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  #1  
Old 05-16-2021, 03:10 PM
donnyb donnyb is offline
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Default Correcting neck/bridge alignment during reset

Thankyou for reading. Im seeking advice.

When doing a neck reset, assuming the neck angle reset sanding to the face of the dovetail tenon has been done evenly and the heel joint fits well against the front of the body, if then the neck centreline is off -centre to the bridge a little, I understand that this can be corrected by sanding the glued in shims on one side or the other of the tenon.

For example: when running a long straight edge along the centreline of the neck, where it projects to the bridge is 2mm to the left ( TREBLE) side of the bridge centre.

I have read that to skew the neck to correct that, you remove material from the shim on the left (treble) SIDE of the neck tenon.

If so far I'm correct, do you sand the left shim face at its existing dovetail joint angle (eg 15 degrees), or should you flatten the angle slightly to provide relief in the joint to help skew the straightedge projection across towards the bass side and thus closer towards the bridge centreline ?

Last edited by donnyb; 05-16-2021 at 06:03 PM.
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Old 05-16-2021, 06:51 PM
mirwa mirwa is offline
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You have a few things happening when resetting a neck.

If you can fit a full length shim on one side of the heel, then that means you can shift the neck position left or right slightly depending on how you shim it to lock in place, but not skew the neck angle

The bulk of the heel area that we typically sand when neck resetting has nothing to do with how the neck sits orientated to the saddle, it simply is about it sits in an imaginary plane projected above the top

To skew the neck so the neck angles better towards the saddle, one must remove wood or add wood in the 3mm zone (area) on the neck heel just below the fretboard, this area is typically untouched during a neck reset
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Old 05-16-2021, 06:59 PM
John Arnold John Arnold is offline
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Your description is not clear. There are two ways to correct this problem.
1) Trim the tenon so that the neck center is shifted toward the bass side of the body. This would require trimming the bass side of the tenon, and adding shim to the treble side. In either case, the angle of the tenon should remain the same, and should match the dovetail mortise in the body. This shift in the center of the neck may reveal bare wood on the body if the neck position is different from the original location. That is why it is generally not favored over the second method.
2) Alter the angle of the neck by trimming on the treble side of the neck heel where it contacts the body, all the way from top to bottom. This is in contrast to the intent of the reset, where no material is removed at the top of the heel.. This side angle change requires very little material removal, and should not affect intonation much. .
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Old 05-16-2021, 07:43 PM
donnyb donnyb is offline
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Quote:
Originally Posted by mirwa View Post
To skew the neck so the neck angles better towards the saddle, one must remove wood or add wood in the 3mm zone (area) on the neck heel just below the fretboard, this area is typically untouched during a neck reset


Thankyou Mirwa.
So is John's option (2) below what you are saying ?

If "yes", should I perhaps try that method first by just taking off a whisker from the treble side and see how much the alignment by straight edge moves towards the bass side of the saddle .
If not enough, try removing the shims on the bass side of the heel and add shims to the treble side to move the neck sideways in the pocket ?
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Old 05-16-2021, 07:53 PM
mirwa mirwa is offline
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Yes, john explained it better
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Old 05-16-2021, 08:53 PM
phavriluk phavriluk is offline
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Default A thought

And these folks mean removing a barely perceptible amount of wood.
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Old 05-16-2021, 11:38 PM
donnyb donnyb is offline
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Quote:
Originally Posted by phavriluk View Post
And these folks mean removing a barely perceptible amount of wood.


Yes . I would guess that with the trig, a small amount there will move neck alignment a fair bit at the saddle. I'll be careful, thankyou.

The sharpening affect on intonation on the treble side shouldn't be too noticeable.

I could hand press and skew the neck when I glue it, as it does come into centered string alignment doing so in the reset jig, but I dont want to permanently stress the heel and block.
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Old 05-17-2021, 12:26 AM
mirwa mirwa is offline
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an instrument that is aligned and stress free when glued up will present less issues long term than an instrument that has things forced in places it does not want to be

Take the time, sand it properly
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Old 05-17-2021, 04:53 AM
donnyb donnyb is offline
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Quote:
Originally Posted by mirwa View Post
an instrument that is aligned and stress free when glued up will present less issues long term than an instrument that has things forced in places it does not want to be

Take the time, sand it properly


Ive taken all on board from each , and spent the last 2 hours scraping and sanding, as I decided to do the shim adjustments to move the alignment, rather than the alternative.

The neck centre to bridge centre alignment is now near perfect and the tenon to pocket is shaping up to be a gentle interference fit. Used a few more shims , and a lot of chalk !

I can fix well enough the consequential exposed heel line on the treble side of the body.

Thankyou again to All for your help.
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  #10  
Old 05-17-2021, 05:24 PM
John Arnold John Arnold is offline
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Quote:
I could hand press and skew the neck when I glue it
If you do, you will create a gap between the neck heel and the body on the bass side. If cosmetics are not a concern, insert a shim there. Minimizing gaps will create a more reliable joint.

I will just reiterate that changing the side angle of the neck requires very little trimming, since the geometry is such that the amount trimmed will be multiplied 4 or 5 times at the bridge. When shifting the neck centerline in the dovetail, there is no amplification. However much you shift the neck over, that is how much it changes at the bridge.
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