Neck joint failure on SG build

ejendres

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I built an SG for a buddy last year. I was up in Nashville visiting and he mentioned the action had basically doubled in height randomly one day. He decked the bridge but was unable to restore the low action. To me this screams neck joint failure. I took a close look and there appears to be a slight gap present now at the heel. Weirdly enough it still holds tune. I'm guessing thats because its a full width tenon and the string tension is essentially wedging it in place.

I used Titebond 2 to set the neck. The guitar was at my house strung up for weeks before I shipped it to nashville and showed no issues. It also was in nashville for around a month with no issues.

My buddy hand painted the body prior to me setting the neck and neglected to tape off the neck pocket for the first couple of colors. I cleaned up all the large bits of splatter with acetone but I'm wondering if the slightly uneven surface caused by the paint splatter caused the neck joint to fail. The neck has a scarf joint that I glued using the same exact glue and it shows no signs of weakening/separation.

Any other ideas of what it might have been? He's works at Gibson so he's going to enlist the help of some of their repair guys and reset the neck himself. I just want to make sure I understand what went wrong so it won't happen again.

Neck joint gap along the heel:
uAyDd4L.jpg


Neck joint after gluing:
QrvZyGz.jpg


Neck pocket after painting:
pJgprSR.jpg
 

CB91710

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My honest opinion is this is a design issue with having the neck pickup too close to the end of the neck on the thinner SG body.
Even being a full length tenon, there just isn't enough contact area on the sides for a secure joint.

Compare to a Gibson SG Special.
I don't know what, if anything, can be done to stabilize that connection. You've got ~100 pounds of string tension on a pair of <1" long lap joints.
That really is a cool build and paint design.

SG-NEck.jpg
 

ARandall

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So did you actually clean the splatter off or not - your description is ambiguous. You said you used acetone, which of course works with Nitro to soften and dissolve it, but will do nothing for other paints.
For wood glue you really do need to remove every last drop of 'contaminant' - as in anything that ain't wood. So merely say scraping the splatter to being flat is not good enough. You really have to chemically strip the paint out of the wood pores/grain too.
 

elephantrider

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can't help ya on the neck joint issue, but bravo on that finish job. looks killer.
 

LtDave32

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So did you actually clean the splatter off or not - your description is ambiguous. You said you used acetone, which of course works with Nitro to soften and dissolve it, but will do nothing for other paints.
For wood glue you really do need to remove every last drop of 'contaminant' - as in anything that ain't wood. So merely say scraping the splatter to being flat is not good enough. You really have to chemically strip the paint out of the wood pores/grain too.


^--this.

Titebond glue (alphiatic resin) works by bonding with the cellular structure of the wood. If you contaminate that surface, fill the pores, lock them closed with paint, etc you ruin the chance of that cellular bonding. Even if you've cleaned the paint off the surface with acetone, etc you've still put a skin on the wood surface that might prevent the glue from doing its job.

It has to be clean, virgin wood, on both surfaces.

Going forward on future builds, it's best to mate your gluing surfaces before any painting goes on. Get that neck joint glued up well before you do any spraying at all.
 

ejendres

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My honest opinion is this is a design issue with having the neck pickup too close to the end of the neck on the thinner SG body.
Even being a full length tenon, there just isn't enough contact area on the sides for a secure joint.

Compare to a Gibson SG Special.
I don't know what, if anything, can be done to stabilize that connection. You've got ~100 pounds of string tension on a pair of <1" long lap joints.
That really is a cool build and paint design.

View attachment 562756

I mean it's way more than an 1". also look at a Les Paul double cut, the neck joint is even shorter than mine.

I'm guessing it's really down to the paint splatter. I probably made it worse by using the acetone because it just ended up spreading the paint and filling more pores. I definitely didn't get it all up, I just spread it out.

I think I'll recommend him resetting it with an epoxy.
 

CB91710

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I mean it's way more than an 1". also look at a Les Paul double cut, the neck joint is even shorter than mine.
I'm looking at the sides, there is no extension of the tenon past the fingerboard, which only has 2 frets inside of the joint.

The DC has about the same amount of glue area on the sides of the tenon as the SG... the neck pickups are still set back some distance from the end.
And the DC body is thicker than the SG at the neck pocket, so there is more depth for the tenon below the pickup.
 

ejendres

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Sides aren't what make a glue joint strong.

I'm not saying more isn't better but I'm confident this neck joint has plenty of surface area. I think it was the paint.
 

CB91710

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I disagree.
The bottom (back) of the tenon is in tension, and that is a very weak connection for wood, whether glued or not.
Yes, the glue is theoretically stronger than the lignin that binds the wood to itself, but how easy is it to pry apart a long-grain lap joint by pulling against the joint, vs rolling it on the side and applying a rotational force to the joint?
And ultimately, the strength of the glue joint is in the fitment, including surface prep.

It doesn't look like it from the picture, but there is also the possibility that the body wood has split and failed where the cutaways meet the neck... again, that is a very thin piece of wood to be holding nearly all of the neck tension.
But I don't see any evidence of failure telegraphing through the finish.
Hopefully it is just an issue with the paint. The surface may need to be milled down a bit, meaning a shim would be needed to regain a tight fit, but glue bonds wood to wood, and shimming to tighten it up will make it as strong as it can ever be.
 

warprider

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Every time I see people building set neck type kits I ask why they painted before setting the neck. Gotta keep those pockets/tenon clean.
 

ARandall

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^ Even the acoustic kit I have been doing recommends that. Then you have to scrape the finish away to glue on the neck/fretboard - and get this, the bridge too (the most important glue joint of all really)

I disagree.
The bottom (back) of the tenon is in tension, and that is a very weak connection for wood, whether glued or not.

Yeah, I'd agree the sides are at least as important as the bottom surface area. As an example in a different situation, my job often involves removing semi buried sleepers on old retaining walls. Removing the soil on the side of the sleeper takes that task from 'hard even with levering type tools' to 'practically doable by hand'.
 

cmjohnson

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If the tenon didn't actually break, then the pickup depth or closeness to the neck wasn't a factor. If that had been the case,
then the tenon would have broken where the tongue meets the heel.

I agree with Dave. You had a contamination issue in the joint. Not taping off the mortise is likely the root cause of the failure.

Always tape off surfaces that are to be glued later when painting now.
 

ejendres

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Every time I see people building set neck type kits I ask why they painted before setting the neck. Gotta keep those pockets/tenon clean.

We painted it first because he wanted to paint it himself and he's in Nashville and I'm in Bethlehem PA. I had asked him to tape up the tennon but he forgot sadly.
 
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ejendres

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Also to anyone saying the sides are super important, I'm not saying they don't help, however the surface area of the bottom of the tennon is more than the surface area of a scarf joint. The scarf joint is also in tension and has just as much load as the neck joint.

You could set a loosely fitting bolt on neck and as long as the bottom surface is nice and flat it wouldn't give you any issues.

This one is down to me not cleaning the joint well enough.
 

fatdaddypreacher

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with the minimal neck tenon, i would suspect you would need full contact of glue surfaces, raw wood to raw wood. if all the paint residue wasn't removed from the joint, the glue up would not have been maximum. titebond doesn't stick well to anything except raw wood. it's best used when moderate pressure is applied to proper joint, and enough glue to barely ooze out. it could well be a combination of not enough neck tenon and paint residue. attention to both of these on your next build should alleviate the issue. i agree...nice paint job.
 

LtDave32

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Much talk around this forum and others about poor design of neck joints on SG's.

While I fully realize there were different tenon / Mortise designs over the years from 1962 to present, I invite all to review on film (youtube) what Townshend has done to them over the years. And a few other makes as well.

Sometimes (Woodstock '69) the whole guitar remains intact.

Other times, everything BUT the neck joint failed.
 

Joe Desperado

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Honestly, seldom is it the actual joint that fails. If the joint failed you would see a clean joint with say..glue residue. More often it’s the wood that has failed around the Joint. Ex: SG heel breaks are most often seen on flat sawn necks where the wood itself has broken on the grain Line. Similar is a headstock break. That is the problem with most SG and double cut LP breaks. Seldom would you see this on a quarter sawn neck on those same models. i have fixed several Les Pauls, and a 335 with a heel break as well. It was not the joint. (This one from the OP was a bad glue joint).
 

LtDave32

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Honestly, seldom is it the actual joint that fails. If the joint failed you would see a clean joint with say..glue residue. More often it’s the wood that has failed around the Joint. Ex: SG heel breaks are most often seen on flat sawn necks where the wood itself has broken on the grain Line. Similar is a headstock break. That is the problem with most SG and double cut LP breaks. Seldom would you see this on a quarter sawn neck on those same models. i have fixed several Les Pauls, and a 335 with a heel break as well. It was not the joint. (This one from the OP was a bad glue joint).
Exactly right, Joe. Flat-sawn wood will split like kindling before the glue fails.
 

dcomiskey

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Isn’t the general consensus that Titebond II should NOT be used for instruments??
 

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