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  #16  
Old 05-04-2016, 09:49 AM
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When the neck pulls away from the body as you've described, that is certainly a failure of the joint. However, such examples are failures in execution, not design. A properly fitted joint will withstand the force of normal string tension indefinitely. Though I own some instruments with bolt-on necks, I am not persuaded that anything is really better than a dovetail as far as acoustic guitars are concerned.
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  #17  
Old 05-04-2016, 10:31 AM
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Bruce Sexauer Bruce Sexauer is offline
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A properly executed blind dovetail/mortise joint is a mechanical connection, and does not actually require glue at all for its strength. In reality getting the joint exactly right is an art that eludes machinists and time card punchers and has quite a learning curve as well. Also, wood moves constantly in the real world, and a bit of glue goes a long way both correcting small discrepancies and insuring that it does not slide apart. No properly fit dovetail should ever be able to allow a 1/8" gap to appear at the heel unless something has actually broken. The rub is that there are plenty of improperly fit dovetails out there, but one must not judge the quality of the joint by the failure of those which were not made correctly in the first place.
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Last edited by Bruce Sexauer; 05-04-2016 at 05:15 PM.
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  #18  
Old 05-04-2016, 11:38 AM
Howard Klepper Howard Klepper is offline
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I use both, depending on the guitar and the preference of the person commissioning it. Same price--there is no significant difference in time and material cost. Fitting the dovetail requires a bit more sophisticated ability to visualize in three dimensions, and more experience to get it up to speed. But I regularly use a dovetail joint on my least expensive guitars because I like making them.

Bolt on is easier to take apart, but what is the big deal about an extra 20 minutes after 15 years?

Dovetail is lighter weight, allows for a more elegant heel shape, and pleases traditionalists.

Neither comes apart on its own when well executed. I use this stuff to keep the bolt from getting loose (do not use the red stuff):

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  #19  
Old 05-04-2016, 12:08 PM
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I use a dab of white wood glue on M&T bolt threads. The cured bond is easily broken with a hex key wrench or nut driver but the bond is firm enough not vibrate loose. As Bruce mentioned I too have fixed a few loose bolts as well. The worst thing you can do is oil or grease the bolt threads before assembly. Learned that lesson ... the hard way
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  #20  
Old 05-04-2016, 12:45 PM
MC5C MC5C is offline
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Where I don't understand the statement " A properly fitted joint will withstand the force of normal string tension indefinitely" is that to me it ignores the fact that the material is wood. Wood is a cellulose and lignin composite full of cells and fibers, and it's remarkably subject to deformation, humidity, stress, rot, insect infestation, et al. So the word "indefinitely" has no place in a sentence referring to wood. In the case of my Epiphone, the failure was partly in the compression of the wood in the joint so the joint got looser than it was when it was new. The wood squashed out, basically. Wood is not immutable therefore a joint made of wood is not immutable, as some think it is. If I'm wrong in my thinking, and wood can last unchanged for centuries, school me in that... I live in a house that is 180 years old - I'm seeing (and sometimes fixing) the effects of time on wood joints pretty much always...
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  #21  
Old 05-04-2016, 05:30 PM
LouieAtienza LouieAtienza is offline
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Quote:
Originally Posted by Todd Yates View Post
IME the "rising tongue" is nearly always an underset neck and the fretboard extension only appears to be rising if you look at it from the wrong reference point.

The Taylor N/T joint is wonderful for manufacture and repair, but the whole thing adds considerable mass to that area of the guitar. It works, but it's not what I'd consider elegant construction.
What you describe does occur but not what I consider a rising tongue. It's more of a neck misalignment caused by either the bottom of the heel joint coming loose, the back and neck block separating at the upper bout, or the back deforming to flat, causing the neck to rotate about the edge of the upper bout. What I refer to as "rising tongue" is the fretboard extension either swollen from introduction of moisture (more common in Strat necks) or possibly a neck tenon set too low in its mortise, all of which the NT joint tries to eliminate.

No question the NT joint is more of a "brute force" approach but it does allow adjustability without making the guitar appearing out-of-the-ordinary. Not elegant construction maybe but more of mechanical engineering, which is fine. As to weight, I don't see that as a major concern as long as the balance of the guitar is not severely affected. It's not moving mass, we would hope, and we're not running uphill with the guitar, so the tradeoff of a little weight for more flexibility in adjustment is fine from Taylor's standpoint. Not saying that this should be the de facto standard for neck joints, but cool nonetheless.
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  #22  
Old 05-04-2016, 05:32 PM
LouieAtienza LouieAtienza is offline
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Quote:
Originally Posted by Howard Klepper View Post
I use both, depending on the guitar and the preference of the person commissioning it. Same price--there is no significant difference in time and material cost. Fitting the dovetail requires a bit more sophisticated ability to visualize in three dimensions, and more experience to get it up to speed. But I regularly use a dovetail joint on my least expensive guitars because I like making them.

Bolt on is easier to take apart, but what is the big deal about an extra 20 minutes after 15 years?

Dovetail is lighter weight, allows for a more elegant heel shape, and pleases traditionalists.

Neither comes apart on its own when well executed. I use this stuff to keep the bolt from getting loose (do not use the red stuff):

I'd agree that it shouldn't matter to any experienced builder which is preferred, as long the voice of the guitar pleases both owner and builder and both are fine with the choice.
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  #23  
Old 05-04-2016, 05:44 PM
jessupe jessupe is offline
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While on the subject, has anyone used carbon fiber bolts/ screws?

for example

http://www.schmolke-carbon.com/carbo...uk/schraub.php
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  #24  
Old 05-04-2016, 05:53 PM
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Quote:
Originally Posted by MC5C View Post
Where I don't understand the statement " A properly fitted joint will withstand the force of normal string tension indefinitely" is that to me it ignores the fact that the material is wood. Wood is a cellulose and lignin composite full of cells and fibers, and it's remarkably subject to deformation, humidity, stress, rot, insect infestation, et al...
Fire will also cause a dovetail neck joint to fail. I wasn't talking about extreme abuse though.

Quote:
Originally Posted by MC5C View Post
...So the word "indefinitely" has no place in a sentence referring to wood. In the case of my Epiphone, the failure was partly in the compression of the wood in the joint so the joint got looser than it was when it was new. The wood squashed out, basically. Wood is not immutable therefore a joint made of wood is not immutable, as some think it is. If I'm wrong in my thinking, and wood can last unchanged for centuries, school me in that... I live in a house that is 180 years old - I'm seeing (and sometimes fixing) the effects of time on wood joints pretty much always...
indefinite: not clearly defined or determined; not precise or exact

Nothing is forever, but I assumed that was understood. We don't have any 10,000 year old guitars to examine, but that's not a practical time frame in this context. My point was that there is no particular expectation that a dovetail joint should fail after a set period of use. For example, it is extremely uncommon to see any vintage Martin dovetail joint fail unless it has been tinkered with somewhere along the way. These joints were extremely well fitted and of the best quality mahogany. I contend that nearly any dovetail failure in acoustic guitars is due to improper construction or poor material choices.
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  #25  
Old 05-04-2016, 07:26 PM
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I have never seen Honduran mahogany "crush" in a dovetail application. This suggests to me that an inferior, or inadequate, piece of wood was used for the purpose. Balsa wood I can picture crushing, or possibly poplar, but even the Catalpa I have use in two cases seems to be up to the task. The forces involved are not all that high, and they are distributed over several square inches of surface.
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  #26  
Old 05-04-2016, 08:52 PM
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The proper term for grain crush, is "compression setting" this is when two or more individual peices of wood swell to a point where they crush the opposing contact edges of each other, then once the swelling is gone, the fit of the pieces will now no longer gapless based on the wood of each piece literally becoming pressure treated and is now actually dimensionaly smaller than when the construction occurred. In any event in order for, or if this occurs, this would imply improper owner care and or stewardship as the moisture content would have to exceed a prolonged min 4% mc above normal for quite some time in order for this to occur. Tis also somewhat gets into material choice for blocks, compression setting is far less likely to happen when a hardwood is joined to softwood, the softwood may compress some, but is far more likely to reswell after being crushed,maple for example, loves to compression set if it is married to another piece of maple.

I agree with Bruce, and as long as this is properly executed, and the instrument is well cared for it's not an issue....

I see Taylors bolt on a way for a large factory to mitigate a bunch of end users that end up with their instruments that don't know how to care for them, or would not be as hyper vigilante as one who paid 10k for a custom may be.

And it may be helpful for them based on shipping to many regional moisture content regions on a large scale

Last edited by jessupe; 05-04-2016 at 09:12 PM.
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  #27  
Old 05-04-2016, 09:40 PM
LouieAtienza LouieAtienza is offline
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Quote:
Originally Posted by jessupe View Post
I see Taylors bolt on a way for a large factory to mitigate a bunch of end users that end up with their instruments that don't know how to care for them, or would not be as hyper vigilante as one who paid 10k for a custom may be.

And it may be helpful for them based on shipping to many regional moisture content regions on a large scale
The most helpful thing at the factory is that setting the neck angle is independent of the geometry of the heel and upper bout, which we all look to perfect when attaching a neck "conventionally."
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  #28  
Old 05-04-2016, 10:05 PM
stringman5 stringman5 is offline
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It seems to me that failure of the neck joint isn't really the issue. My understanding is that, over time, the soundboard and sides can become deformed due to stress from string tension, making a neck re-set necessary to properly re-adjust the neck angle.

The Taylor bolt-on neck technology accomplishes this quickly and inexpensively. My understanding is that resetting a dovetail neck joint requires a very skillful luthier and is therefore rather expensive.

I once read that luthier Linda Manzer said that it is inevitable that an instrument will need a re-set at some point in it's lifetime. If a re-set is inevitable, isn't better to utilize a design which enables this to be done more quickly/inexpensively?
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  #29  
Old 05-04-2016, 10:12 PM
H165 H165 is offline
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Quote:
Who still uses a traditional "dove-tail" neck joint?
Martin. Depends on the model.
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  #30  
Old 05-04-2016, 11:26 PM
jessupe jessupe is offline
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Quote:
Originally Posted by LouieAtienza View Post
The most helpful thing at the factory is that setting the neck angle is independent of the geometry of the heel and upper bout, which we all look to perfect when attaching a neck "conventionally."
yes, probably save them a bundle in time and making it so less skill is needed to assemble.
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