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!
Repair of a bolt on threaded insert failure.
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Kevin in California
- Posts: 2716
- Joined: Mon Dec 19, 2011 4:19 pm
Repair of a bolt on threaded insert failure.
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Re: Repair of a bolt on threaded insert failure.
I believe the course thread 1/4-20 inserts are the type that should be used for this function -- Actually that's what Martin uses and I just copied. Its also important to use a Bellville compression washer. And perhaps most important -- don't over tighten the screws, (that's when the glue line can be breached) just enough to get some compression on the washer -- it does not take much torque.
The barrel nuts introduce a new batch of problems -- your tenon is quite long so its not likely that you will get end grain collapse and tear out an all too common issue with that arrangement.
The barrel nuts introduce a new batch of problems -- your tenon is quite long so its not likely that you will get end grain collapse and tear out an all too common issue with that arrangement.
ken cierp
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http://www.kennethmichaelguitars.com/
Store Front
http://www.cncguitarproducts.com/
KMG Guitar Kit Information
http://www.kennethmichaelguitars.com/ki ... ckage.html
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Kevin in California
- Posts: 2716
- Joined: Mon Dec 19, 2011 4:19 pm
Re: Repair of a bolt on threaded insert failure.
Right Ken I do use Bellville washers. I probably also go tighter than I need to so I'll try and watch that.
I make my tenons 3/4" deep so there should be plenty of material ahead of the barrel nuts for strength I'd think. I realized too late that I'd got the wrong inserts. Thanks for the input. The neck is back on and all looks good. I didn't need to glue down the fretboard extension this time as it lays nicely on the top.
I make my tenons 3/4" deep so there should be plenty of material ahead of the barrel nuts for strength I'd think. I realized too late that I'd got the wrong inserts. Thanks for the input. The neck is back on and all looks good. I didn't need to glue down the fretboard extension this time as it lays nicely on the top.