Belleville washers?

[peter havriluk]

Time to consider neck fasteners on my current project. Bolted necks seem more often than not to use Belleville washers. I bought a bunch of 1/4" Belleville washers a while ago mimicking an attachment scheme I found online (Mottola), but I'm also now using some #10 studs to attach the fretboard to an extension of the neck block, and a vendor's instructions (Luthier's Cool Tools) specify using Belleville washers. These things ain't cheap and gotta be mailordered from McMaster-Carr.

Question for today is are these specialty lockwashers necessary? Do they do something necessary that can't be achieved with normal flat washers? I can get all the stainless #10 washers I want a mile away at my local True Value.

Thanks!

[Tim Benware]

They are a spring washer aren't they? The back tension I guess would keep things in place more securely than a flat washer. I suppose it depends on the application if they are really needed or not.

[Daniel P]

The theory is that a Belleville washer (coned-disc spring, conical spring washer) can help ensure that the neck bolts won't loosen overtime due to compression/shrinking of the wood, or to a lesser degree, could help prevent splitting during expansion of the wooden neck block.

The conical shape of the Belleville spring washer maintains tension even if the overall thickness of the neckblock changes within a range +/-. One might be tempted to use a lock washer to keep the bolt from turning loose, but it functions differently than the pre-load conical spring washer.

In reality, I bet there are a lot of great bolt-on necks without Belleville washers that work and play wonderfully—but it's cheap insurance.

[John Parchem]

Heel block shrink and expand with changes in humidity. The Belleville washer very cheap in quantity helps keep the neck tight. Besides the obvious advantage of taking up the slack when the block shrinks, If a block expands in high humidity the washer inverts as it is being pulled into the wood the outside of the washer is not pulled in. I have had necks loosen without them. I would encourage their use.

[peter havriluk]

Thanks to all for answering. Short version from here, I'm pleased to own all the 1/4" ones I'll ever need, and I'll go buy some #10's.