


41. Laying Out the Tenon Graft for Final Shaping. This small pencil which has been cut in half and sanded flat will mark the bottom of the tenon graft on the heel of the neck.	42. Laying Out the Tenon Graft for Final Shaping Cont. It's tough to see in this photo, but the tenon graft is just a bit too shallow. That's okay, because the graft is a wedge. Since it's only cut to rough length I can shore things up a bit.


43. Establishing the Thickness of the Tenon Graft is a quick affair with the disc sander.	44. Preparing the Hide Glue. Hide glue comes to us in dry, gran- ual form. I'm mixing the granuals with distilled water in a 1:1 ratio. While the granuals soak up the water I'll continue the preparations for gluing the scarf joint.


45. Gluing the Scarf Joint. As the pieces making up the scarf joint are essentially two wedges, I can't clamp them together with only downward pressure as the parts would tend to wander. Therefore I developed a more elaborate clamping scheme. The three cam clamps to the left hold the neck into a radiused block that matches the radius of the fretboard. The block, in turn, holds the neck square against a 2" x 4" that's affixed at a right angle to the work-board.	46. Gluing the Scarf Joint Cont. A scrap block clamped to the work- board to the right of the work piece acts as a stop. I've tapped a wedge between the stop and the tenon graft to prevent the graft from slidding as the large c-clamp holds the graft to the tenon. A complicated clamping situation for sure, but effective none- the-less.


47. Sanding the Heel Flush with the sides. This is done with fine grit sandpaper for maximum tone transfer as well as a clean looking mating of neck and body.	48. Marking the Bottom of the Graft. By rubbing the neck back and forth through the mortise the bottom of the tenon will be have sanding marks at the "high spots" or the points where it contacts the bottom of the mortise.


49. Final Shaping the Bottom of the Graft. I'm using a razor blade with a burr like a scraper to lower the high spots insuring maximum contact between the bottom of the mortise and the bottom of the tenon.	50. Fitting the Bottom of the Shim. Since I had to cut away some of the mortise and tenon to get past the damage and epoxy from the previous repair, I'll now have to fabricate two shims for the mortise cheeks.


51. Establish Full Contact between the shim and both the mortise and tenon is important for tone transfer as well as the strength of the glue joint. Here I'm lightly sanding the shim simply to rough up the surface of the shim.	52. Dry Fitting the Shim. Where the tenon makes contact with the shim, the shim's sanding marks are compressed leaving a shinny spot.


53. Shim Marked for Scraping. The shinny spots are the high spots, or the parts of the shim that are making contact with the tenon.	54. Scraping Down the High Spots. I'll repeat this process of sanding, dry fitting and scraping the shim until I get full contact between the tenon and the shim.


55. Gluing in the Shim. Some hot hide glue and a few little go-bars or spreaders will create a strong glue joint.	56. Finish Touchup begins with a little beutyl cellusolve. This stuff is a sort of fancy lacquer thinner that soften ups the old lacquer allowing the new lacquer I'll be applying to burn into the original finish. This will make the touchup look a little more subtle.


57. Tinted Lacquer will help hide the repair. I'll apply a few coats of lacquer then set it aside for a couple weeks to cure.	58. Scraping the Lacquer flush with the surrounding finish. This razor blade has a burr like a scraper and a couple pieces of scotch tape wrapped around the edges of the blade. The tape both protects the surrounding finish and acts as a stop so the new lacquer will be just a touch higher than the original finish.


59. Sanding and Polishing the touchup and surrounding finish. I sanded away the scraper marks with 1000 grit sandpaper lubricated with some water. This also leveled the new lacquer with the old. I'll polish the finish to 12,000 grit with sanding pads, then hand buff the area.	60. Pencil Marks will help me identify where the second shim is making con- tact with the mortise cheeks.


61. Pulling Sandpaper Through the Joint will reveal where the shim is making contact.	62. Trimming Down the High Spots. Where the sandpaper removed the pencil marks the shim is making contact. To insure full contact I'll repeat the process of marking, sanding and trimming the mortise cheek until the shim has full contact with the mortise.


63. Roughing Up the Shim where it will come into contact with the tenon will serve as a visual aid in identifying the high spots.	64. Dry Fitting the Neck will leave shinny compression marks on the coursened shim thus revealing where the tenon is making contact with the shim.


65. Scraping Back the High Spots. I'll repeat this process of scuff sanding the shim, dry fitting the neck and scraping the shim until the neck fits tightly with full contact. I've actually given the tenon and the shim a slight taper so that the shim will be thinner at the top (fretboard end) of the joint than it will be at the bottom of the joint. This makes the process of setting the neck a little easier, quicker and improves the contact between the shim and the tenon.	66. Cutting Off the Excess Graft.


67. Gluing in the Neck. I dry fit the neck so that a quick grip bar clamp would seat the neck without glue. This insures that the joint doesn't fit too tightly, preventing the massive force of the c-clamp from breaking the joint during glue up. I used hot hide glue for gluing in the neck. Infact, all of the repairs I've done on this neck joint and body have been glued using hot hide glue.	68. A Look at the Repaired Neck Joint. A view from the pick-up cavity shows the back of the repaired neck joint. See how tightly those shims and the graft glue joints are? Also, I was careful to maintain grain orientation consistent with that of the remaining portion of the orig- inal tenon.


69. Touched Up Cracks. The crack repairs are still vissible, however they look a lot better now that they've been touched up.	70. Touched Up Cracks Cont.


71. A Properly Fitted Heel.	72. All Done. It was a lot of work but this guitar is solid. Since I used hot- hide glue and carefully fitted the graft and shims this repair should prove a lot more resilient than the original epoxy repair.