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Very cool.

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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

Neat!

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Bryan Bear PMoMC

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

Definitely cool and out of the box.

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Steve Smith
"Music is what feelings sound like"

Wow, that's a really cool idea, it suits you project!

For filling with hide glue on marquetry projects I've mixed very fine sawdust (walnut in my case, but cuban mahogany is the traditional choice for marquetry) with HHG and a little hot water plus black tempura powdered paint to make a thick paste that can be spread. You could leave out the black paint if you wanted more of a wood tone in the mastic.

Mastic applied using a putty knife


After sanding level and finishing with clear lacquer

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Blog on Making Stuff: http://www.McGlynnOnMaking.com

No new progress yet. I'm having a very difficult time deciding between my usual integral neck style, or doing a bolt-on M&T in order to properly confirm that the plan I drew up will come out just right if built without any modifications.

Have you done a bolt on before? If not, you can just call it something new. . .

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Bryan Bear PMoMC

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

Yeah, my first two used bolts. It would be a no brainer if it was a large non-cutaway guitar, but on a small one like this the added weight will be significant, plus I can't do the curvy cutaway transition I like.

I think I will do integral. I really can't think of anything that would go wrong building from the plan directly, and with Gregor guinea pigging it as well that should be enough testing.

And in that case, I'm gonna need some more cherry for the heel...

I'm curious, are you concerned about the weight of the hardware relative to the total weight of the guitar, or the overall weight balance?

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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

Both. But I'm mostly just being eccentric The total mass should be in the 1350g area, and switching to bolt-on would add 50-100g more, which would not be significant to anyone other than myself. And the balance point probably won't be affected by more than 1cm or so, since the center of mass will already be very close to where the added bolt and headblock mass would be, and I could counteract that by adding a little bit more to the tail block.

Guess I'm partially eccentric - I'm going to use a dovetail cause I don't want to add the weight and I also want a traditional neck joint. But I am going to use a trussrod so that will add a bit of weight.

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Steve Smith
"Music is what feelings sound like"

My opinion is that a little extra mass in the neck/headblock joint might be a good thing.
I have no real justification for that opinion.

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A man hears what he wants to hear, and disreguards the rest. Paul Simon

Dennis tries to get his instruments light enough to float. Not in water, in regular room air. I once saw one of his guitars sitting on the table when someone turned on the AC. As the temp and humidity dropped it slowly rose to the ceiling.

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Bryan Bear PMoMC

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

I hadn't really given much thought to the weight of the bolt hardware before so I weighed two each of the bolts, barrel nuts, and brass washers I've been using and they came to 22 grams. My guitars aren't as feather weight as Dennis's guitars. They come in at more like 4 lb 3 oz (~1875 g) so the hardware is just over 1% of the total weight.

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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

Lately I've been using Gibson style single compression truss rods, which are about 70g as opposed to 130 or something for most two-way rods. Also dirt cheap and fun to make

But even better will be when Stuart Gort starts selling his 27g composite two-way truss rods.


Hmm, I guess I need to look for some lighter hardware. Mine are 45g for two barrel nuts, two bolts, and two washers. But then the headblock needs to be a fair bit bigger as well when the external heel isn't part of it, and that won't change with different hardware.

I have considered trying a dovetail as well since it can use a bit smaller headblock and avoids the hardware. But it comes with its own drawbacks of being more difficult to make and adjust, and still can't do the curvy cutaway transition heel shape either.

Yep, I expect they are going to be awesome - hope I can afford them

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Steve Smith
"Music is what feelings sound like"

Hanger bolts with a butt-joint don't need inserts or barrel nuts and the heel-block doesn't need to be too big either. If you drill and counter-bore your holes in the block before you glue it in, you could even use a "U" shaped block with bigger surface area on the top and back with the middle section reduced. Just make a large block and counter-bore your holes to establish the flat surface for the bolts to register against, then saw out the "U" shape making sure you don't cut it so deep that you cut away the flat surfaces. You could even carve the remaining wood into a slipper foot shape.

All that said, this is a solution without a problem since I'm confident you will do a good job without doing a bolt on. . .

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Bryan Bear PMoMC

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

Bryan--
The only issue I've had with hanger bolts is that the wood screw side on the #10 ones you can find at your typical hardware store are at least an inch if not more long. They are just too long for my typical heel which is only about .5" at the bottom. Obviously the heel gets thicker as you move up towards the fingerboard. Just not enough at a point 3/4" from the bottom where I would normally place the bottom bolt.

Do you have that problem?


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Yeah, hanger bolts would be a little lighter. I'd definitely still be using a tenon with them, though. I like a very slim heel, especially on 12 fret cutaways like this. Gives almost the same playability as a typical 14 fret cutaway, since you can keep your thumb on the back of the neck all the way up to the 11th fret.

No, I just cut off the ends of the wood screw part. I put a cross grain dowel in the heel so the threads are biting only into endgrain. I drill my pilot hole and screw the hanger bolt in almost as deep as I want it. Then I cut off whatever length of wood screw thread I don't want and screw it back into the treads it cut in the wood and then to final depth. I use some CA to firm up the wood around the bolt but that is probably not needed.

I also have been known to cut the machine threads down on small instruments. I use those allen headed furniture cap nuts (the name always escapes me) so I can't have the threads too long. I measure how much length I need, thread on a wing nut then cut off the extra threads. Unscrewing the wing nut cleans the cut threads up well enough. I suppose a die would be better. . .

In reality, I suspect that tapping machine threads into the heel and using a regular bolt would be more than strong enough for this joint but I have not yet tested this. That would be really convenient!

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Bryan Bear PMoMC

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

I remember reading a research paper somewhere testing the strength of machine threads cut into wood, and the strength was much higher than I expected. IIRC, it was pretty close to aluminum, so probably easily strong enough for a neck joint.

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A man hears what he wants to hear, and disreguards the rest. Paul Simon

One of these days I will make a test rig to prove that it is okay with the forces we deal with. I think the test you are talking about was with force pulling straight out (I could have that wrong). The force on a neck joint is pulling with a levering action at the heel. It is not necessarily super strong, but pulling on the side of the wooden hole could be an Important difference. I don't have any taps that can cut into a blind hole and never get around to getting one. Now that I think about it, even a really poorly made tap will be up to the task of cutting hardwood. I should just grab a Harbor Freight tap set and get on with it.

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Bryan Bear PMoMC

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

Great idea! I agree, it should be plenty strong for just the string force. Especially if you use something with extreme hardness like ebony or African blackwood for the reinforcement dowel in the heel. The two things I'd worry about are humidity expansion of the headblock adding more pulling force on the bolts, and impacts shocking the threads on top of that. But with belleville washers I think it would still be ok. A bit of springy padding for impacts, and movement range while maintaining tension on the bolts so you don't have to overtighten them in fear of humidity contraction later.

Bryan, I would read with great interest your results. I use inserts, but not in love with them. Alignment is difficult, it adds a step, and I have one guitar strung with heavy flat wound strings (188lbs tension set) where the inserts pulled out.

I would love to use the hangar bolts, if just .5" of thread is enough to hold.


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I bought a tap and die set years ago, just because the sale price was ridiculously low, and I've never regretted it. I have used it for making many shop jigs out of wood, aluminum, steel, UHMW, etc.
It's one of those things, like having a compressor in your shop that you don't know how you did without!

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

You've had inserts pull out!?! Did you use a cross grain dowel or were they screwed into endgrain? What kind of inserts? What was the neck wood?

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Bryan Bear PMoMC

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