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Shimming Acoustic Bolt-on Neck


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I finished my first acoustic. Oh happy day!

The action is too high, about 1/4" above the frets at the highest. I built the guitar with no neck angle, following a plan of a Martin OM. The total height of the saddle is about 9/16" if I remember right.

I'm thinking the best thing would be to angle the neck back slightly with a shim in the pocket and then lower the saddle if it's still needed. This is a bolt on neck, so shimming it will be easy.

Any thoughts? Is that a good way to proceed?

Thanks.

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Shim to set the action right, assuming the bridge is where you want it - at least 1/8@ of protruding saddle, and at least that amount (preferably more) embedded in the bridge - and then shave the neck/heel until it sits properly. At least, I'm assuming you have a mortise/tenon bolt on joint and not some weird Fender-style bolt on in an acoustic setup, in which case shimming would be a good option.

For future reference, draw out the side profile. I've yet to see an acoustic guitar without some sort of neck angle. They've pretty much all got some back set. I usually final-adjust/set the neck angle when the bridge is glued on, and set the straightedge to hit the top of the bridge when its resting on the fretboard (fretted).

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Thanks Mattia. I shimmed the neck with a piece of heavy guitar pick, and the action is now excellent.

Just for clarification and future reference... when you say this...

I usually final-adjust/set the neck angle when the bridge is glued on, and set the straightedge to hit the top of the bridge when its resting on the fretboard (fretted).

...the saddle is not installed yet, right? I guess it's obvious, but I just want to be sure I understand.

I've yet to see an acoustic guitar without some sort of neck angle.

I was pretty sure they usually have a neck angle (~2deg, I seem to remember), but this Martin plan from LMI didn't show one. I figured, with my method, I could shim the neck if it was wrong.

Edited by Geo
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Thanks Mattia... I'll try to post a picture some time, but I'm moving tomorrow so it probably won't happen. :D

Essentially, this is a bolt-on mortise and tenon joint. The tenon is about 20mm deep and I'm going to say ~35-40mm wide.

I realized that the neck is now leaning slightly to one side, so that the bass E is closer to the edge of the fingerboard than the treble E. I think this is because the shim I used (part of a guitar pick) has a curved side, which is facing up and providing a slight point of rotation for the neck. The lean is not really noticeable in playing, but now that I see it it's bugging me. The neck was aligned without the shim.

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  • 2 weeks later...
Shim to set the action right, assuming the bridge is where you want it - at least 1/8@ of protruding saddle, and at least that amount (preferably more) embedded in the bridge - and then shave the neck/heel until it sits properly. At least, I'm assuming you have a mortise/tenon bolt on joint and not some weird Fender-style bolt on in an acoustic setup, in which case shimming would be a good option.

For future reference, draw out the side profile. I've yet to see an acoustic guitar without some sort of neck angle. They've pretty much all got some back set. I usually final-adjust/set the neck angle when the bridge is glued on, and set the straightedge to hit the top of the bridge when its resting on the fretboard (fretted).

I am trying to save a vintage (or "wierd" ) accoustic fender malibu w/bolt on neck. It's going well I think. I did shim the neck some but might need more. My action is a bit high still. The saddle seems low already. should I shim the neck more (bigger shim)?

How much is too much neck angle? I used a hard wood tapered shim(seemed more solid than a pick). Also, the saddle is loose, it falls out. Is this normal? What ideas do you have about fixing screw holes in the top that the prior owner drilled to secure the pickguard? Can I make a new guard? Please explain. Thanks

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