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All of my acoustic builds have used dovetail joints. I have never had a problem with any of them on flattops -- the joints have held perfectly (some for over 15 years). But I have also made 3 archtops using the Benedetto dovetail. Over time, the Benedetto dovetails all separated at the heel. My latest archtop build -- last year -- now has a 3/32" gap at the bottom of the heel, and I have to lower the bridge as far as it will go to keep the action acceptable; it was perfect when I finished it last year. Very frustrating.

So, I'll steam the neck and re-do the joint. But given the fact that I have never figured out how to get the Benedetto style dovetail to work, I'm considering converting this to a bolt-on neck. My approach would be to remove the neck, trim the dovetail on the neck so that it looks like a traditional tenon, shim the mortise so that it fits the tenon, and then add the bolt-in hardware to the neck and bolt it on. The alternative would be to take another stab at shimming the dovetail and see if it finally works. (But then the definition of insanity keeps repeating in my head...)

Has anyone tried converting a dovetail to a mortise-and-tenon bolt-on joint before? Has anyone ever figured out how to make the Benedetto joint work consistently?

BTW, I've currently got three flattop builds under way. All of them are going to be bolt-ons. I'm struggling to see any reason to continue using dovetails, especially given my frustrations with the archtops.

Thanks.

Since no one else has responded, I guess I will jump in. I have only made one Benedetto style archtop with a dovetail. All my other guitars are flattop with bolt on necks. I have to say that the only way the heel can come loose from the body is if the dovetail did not fit the mortise when constructed. The normal fix would be to reset the neck and shim the dovetail. But you would need to make sure you get it tapered correctly and fit snugly so this doesn't happen again. Converting it to a bolt on would be the last ditch option.

Kelby, I had the exact same frustration with my first archtop and came to nearly the same solution.

However, I see no need to change the joint to employ bolts. Instead of changing the joint (to a rectangular tenon), or the like, I merely added two bolts to the dovetail joint and called it a day. I was emboldened by the fact that great guitars are built with only a plain butt joint (Mario). Apparently, a tenon is not really necessary.

Fortunately, my neck block was robust enough. Take your neck off and drill holes for the two inserts. Getting the placement of the holes in the neck block (drilled from outside) is tricky. I had one perfect and had to elongate the second one for a good fit. I believe the well-aligned hole keeps the neck from sliding out of position. YMMV

My adaptation works perfectly and I have no regrets - it's been perfectly stable for a half-dozen years and I see no reason to fret about it. To me, "last ditch option" seems unnecessarily judgemental. (No disrespect meant Barry). I know you are a hobbyist like me, and since it seems to work fine, I think it's an ideal way to solve the issue.

I had to find a tool to fit through the end pin hole (mine has a jack assembly for a single pickup) and reach all the way to the neck block to tighten the bolts. That is the only special tool you might need.

Good luck.

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I wan't being judgmental. It is just that a conversion to a bolt-on will be irreversible. Why not try to reset the dovetail? Nothing to lose and he might learn something.

Kelby, I want to ask what is different between your flat top dovetails and your Benedetto dovetails. Is it the joint itself? Or is it the angle at which the strings pull the neck (and the dovetail joint) back?

Kelby, are you using a router and a holding fixture as Benedetto does or hand cutting the joint? I have had no problems with this joint on any of my many archtops, so I know it is a good joint. I think Bob's instructions say it best, "Remember, its a good practice to fit the dovetail so that the heel end is slightly tighter." With the heal tight the joint is not as likely to pull away. A well fit joint will hold with almost no glue to bond it. I think if you shim to get a good fit you will have no problem with a re glue, provided the neck and neck block are stable. I have never tried a bolt on neck but it does sound doable.

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Thanks to all for your comments.

My flattop dovetails are cut using a StewMac template and bit, and I've never had any problem with them. They are the traditional V-shaped dovetail.

Benedetto does this weird thing where the dovetail is not in a V-shape. The tenon is the same width all the way down, and the mortise is 1/16" too tight at the bottom. You squish the neck into that 1/16" of material and glue it there. I've tried to do that several ways and have never had success. I do believe that other people (including Benedetto) are getting the joint to work fine, so I don't believe it's inherent in the joint. It's something about the way I'm doing it.

I like the idea of simply adapting the existing dovetail joint to a bolt-on without converting it to a mortise and tenon joint. That sounds like a straightforward solution that is virtually guaranteed to work.

BTW, I have been using a router to cut the joint, and it is a very clean and tight dry fit. The joint held up for quite a few months. But now the guitar is a year old, and the heel is separating.

Thanks to all for your suggestions.

Those Benedetto joints were the bane of our existence at Palomar College during the archtop building class. MANY of us discovered the utility of a strap button strategically placed on the heel!

Seriously, that was the last time I did one of those. I have a shop made long reach allen wrench and do bolt ons through the end pin on all my guitars now.

All my archtops have been bolt-ons reached through the end pin/pickup opening. They have held up well. I play one that is five years old and has not required tightening so far.

One thing, the neck angle is a lot more than a flat top and it's nice to have a system that self-aligns. The Cumpiano barrel nut thing has worked well for me. I would worry about asymmetrical stresses on threaded inserts unless they were placed at a slight angle to align with the face of the headblock.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Terence, good point on the angle. I was planning to have the inserts align with the face of the headblock.

Since this is a finished guitar, the one thing that will be a hassle is that I'll have to drill through the heel cap, which will require a patch and re-finishing the heel cap. I can't see any way around that. let me know if anyone has creative approaches for avoiding that.