My process for establishing NECK ANGLE for scratch neckbuild

[ColestineGuitar]

Now THIS is an interesting thread. Your process takes both "in theory" and "real world" into account, and does so quite simply. I'm going to save this information for reference on the next guitar.

[tippie53]

that is too high but you sure don't have to take my work on it . When I set my line I am looking for about .375 off my neck to the point of the saddle. I had done a few with that higher setting you have and ended up resetting all of them. Just my experience.
Are you getting the string line and the fret plane crossed ?
When I set up my guitars I do the geometry on the sides so that I don't thin the top. My target using the plane of the neck is .090 at the saddle.
Feel free to call me. I may be misunderstanding what you are going for and I would hate to see you make a mistake I have already made.

[Darryl Young]

I'm trying to take this formula and modify it to use for sanding the angle into the rim (instead of the top) on the Cuban Mahogany 00 I'm building. I've not been able to work on it lately and when I have a little time, I can't do much till I figure out the angle to sand into the rim. So I took a little time this afternoon to try to address this.

My thought is the formula Dan gave for the NEH should work just as well for sanding the angle in the rim as it does for sanding the angle in the top.......IF the top has a constant thickness. However, my top is radiused so I will have to add to the formula to allow for this. So when I reference NEH in this post, it is referring to Neck Extension Height above the plane of a flattened rim.

So here are the measurements I used and how I adjusted the formula. Please take a look and see if you see a flaw in this logic.

Bridge Height(BH): I want to leave as much saddle showing above the bridge as possible without damaging the bridge. Todd Stock says 0.180" is the highest he will leave a saddle sticking up above the bridge. A thinner bridge keeps the bridge mass to a minimum. I'm wanting 1/2" string height at the saddle so if I go with a saddle height of 0.175", my bridge height will be 0.325".

Finger Board Thickness(FT): My fingerboard is 0.250" thick and I'll use 1/32" for the height of my frets so I'll use 9/32" for my total fingerboard thickness.

Settle-In(SI): This is a little more difficult to guess without experience so I'll use the numbers suggested in Dan's original thread on NEH. Start with 1/16". Subtract 1/16" for using the Martin Short scale. Subtract 1/64" for using a small body (00). So my Settle-In is a negative value..... -0.016".

Radius Depth (RD): No guidance here so I'll make it up. <smile> I'm using a 28ft radius and the 00 body is about 14 3/8" wide at it's widest point in the lower bout. Since I'm using a 12 fret neck on a 14 fret body, the location of the bridge is roughly in the center of the lower bout where it's widest so I'll go with the widest width. Now it gets a little complicated. Instead of sanding the top of the rim with a radius dish, I plan to leave the top flat (except for sanding the neck angle above the soundhole). So essentially I'm springing a radiused top onto a flat rim. This will flatten the top around the perimeter (hopefully loosening the perimeter for a good monopole mode) so it won't actually be radiused the entire width. So how much area will be flattened? The rim + lining is 5/16" wide so I know that will be flat. I'm guessing it will be flat a little further before the tension in the top curves it up. So since it's just a guess, I'll go with an additional 3/16" and assume 1/2" on each side will remain fairly flat. That would make the radiused width 13 3/8". Using chord calculations I put in a spread sheet, a 28ft radius over a span of 13.375" rises 0.067" at the midpoint.

So here is my modified version of the formula Dan provided for NEH above the plane of a flat rim:

NEH = BH+RD+SI-FT

So for the 00 I'm building:

NEH = 0.325 + 0.067 + -0.016 - 0.281 = 0.095"

So what do you think? Does this sound reasonable? If so, I could thickness a piece of wood to 95 thousands, clamp it to the rim at the saddle location, and use it to sand the correct angle into the rim prior to glueing the top to the rim.

Let me know if you see a flaw in my logic, calculation error, etc.

Thanks!

[Darryl Young]

I'm still thinking through this and one thing is bothering me.........why should the NEH (before or after the top is glued in place) have anything to do with the bridge height? (I'm assuming NEH means height above the soundboard and not height above the bridge) Seems string height at the bridge should be used in calculating the neck angle......who cares what percentage of the total height is from the bridge and what percentage is from the saddle (at least for this calculation).

So if two guys have identical guitars and both want 1/2" total string height at the bridge, if one uses a 0.350" bridge and a 0.150" saddle and the other uses a 0.325" bridge and a 0.175" saddle.......wouldn't both still want the neck set at the exact same angle? Sure seems so. If that is the case, why would this formula use bridge height in the fomula and not string height at the bridge? Doesn't this formula give these two guys a different NEH.....which would mean a different neck angle.....so both couldn't be correct could they?

Please explaing this so I can get some sleep tonight! <smile>

[Dan Bombliss]

I can't tell you exactly what the different "angles of attack" make on the guitar or bridge, but one thing to consider is that the higher saddle to make up for the shorter bridge, will have a different sharper angle from the strings to get over that saddle.

Secondly is generally, from what I know, is that the whole point in shooting your neck angle to the front of the bridge is to have a certain saddle height. If what your saying is accurate, then that would mean there would be no point in doing neck resets.

So with the target of setting your neck being the front of your bridge, that dictates the bridge height. If you are set on a 1/2" height over your top at the bridge location, that that dictates you're bridge height.

Also, keep in mind that nothing in this formula considers string height. It's irrelevant at this point. The angle is what the measurements would be with a straight edge, and if this is done right then you won't have issues with string height, like being force to make a saddle that is too low, or a saddle that has excess height (which if it's too tall the leverage of the strings will break it).

I'm rambling a bit because I'm exhausted right now, but I keep trying to recap in my head as I type this as to what it was your were asking, and to organize my thoughts I'm going to go over the geometry of the neck angle really quick.

Your bridge dictates the height that you are going for over your top... 2 guys going for an identical 1/2" over the top would in theory have the same bridge height, because the general rule is to kiss the top of the bridge. One of the 2 guys aren't going to diliberatly set their neck angle 1/8" over the bridge to get that 1/2" at the top... They would make a taller bridge to go with that height.

With that said, 2 guys going for the same NEH could have different bridge heights or heights at the top, but they would have a fingerboard that is proportionately the same height as the bridge if that makes sense. To be simple this is 32's:

If one guy has 12/32" bridge height and 8/32" fingerboard, the other guy could have a 13/32" bridge height and a 9/32" fingerboard, but the NEH would still be the same, meaning the same angle.

Hope that clears it up.

-Dan

[Dan Bombliss]

I just saw your first post, and read that. I'll give some thought to that and try to organize my thoughts on your idea.

As far as the negative settle in goes, I wouldn't actually factor a negative settle in, as it's impossible for your top to sink when you string it up. I'd just call it 0 settle in.

It makes sense to "factor" settle in and try to compensate it at this point, but like I said, the top will not possibly sink with string tension on it, so I would just rule settle in out with your specs.

I'll try to factor your equation here when I get a chance and try to brain storm the sanding the rim deal.

-Dan

[Darryl Young]

Dan, in your example at the end, you are assuming that everyone wants/uses the same saddle height above the bridge and that's not always the case (see the example I gave about Todd Stock). The angle of the neck is set to give a good action when the strings are at the desired height at the bridge. The action and the angle remain the same if you have a short bridge and tall saddle or tall bridge and short saddle. Surely there is a way to adjust the formula to use string height at the bridge instead of bridge height so the formula works with different bridge/saddle combos. And I do realize there are limits to how far the saddle can protrude above the bridge.

What bridge thickness (height) are you using with this formula? Oh, good point on not using a negative "Settle-In" value.

I can't tell you exactly what the different "angles of attack" make on the guitar or bridge, but one thing to consider is that the higher saddle to make up for the shorter bridge, will have a different sharper angle from the strings to get over that saddle.

Secondly is generally, from what I know, is that the whole point in shooting your neck angle to the front of the bridge is to have a certain saddle height. If what your saying is accurate, then that would mean there would be no point in doing neck resets.

So with the target of setting your neck being the front of your bridge, that dictates the bridge height. If you are set on a 1/2" height over your top at the bridge location, that that dictates you're bridge height.

Also, keep in mind that nothing in this formula considers string height. It's irrelevant at this point. The angle is what the measurements would be with a straight edge, and if this is done right then you won't have issues with string height, like being force to make a saddle that is too low, or a saddle that has excess height (which if it's too tall the leverage of the strings will break it).

I'm rambling a bit because I'm exhausted right now, but I keep trying to recap in my head as I type this as to what it was your were asking, and to organize my thoughts I'm going to go over the geometry of the neck angle really quick.

Your bridge dictates the height that you are going for over your top... 2 guys going for an identical 1/2" over the top would in theory have the same bridge height, because the general rule is to kiss the top of the bridge. One of the 2 guys aren't going to diliberatly set their neck angle 1/8" over the bridge to get that 1/2" at the top... They would make a taller bridge to go with that height.

With that said, 2 guys going for the same NEH could have different bridge heights or heights at the top, but they would have a fingerboard that is proportionately the same height as the bridge if that makes sense. To be simple this is 32's:

If one guy has 12/32" bridge height and 8/32" fingerboard, the other guy could have a 13/32" bridge height and a 9/32" fingerboard, but the NEH would still be the same, meaning the same angle.

Hope that clears it up.

-Dan

[Dan Bombliss]

I suppose it still just doesn't make much sense to me why you'd want the saddle taller, although I haven't ready into Todd's reason as to why. If he says he likes the bridge thinner, I would just think set your angle to a thinner bridge. As far as how the engineering behind the neck angles change the effects of sound in an instrument, I haven't gotten into that much myself, so I've been sticking alot to the basic geometry of the neck angle.

What's the reason for wanting a 1/2" bridge height? Are there benefits to that neck angle? Also, keep in mind that a 1/2" at the bridge location doesn't mean much if you're fingerboard/frets are thicker/thinner. It's the relationship between the fingerboard thickness and bridge height (location height) that make up that angle.

Exaggerating of course, a 1/2" thick fingerboard, and a 1/2" thick bridge makes no neck angle, where as how an 1/8" thick fingerboard and 1/2" bridge make a sharp angle.

A bit of missing information on the Todd Stock info is his fingerboard height. Also, you haven't mentioned what action height Todd's shooting for with this .175". I would like to think all of those would be factors. As both the fingerboard thickness would reveal information on his thoughts on saddle height, and also desired action I would think. For example since I like my action about as low as I'm willing to go with out buzzing .075"-.050" (E-e) I wouldn't want a saddle height at .175" if Todd's saying .180" is the maximum saddle height you'd want.

Another huge factor about trying to predetermine a saddle height is what time of the year are you building this, and again what action are you looking to get for an outcome? If the middle of summer in the midwest with spiked humidty, you're shooting for a .175" saddle (close to the max) and your top is swelled, it may swell more after it's built, and set you with high action. Or, maybe it's already swelled to the max and you set it in the peak of summer to the .175", and all of a sudden winter comes around and your top sinks. If your like me setting .075" and your top sinks in the winter, there's no room to raise your saddle height. This may be exaggerated, but if your top sinks .100" from peak of summer to middle winter, you'd have to have a .275" saddle to make up for it. So in this made up scenario, this guitar is not playable in the winter.

Basically, in my personal opinion, the idea of predetermining your saddle height to an extent, wouldn't be my choice, for that exact reason. I'd like to have the leeway in both directions, to both shim/remake a taller saddle, or lower the saddle that's in there, depending on the season. Again though, I haven't heard Todd's reasoning for wanting a taller saddle.

-Dan

[tippie53]

if you are at 1/16 with the frets you should be fine. After doing over 300 neck sets it comes as 2nd nature. For absolute best results you want to set the neck then plane the fretboard on the guitar and fret , that makes the fret board trued to the position it will be it , also you can tweak the bridge at this point .
I think you should have a fair result. I go for about .090 at the saddle off the neck plane .Keep us posted

[Darryl Young]

I'm at work so just a few thoughts.

I suppose it still just doesn't make much sense to me why you'd want the saddle taller.......

Possible Reasons: (likely pros and cons to these points, but here are some pros)
- As the neck rises over time, you have more saddle to trim to delay a neck reset and maintain a resonable playing action (probably at the expense of loosing a little volume).
- Using a taller saddle means you can use a less tall bridge so it will weigh less. Some folks are fanatical about minimizing bridge mass.
- Sharper break angle of the strings over the saddle. Some folks slot the bridge to get a sharper break angle and a taller saddle has a similar effect.

Secondly is generally, from what I know, is that the whole point in shooting your neck angle to the front of the bridge is to have a certain saddle height. If what your saying is accurate, then that would mean there would be no point in doing neck resets.

I would disagree with that assertion......at least on new builds. Thickness/brace your top for a given string height at the bridge, then set the neck angle to get good action while at that string height. The neck is set at an angle that aligns the fretboard with the strings. Typically the string height is measured at the 12th fret to determine how well the fretboard aligns.

I go back to the example I presented earlier about two identical guitars each with 1/2" string height at the bridge and one has a 0.325" bridge/0.175" saddle and the other has a 0.375" bridge/0.125" saddle. This time I'll add one more constraint (forgot this in the last example)......both guitars want the same action height meaning the string height at the 12th fret should be identical on each. To achieve this, the neck is set to the exact same angle on both guitars.......so the string height at the bridge will be identical on both. If the method of setting NEH based on bridge height is used on these two guitars, then the neck angles would be different and one of the guitars would NOT have 1/2" string height at the bridge.

As to the magic of 1/2" string height at the bridge. I personally don't think it's magical though many with way more experience than I believe it is optimal (and there is a limit to how much it can be changed and everything work well). I do know that if the top is braced for a 1/2" string height at the bridge and you lower it (as would happen on the guitar with the less tall bridge if NEH were based on bridge height) then you will change the sound of the guitar (probably less volume and responsiveness and possibly less bass). So I know that the string height at the bridge is an important factor......no matter what percentage of the height is made up of bridge height or saddle height. So since it's importatant to the sound of the guitar, I want to control the string height at the bridge.......so would rather use an equation based on that. Then the neck angle is set properly no matter if the builder chooses a tall or short saddle.

I will point out that once a guitar is built and the bridge glued in place.......then you live with what you have. At this point, basing the neck angle off the bridge height is very resonable as you have no choice (unless you want to replace the bridge). So my points are for a builder or for someone replacing a bridge and setting the neck. So from a repair/maintenance point of view the NEH based off bridge height is legitimate. A builder has a few more options.

Does that make sense? I think I can come up with a formula tonight when I get home and have more time.

To help with this formula, what bridge height have you been using that works well with the NEH formula you've been using? 0.375"?

Thanks!