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attaching bolt on neck- OM

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attaching bolt on neck- OM

Postby Bob Howell » Sat Mar 25, 2017 11:24 am

I bolted my Steel string neck on to my newly assembled OM sound box. I have a 3/64-1/16"gap between neck and top of sound board. At the approximate location of the bridge it 3/32". It is straight with the center seam. I have read Campino and see no mention of this. So I think I just move ahead and put veneer in the gap under the fret board.
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Re: attaching bolt on neck- OM

Postby Peter Wilcox » Sat Mar 25, 2017 2:14 pm

I may be missing something here :? , but the fretboard needs to be flush with (touching) the top when the neck is bolted on. It sounds like your bolt holes need to be "adjusted." A picture would help.
Maybe I can't fix it, but I can fix it so no one can fix it
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Re: attaching bolt on neck- OM

Postby Bob Howell » Sat Mar 25, 2017 3:10 pm

I need to add more information- sorry:
I 'm using The bolt Joint on Campino's web site.
I am about to install the truss rod but I can still plane a 1/16" off the top of neck and bring it together. It is 7/8" thick.
I shaped the head block to mate with the neck and allowed a fat 1/8" for the top. It has come out 1/16" less.

Seems the height at the bridge would be important also but I see no mention of that anywhere.
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Re: attaching bolt on neck- OM

Postby Barry Daniels » Sat Mar 25, 2017 7:13 pm

Yep, the height at the bridge is critical. But it depends on the thickness of the fretboard and the bridge.
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Re: attaching bolt on neck- OM

Postby Bob Howell » Sat Mar 25, 2017 8:26 pm

Thinking this over today I see the bolt joint allows me to drop it down 1/16" with slight realignment.

I'm going ahead and install the trust rod.

I like to know where I'm going. How I'm going to get there.
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Re: attaching bolt on neck- OM

Postby Todd Stock » Sun Mar 26, 2017 5:04 pm

For a 1/2" string height at the saddle, the projected neck line from bare neck (no fretboard) should show about .085" clearance at the saddle location. The neck should be flush with the top, so if the curvature of the top interferes with use of a straight edge, use a couple offset blocks of equal thickness (one at first fret location, one at 12th fret location, and one at saddle location).
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Re: attaching bolt on neck- OM

Postby Freeman Keller » Mon Mar 27, 2017 4:22 pm

Another way to say what Todd is saying is that the fretboard plane should hit the top of the bridge (this takes care of the thickness of the bridge). In this case the f/b isn't fretted yet so its 30 or so thousands below the bridge, once I get the frets in and the bridge glued on I'll floss the heel until it just hit the top. That will give me an action of 60 to 90 thousands and a saddle about 1/8 inch out of the bridge

Image

The f/b extension is sitting on the top and will be lightly glued down
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Re: attaching bolt on neck- OM

Postby Todd Stock » Tue Mar 28, 2017 4:50 am

Start from where you want the string height to be and work down:

Desired string height over top at saddle (string plane-to-top) distance = .500"
String plane to fret-top plane distance at saddle = ~ .165" (scale length and action dependencies)
Fret-top plane to fretboard-top plane distance at saddle = ~ .045" (range of .035 to > 0.050)
Fretboard-top plane to neck plane at saddle = .250" (dependency on board taper)

So desired string height at saddle - String plane to fret-top plane distance at saddle - Fret-top plane to fretboard-top plane distance at saddle - Fretboard-top plane to neck plane at saddle = uncorrected height of neck plane at saddle = 0.040" for the example

The degree of correction depends on a lot of things, including string set used, scale length, body config (12 fret/14 fret), size of body, overall method to transfer string loads to body, back bracing config, etc., but is usually between about 0.030"-0.060". For the stuff that I build, .045" works out (I use closer to .060" for 0000 and D bodies), so:

Uncorrected height of neck plane at saddle + body distortion correction = corrected height of neck plane at saddle, or 0.040" - (-0.045") = 0.085"

To the point on fret board plane, 0.085" + 0.250" = 0.335; this is slightly below the .350 bridge thickness value I use, but because I generally do not make up the bridge until after the neck angle is set (have to do something while the guitar is in the drying box), I primarily use a custom tool that has points of contact at 1st and 12th frets, and a dial gauge at saddle location - this tool lets me directly measure with fretboard on or off, frets on or off, etc.
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Re: attaching bolt on neck- OM

Postby Todd Stock » Tue Mar 28, 2017 7:59 am

I should mention that the correction above is as a result of body distortion due to string tension, or what some call 'top rise', because the net result is what appears to be a rise in the top and less distance between the top and string line plane, with the result being being an underset neck.
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Re: attaching bolt on neck- OM

Postby Bob Howell » Tue Mar 28, 2017 8:15 pm

I have corrected my neck to now hit at the sound board and, without the fret board, it is up 1/23-1/16" at the bridge position. That's with no additional neck angle adjustments. So I am very close to start with. Thanks for the help.
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