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I had a mandolin in for repair recently to repair and reattach a broken neck.

The neck joint was a straight mortise and tenon, fixed with hide glue and machine screws into threaded inserts. The threaded inserts tore out of the narrow tenon.

The challenge was to install new threaded inserts without damaging the narrow tenon (crack), have suitable pull-out resistance, and consider future repair if ever needed again.

So I chose a large dowel into which I could thread and epoxy a new threaded insert without concern for cracking. After cured, the dowel was then turned on my mini-lathe to a reamer matched diameter just larger that the threaded insert.







The torn out hole in the neck tenon was reamed to clean and size the hole in preparation for the insert without cracking the tenon. The turned insert was sized about .003" smaller than the reamed hole.



Now the turned insert is glued into the prepared hole using hot hide glue.







With test samples prepared for destructive testing a Robertson head machine screw head stripped before any sign of the insert unseating. The insert is installed without stressing the tenon and potentially causing a crack. To remove the insert heat the insert with a soldering iron to release the hide glue. So all my repair objectives were accomplished.

I'm not sure if this repair method has been shared before, regardless it's new to me and proved to yield great results. I would probably use the method to install on new builds in addition to repairs.

Cheers!

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David Radlin
http://www.facebook.com/radlin.guitars

Very nice way to do this.

From your description - it sounded like you were reporting a failed test.... When really you are reporting a success. It took me a couple reads to realize it worked out properly and is a complete success.

I like the way that came out. I like reusing old necks off beater guitars. This may be a great way to do it without danger of splitting the tenon or stripping out old wood.

Thanks

Good save Dave, probably the inserts are stronger than the original.

Fred

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Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

Thanks guys, hope it is helpful to others...

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David Radlin
http://www.facebook.com/radlin.guitars

Pretty savvy technique, I'd say. Well done, and thanks for sharing.

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"Act your age, not your shoe size" - Prince

That's very clever and in fact a viable technique on a new instrument as well I'd say.