Set Neck to Bolt On Conversion

[John Gibson]

What do you think of this? I know that this is a controversial subject. I have never done it and would not consider it except that this guitar has some unusual circumstances.

Custom built 12 string circa 1995. Two years after build it was returned to the luthier for high action. Evidence shows the neck was reset. One year after that the high action returned and the once again the guitar was returned to the luthier who advised that the owner just tune down and capo on the first fret. The guitar was brought back home and has sat in its case since then.

When the guitar was brought to me, the action was extremely high and the guitar was unplayable. The neck was pulled way up and there was an obvious gap at the heel where it appeared to be pulling out of the joint. After removing the neck I found very thick paper shims had been used to tighten the joint. I mean really thick. The deterioration of the paper had resulted in allowing the heel to start to pull out.

Once I removed the paper and glue, the joint is very sloppy. More than I have ever seen. It was obviously not well constructed to start with. Another luthier that I have worked with recommended converting the neck to bolt on. His feeling was this joint would always be troublesome and this would be the best way to stabilize it.

I was real leery of this until I found an article on Frets.com where Frank Ford converts a set neck to bolt on. So to me, that lends this method some credibility. The major difference though, is he saws off the neck, leaving the tenon glued in place. This leaves a lot of wood and installing inserts is not an issue.

My concern is the tenon has close to a 45 degree angle and does not have enough wood to handle the stress of installing the threaded insert.

Has anyone handled a similar situation? Should I forget the bolt on and try to repair this joint?

Thanks in advance for the help!

[Mark McLean]

There are notable advantages, and very few drawbacks to a bolt-on neck joint.  It sounds like a good solution for this particular instrument, which has obviously had lots of problems arising from the current dovetail joint.  It might be a bad choice for a vintage or classic guitar by a notable maker - but this is not the case for this guitar.  You say the end of the tenon is too narrow to install threaded inserts.  In any case, those are not the best form of attachment as the inserts have a tendency to pull out of the end grain of the tenon.  Instead, you could install barrel nuts deeper in the tenon.  The strongest method of all is a rod or bar (or barrel bolts) inserted in the heel (covered by the heelcap) with threaded holes so that long bolts can engage deep inside the heel of the neck - after passing through the tenon and the neck block.  This last method is in the Gore & Gilet books, and is similar to the Collings method.  If you do some Google searching you will find images to illustrate this better than my words do.  There are lots of ways to skin this cat - but bolts will be your friend for this job

[Roger Häggström]

Even with big gaps in a sloppy dovetail, I can't see no reason not to use shims and glue as usual. Cardboard shims are a joke of course, but hardwood like maple will make reliable shims to the dovetail. With a tight fit that neck will be secured. Pictures may tell another story...

[John Gibson]

Thanks for the excellent advise given so far. I think I will go ahead and do the shims first. The barrel bolt plan is also excellent. I had seen that used in others, but only on new necks. I may end up doing both shims and the barrel bolt for insurance.

Here are some pics of the joint. It was hard to get one that really showed how sharp the tenon angle is. 

[Roger Häggström]

The tenon looks a bit thin. I would glue tight fitting shims to the tenon instead of the pocket using epoxy. Just to make it a bit stronger.

[George Roberts]

The tenon also looks very short.  As a result it is losing a lot of the mechanical advantage, and making it easier for the tenon to pull out at the bottom.  On the other hand, the heel itself looks quite substantial and could probably handle a bolt beneath the heel cap quite well.

I have never done a bolt on conversion, but this looks like a reasonable candidate.

[Mark McLean]

I hear Roger's argument that you could make the dovetail joint good with hardwood shims.  Probably true.  But remember that this is a 12-string.  How long before that string tension makes another neck adjustment necessary?  If you convert it to a bolt-on the next neck reset is going to be a walk in the park.  But if the neck joint is a patched, shimmed, glued dovetail - I wouldn't want to be the guy trying to do the next lot of work on it

[Roger Häggström]

Looking one more time on the picture, the tenon is too short as George said. That luthier did not know what he was doing.