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Thread: Help me understand mortise and tenon neck joints

  1. #1
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    Default Help me understand mortise and tenon neck joints

    While traditional dovetails are considered to be the best neck joints, there are many builders who use the straight mortise and tenon. For example, all Weber neck joints used to be mortise and tenon. Now just the Gallatin and Bitterroot use it. But that Weber mortise and tenon also uses bolts in addition to glue. And Martin used to use a straight mortise and tenon on all the series below 18. They have now switched to an “improved dovetail” which is actually still a sort of mortise and tenon, not a true traditional tapered dovetail. A lot of people don’t know that there is actually a screw in that joint. The screw head is hidden by a wooden “plaque” on the heel block. I guess my point is, I don’t know of a straight M/T that uses glue only with no screws or bolts.

    Now, with that background, what do the builders say about a straight mortise and tenon neck joint that uses glue only, absolutely no bolts or screws. Would such a joint,assuming it is well made and closely fitted, be stable enough? In this hypothetical scenario, the back button would cover the neck heel, and the fret board extension would be glued to the top. I thank you in advance for your thoughts on this.

    Don
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  2. #2

    Default Re: Help me understand mortise and tenon neck joints

    Unless it's failing, a properly sized mortise and tenon joint would not be substantially strengthened by the addition of a screw.
    A 1"x1"x1" mortise and tenon joint, or similar, has several times more strength than is needed to support the forces involved.

    I guess one thing you could think about is the size of joinery on furniture, and the amount of force they have to withstand. A well-made table need not be especially well constructed to hold a thousand pounds or more. Much of that is dealt with by the vertical legs bearing directly, but there's still a lot of lateral forces they experience in daily use, and the last a very long time. I'm writing this on a 250 year old pine table which has never had anything done to it than a new coat of varnish from time to time. It's made of 1" thick pine throughout. And it's super sturdy, even after several generations of rowdy kids climbing on it.
    Last edited by Marty Jacobson; May-04-2019 at 7:15pm.

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    Registered User sunburst's Avatar
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    Default Re: Help me understand mortise and tenon neck joints

    In an ideal world; one where players never abuse their instruments, never forget and leave them in the hot car, never have dogs or kids, never collide with other musicians on stage; a well fit straight mortise and tenon neck joint should hold up fine for centuries. In "the real world" hot cars, dogs, kids, bass players and stuff exist. Thus even well fit dovetail joints sometimes fail.

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  6. #4

    Default Re: Help me understand mortise and tenon neck joints

    And don't ever set your mandolin down in a bowling alley.
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    Default Re: Help me understand mortise and tenon neck joints

    Thanks for the responses so far. Yes I am aware that any neck joint can fail. And that in an ideal world any sort of joint can be ok. But I’m looking for a bit more detail. Here’s what I know. Modern Gibsons all use the traditional dovetail. In the recent past, when Bruce Weber was there, they used mortise and tenon with two bolts. Weber is now using traditional dovetail, except for “ entry level” instruments. In the past they all used M/T with bolts. Breedlove, when they were made in USA, used a bolt on neck with no glue, sort of ala Taylor, but no M/T at all but just a flush fit butt joint. I don’t know what Collings uses. Builders who use the Siminoff joint use a straight mortise and tenon but reinforce it with two dowels. Martin uses a screw to stabilize their M/T.

    What do all of the above mortise and tenon joints have in common? None of them stand on their own. All of the above builders seem to think their mortise and tenon joints need something extra. Bolts, screws, dowels, whatever. They need something, it would seem. Dovetails apparently need none of that. Now I have run into a builder. I will not name him out of respect. He uses the joint I describe in my original post. Straight mortise and tenon, glue only. Given the reply’s above by two very respected makers, this should not make me run the other way. And yet, if a straight mortise and tenon held in with only glue is more than strong enough for the job, and if extra reinforcement is not necessary, why do so many include it? And while I’m at it, why do so many builders (mostly smaller shops) not even list the type of neck joint in their specs? This particular builder only disclosed that information when questioned about it. In my opinion, the type of neck joint used in construction should be as much a part of the builder specs as anything else. As a buyer, I want to know that.

    Don
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    2011 Weber Bitterroot A
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  9. #6

    Default Re: Help me understand mortise and tenon neck joints

    I've thought that perhaps the use of a screw was simply just to fully seat and clamp the joint as the glue cured allowing alignments to be checked and the screw itself assisting in maintaining the alignment while the glue dries. The screw also inhibits creep. In electric solid body guitars there is no screw used. Some joints are frighteningly minimal but then the string tension is about half.

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    Registered User Charles E.'s Avatar
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    Default Re: Help me understand mortise and tenon neck joints

    I remembered this article from Fine Woodworking back in 2016.......

    https://www.finewoodworking.com/2016...tronger-tenons

    Having a perfect fit is key.

    I realize that the article does not pertain to mortise and tenon joints in musical instruments but I thought it was interesting none the less.
    Last edited by Charles E.; May-05-2019 at 9:39am.
    Charley

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  13. #8

    Default Re: Help me understand mortise and tenon neck joints

    Two reasons for bolts:

    1. Bolts can be used without glue. This makes later neck adjustment much easier.

    2. If a tenon is glued with Titebond, excess heat (e.g. left in a car on a sunny day) could soften the glue so the joint moves - the bolt is insurance against this. I've made one guitar with glued tenon and no bolt, but I used HHG for this reason.

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    Default Re: Help me understand mortise and tenon neck joints

    Well fit mortise and tenon joint don’t ‘need’ any reinforcement, Siminoff and Martin included. Martin was 50 years behind Gibson in neck design, ie, no adjustable truss rod. Siminoff, for all his other virtues, was not an experienced woodworker. No other instrument maker ever used such a joint commercial production.

    It’s easier to draw a dovetail tighter than a m/t joint, but in neither case is the stress directly trying to pull the neck out of the joint.

    Commercial joinery often has more to due with cost and ease of machining/assembly than any other factors.
    Play it like you mean it.

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    Default Re: Help me understand mortise and tenon neck joints

    I have been interested in this issue for some time and started a thread on this forum "Neck Torque" on April 10th 2014. In this I showed the results of an experiment I performed that seemed to indicate that a simple mortise/tenon joint like used on violins is sufficient to keep the neck joint from failing. Sorry, I don't know how to give a link to that thread but it is shows up in a simple search.
    -Newtonamic

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    Default Re: Help me understand mortise and tenon neck joints

    Don't forget the word marketing. Tout something as superior often enough, and charge extra as validation, and people take it as gospel. Weber is subtle. You don't want that old joint, do you? But you do want the new one, so upgrade.

    Play the mandolin, like the mandolin, buy the mandolin. Both designs work.
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    Registered User artdeco's Avatar
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    Default Re: Help me understand mortise and tenon neck joints

    The one advantage I can see for the M/T is you can make the entire neck in one piece - no 15th fret 'hump' in future.
    MLAtkinson
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    Default Re: Help me understand mortise and tenon neck joints

    I transitioned from the so-called “Siminoff” V neck joint, which is a mortice and tenon joint similar to violin neck joints, to the traditional Gibson style dovetail neck joint. In the process, I built a number of neck and block pieces to simulate straight and almost straight M/T joints. Pulling and tugging on all these without glue and without top and bottom coverings, I was not impressed with the strength of the straight joints in any direction – no matter how perfect the fit. Putting a screw or bolt in them seemed like a short term fix, although I guess if it lasts 5 or 10 years maybe that's good enough for some folks. I know Taylor and Martin changed their bolt systems several years ago because the old systems were coming loose too much. Seems like Weber may have made some changes too. I know there are builders of different instruments using straight M/T neck joints with success. I have so far been unwilling to take the risk, especially since the V joint and the dovetail are easy enough to do and are very stable.

    I think every style of joint has it's strengths and weaknesses. The dovetail has it's share, but I think it's biggest strength is superior sound transmission – at least to my ear. Also, it is the king of marketing.
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    Default Re: Help me understand mortise and tenon neck joints

    Quote Originally Posted by Larry Simonson View Post
    I have been interested in this issue for some time and started a thread on this forum "Neck Torque" on April 10th 2014. In this I showed the results of an experiment I performed that seemed to indicate that a simple mortise/tenon joint like used on violins is sufficient to keep the neck joint from failing. Sorry, I don't know how to give a link to that thread but it is shows up in a simple search.
    Violin makers use a dovetail joint to set necks.
    Charley

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  24. #15

    Default Re: Help me understand mortise and tenon neck joints

    Seems to me that "bolt-on" necks work just fine in the guitar world -- perhaps better than traditional dovetail neck construction, because of the "adjustability" that is inherent in the bolt-on design. Glueless neck joints make eventual resets a breeze.

    Why wouldn't this work as well for mandolins?
    Perhaps it's "tradition" that keeps bolt-on necks out of mandolin construction?

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    Registered User Marc Berman's Avatar
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    Default Re: Help me understand mortise and tenon neck joints

    Quote Originally Posted by Charles E. View Post
    Violin makers use a dovetail joint to set necks.
    Actually they use mortise and tenon not dovetail.
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    Registered User Charles E.'s Avatar
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    Default Re: Help me understand mortise and tenon neck joints

    The joints are tapered in two planes, not parallel as with a mortise and tenon. The dovetail is not as dramatic as with guitars and mandolins but it is still a dovetail.
    I worked in a violin shop for twenty six years building violins and doing set up and restoration. I have set necks on well over a hundred violins, violas and cellos, I know what I am talking about.

    Sorry Don, I don't mean to hijack your thread.
    Last edited by Charles E.; May-05-2019 at 3:33pm.
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    Default Re: Help me understand mortise and tenon neck joints

    Quote Originally Posted by Charles E. View Post
    The joints are tapered in two planes, not parallel as with a mortise and tenon. The dovetail is not as dramatic as with guitars and mandolins but it is still a dovetail.
    I worked in a violin shop for twenty six years building violins and doing set up and restoration. I have set necks on well over a hundred violins, violas and cellos, I know what I am talking about.

    Sorry Don, I don't mean to hijack your thread.
    Yes violins use a dovetail, it may not look like it, but it is. Very similar to some very old parlor guitars.
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    Adrian Minarovic
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    Default Re: Help me understand mortise and tenon neck joints

    Quote Originally Posted by pops1 View Post
    Yes violins use a dovetail, it may not look like it, but it is. Very similar to some very old parlor guitars.
    If you ask any better violin maker he will tell you they DON'T use dovetail. The violin neck joint is equivalent of the Siminoff joint (minus the dowels) but it is very shallow. If you consider the wedge shape caused by widening of fingerboard towards bridge a reason to call it dovetail, I don't think it is correct as the difference within the depth of the joint is negligible and doesn't add any extra strength and tightening to the joint like the "tail" surfaces of "real" tapered dovetail do.
    I'd call it tapered mortise and tenon and in this case it mostly depends on the weak end-grain joint and back button to neck joint strength.
    Adrian

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    Adrian Minarovic
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    Default Re: Help me understand mortise and tenon neck joints

    To the OP. I do the tapered dovetail as if fit properly it will hold without glue at all, the glue is there just to hold it in place inserted inside and even weak glue will suffice and even if the instrument is treated badly it won't fail before the wood deforms (shrinks cracks etc.) if dovetail fails without mistreatment it is because it was not fitted properly to start with (search for my F-9 rework thread for some pics of such failure). On the other hand the tenon holds merely by action of glue. So once the glue releases the joint will slide open under tension of strings. Bolts will work without glue and as such they provide safety to the glued tenons. If carefully selected you don't need the glue at all and can use bolt on neck. The only negative is vibrations and seasonal changes in wood that can loosen the bolts over time...
    If you look at traditional japanese joinery you can see what I'm talking about of tapered dovetail. In some joints thay prepare all the pieces for tight fit and one long tapered pin will hold the whole together, no glue or bolts whatsoever. Glue replaces the tapered pin in dovetails but principle is the same - wood against wood to hold the forces.
    Adrian

  31. #21

    Default Re: Help me understand mortise and tenon neck joints

    I think it also comes down to a long established furniture making tradition that a joint should meet its function with or without glue. I remember my high school woodshop teacher saying this. The idea that the design and craftsmanship is primary and the glue and finish is secondary. You can even see this in old homes and boats -- no nails and no screws.

    A well fit violin or cello neck will actually stay in place on its own but certainly not under any string tension. Dovetail... yea... you might call it that but its stretching things a little and I'm in agreement with Adrian. The author and luthier Henry Strobel refers to the gap in the body for the neck as a mortise but I personally use a lot of nonstandard terms at my shop which are and are not accurate according to my contemporaries.

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    Registered User Charles E.'s Avatar
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    Default Re: Help me understand mortise and tenon neck joints

    Quote Originally Posted by HoGo View Post
    If you ask any better violin maker he will tell you they DON'T use dovetail.
    My employer is a long standing member of the American Federation of Violin and Bow Makers.....https://www.afvbm.org/

    These are some of the best makers in the country if not the world and I have only heard the neck joint of the violin family described as a dovetail joint. Perhaps it is different in Europe.
    Charley

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    Registered User Marc Berman's Avatar
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    Default Re: Help me understand mortise and tenon neck joints

    Quote Originally Posted by HoGo View Post
    If you ask any better violin maker he will tell you they DON'T use dovetail. The violin neck joint is equivalent of the Siminoff joint (minus the dowels) but it is very shallow. If you consider the wedge shape caused by widening of fingerboard towards bridge a reason to call it dovetail, I don't think it is correct as the difference within the depth of the joint is negligible and doesn't add any extra strength and tightening to the joint like the "tail" surfaces of "real" tapered dovetail do.
    I'd call it tapered mortise and tenon and in this case it mostly depends on the weak end-grain joint and back button to neck joint strength.
    Charles E. and pops1 - I always thought is as HoGo states. I'm not a luthier but I like to read and I've only seen it referred to as a mortise. That said I defer to more knowledgeable people
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    Default Re: Help me understand mortise and tenon neck joints

    Maybe it’s just a matter of semantics? A dovetail is technically a type of mortise and tenon. When the term “dovetail” is used there is nothing about depth, amount of taper, or in how man directions it’s tapered, unless there are qualifiers. Martin’s “improved dovetail”, for example, flares outwards but is not tapered top to bottom. So, in the case of the violin joint that seems to be causing so much controversy, maybe some call it a dovetail because of a slight taper in one direction? I think they are tapered top to bottom only. Incidentally, I believe I read somewhere that Stradivarius used to drive nails through the neck block into the neck to hold it on!

    J. Albert, the Breedlove mandolins that we’re made in USA, no longer made, had glueless bolt on necks. But obviously the concept didn’t take the mandolin world by storm.
    Don

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  35. #25
    Adrian Minarovic
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    Default Re: Help me understand mortise and tenon neck joints

    I'm not a violin maker, though I repaired many violin family instruments and have been on Maestronet forum for nearly 20 years (kinda equivalent of M-Cafe, but best violin makers of the world contribute there) There has been some disagreement about what is and what is not dovetail and some are strictly sticking to dictionary definition (that angled sides means dovetail) and some rely on woodworkers' oral definition af mechanical joint that can hold without glue (at least initially) by forcing "wood against wood of the tail" would not call it true dovetail as the typical violin joint just barely holds together without glue (a tight straight tenon would hold just as much) and mostly relies on the joint of back button and endgrain of neck root.
    I believe the violin neck joint should be in a category of it's own...
    I prefer to stick with woodworkers and not fully agree with dictionary (and encylopaedia) writers who quite often know nothing about he terms they define or describe.

    "Real" violin dovetail is in this thread:
    https://maestronet.com/forum/index.p...int-technique/

    This is commonly used on basses or cellos but rarely on violins (except one or two of those old factories of the past and few modern eccentric makers)
    Adrian

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