Repair of a bolt on threaded insert failure.

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Kevin Sjostrand
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Joined: Sat Feb 09, 2008 8:06 pm
Location: Visalia, CA

Repair of a bolt on threaded insert failure.

Post 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!
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MaineGeezer
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Re: Repair of a bolt on threaded insert failure.

Post by MaineGeezer »

Threads into end grain are never very reliable, in my experience. The barrel nuts ought to be more secure, indeed.
Don't believe everything you know.
Anything is possible if you don't know what you are talking about.
When things are bad, try not to make them any worse, because it is quite likely they are bad enough already. - French Foreign Legion
tippie53
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Re: Repair of a bolt on threaded insert failure.

Post 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.
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
ruby@magpage.com
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Re: Repair of a bolt on threaded insert failure.

Post 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.
Ed M
Kevin Sjostrand
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Location: Visalia, CA

Re: Repair of a bolt on threaded insert failure.

Post 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.
sylvan
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Re: Repair of a bolt on threaded insert failure.

Post 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!
Sylvan Wells
Wells Guitars
Bay State Guitars
http://www.wellsguitars.com
http://www.baystateguitars.com
kinspeed
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Re: Repair of a bolt on threaded insert failure.

Post 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
johnnparchem
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Re: Repair of a bolt on threaded insert failure.

Post 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,
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