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Sliding Neck Joint
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Sliding Neck Joint
Has anyone ever tried a Martin Keith style neck joint? I am thinking of using it on my first acoustic guitar using standard t track. I am curious if there are any tricks or tips to its successful implementation as I can only find limited information on it.
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16 Replies
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Hey Nicholas. I don’t know much about the construction of this neck joint. I remember him talking about it in detail on the Luthier on Luthier podcast. It is similar to a Ken Parker joint but less Ken Parker. I have read quite a lot on a tilting neck joint. Is there a reason you prefer the sliding over a tilting?
I would listen to the podcast and check out some forums for information on this. If I find some time, I will do the same and report back.
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That podcast is where I initially heard about it. I have found a couple other mentions of it elsewhere. I will add the links when I get back home.
I don’t have a preference really. I am just playing around with different joints to see how I like them and want to proceed. I played with the dovetail a bit this weekend and plan to play with a gore gillet style Bolton as well as another one I can’t remember the name of but will link to tonight as well. All that said I have heard that these vertical adjustment designs don’t affect the tuning as much (at all) and I like the greater contact between the body and neck. One thing I don’t like if for no other reason than string changes are joints that depend on the string tension to hold the together.
There was one other I was interested in and that was a Lambert that Chris Jenkins from Lamehorse mentions and uses. He mentioned he thought the mechanism might be going commercial several years ago but I haven’t found anything but that about it. I know he’s on here and was going to message him separately about it.
One final thing I want to make clear is that I am not trying to steal anyones IP or copy designs directly. Just trying to find what’s publicly available and to learn so I can make the best guitar I can in the most respectful way possible. So if something is protected etc please let me know that too so that I don’t accidentally step on toes. In Martin’s case he specifically has stated he’s not trying to obscure anything to someone serious about it.
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This is the main threads outside of the podcast that I have been able to find. https://www.acousticguitarforum.com/forums/showthread.php?t=283715
https://www.acousticguitarforum.com/forums/showthread.php?t=552744
http://www.mimf.com/phpbb/viewtopic.php?t=1794
mimf.com
Cumpiano's Hardware Based Neck Joint VS Tapered Dovetail Joint - MIMF
Cumpiano's Hardware Based Neck Joint VS Tapered Dovetail Joint - MIMF
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This is what I’ve been using, I think it’s the “Trevor Gore” neck joint. I’ve done 4 guitars with it, and I’m slowly refining it. I think you can see how it works from the pictures. Basically the neck pivots on a tab, there is a slot in the neck heel to ride on the slot. With the strings on you can lift the guitar by the neck. It mostly stays in tune even with adjusting the neck.
On the classical guitars I did, it was really hard to get a tight fit to the heel with the sort of traditional wineglass heel. Going forward I’ll be doing a square Somogyi kinda thing…same with the Gypsy guitars. Or maybe a V shape that transitions into a wineglass, but whatever way the sides of the pocket will be straight.
The one thing I don’t like about this is that in a cutaway guitar you have to have a lip on the cutaway side (the cutaway can’t terminate flush with the neck). I have not had anyone comment on that as being an issue but I don’t love it. You could have a flush side with a sliding tenon thing, but the adjustment would be worse. I’m not averse to trying that at some point, but right now this is working.
Crazy crazy easy to adjust even on the fly.
Geometry is sort of tricky to work out, and I’ve had to fudge a lot.
The guitars I’ve made with this sound very good, I don’t think there’s any significance to the neck joint at all, as long as it’s more or less rigid.
Also it’s very nice to me able to finish the guitar and neck separately. Huge really.
Kind of a random bunch of pictures but I think you’ll get the idea. There’s a video in there too of the adjustment
https://photos.app.goo.gl/xjNawya1rFZ6itC29
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oh and the other sort of annoying thing is that it might get in the way of your truss rod if you’re running your truss rod near the end of the neck (I still haven’t figured out how far I want the rod to go).
I think on the next necks, if I decide to run the rod all the way, I will offset the set screw to the treble side where I’d potentially want more stability anyway. I don’t think it will make any difference. Very worse case scenario I could use to screws.
I’m also using 1/4″ carbon fiber square tubes from Dragon Plate on either side of the rod (or no rod at all for the classicals).
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If you find a mechanism for the sliding joint, I’d definitely like to see it.
One thing you could do, without a mechanism, is have the neck sliding on some sort of channel but just have a set screw retaining it. So loosen the screw and slide it where you want it and then tighten it. Logical place would be to put the set screw in the heel, I just don’t love that aesthetically (perhaps some people don’t like my set screw in the fingerboard but I think it’s less noticeable with the visual noise from the strings).
I’m interested though, I don’t love that lip on my guitars.
The other thing I like about the design I’m using is that it puts the stress against the long grain of the neck (I have a fairly significant tab below the fingerboard that’s sunk into the body, and a big neck block below that). I don’t really love that on the designs where the adjustment is in the heel it’s stressing the short grain of the heel. I’ve not heard of them breaking at the heel but it doesn’t seem ideal to me. In the Gore design, the heel is basically non-structural passed the slot where the tab goes in.
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shit sorry. One more link:
https://uptonbass.com/shop/upton-bass-adjustable-removable-neck-upgrade/I imagine this is somewhat like what the Keith joint is talking about? This is very very common with modern upright basses. I don’t know what the mechanism actually looks like. I think they sell it to luthiers for retrofitting to other instruments. Some sort of track system with a screw of some sort.
uptonbass.com
Upton Bass Adjustable / Removable Neck Upgrade
Double Bass Removable Neck Upgrade Travel Bass
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@PaulMcEvoyGuitars Those are some nice guitars you make. I have the Gore/Gillet Books and while their neck joint looks very similar its a pure bolt on/off and doesn’t pivot. I have seen something similar to what you have before pivoting on the CF Pad. Unfortunately I can’t remember where I did and heck it may have been a post by you in another forum.
As for your design if I am understanding what is going on is that there are two bolts in the finger board extension. One that is used to hold the neck and body together and another that pivots the neck changing the action. Is there anything in the heel itself holding things together? the bolt on top that doesn’t adjust the action how loose/tight is that kept to allow for adjustment but not rattle? I am also assuming that the neck is held down with string tension.
As for the sliding joint I will definitely share anything I come up with. The links I posted above are all I have right about any of it. In playing around with the t track this weekend I have come to the conclusion there is too much slop to get a satisfactory neck joint in the commercially sold pieces. This is probably what Martin ran into as well and why he buys one piece commercially and has the other one milled then ends up fiddling with more himself to get a good fit. In any case Im going to try casting a fitting piece if for nothing else than for testing purposes so we will see how that goes. Using a simple set screw is an interesting idea too, sometimes the simplist solutions are the best.
I saw the mention of those basses in one of the martin threads and I looked briefly but didn’t see anything having a good view of the neck mechanism so thanks for linking what you did.
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There’s nothing in my heel at all. There’s a gap in the block so the heel can move in and out, that’s all buried in the heel pocket.
This isn’t described in the Gore book but in some forums I’ve seen him posting in after the books came out. I’m not sure if he’s still using it.
I was using two bolts originally, one that was just loose in a slot to hold the neck on if there were no strings on it, but it was annoying to have to reach in to put it in, and in the case of the Django guitars, impossible to get to because of the small sound hole. It really doesn’t serve much of a purpose. So now it’s just the single set screw.
I was using threaded inserts initially to hold the set screw but saw a youtube video testing threaded inserts as not being any stronger than threaded wood. So I’ve been tapping the wood instead. I chase it with some CA glue and retap it. So far so good.
For the record, if it’s your first guitar build, depending on your woodworking and design experience, you might want to try a bog standard mortise and tenon…I’m glad I built a few dovetail guitars at first. Although in many ways the joint I’m using is simpler to fit than a traditional joint, I have pooched the neck angle measurement on the last two fairly significantly and was able to adjust the height of the slot in the neck and compensate for it. I did it all on CNC…I might or might not find it challenging without that (I mean, I made all my jigs on CNC and then used a router to route them, and made the neck on the CNC, but I would have trouble making all the jigs work without the CNC, I think).
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To answer your question about the 2nd bolt though I was using a nylon one, no rattling but still annoying. And yes, the strings hold everything together. It’s not particularly difficult to string up from scratch but definitely preferable to leave 3 on and change the other 3. One string at tension is enough to hold it together for a restring.
I should note that this may or may not be descendant from a “Stauffer” style neck joint. Gary Southwell has a more traditional Stauffer style neck joint, and the guys at Miles End Guitars in Montreal, who are all kind of amazing, use a modified Stauffer style, as does Sergei Dejonge when he does adjustable necks.
If you’re not familiar with those guys, they are on instagram, 52 Guitar Company, Mike Kennedy and Larkspur guitars, there’s a few more of them and they are all very very good and very innovative and they collaborate on ideas.
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Definitely Stauffer inspired/influenced. The simplicity is very attractive. I will confess I am a bit nervous about getting the neck angle right and admit that I thought well since I was interested in an adjustable neck joint anyway why not kill two birds with one stone
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I get that, totally. That’s sort of what led me to do it at first.
The one thing I would say is that if you’re interested in repair work or just being a well rounded luthier, understanding dovetails and tenon/bolt on necks is fairly essential stuff.
And the other thing is that you’re in uncharted territory with these adjustable necks. They are very uncommon and if you get into a spot where you need advice there really isn’t any. If you screw something up on a bog standard Dreadnought, you can ask a million people, and also there’s tons of educational stuff available.
But for me I’m glad I did it when I did it. I think it makes a superior guitar and has tons of advantages. It definitely changes the guitar you make, particularly if you’re doing cutaways, but so far the few trade offs have not been an issue for me.
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Several classical guitar makers are doing something similar to this. Garrett Lee in New Jersey is one of them. See his website for pics:
https://www.garrettleeguitars.com/adjustable-action-neck
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Pretty sure Greg Smallwood invented that specific joint but I’m not totally sure.
Common on classical guitars. I’m not sure who else is doing it on steel strings, it seems to work for me…my oldest 2 are just over a year old with zero issues.
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Thats great to hear. I will likely try this on my next build or maybe even on my current one as I’m not past the point of no return yet.
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I’ve done this so far on Gypsy Jazz and Classical guitars.
My one concern is that it puts a lot of tension on the tongue of the neck. I haven’t had any issues but it’s something to be mindful of.
I have always put two 1/4″ carbon fiber square tubes in all of my necks (from dragonplate) and these extend all the way to the end of the neck. My adjustment screw goes between them. I can’t say that this additional stiffness in that area makes a big difference but I’m not going to not use them to find out.
Good luck with it.
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