I posted this in Mandolin Cafe, but someone over there suggested I post here as well.
I have an older mandolin with a broken neck. It was repaired once by a professional luthier, but it gave way about a year later.
I've decided to attempt the repair myself, as the cost of paying someone plus what I've already invested is not worth further
With a fresh wound nothing is better than hot hide glue. If there is some modern inferior glue used for the previous repair, the surfaces must be cleaned up before regluing. Not easy at all.
Slow hardening Epoxy is an alternative in the later case. It's really sticky and the cleanup don't have to be perfect as it needs to be to use hot hide glue. This is not something that needs to be opened up later, so you can use the "weapon of mass destruction" when it comes to glue; epoxy. You will never be able to open up that crack again, you better do the job right the first time. I always wrap the instrument in plastic wrap and use plastic gloves when I use epoxy glue. That sticky stuff gets everywhere and is toxic to my hands!
Roger. thanks. I'm sorry, I forgot to mention that the previous repair was done with Titebond.
Thanks for your feedback,
If you don't have any experience doing neck repair, it is too easy to hose this up. The simple act of trying to clean up the residual glue can be a daunting task.(Edit: just read the Titebond comment) Do you have experience making jigs to provide the stability and accuracy for the re-attachment? How about making splines? A guitar neck is a much easier task due to the amount of wood you have to work with. This really needs to be accomplished by someone who knows what they are doing. BTW, there is nothing wrong with Titebond. Assuming it's Titebond I, it can be softened with heat and is easier to remove than some of the alternatives.
If the previous repair has failed after only a year, you didn't get "professional" help. If you paid for that repair, I'd go back on the shop and demand some money back. Ahh, but don't let him touch it again...
For a repair that needs to be redone or glue joints that will have to be opened some time in the future (bridge, neck), everything is wrong with TiteBond and other modern glues. For this scenario hide glue or fish glue is so much better.
Well, it does want a backstrap overlay, but failing that, my choice would be an adhesive that has great cohesive strength. It's too late to get a perfect fit back together because of the old glue, so you'd want something that needs less precise clamping and fit, leaving epoxy and thick-bodied cyanoacrylate as the most reasonable choices. Both have issues of cleanup and must be handled appropriately. Both could easily freeze up the truss rod nut, so you'd want to protect that, too.
A good grade of (NOT FIVE-MINUTE!) epoxy should hold thing together very well.
Allan & Frank, thanks for taking time to post.
Allan, actually, the first repair was done by one of the most respected luthiers in Los Angeles (no names mentioned). However, this person did a repair on an archtop a couple years back on which I made beaucoup bucks. I owed him one. So that's why I'm not making a big stink about it.
Thanks again to you both.
What frank said, plus if its messy inside with the residual glue from the previous repair a medium thickness Cyanoacrylate is well suited to bonding to a disparate surface mix whereas epoxy likes a clean surface (but does OK regardless). However, a backstrap is the go here as surface area versus tension on mando necks is probably part of this issue.
And while I'm here: Modern glues work fine providing you can read, and understand their application. We use Titebond Original (or equivalent +50) for all our Gibson (and others - its just that Gibson neck breaks are part of my retirement plan) neck breaks and reconstructions, as does Gibson and have not had a return or a separation in over 20 years. We also wick Cyanoacrylates into to shattered areas as well (contrary to the old guys and "woodies" its fine to mix glue types across a wood repair area).
I'm not wedded to Franklin Titebond but I tire of having to point out that if you study and understand glue technology and execute sound repair procedures you will not have problems. HHG is just another glue which is bound by the same pluses and minuses but there is no voodoo.