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In my current build, I was inclined to forego the tenon/mortise and opted to bolt on straight to the face of the ribs.
It made me pause and wonder why I've spent as much time as I have perfecting the tenon and mortise.

Can any of you please comment as to the benefits of the t/m versus bolting the neck flush without a t/m.

I don't glue it in place and never have. So why should I bother.


Thanks in advance for any insight you can lend.


Dave

I don't bother with the mortise and tenon any more, so I will give you the "go for it" perspective.

As long as you use a heel that is a little beefier than average, I think a simple bolt on butt joint works great. I put a dowel in the heel, so that the threaded inserts aren't just hanging onto end grain.

Alignment is one reason for the mortise and tenon; another is to have more wood for the attachment system than a mere skinny heel. I think alignment goes fine without the mortise and tenon, and putting more wood into the heel gives enough wood to do the job. So, I have stopped using the mortise and tenon. Just my perspective.

I don't bother with the m&t either. Makes fitting the neck to sides easier. That said, I do worry about drilling through for inserts or hanger bolts every time I do it. So far, I've never had a blowout; but I'm sure I'll make a mistake someday.


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I only use the M&T if I need to make a really thin heal like on a Selmer guitar for example. Otherwise it's a straight up butt joint. Nice and simple and very easy to floss for future neck angle adjustments. If you glue a dowel in through the heal with the edge grain away from the bolt inserts it will not only give you some extra strength for the inserts but also help hold the heal together real well.

Well, I like M & T because I like slim heels, and for flossing, because it locates and steadies the neck position.
But I never have make a butt joint.

_________________
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Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

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We do butt joints, M&T, and dovetail, depending on the project. I may develop a preference over time, but at this point, each joint has its strengths and weaknesses.

Alignment of threaded inserts seems very sensitive compared to the range of misalignment that a barrel bolt/tenon design can tolerate, but I suspect that it's more of an issue for neck resets than new construction. We use reinforcement in both designs to address their respective weaknesses - we insert a hardwood dowel from fretboard to heel cap for butt joints to increase resistance to withdrawal of the insert and insert graphite in the end of the tenon to protect against bearing failure adjacent to the barrel nut.

Heels like Mr. Somogyi's low profile design or older square-heeled Guilds are not deep enough in the longitudinal direction to use an insert, so we use either M&T or dovetail for these block-style heels, and for the older, more graceful Martin-style heels which lack much depth in the areas where the inserts and reinforcement must go.

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A constellation only takes shape when one maps the whole.
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Sorry, not a real woodworker here (unless you count 6th grade woodshop). When you say a butt joint, you're saying the end of the neck is flat and it just butts against the flat sides? There's no pocket at all? Yeah, I know that sounds like a stupid question seeing as it's called a butt joint, but I just want to make sure I understand. My guitar used a t&M and two bolts, plus the fretboard is lightly glued to the top. I assume you glue the fretboard to the top?

Just wondering about twist. I imagine a couple of "el kabong" overhead swings of the guitar could loosen things up. Sometimes you just have to beat those drunken patrons back a step or two. Seems like with two bolts like there could be some slop over time and allow for twist. I don't know if that would affect the tuning at all but maybe the finish...?

I would think that even a shallow MT would eliminate that, but it sounds like it is not a concern?

Robert--

Right; the end of the neck just butts up against the sides at the neck block area. Bolts go through the neck block and sink into threaded inserts in the end of the neck heel.

Once you snug up the bolts properly (using some sort of compression washer is a good idea), there is no real opportunity for the neck to move around. Leaving the bolts too loose can cause an issue, I guess. The answer is to get the neck aligned right, bolt it down using compression washers (I use Belleville washers), and not mess with it unless/until you need to take the neck off.

Many folks glue down the fretboard to the top, but some don't. I don't any more. I use smaller bolts. I like being able to take the whole neck off without removing any glue. Note that deciding to go with this sort of neck attachment system calls for some modest modifications inside the box. You really need a solid bit of wood between the neck block and the upper transverse brace in order to get away with not gluing down the fretboard.

In the larger scheme of things, the minor help that a mortise and tenon could give me for alignment is not worth the hassle of creating the mortise and tenon. Remember that the neck block needs to be thicker in order to have room for the mortise and still be solid enough to hold the guitar together. I would just as soon have the neck block be a bit thinner, beef up the heel of the neck a little, and just do a butt joint. I find it to be a lot easier to deal with. To each his/her own.

Yup butt joint is flat. I've always considered gluing the FB down as part of the joint. Here's a shot to show the dowel and the flatness of the joint, actually that one was arched a bit later to fit the profile of the arched headblock on this parlor guitar.

huh... that's surprising. Thanks for the picture. I would have thought the dowel would have been a bit deeper into the heel. We did the barrel bolt thing on mine, but I can see the benefit of using a glued dowel... larger surface area and all that.

Don... I was thinking that there could be a minimal M&T joint only to prevent twist... wouldn't even have to be through the side thickness... so no extra depth on the neck block.... but even if that's not needed.... hmmm.
certainly simplifies things. of all the parts that go into a guitar, the neck joint is the most daunting to me.

For me it's a matter of playability. If there's no cutaway, then the limiting factor is when your hand runs into the shoulder of the guitar, so a butt joint is fine. But if there is a cutaway, then the limiting factor is when your thumb runs into the curve of the heel, so the slimmer you can make it, the better, and a tenon is definitely necessary.

A 12 fret cutaway with slim heel has about the same range as a 14 fret cutaway with fat heel.

Robert, that dowel goes almost all the way through. I think there is about 1/8th inch wood before the fretboard. Then it's capped with the ebony heal cap.

The receiving end looks like this:

Oops sorry about the huge pic, I don't know how to resize that.

I'm going to argue for the tenon.

Any time you put hardware into wood you create a stress riser, or, at least, a high probability of one. Even when the hardware fits perfectly, it only requires a bit of over tightening of the bolts to put a lot of stress on a small area of wood. With threaded inserts you should tap the holes before screwing them in, to avoid pushing the wood aside with the chance of producing cracks. With cross dowel nuts they should fit tightly into the holes to avoid a big stress riser. I've seen failures with both, and even if they're rare, they should be guarded against.

A helpful principle is always to think about making a joint that 'fails well'. That is, assuming that it may fail at some point, you want it to fail in a way that is not catastrophic. With a bolted butt joint that's hard to insure; if the wood breaks there's a pretty good likelihood that the neck will come off, and you could end up dropping the box.

With a tenon you can design the joint so that any failure splits the neck along it's vertical center line, rather than across the heel. This might be hard to do with threaded inserts, but with a cross dowel nut you simply align the nut vertically, perpendicular to the surface of the fingerboard. This will split vertically, and, with the two halves of the tenon enclosed in the mortise, the neck will stay put, held on by the bolts, even if the split goes all the way through. Note that drilling the cross dowel holes across the tenon, parallel to the fret board surface, can allow the neck to split off the body. This happened to one of my students. He over tightened the bolts, putting a lot of spitting stress on the wood, and when he picked the guitar up, with no strings on, he hit the head lightly on a beam in the ceiling. The hell split, the neck and body parted company, and the body was damaged when it hit the floor. Had the nuts been aligned correctly over tightening them would not have caused the sort of damage he got because the tenon would have been retained in the mortise.

"Any fool can learn from his own mistakes: a wise man learns from the mistakes of others"
Bismark

I think tenon-less bolt joints are much less likely to stand the test of time.

Even the big boys, with plenty of money for engineers and testing, have struggled to mount necks on with bolts.
The ones still holding are relatively young.

As a repair guy, I see a lot of broken stuff. A broken neck joint is an expensive come back.

If I had to bet on any version of a bolt on, it would be a Collings. w/ a tenon, a dowel, and threads very deep in the wood.

Remember, every once in a while, someone is going to "snug up" the bolts just be sure. After 10 rounds of that, the wood is going to be working pretty hard.

Dovetails might be a pia, but man, they hold like the devil. For a long time.

Some may recall that the original Taylor's had butt joint necks. Purely speculation on my part but I suspect that Bob Taylor knew that competing with Martin and Gibson in the high end market with such a design was a long term loser.

While I know that properly thought out butt joints work, I too will take the side of the MT. If nothing else, right or wrong my sense of structural integrity leads to multi-surface inter-locking joints and beefier is better.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Interesting points being brought up and much of it stuff I'd never thought of before.

Would love to hear more ideas on the subject.

Isn't the current Taylor neck joint, the NT neck, just a butt joint set into a shallow pocket? I guess my point is this: we all have our preferences, but Taylor is not in the business of building guitars that fall apart. If a butt joint was shaky, they would not still be using a version of it.

No -- There is actually a hefty section of the neck running under the FB extension that is secured with a third fastener in a mortised cantilevered neck block.

http://www.frets.com/FretsPages/Luthier ... joint.html

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Ken Cierp

http://www.kennethmichaelguitars.com/

Ken--

I understand about the section under the fingerboard, but my focus is on the fact that the heel has no tenon, and it is connected to the body with bolts and threaded inserts.

I think Taylor gave it up because of the backlash that.. OMG??? A butt joint??? Had on the public.

I don't see how a tenon that is not glued in has any real multi surface structural integrity. I have thought about the twisting action that might take place at the heal but isn't it minimal? I do make sure that my butt joint is flush, no light can be seen through it, so the friction is maximized but even so I would think twisting there would be minimal enough to not worry about. In fact you could probably really just get away with one bolt lower towards the heal cap, I use two like most do, but the majority of the string tension force is right up top under the fretboard.

I suspect the over torquing of bolts, but quite a few have come through my shop with stress cracks around the insert area.
Maybe part of a dovetails longevity is it's tamper proof from the outside.
Peel back the label with a bolted neck and anyone with a 7/16" socket is in the neck reset business.
You can argue Martins bolt was just supposed to be a clamp for the tenon glue joint but from what I have seen, the convenience of bolt on necks appears to come with increased long term risk.

Has anyone seen a Collings neck joint failure?
Like all bolt on necks they are relatively young but I never have. I'm curious if this points to a more successful design or just the small sample of one repairman.

Someday, I would like to learn to do a dovetail that is held with bolts instead of glue. I know that there are several folks who have been doing it successfully for years, and it seems like the best of both worlds to me.

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"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
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bolt-on necks sure are not anything new. Check out the 1930's Kay bolt -on ( http://littlebrotherblues.com/Gear/Kay-Bolt-Ons-1930s/ ) I also prefer bolt-on mortise & tenon, although I used a dovetail on the last build.

Don, that doesn't make any sense to me? I'm not trying to be argumentative but rather try to understand. The dovetail is a mechanical locking joint, hardly even needs any glue really. The bulk of string tension force is right under the fretboard where the binding is and the tension tries to fold up the neck like a book. That means that the bottom of the joint where the heal cap is, is rotating out opposite of the direction at the top under the fretboard. So the very tip of the tail of the dovetail joint and it's cheeks lock due to that very tension. If you were to put a bolt there through the head block would you not be defeating that purpose? In that case I think it would act just like a bolt on M&T. Unless of course I suppose you could balance the torque of the bolt with the locking rotating action?