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Repair of a bolt on threaded insert failure.
Posted: Mon Dec 12, 2016 7:31 pm
by Kevin Sjostrand
I have been using the brass threaded inserts in my tenons for my mortise and tenon neck joints. Apparently I've been using the wrong ones, too fine a thread. I've always flooded CA around the insert too, but I've had two of these fail, so I've started using barrel nuts instead. This guitar is the crossover I made for myself and the bottom of the heel started pulling away from the guitar.....I knew what it was. This was the second time on this guitar for this to happen. I decided to fix it once and for all.
I had used minimal glue on the fretboard extension, so that released easy enough. The inserts came out pretty easily too. So I drilled in from the side of the tenon for the barrel nuts, put them in and the fix is done. These can't come loose and I like that, so I used them in the last OM I made and will be using this type of fastener from here on.
Using this system requires a longer bolt then I had yesterday, so I'll put it back together tonight and string it back up, good to go!
I was glad that I could fix it!
Re: Repair of a bolt on threaded insert failure.
Posted: Tue Dec 13, 2016 6:15 am
by MaineGeezer
Threads into end grain are never very reliable, in my experience. The barrel nuts ought to be more secure, indeed.
Re: Repair of a bolt on threaded insert failure.
Posted: Tue Dec 13, 2016 7:36 am
by tippie53
http://www.essentracomponents.com/shop/ ... reId=10152
these are the inserts I use and CF Martin uses. I have yet to see one fail other than catasrophic damage ( Backed over by a car ).
These bite will and are installed with the slot first. I use a shoulder bolt to set them in.
In your case I would epoxy the lower one plug the upper and redrill and use these.
Re: Repair of a bolt on threaded insert failure.
Posted: Tue Dec 13, 2016 9:23 am
by ruby@magpage.com
Another technique I have seen that I think I will try is to drill down from the top to the bottom of the tenon and epoxy a dowel into the hole. Then your threaded insert is into the side grain of the dowel some rather than all of it in the end grain of the tenon.
Re: Repair of a bolt on threaded insert failure.
Posted: Tue Dec 13, 2016 12:01 pm
by Kevin Sjostrand
John, thank you advice taken, but is already a done deal!!! Neck is attached again and should never again fail me! :)
Yeah Ed I've seen guys do that too.
Re: Repair of a bolt on threaded insert failure.
Posted: Thu Feb 23, 2017 4:27 pm
by sylvan
I agree with John. I have been using threaded inserts for 20 years and never had a failure. The barrel nuts will also work great but, in my experience, they require drilling holes from the side and the back. Additionally, I use a 3/4 tenon and the barrel nuts have to be cut down to 3/4 for them to work for me. Just too much trouble for me!
Re: Repair of a bolt on threaded insert failure.
Posted: Thu Mar 16, 2017 11:34 pm
by kinspeed
Liutaio Mattola has done testing on inserts, without a tenon, and found these to hold the best.
Part# 90240A001
https://www.mcmaster.com/#catalog/123/3325/=16rqc0q
Re: Repair of a bolt on threaded insert failure.
Posted: Fri Mar 17, 2017 1:13 am
by johnnparchem
tippie53 wrote:http://www.essentracomponents.com/shop/ ... reId=10152
these are the inserts I use and CF Martin uses. I have yet to see one fail other than catasrophic damage ( Backed over by a car ).
These bite will and are installed with the slot first. I use a shoulder bolt to set them in.
In your case I would epoxy the lower one plug the upper and redrill and use these.
I just bought a bunch of these, they are perfect for the task. Thanks for the information,