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I've got a custom acoustic that needs a neck reset. It's a double m&t joint, so there's no glue at all. As a matter of fact, I've had the neck off to take a look at things.

I've never done a neck reset primarily because I don't understand the geometry of what happens. Here's where I need some help...

Logically, when you move one end of a lever down (headstock), the other end (fretboard end by sound hole) goes up. But lots of other things move as well. For example, the part of the joint circled in green below, doesn't that move away from the body? And don't the holes through which the bolts go change position?



I'd really like to tackle this job myself because I don't want to ship it back to the builder, and there's no one around who I trust to do the job. Also, I just enjoy learning things. I build electrics for clients, so I'm fairly knowledgeable but have no acoustic experience at all.

So, how do you handle a reset and account for the movement of all the parts (fretboard end, mounting holes, etc)?

Green circle---no, it should not move away. You should be able to floss a perfectly flat line on each side starting from the fingerboard to the heelcap. It should rotate backwards, fulcruming at the intersection of neck and body as you sand away the area between FB and heelcap...

Depending on construction style, there will either be a hinge point in the fingerboard at the join, or it will be fully supported with a continuous section of wood underneath.

If it hinges, you're probably looking down the neck and seeing a hump up at the body. So you can get your angle right, tighten the fingerboard tightens red, and it will bend at the 14th fret and cinch down to. Set the top, giving a bit of fallaway at the neck join which is something I like to see.

There's usually a bit of wiggle room with the bolt holes anyway, and they're only going to be displaced by thousandths of an inch...

Pictures would help. How expensive was the guitar? If it was a 3K+ handmade ax it might not be the best idea to cut your teeth on it.

Nothing wrong with calling the builder and asking for their advice. Isn't one of mine is it?

Terry

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

Thanks. That's a lot of the info I was looking for. The 14 fret hump is one of the things I was worried about as well.


It is a fairly expensive, hand-built guitar, but to be honest, I'm not nervous about giving it a shot. I guess that comes from seeing it more as a mechanical system, not something ultra special. Don't get me wrong, it is a very special guitar to me. I commissioned it to commemorate a big event in my life 10 years ago, but I play the heck out of it, and it's got dings and dents and finish chips. In the end, it's just a thing, and I'd value the learning experience quite a bit.

14 fret hump should go away when you get the neck angle back to where it should be.

How's the saddle? Has it been cut down in effort to bring the action down?

If so, I would cut a new saddle that gives you your ~1/2" string height above the soundboard, then carefully bring the angle back. Count your flossing strokes. Three left, three right, check, make sure you've hit the centre of the heelcap so it doesn't keep things lifted. Don't go to far. Compared to bringing it back, which is simple, bringing it forward can be a real nightmare...

And take all the relief out before you begin. And the bolts should be in place in the neck but loosened...

I use sandpaper 100-120 grit with packing tape applied to the back. Prevents scratches and strengthens paper...

I'm still a bit confused about the 14 fret hump. You say it should go away when i get the neck angle correct, but wouldn't further angling of the neck cause the actual hump?

Yes, the saddle's been sanded down. I'll definitely need a new one. Luckily I make all my own bone nuts for my electrics, so crafting a new saddle shouldn't be too horrible. I'll be sure to keep my old one for reference for the intonation.

When you look down the neck as it is, does the fingerboard appear to hump up where it hits the body?

I can't recall. I'll take a look at it tonight and report back. I'll also try to get some pics of the situation as well.

Pics help.

I'm slightly puzzled by the double mortise and tenon thing ... nobody else appears to be puzzled, so obviously it's my knowledge that is deficient.

Presumably the joint has twin tenons, is that correct ? Are these side by side, or one above the other , vertically?

I'm having a hard time visualizing it ...

If it's your guitar, sure, why not take a crack at it. A couple of good pics to get would be one with a straight edge along the frets under string tension and seeing where it hits the bridge. Then we'll know if it's a big reset or a tweak.

While you are at it take one without string tension as well so you'll see how much the neck moves under string tension. Measure that movement, it'll tell you how much you need to overset the neck.

Also a shot of the extension under string tension with the straight edge along the frets so we can see if you have a rising extension or there is still some drop off. Usually if the neck is settling the extension will rise. The reset recreates the drop off.

A shot of the neck attachment system would be good too so we can see if the extension is free floating with it's own tenon or supported by an extension of the neck itself.

Get the pics and we can go from there. Neck resets are not as simple as one might think if the goal is a perfect neck/body junction, optimal saddle height and a perfect setup.

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

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Thanks, Terence. I'll try to get all those pics next week. I've got to play in the worship band this Sunday, and I won't have time to get it torn down and back together by then with the holiday and work and everything else going on.