Official Luthiers Forum!

Nope.

The insert is there so that the neck,which is finished off of the guitar, can be handled during spraying.

You really do make it a challenge to have a bit of fun...I was just about to post this:

Good eye! But rather than being used to retain the neck, those threaded inserts are part of the soon to be announced second generation of their Vintage Tone System (VTS II). This new acoustic tuning technology employs a precisely manufactured bell brass sleeve inserted into the dovetail, and a series of tuned weights which are threaded into the sleeve at precisely determined distances based on the results of individual neck testing using the Dynamically Interpolated Mass & Weight Interferometry Transducer. With the DiMWIT readout, Martin craftsman can easily adjust each neck for optimum response.

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For the times they are a changin'

- Bob Dylan

Woodie, that is a classic, true inspiration. Shame you didn't get in first.

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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.

Getting back to the OP.
If you make your own barrel nut, and insert it in the heel, you should be fine. If you want to strengthen it because you’re worried it will split the heel, try inserting a dowel in the heel, then drill a hole in the dowel an put a barrel nut or two inside the dowel.

You could do long barrel nut and tap threads for two bolts in it.

I think it would work great, but I would test on scrap before putting it on an instrument.

dl

So from what I'm reading, a properly fitted dovetail joint should not be too tight because of wood swelling, and that when you pull on it the same way strings would pull on it the heel should not pull away from the body, even slightly?

What about shimming the joint, which has to be done because the thing will always be undersized when re-fitting them?

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

I think the best thing you can do to satisfy your curiosity about dovetails is to get on YouTube and watch all of John Hall’s videos (all of them, including an addendum) on fitting a dovetail.

As for your distaste for the joint, all I can say is that you should use what you want to use. However, it sure seems like you have convinced yourself that a dovetail is a terrible neck joint. Well, there are decades of the joint being used on untold numbers of guitars that show you are incorrect about that. You probably had a bad experience with making a dovetail, and that convinced you that it is a bad neck joint. A more accurate conclusion to draw from this evidence (i.e., it has been a widely used neck joint for a long time, but you had a bad time of it) is that your work on the joint was not optimal. I don’t mean to offend, but wouldn’t you agree that is the most logical conclusion, given the evidence?

Along those lines: shims are normal and acceptable, but not inevitable. And yes, the heel should not pull away from the body when string-like pressure is applied to the neck. If that happened on a guitar for which you fitted the dovetail, then there was something you were not doing right. Most likely, you had a snug fit at the top (wide part) of the dovetail, but too loose of a fit at the bottom (narrow part) of the dovetail. John Hall’s videos can help you avoid that in the future.

Shims may be avoided in a new instrument by manufacturing the tail slightly oversized and trimming to fit, but I don't see any correlation between shim use and 'goodness' of the joint - the dovetail worked so well for Martin and Gibson because it accommodated a reasonable range of outcomes from the body and neck construction process without too much in the way of consequences to final setup. A worker familiar with the process could fit using what appears to us to be a fairly standard thickness shim on one side of the dovetail, then quickly perfect it with file and block. We have not seen any Martin or Gibson in for initial reset that did not have at least one shim in the socket on neck removal, and guitars getting a second or third reset usually show two shims. Shim material does not see to matter all that much to security of the joint - we've seen fiberboard shims that seem to have worked as well as maple and mahogany (although we use wood!).

As to fit, we look for a perfect, no-movement fit at top and bottom of the joint under light clamp pressure with the extension just clear of the top...0.015"-0.020" is usually about right for a mahogany neck and neck block, and a bit more for spruce or poplar neck block and poplar neck. Hot hide glue is a lubricant until it tacks, so the joint will always clamp up a little deeper than the dry fit due to reduced sliding friction.

We've made barrel nuts in the shop for a Taylor-like application (Taylor uses an aluminum insert in the NT neck which is essentially a fixed barrel nut), but if I were the OP, I'd see if the cost of having some kind soul on the site posting 200 or so 18mm x 1/4-20 barrel nuts to Taiwan is affordable versus the time spent milling them out of 10mm round stock.

_________________
For the times they are a changin'

- Bob Dylan

I had ordered some belleville washer too, from China. No idea where to find it in Taiwan because all they have is the split ring washer which I read doesn't work as intended.

I'm not building 100 guitars a month, a few minutes spent milling out a barrel nut isn't a big deal for me.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

I cannot take credit for the DiMWIT gag. About a decade ago, Mr. Morelli fabricated the DiMWIT from an old amplifier enclosure and dozens of spare parts salvaged from various electronics products. The only operative part of the box was a transformer that powered the heaters on several tubes and a circuit that powered a jewel lamp (labeled 'CONNECTED) when the 1/4" stereo plug of the 'INPUT FROM INSTRUMENT' line was connected to a mono jack. The other lights, switches, and gauges (old-style moving needle-style gauges) did nothing, despite all sorts of interesting labels (e.g., TRANSDUCER VOLTAGE LOW; OPERATOR RESISTANCE ERROR; LOW-SIDE VOLUME GOVERNOR FAILURE, etc.). The story goes that Mr. Morelli presented the DiMWIT to the boss in hopes that it would be used for basic aptitude testing of students after what is still referred to as 'The Steve Incident.' The box had been retired by the time I arrived on the scene, but I think I can imagine how it was used, given the natures of those two gentlemen.

I found out about Steve (most definitely NOT our own esteemed collegue, SteveG) and the DiMWIT about a month after I started here, when a framed certificate showed up above my bench proclaiming that:

"...having been observed and examined by a board of super-qualified, really handsome, and very clever luthiers, _____________is officially found to be lacking in any Steve-like qualities and designated a fully qualified and acceptable FNG-L, with all of the rights and other made-up stuff that goes with that."

A few weeks later, I locked the boss's roll-around drawers (despite the tops being open) with some rare earth magnets, and a few weeks after that, used Mr. Morelli's spare key fob (inexplicably stored in his vehicle's glove box) to periodically re-lock his vehicle as we approached the car after a nice lunch at a local eatery. Through trial and error, Mr. Morelli eventually determined that his key fob appeared to work only when held at a particularly awkward angle, and the vehicle could not be started without the trunk lid triggering. I did hand him the spare fob when he asked for it, although he seemed momentarily puzzled as to why it was in my jacket pocket instead of the glove box.

Surprisingly, the good-natured hazing became quite rare after those events.

_________________
For the times they are a changin'

- Bob Dylan

Sounds like you've had fun working there, please give my best to all.
I saw many pranks at work, including raw recruits being sent for the key to the Vidor (drill pipe entry to the rig floor, door but never with a lock) and coming back with a 5 foot long 75 kg facsimile of a key from the stores.
Kind of miss working offshore in some ways now I'm retired, but hey, I can build full time time.

_________________
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.

As far as reinforcing the tenon for barrel nuts I did some testing in a test jig years ago and reported it here. Without reinforcement the tenon cracked fairly easily. With two Maple or carbon reinforcing bars installed the jig began to pull apart and the tenon was still OK. As Woody said, this kind of reinforcement works. I use Maple now. 1/8" thick and deep enough to reach about halfway into the hole for the nut. I probably could have made the ones in the picture slightly longer.

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It's not what you don't know that hurts you, it's what you do know that's wrong.