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I used to use the lmi hardware which came with a domed lock washer that seems to be a good idea for insurance. I recently switched to those flat head furniture bolts. They have a little flange under the head that looks like it ads a little friction. Anyone using lock tight or...? Maybe some type of lock washer?

Actually, that domed washer seems like a good idea to account for possible wood movement.......hmmmm

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Pat

Bellville compression washers like LMII use are very well suited for this application. A star or lock washer will help prevent the nut from vibrating loose. The Bellville compression washer will actually maintain similar torque even if the wood changes a bit from humidity etc. The guys over at McPherson really make a "real big deal" out of their selection of Bellville washer tension for their neck design. I would not put Loctite on neck fasteners.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Pat: I use the furniture bolts and put nothing under the head and have not had any problem. Maybe I have a horseshoe in the right place.
Tom

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A person who has never made a mistake has never made anything!!!

Same here as Tom but when I used other bolts I also used the Bellville washers that Ken mentioned. When my stuff comes back say from a tour, etc. I always check the neck bolts just like I do in our commercial repair shop. Unlike in the repair shop my Heshtone Guitars bolts are never loose beyond some slight compression of the wood. There are some major maker guitars though that the bolt does come loose and we even had one the other day that the bolt came out and was either lost or never put in at the F*ctory.....

Two manufacturers come to mind and no I'm not going to say who because that's not why I'm here... But during the triage process you can often see a gap between the neck heel and body and sure as shootin when I access the bolt(s) they have come loose. Neither of these two f*ctories use Bellville compression washers or the furniture bolts.

Sorry - forgot to answer the original question. I personally would not use any thread locker for two reasons. First it's not necessary with proper bolts and/or some kind of locking washer. Next when we are up to our elbows in a sound hole, no jokes please.... you don't really want to need a Crapsman 55 piece socket set with long handled wrench to loosen the bolts. A slip of hand in this situation could be a very sad day indeed.

There is two different kinds of Lock Tight though. I can't remember which is which, dyslexia is a bish, but one is red the other blue and one is a weaker glue. I've used it on bike parts where you one day want to actually unbolt the thing but not have it rattle free. I started using furniture bolts too and have used different fasteners and washers and so far have yet to have a problem but I have thought about the lock tite too. Problem is that if there is shrinkage in the block or compression in the wood then it won't help anyway and it will need to be cinched up. But it would at least help with rattling free though my guess is that is less of a concern?

Containing loose bolts is what the stickers are for!

Bellville washers.

I would worry that locktite would cause the neck insert or wood thread of the bolt (hanger bold) back out to some degree when you break the threads loose.

I'm intrigued by the belville washer idea. At first thought I got all excited because I thought about it being able allow for a little bit of wood movement in the heel block. The more I think about it though, the more it seems like the stiffness of the washer would be critical (and different for many applications). If the washer is too stiff it will just crush the wood like a bolt would; when the wood shrank again the crushed section would not spring back anyway. If the washer was flexible enough to not crush the wood, it wwould probably be too springy. One of the common uses of the belville washer is to provide damping which is something I would think we would want to avoid in a neck joint.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

You can get Belleville's in a variety of strengths. They are pretty ingenious little items. If you stack two the same way, like spoons, the force is doubled. If you appose them, like cups facing each other the travel is doubled but the force stays the same.
I don't think they have to be perfectly torqued and matched to work. Even if someone crushes them into the wood and the wood shrinks they will keep on pulling the neck in at their specified weight until they run out of travel.

Now that you have me thinking about it, Bryan, two apposing would really be the chump. The one on the bottom would press into the wood and spread the load of the rim contact on he upper one. And they would have twice the travel. I'm gonna do it.

I'm not afraid to say that where they are needed is on Mart*n's straight tenon necks. Without tension on that one bolt, a wing and a prayer is holding those together, (or not).

I use a Bellville washer along with a regular flat washer that has a larger diameter. I don't see any wood crush after years of use in the guitars that are in the family. I certainly do not know for sure but I suspect DIY'ers and newbie builders tend to over tighten the neck fasteners. I might add that a nice dry well seasoned neck block is not prone to shrinkage.

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Ken Cierp

http://www.kennethmichaelguitars.com/

I'm thinking that something that carries a 200 lb neck load is not going to be absorbing string vibrations.....

Does anyone have a good source for Bellville washers? Looks like McMaster is $6-8 per 12.

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Pat

Lowes carries a "Wave" washer which looks similar to a Belleville.

you should use both a washer and a belleville. In most cases the nut or bolt loosens because of wood compression. I would not use any locktight.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Actually David is not kidding about stickers. Two examples of bolt-on neck implementations use either a sticker or a wooden plate over the bolt(s).

Some of the Godin family, Seagull, A&L, etc. with bolt-on necks have a stick-on label over the bolts. These bolts do come loose anyway but they won't come out unless the label has been off before and not put back on very well.

It's often the case with these guitars that the bolts loosen over time beyond wood compression and you can see a gap between the neck heel and the body. Removing the label, carefully with naphtha applied with an eye dropper and it's possible to get the label off in one piece. Tighten the bolts, this changes the neck angle more in line with the manufacturer's original angle, use a quality double stick on the now dried out label and reinstall. It's not a fix unless you reengineer the bolt/washer implementation but it does restore the neck angle and snug up the neck for some time to come.

Martin uses a wooden plate over the Jesus bolt and the wooden plate with double stick prevents the bolt from backing out all the way but they still come loose anyway and that can compromise the glued mortice and tenon neck joint.

Back to the furniture bolts. After I switched to them because they do look WAY better and you can get them in antiqued finishes which is what I did I was sure to check the bolts at every opportunity for some years. I don't use any washers with these bolts mind you. I've never found a loose one and the only additional snugging that they would take over time is likely due to wood compression. With these bolts I would be pretty OK not recommending any washer at all and this is based on my own experience over something like 8 years now with these bolts.

Bryan makes a really good point about the threaded inserts which can come loose too and we have had a number of threads about that actually happening on this forum in the past. The force required to break even the blue lock-tie, the one that will give may cause the inserts to back out too. Good point!

Conclusions:

A dovetail is a pretty beautiful thing in all respects!

Bolt-on necks when implemented well can be a beautiful thing too!

I'm chuckling here because yesterday, my day off, Dave took in a Taylor with the very cool Taylor neck joint and in assessing the instrument for a neck reset he actually decided to just do the reset since he was in there. 5 minutes later it's done. Impressive engineering and Lutherie!

Ok, lock tight is OUT. Conclusion; I am going to use the furniture bolt with a belleville and a flat washer. The best of three worlds. Just need to find a good buy on a bunch of bellvilles.

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Pat

Hey Pat you might want to see how the washers fit the furniture bolts. The bolts that I use with no washers at all have a pretty profound filet or transition from the bolt to the bolt head and if the washer's holes are too small they won't seat well on the furniture bolts and would give a false snug feel when they are not really snugged down.

I've never had a bolt come loose with no washers so that's something to consider too.

I think if your going to use furniture bolts and leave them exposed, you don't need to get wrapped around the axle about them loosening up. It's simple for anyone to check and tighten them up.
When bolts are hidden behind a label or plugs, most owners will feel they need to take it to a luthier and may blow it off/ not notice until things are out of hand.
Bob Taylor did his part to legitimize bolts, maybe the next step is allowing them to be visible though the sound hole. the horror!

Yes, that's the " little flange" that I mentioned in the op. Looks like they make'em the right size for that and also a similar od to the furn bolt. Both of them in there should only add about .07 behind the bolt itself and should not be noticeable.

I've not had one come loose either, but I would consider a guitar coming back with a loose neck at any point in the future a pretty major issue for a custom guitar. Especially since according to our repair people, the "martin bolt-on" has nearly become a byword. Not to mention the Canadian varieties.

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Pat

I too have only ever only used the furniture bolts and have not had one come loose. It begs the question, what in the world is it about these that helps prevent it from happening. I can't think of anything that would make it drastically different than a nut and washer.

even though I have not had a problem, I do like the idea of a belville washer along with a regular washer behind the furniture bolt. I'm going to look into this option and see how it looks through the sound-hole. If it is not too ugly, it will be a nice bit of insurance.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

I'm certain now that it's that little flange under the cap that keeps it tight. It compresses the wood. Nice design actually. So, no need for any kind of thread lock. I see wood shrinkage as the only issue. Proper wood of course should yield no significant movement in the near future. However, in a game of .001ths, for the long term, has anyone had a furn bolt in service for 20 years? 30?

But then again, as long as it holds out till neck reset time.....

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Pat

I used a dovetail in my commission. I don't want the stuff coming back because a bolt came loose. If the dovetail came loose it's often because the instrument was exposed to heat (which is the owner's fault)

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

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