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One way to keep some thickness in the heel of a butt joint bolt on neck without it looking too fat is to recess the heel into the body. I do this on my travel guitars because I cut the fret board between the 12th and 13th fret and want the 12th fret to fall on the neck/body joint and not have any fretboard overhanging the neck. It also makes resets easier, because I can carve an angle into the neck pocket rather than flossing the heel. If I overshoot it I can add back some wood in the pocket. For the travel guitars where the neck is meant to come off I will "overset" the neck and allow the action to be dialed in by the bolt and held in place by the tension of the strings.

Yes this is true. I see now what you mean. If you rout out a recess along the border of the butt joint then you would easily be able to floss it with hangar bolts. That's a good idea and something to think about. Many ways to crack this nut. In the end I'm a big fan of the simple butt joint.

That’s what I do. I’ve been able to get up to 3/32” action adjustment without even ungluing the tongue…just pull the bolts, slide in a thin piece of sandpaper backed with packing tape, and off ya go.being mindful not to push too far forward as you create a gap for the paper.


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Yep!

I recently had to do my first neck reset on one of my bolt on butt joints. Sadly it was brand new. Somehow, I miscalculated and under set the neck (even though I made two at the same time and the other was right). After I strung it up, I realized it would already need a reset. I was pleased by how easy it was. I first tried to do it without ungluing the fretboard extension fully expecting that to not work. To my surprise, it worked just fine.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

I'm really liking the square bar inserted into the heel. Interestingly I just saw this sort of approach for the first time when I happened to be staying with family at a Air BnB in Vermont. Turns out it's the home of George Morris's Vermont Instruments. I unfortunately did not have time to spend hanging around the shop, but the one thing he and one of his students showed me was his bolt on design. He uses a round rod inserted into the heel instead of the square. But it served the same purpose. He also avoided the whole glue down or bolt on fingerboard extension by extending the neck under the entire fingerboard, sort of similar to a cantilevered extension on an archtop. The whole neck/fingerboard extension is set into a routed pocket in the upper bout. He has a couple mm of play up and down to help with the setup and eventual change in geometry as the guitar ages. I'm still wrapping my head around whether I like that or not, but the round or square rod set in the heel seems like a great approach. I've got a square mortise jig for my drill press, so I'll likely be playing around with that in the future.

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Tony Thatcher
Bozeman, Montana

The square bar style is slightly more time consuming to make, but stronger in that, at least theoretically, a round rod has somewhat of a wedging effect as the bolts are tightened. The concern being that it could split out the heel/tenon if overtightened. How likely this is in practice, I don’t know. The fact George Morris has been using it suggests it’s fine.

I think there is a point where enough strength is enough, and any point after is pointless.

I've had trouble with Spanish cedar where the inserts have let go, and was easily remedied by retrofitting a dowel for salvage. But I've never had mahogany or khaya fail in standard practice without a dowel.

It’s probably freakish bad luck but I’ve had both threaded inserts (couple different types) and hanger bolts fail in mahogany and one of the African mahogany substitutes (think it might have been sapele but can’t quite remember) … which led me to the bolt bar method. The failures of the inserts and hanger bolts were not catastrophic and were easily fixable (with epoxy) but it left me a little nervous.

For me, the dowel in the heel is about 1) letting the treads of the insert or hanger bolt bite into side grain instead of endgrain and 2) to provide a cross grain brace against a splitting heel.

I’m not sure I buy the wedging effect from a round rod in the heel; I could be wrong. The square bar would concentrate the stress on the corners of the mortise. That seems like it would make it easier to break the wood along the grain right at the corners. If you look at the picture above, the square rod is in a heel with a tenon. That tenon greatly increases the length of the wood beyond the corners of the rod protecting against a split along the grain. I would worry about that square bar in a butt joint. There would be a very shallow span of short grain between the end of the heel and the stress riser of the bar.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Absolutely, I’ve never attempted the bolt bar for a butt joint, for the reasons you identify. Only ever with a tenon.

As a geologist in a former life the most natural shape for something to be in nature is round. It's called spheroidal weathering. It's basically a defense mechanism against the forces of erosion. But this concept can be applied more broadly too. If anything I would think that the rounded shape would offer better stress relief.

I used to make the holes over sized and just epoxy them in and never had a problem. But the dowel allows me to make the heel thinner.

As per usual in guitar making almost always all methods work well when done right. We just like to adapt to our own way of doing it.

Oh and... How do you make a square hole like that in the heel?

Mortiser.
https://www.amazon.com/WEN-43012-5-Amp-Mortiser-Chisel/dp/B07HFVLZJP/ref=asc_df_B07HFVLZJP/?tag=hyprod-20&linkCode=df0&hvadid=309807921328&hvpos=&hvnetw=g&hvrand=1091478978269553758&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9013385&hvtargid=pla-589771987653&psc=1

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Steve Smith
"Music is what feelings sound like"

Not having a mortiser has stopped me in the past from trying this. Has anyone had success using a morticing bit on drill press for drill into the heel?

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http://www.Harvestmoonguitars.com

We did dovetail, M&T with barrel nut and bolt, and butted with hanger bolts. For the M&T, we used cross-grain carbon fiber inserts to increase resistance to tenon failure... these strips were epoxied into slots easily milled in the tenon on a table saw. For butted necks, we drilled and epoxied in a cross-grain dowel to both increase resistance to hanger bolt end-grain tension failure and to reinforce the heel and allow a prototypical profile.

A square, threaded bar sounds interesting, but it seems like both a difficult shape to mill without a hollow chisel mortiser (we had one in the shop, but only used for Arts and Crafts-style projects and a few chair projects), and a stress riser where we want more gradual transition for the load into the remaining neck material.

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For the times they are a changin'

- Bob Dylan

Any particular species dowel and what size would you recommend?

I'm not crazy about the square hole thing. My gut says it won't stand up to a fall. These things happen I made some cam clamps and went the easy route of building in layers. Well the filler piece came right out when I applied too much pressure. Not enough length for gluing. My bars were wood so that's part of the issue as well.

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Hutch

Get the heck off the couch and go build a guitar!!!!

Regarding the square rod and hole: I'm not a devoted disciple or anything, but I do think it is useful to consider the fact that this is the bolt-on method outlined in the Gore/Gilet books. Those guys are some of the sharper knives in the drawer.

Focusing (always) on the question of how to get the most performance for the least amount of work: Gluing a wooden dowel in the heel, right in the middle of the heel cap footprint, with the dowel running through to the bottom of the fingerboard, is easy to do during the rough construction of the neck, and it does a whole lot of good when using either threaded inserts or hanger bolts. The threads of the inserts/bolts go into the dowel, which provides a stronger "grip" because it is cross-grain instead of end-grain, and the presence of the dowel makes the dainty end of the heel less likely to snap off. Even the smallest drill press would allow for the drilling of the hole for the dowel. What's not to like?

As I said above, I'm a dovetail guy at the moment, but if I use inserts/bolts again, I will either go fully glue-less with the Gore/Gilet design, or go with the simple glued fingerboard extension, bolted heel design, using a dowel in the heel. Those are the designs that make the most sense to me, if I wanted to use metal hardware to attach the neck.

Used one for years, filed the top of the square chisel 5/10mm to get required extra depth I want.
Workpiece needs held down in use.

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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 had one of the Delta hollow chisel mortisers for my drill press. It worked well but I was using it for making furniture and never used it for guitar making.

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Steve Smith
"Music is what feelings sound like"

It seems that everyone has gone with a two bolt design whether it is a butt or MT joint.

Something I have been wondering is - is one bolt good enough? It seems to me that with one bolt, lower close to the heel cap, and a glued on FB extension would be good enough. IF you have ever tightened strings on a guitar with a loose neck you can observe that it really doesn't take much to hold the neck in place as the string tension pushes the neck to the side body head block in line with the tension of the strings. Since it is on a slight angle it will of course flip the neck over and fold up like a book but it really is surprising how litle force is necessary to hold it in place.

Makes perfect sense to me. I had that discussion with my brother who is stair railing designer for high rise buildings. He told me the top bolt comes loose than the bottom bolt doesn't stand a chance of holding. This id directly related to what you said about the bottom bolt on a guitar but in reverse.

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Hutch

Get the heck off the couch and go build a guitar!!!!

As you describe, one bolt ought to be good enough. But, the guitar neck experiences more forces than string tension. It has to be handled and transported. Some people even put at strap on it attaching to the peghead. I’ve been doing a butt joint with two inserts screwed half into a vertical dowel in the heel for well over a hundred guitars. As of this minute, I’ve heard of no failures. When I did a slide guitar where if was to be played flat hanging from a strap at the peghead and tail, I used hanger bolts just to make sure. I don’t use the hanger bolts normally because they get in the way of flossing and a possible reset.

I too suspect that one bolt would be adequate most of the time. I made a mandolin with only 1 bolt and it has held well for 8 years. Bob's point is valid. There are lots of other stresses that can and do get applied to the neck. The neck is a pretty long lever compared to the small footprint of the heel. The cost of two bits of hardware compared to just 1 is not worth the risk for me.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Thanks for reminding me of the term floating tenon. I came up with this approach for my guitars too, although the sequence of assembly steps I use is a bit different. I also found the same bonus side effect of being able to cut the final neck angles (both set angle and skew angle) before the tenon gets glued into the neck. I cut the angles using a jig on the bandsaw and it allows me to dial in both angles so well that I don't need to floss the heels at all to get a tight fit. The floating tenon I use is a 3-layer laminate for extra strength.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I did the vector diagram analysis for a 14-fret guitar with a 25.4" scale some years ago and calculated that the pull on the bolts was only 12-15 lbs depending on the gauge of the string set used. The bolt closer to the heel cap gets most of that because it's further from the fretboard plane, but it's still not much force.

I like having the second, upper bolt because it ensures that the heel is pulled in fully tight to the body all along the heel-to-body joint when gluing down the fretboard extension.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Hey Jay, I'm assuming your vector analysis was for the static load only?

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Steve Smith
"Music is what feelings sound like"