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| Martin DM neck joint http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=35956 |
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| Author: | Tai Fu [ Fri Mar 30, 2012 7:39 am ] |
| Post subject: | Martin DM neck joint |
What are these guys thinking? A customer brought in a Martin DM who says the neck joint comes apart when he strings it up. So I spend a few minutes figuring out what's going on, because these modern Martins are nothing like the older dovetail Martins. Well after a while of guessing and trying to reproduce the problem so I can see what he's talking about (as it looks intact from the outside) I pry off the Martin plaque that was stuck to the neck block to find a neck bolt that is completely LOOSE! Why can't they just use a compression washer to make sure that something like this never happens? Any suggestions on how to make sure that it will never happen again? Since the nearest Martin authorized repair shop is over 10,000 miles away... there's no chance of fixing that on warranty because the cost of transport would be more than the cost to fix it. |
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| Author: | Alex Kleon [ Fri Mar 30, 2012 9:46 am ] |
| Post subject: | Re: Martin DM neck joint |
Maybe a dab of lock-tite on the threads will help keep it from coming loose. If there isn't enough bolt to use a compression washer, you can try to do a countersink to accomodate the washer, or just get a longer bolt. Alex |
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| Author: | Link Van Cleave [ Fri Mar 30, 2012 10:26 am ] |
| Post subject: | Re: Martin DM neck joint |
One thing that could have happened was that guitar could have been very hydrated at one point. ie. Taiwan. (You have said how humid it is there.) So bolt is tight from factory, guitar gets hydrated, wood swells, compresses against bolt head, guitar drys a bit, wood shrinks, bolt is loose. Even if the wood gets wet again the compressed fibers will never come back. Lose bolts. One possibility. L. |
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| Author: | Tai Fu [ Fri Mar 30, 2012 10:50 am ] |
| Post subject: | Re: Martin DM neck joint |
Todd Stock wrote: Martin's neck joint is a glued M&T, rather than a bolt-on M&T...the bolt is only there to hold the neck in position until the glue dries. So if that's the case, then how is it that the neck was separating when it was stringed up? if it was glued in it shouldn't be doing this... Or is there a bigger problem? I couldn't get the neck to separate when I put pressure on the neck to simulate string tension, but the owner said he was able to get enough of a gap when the guitar was strung up to stick a coin into it. Also besides, if the bolt works loose the loose bolt would vibrate causing weird sounds, which just isn't good. |
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| Author: | Tai Fu [ Fri Mar 30, 2012 11:25 pm ] |
| Post subject: | Re: Martin DM neck joint |
Todd Stock wrote: Yup - always have thought that depending on glue to hold a M&T is a bad move. Have probably 'reset' a few dozen 16-Series and below Martins by tightening up the bolt...always fun to get someone in that thinks the repair bill will be huge, and it's more like 20 minutes worth of time. Well I was going to bill the customer for an "easy" neck reset (basically what I call when resetting a guitar that uses a fully bolt on neck joint, like Taylor) but in the end told the customer that I'll only bill him for less because I cannot in good conscience bill him a lot of money for 20 minutes of work... |
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| Author: | David LaPlante [ Sat Mar 31, 2012 7:09 am ] |
| Post subject: | Re: Martin DM neck joint |
This seems to be a common problem with the Martin M&T guitars. I have a friend who is a Martin authorized repair person who insists on steaming these necks off and properly re-gluing them. |
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| Author: | Tai Fu [ Sat Mar 31, 2012 8:08 am ] |
| Post subject: | Re: Martin DM neck joint |
David LaPlante wrote: This seems to be a common problem with the Martin M&T guitars. I have a friend who is a Martin authorized repair person who insists on steaming these necks off and properly re-gluing them. Well, the owner says he doesn't have a lot of money, and the bill to steam it off and reattach it would have been about 3-400 dollars. I can talk to him about it and see what he thinks but I doubt he'll be able to foot the bill for that. Besides, what guarantee is there that the glue won't loosen again and the same problem happen? M&T isn't really designed to be glued in (unless the fit between the mortise and tenon is very tight), it would work better with a fully bolt on solution. They could at least locktite it or use some kind of a compression washer to prevent this from happening, even with the neck glued in and a loose bolt that does not compromise joint strength, you still have a loose bolt inside (that the player won't know is there) rattling against the vibration of the guitar. |
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| Author: | bluescreek [ Sat Mar 31, 2012 8:29 am ] |
| Post subject: | Re: Martin DM neck joint |
I agree that the neck should be taken off and reglued. Also NO LOCK TITE. The glue is in shear and as then neck and block expand at different rates . the glue line may fracture and the result is a loose joint. It is a flaw in design. I am an authorized martin center and it is recommended to reglue the neck tenon when this happens. |
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