Double-checking neck bolts

What're You Doing?
Stray Feathers
Posts: 677
Joined: Sun Sep 08, 2013 11:39 pm
Location: Ladysmith, BC

Double-checking neck bolts

Post by Stray Feathers »

I was concerned when I discovered cracked and flaking lacquer at the neck-to-body joint on my third guitar (strung up last summer) - see photo. I had issues with the finishing on that one, so was not sure what was going on. I put it on the bench and loosened the two middle strings so I could slip a ratchet in the soundhole with a 5/32" hex head "socket" on it. Both bolts were loose; I tightened them through 10-15 clicks on the ratchet so I'm guessing close to half a turn. That tightened up the neck joint, and I am now doing some delicate sanding and dental pick-ing and touching up with lacquer using a fine brush, and will have to sand and buff the bad area when the finish is built up a little. I also checked my #4, a 12-string, and those bolts were a little loose too. My first build, now 4 years old, was also a bit loose (water-based finish on that one) but no cracks showing on either of those. Is this a known issue, a maintenance item? We heat with wood in winter, but my little hygrometer shows the RH at around 40%-50%. I am aware of humidity concerns with instruments but until now have had no issues, including 32 years with a L'arrivée in various homes. I live on Vancouver Island in BC. Bruce W.
You do not have the required permissions to view the files attached to this post.
TEETERFAN
Posts: 342
Joined: Fri Sep 07, 2018 12:43 pm
Location: Kansas City, MO

Re: Double-checking neck bolts

Post by TEETERFAN »

The looseness could come from the bolt pulling out of the neck ever so slightly. Another thing to consider is retightening the nuts after the initial assembly. Perhaps a week or two later. In the world of hot rodding, engine builders retorque the head bolts after the engine break period, since things squish and change dimensionally after a bit. Certainly a guitar has way fewer extremes of heat and humidity, but things could still be effected. I don’t know if any loosening has been observed by other luthiers who do bolt ons.
Kevin Doty
Kansas City
Stray Feathers
Posts: 677
Joined: Sun Sep 08, 2013 11:39 pm
Location: Ladysmith, BC

Re: Double-checking neck bolts

Post by Stray Feathers »

Well, in the same way that fretboards "shrink" leaving fret ends sticking out a little, I am assuming other wood components (like heel blocks) may shrink too, leaving the hardware a little loose. I thought I was making sure the bolts were tight before finishing, but the wood may have shrunk more since then. I wonder also if the same thing can happen with dovetail necks?
phavriluk
Posts: 554
Joined: Mon Jul 09, 2012 9:49 pm

Re: Double-checking neck bolts

Post by phavriluk »

This is one of the incentives for some builders to use Belleville washers under bolt heads/nuts; they take up minor changes in fastener tightness.

I agree that tightening fasteners after a while (and periodically, like during string changes) keeps these little adventures from intruding.
peter havriluk
Kevin Sjostrand
Posts: 3712
Joined: Sat Feb 09, 2008 8:06 pm
Location: Visalia, CA

Re: Double-checking neck bolts

Post by Kevin Sjostrand »

I always use Belleville washers. They are getting harder to find though
tippie53
Posts: 7011
Joined: Fri Mar 03, 2006 7:09 pm
Location: Hegins, Pa
Contact:

Re: Double-checking neck bolts

Post by tippie53 »

in 20 yrs of this , this is the weak link of the bolt on , but with 2 bolts and the bellville washers they can be
much improved
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
Bob Gleason
Posts: 412
Joined: Fri Jul 03, 2015 2:45 pm
Contact:

Re: Double-checking neck bolts

Post by Bob Gleason »

I've never heard of a Belleville washer, but I see they are available on Amazon. So, if you use these things how tight do you crank them down? Not having seen one yet, do you have to tighten them until they distort for the spring action to work? Thanks, Bob
Stray Feathers
Posts: 677
Joined: Sun Sep 08, 2013 11:39 pm
Location: Ladysmith, BC

Re: Double-checking neck bolts

Post by Stray Feathers »

I think, now, I may have seen one but not realized its function. It makes obvious sense, but how is it different from a lock washer? And I assume there should be a flat washer against the wood? And is there any idiot's guide to how tight you can make it before you strip the threaded insert? (I have not used the furniture bolt type in a guitar).
phavriluk
Posts: 554
Joined: Mon Jul 09, 2012 9:49 pm

Re: Double-checking neck bolts

Post by phavriluk »

I just did a Google search on 'belleville washer'. Way too much information from the manufacturer to paraphrase. I suggest a search.
peter havriluk
tippie53
Posts: 7011
Joined: Fri Mar 03, 2006 7:09 pm
Location: Hegins, Pa
Contact:

Re: Double-checking neck bolts

Post by tippie53 »

I have used lock washers if I have nothing else
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
Post Reply