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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.

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.

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?

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.

I always use Belleville washers. They are getting harder to find though

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

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

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).

I just did a Google search on 'belleville washer'. Way too much information from the manufacturer to paraphrase. I suggest a search.

I have used lock washers if I have nothing else