Bolt on guys - bolts loosen with dry humidity?

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Bolt on guys - bolts loosen with dry humidity?

Postby Brian Evans » Sun Feb 03, 2019 12:54 pm

Does this ever happen to your guitars? Particularly in their first winter? I've been checking mine, they needed a tweak.

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Re: Bolt on guys - bolts loosen with dry humidity?

Postby Bob Gramann » Sun Feb 03, 2019 1:43 pm

I’ve done well over one hundred with bolt-on butt joint necks. I’ve never had one loosen. I install a 1/2” maple dowel vertically through the heel such that the edge of it is 1/4” back from the butt face so the inserts have some non-end grain wood to bite into. I do use a wavy spring washer unter the bolt head, but that doesn’t supply much tension.

If yours are coming loose, I would worry that some of your wood was not as dry as you hoped when you built or that something else is going on. Some serious investigation is in order.
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Re: Bolt on guys - bolts loosen with dry humidity?

Postby Barry Daniels » Mon Feb 04, 2019 10:38 am

Instead of a wavy spring washer you might want to check out Bellville washers. They supply more tension.
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Re: Bolt on guys - bolts loosen with dry humidity?

Postby Bob Gramann » Mon Feb 04, 2019 10:51 am

I did some testing with Bellville washers. The ones I had didn’t spring back after they had been tightened down for a while.
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Re: Bolt on guys - bolts loosen with dry humidity?

Postby Mark Wybierala » Mon Feb 04, 2019 11:09 am

Its quite a common thing to find screws that can be tightened a bit on new guitars in the first year. Not so much that they are loose but they just aren't as tight as they should be. It ain't no thing and not really a problem. The same goes for every other bit of hardware.
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Re: Bolt on guys - bolts loosen with dry humidity?

Postby Brian Evans » Mon Feb 04, 2019 3:07 pm

The thing that made me check was I have my buddies 1978 Jazz bass in house, I am making him a black cherry version. This is a virgin MIA left hand bass, and the neck screws were barely in there, less than finger tight with a screw driver. Made me wonder so I tried a few others, most were not tight, not loose either. I am going to look into belleville washers, we used to use them as suspension tuning springs on some race cars.
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Re: Bolt on guys - bolts loosen with dry humidity?

Postby Daryl Kosinski » Tue Feb 05, 2019 12:16 pm

When I built my banjo I used a steel rod in the neck heal drilled and tapped. I left a little clearance for seasonal wood movement.

If I ever build another I would use a piece of square stock brass.
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Re: Bolt on guys - bolts loosen with dry humidity?

Postby Timothy Gregory » Thu Feb 14, 2019 12:28 am

hi friends romans and luthiers
this is a good discussion and points of view
to me a bolt-on is a luxury when you are the one who has to remove it for repairs and such.
almost a no-brainer and some of the designs make the neck more easily adjustable.
still pure wood guitarists might reckon the trad neck wood joinery of taper dovetail is best.

in the case of my banjo-mandolin the neck is attached by a screw into the neck end-grain.
the neck butt end is concave shaped in the right diameter curve to fit the circular shell
and this curved end sits against the cylinder rim of the body which supports the neck
the neck can't tilt at all either side to side or up and down due to the matching curved surfaces.
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Re: Bolt on guys - bolts loosen with dry humidity?

Postby Steve Sawyer » Thu Feb 14, 2019 10:18 pm

I've only built one bolt-on (shoot, I've only built one guitar) but put brass threaded inserts into the neck. I always try to do that on anything that I expect will be dis- and re-assembled. I have no idea if this has any effect on the issue at hand, but I haven't had to make any adjustments at all since starting to play it almost daily about two years ago.

Note that the maple for the neck was super well-seasoned having been 50- or 60-year-old stock reclaimed from a local school that was doing some remodeling.
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Re: Bolt on guys - bolts loosen with dry humidity?

Postby Roger Rosenberger » Thu Jun 06, 2019 1:29 pm

I've built a half dozen guitars with bolt on necks and have always used the brass inserts with stainless steel machine bolts. I don't know of any of them coming loose.
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Re: Bolt on guys - bolts loosen with dry humidity?

Postby Steven Smith » Thu Jun 13, 2019 2:01 pm

My oldest bolt on is about 10 yrs old now and never had a loose bolt (no problems on the other ones either). Like Bob said, make sure your wood is dry. My shop has been at 45% RH for the 12 years since I moved in and I let all my wood acclimate for at least a few years before building with it.
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Re: Bolt on guys - bolts loosen with dry humidity?

Postby Mark Wybierala » Sat Jun 15, 2019 10:12 am

As a professional tech, its something that I need to remember to check on every guitar setup that crosses my bench so its become part of the routine of cleaning the instrument and checking every piece of hardware as soon as the strings have been removed. The last thing I want is to go through all of the setup process, find mojo, and then discover that the neck is loose. A loose neck can also make you chase your tail when your trying to find the perfect trussrod tweek. So I make a point to check every screw and nut. Maybe two out of ten guitars with bolt-on necks have less than tight screws. At the same time, you don't want to monster-tight these screws. On some poly finished imports you can cause a fracture in the finish.
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Re: Bolt on guys - bolts loosen with dry humidity?

Postby Steven Smith » Wed Jun 19, 2019 12:41 pm

I have to agree with Mark there, every guitar I repair gets every nut/bolt/screw checked to be sure it's snugged up the way it should be.
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