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Repair situation, converting a dowelled neck joint to a butt joint.
Also, epoxy in, or wick in thin ca glue?

Are these suitable for a butt jointed neck?

https://www.amazon.co.uk/Z-LOK-400-M6-Threaded-Internal/dp/B002WC8TRA/ref=sr_1_6?crid=2RPLGBLR03BJ3&dib=eyJ2IjoiMSJ9.VKpbT326RL7jIgjD2Fsyg9l67EtyRMytxYHclGi5bAxsUDsPko2WvpUXaSlMzIVyd3KmiIiqb5JZ8dmEC9swjZLhA6UbLtmnPxiczE3OKlMId9Q_gkl6oXPYV7iJLhbTrRkbAJvutyn5MJll-bDpnOecxa8b8E-ver6hLZSw32CVDlzEemKvqTSHgGAxDE-yoJR1gtfQy0JeUp3J2UwIbSSID24k8GUlilQRAkGfKs_q_aFbifLmR6_aAeKFT2pUHSWncbQ0BWz0I4Z5WbZGee02cYIFwC9yE1GMY7M7MYA.nmuEN7pEHKVltVWUy39zfhoLW87eHEUppZXBJQaZLT4&dib_tag=se&keywords=threaded%2Binserts%2Bez%2Blok%2Bm6%2Bfor%2Bwood%2Bbrass&qid=1761054051&sprefix=threaded%2Binserts%2Bez%2Blok%2Bm6%2Bfor%2Bwood%2Bbrass%2Caps%2C152&sr=8-6&th=1

Or should I use steel ones?

https://www.amazon.co.uk/Z-LOK-400-M6-Threaded-Internal/dp/B002WC8TRA/ref=sr_1_6?crid=2RPLGBLR03BJ3&dib=eyJ2IjoiMSJ9.VKpbT326RL7jIgjD2Fsyg9l67EtyRMytxYHclGi5bAxsUDsPko2WvpUXaSlMzIVyd3KmiIiqb5JZ8dmEC9swjZLhA6UbLtmnPxiczE3OKlMId9Q_gkl6oXPYV7iJLhbTrRkbAJvutyn5MJll-bDpnOecxa8b8E-ver6hLZSw32CVDlzEemKvqTSHgGAxDE-yoJR1gtfQy0JeUp3J2UwIbSSID24k8GUlilQRAkGfKs_q_aFbifLmR6_aAeKFT2pUHSWncbQ0BWz0I4Z5WbZGee02cYIFwC9yE1GMY7M7MYA.nmuEN7pEHKVltVWUy39zfhoLW87eHEUppZXBJQaZLT4&dib_tag=se&keywords=threaded%2Binserts%2Bez%2Blok%2Bm6%2Bfor%2Bwood%2Bbrass&qid=1761054051&sprefix=threaded%2Binserts%2Bez%2Blok%2Bm6%2Bfor%2Bwood%2Bbrass%2Caps%2C152&sr=8-6&th=1

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Both links go to the brass kind which I hate furiously with the burning passion of a thousand suns.

These are my jam. https://www.mcfeelys.com/1-4-20-x-591-i ... y-100.html. You can find matching bolts everywhere.

The hex key insert makes getting them in there so much easier. I have not felt the need to glue or epoxy them in for a long time now. Unless you’re using some soft wood like Spanish cedar, they will hold nicely. The actual ones I use are only 1/2 deep but I didn’t find them on a cursory search, but I wanted to show the type.

Thanks for the reminder that I need to buy more!

I prefer these inserts: https://www.amazon.com/Hillman-Group-30 ... C88&sr=8-8

They require a smaller hole (5/16”) than the ones you cite and the coarser threads are less likely to turn the end grain into particles. I like the brass because is less likely to spall with a steel bolt. I also like to have a 1/2” vertical dowel in the heel with the center set back 1/2” from the edge for the insert to bite into. The insert is being set into end grain in the heel and has the possibility of pulling out. I use thin CA wicked in after the installation of the insert. If anything goes wrong on the installation, you don’t want glue holding it in the wrong place.

My experience on the inserts is only on new builds. I have never done a retrofit like you describe. I imagine you would have to remove the heel cap to install the vertical dowel.

Here’s a hint on the insert installation: if you have the neck clamped in the drill press to drill for the insert, after drilling a hole, without changing the alignment, replace the drill bit with a bolt with the insert on the end and turn the insert in by hand using the drill press to keep it aligned. It’s a lot easier than trying to free hand it in.

This is a great tip for general use of threaded inserts in anything, not just for neck inserts. Cut the head off a bolt and chuck it, thread on two nuts and jamb them together as a stop, thread on the insert under the nuts, then turn/lower the chuck by hand (no power!). The inserts cannot help but go in straight. I use this all the time for making jigs.

I use a tenon on my necks and had an old dowling jig. Beau Hannam put up a video on Youtube using that dowling jig to both drill the hole in the heel and screw in the insert and this works great

Kent

Yes, I've seen it. That would be nice, but I don't have the possibility if making this repair with a tenon.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I use a butt joint with M6 steel inserts in my builds and have had no problems. I do not use adhesive on the inserts but I do glue in a 12mm hardwood dowel so that almost the whole of the inserts are in cross grain.
In your repair circumstance that will be difficult.
I took this method from R.M. Mottola and as far as I could tell these were the type of fittings that he recommends. Also it is worth noting that the slot is there to cut the thread, not to use a screwdriver. I made up a driver from threaded bar so that the inserts can be driven slightly below the surface of the heel to give some leeway to use a chisel when fitting. The tape is there to shim to size for the dowel jig.
Apologies for the picture quality, that is how it turned out after size reduction.

Thanks Roy, 12mm dowel all lined up.
I plan to go up through the heel cap area, then replace it - I have removed it anyway to facilitate clamping of the heel break.
I checked the website for the inserts you show, they seem to be for metal, with fine external threads - with this being a 12 string, I aim to get everything as solid as possible.
I already have some other inserts which have coarser. deeper threads for wood.
Link to a post about the guitar involved here - http://www.luthiersforum.com/forum/viewtopic.php?f=10137&t=57388

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

this is a case of a lot of misinformation
most of the inserts shown were not for wood
this one is the one you want to use.

https://www.amazon.com/hz/mobile/missio ... MX8QM1MCCF

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Got that John, my first post was suggesting the E-Z Loks.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Encourage you to try the zinc for hardwood with Allen key that I linked at least once. It’s great misinformation.

I use the ones that are in the link that John shared. I should not have to say it but I have seen people using the slot as a screwdriver slot. It is not as it is a thread cutter.

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http://www.Harvestmoonguitars.com

Good point John
these are sharp and cut into the block very well the Zink ones are not as sharp and like I said Martin used these for 30 years and I have never seen one fail . The fine threads for plastic don't work in wood.

I use a should bolt to set them into the tenon

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Where does Martin use treaded inserts?

not trying to be a killjoy, but considering the tool EZ lock has for driving the inserts utilizes the slot as part of its function I'd argue that slot is precisely for a bladed screwdriver...the trick of course is the correct size as has been noted that slot is a weak spot.

tip regarding bladed screwdrivers: arguably the most important dimension is the thickness as opposed to the width. anyone who has marred the head of a nicely custom finished slot head screw knows the difficulties in these types of drives. pan head screws are pretty simple, but flat heads going into a countersink is where the problems begin. I finally figured out that using a larger size blade and dog earing the edges was what was needed to drive the screw in without mucking it up and at the same time not muck up the countersink. the same thought process applies to threaded inserts and if needed one could make a thicker blade narrower to fit in the hole properly...also be aware most blades taper so you can simply remove material at the tip which results in a thicker tool.

as a note: nobody ever taught me to correctly install threaded inserts and the pro tip of using a bolt with lock nuts is clearly a great method...using a boring jig (cheap one via Kreg tools) at least gives a perpendicular hole into the material.

This is the heel of a Martin guitar before assembly.
I believe they put a treaded insert in the hole the arrow is pointing to.

On the guitars I build I use 2 inserts installed when the hole is drilled using a shoulder bolt.
I put the slot in first to cut threads, that's how I was taught and it works slick.

Screw drivers, hollow ground is a better option than flat (taper) ground

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Say what you do, Do what you say.

Amen, and amen Brother Dave. Easy to do oneself if you can't buy one.

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

Thanks for the clarification. I remember seeing a Martin video with them showing their newfangled neck joint and stating (a tad bit snobbishly) “Martin doesnt do bolt-on necks”. I see they do.