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Cocobolo Scarf Joint

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Would I recommend one? Only if a one-piece neck is too wasteful or the grain runout would weaken the headstock.

Luis is correct about epoxy however I would add that Titebond is not necessarily a bad glue for Cocobolo. It just requires a high level of attention to the mating surfaces being perfect with the surface oil and oxidation being removed immediately prior to glueup. The strength of adhesives like Titebond rely on their ability to penetrate and wet the surfaces being glued. If they sit on the surface (or are repelled by the presence of excessive oil/oxidation) then the joint is purely mechanical and hence far weaker. Too many people apply glue to one surface only, hoping that the glue will transfer and wet the second mating surface which often it just doesn't do. This just gives the glue an undeserved bad rap.

In short, epoxy relies less on surface prep but requires more work to mix and clean up whereas Titebond works straight out of the bottle but requires a far higher level of prep on the joins. Go with the option that best suits your working techniques and abilities however epoxy can hide all manner of sins.

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I agree with Prostheta. Titebond will hold cocobolo well, you just need to make sure to prep it properly. Denatured alcohol is usually pretty good for breaking down that oil. It can get a little messy, as rosewoods bleed quite a bit with alcohol, but it works. You also need to make sure you glue it shortly after the alcohol dries because the oil doesn't take long to start "coating" the wood again.

I've heard some people say oily woods will eventually push the oil/waxy layer into the glue and cause it to come loose, but I've never experience that. If you think about it, it doesn't even make much sense. The oil isn't being pushed out, it just goes wherever it can naturally. If a solid wall of hardened glue is in it's way, it's just going to seep elsewhere.

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I should probably scan my adhesives papers but they're all in Finnish. Yeah, once the glue penetrates the surface and wets it the oil won't be able to "push it out" at any rate. It could possibly contaminate the glue but it would really need to be pissing out of the wood....if that happens you are unlikely to get anything to glue it easily and that bit of wood is just problematic.

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