my neck is not lining up with the body centerline now what?

[Jason Brown]

I need some help with this one. After preferring the neck to the body it is misaligned by about 15 degrees. How do I fix this? I cut the mortise and tenon by hand and thought I had it properly aligned with the center line. It's a small body thin line acoustic with a 25' top and back.

[Mark Swanson]

Well, you are going to have to make it fit! Removing a little more wood from the side of the neck shoulder that needs a little more angle, and shimming the dovetail is where I would start. A little bit at time, and keep checking as you go.

[Bryan Bear]

Can you post some pictures of the joint?

[Barry Daniels]

15 degrees!!??

[Clay Schaeffer]

Is it a "bolt on" mortise and tenon?

[John Sonksen]

15 degrees!!??

I've gotta think that's supposed to be 1.5 degrees, otherwise it's hard to imagine something that far off

[Jason Brown]

Yes Clay it is a bolt on mortise and tenon. I've been trying to shim the bottom of the joint to get the neck flush with the top. Is the neck angle produced from the cheeks of the tenon meeting the body at a precut angle?

[Alan Carruth]

"Is the neck angle produced from the cheeks of the tenon meeting the body at a precut angle?"

Yes, and you have to adjust that very exactly to get the bridge height to come out right and have the center lines of the neck and box line up. This is where what I call the 'koan of lutherie' comes in:"the slower you work the quicker you get done". The idea is to take off only tiny amounts of material to make the adjustments. Each one only gets you part of the way there, but there's very little chance that you'll overshoot by taking too much off. This is where you find out if you really can sharpen a chisel.

It's still a little unclear to me what the problem is. In the OP you wrote:
"After preferring the neck to the body it is misaligned by about 15 degrees. How do I fix this? I cut the mortise and tenon by hand and thought I had it properly aligned with the center line. It's a small body thin line acoustic with a 25' top and back.",

and now you say:

"I've been trying to shim the bottom of the joint to get the neck flush with the top."

The first post implies that the neck is set to the correct depth, but the centerline doesn't line up, placing the bridge off center by what would be a large amount if it really is 15 degrees. The later post says that the neck is too deep in the pocket, so that the surface of the neck is below the level of the top. Until we get a definitive reading it's a little hard to say how to proceed. you can shim it up if it's too deep, but shims are not considered a proper fix for a misalignment of the center line.

[Doug Shaker]

I think we really need photos before we can give actionable advice.

[Michael Lewis]

Having common terms will be helpful, especially in a case like this.
PITCH refers to the neck angle that determines the height of the bridge,
YAW refers to side to side position of the neck which determines if the bridge sits on the center line or has to be moved to the side, and the center line of the neck and center line of the body should be the same
ROLL refers to the twisting motion along the long axis of the neck that determines if one side of the fingerboard is higher, lower, or even with the other side of the fingerboard in relation to the soundboard.

So, where exactly is the misalignment?

[Jason Brown]

At this time the pitch is not set. The yaw is off making the neck slant to the left. I need to adjust the depth of the neck in the pocket to make it align with the top.

[Randy Roberts]

Jason,
And again, we ask, 15 degrees?
And I'll also repeat, can you post a picture for us to be clear what we are attempting to fix before we send you down the wrong path?

[Jason Brown]

I might be wrong on the 15 degrees. It is slanted to the left though and the neck needs shimmed in the pocket. I'll post pics as soon as I can.

[Clay Schaeffer]

The "shoulder" of the tenon needs to be fitted to adjust the "pitch" and "yaw" of the neck. The "face" of the tenon is also fitted to adjust the "yaw" (neck/ body alignment). You may need to trim a small "wedge" off one side and glue it to the other to keep the neck on center and aligned If the mortise is already cut.

[Clay Schaeffer]

To elaborate a bit on the method:
First you should trim the face (side) of the tenon to allow the neck to align with the body. This will most likely cause the tenon to be tapered rather than have parallel sides and require adding a tapered shim to to the other face to make for a snug fit in the mortise.
Second, sliding the tenon into the mortise and holding the neck at the required angle for proper string height, you can see where the shoulders need to be trimmed to make the heel tight to the body.
Clear as mud?

[Michael Lewis]

I would get everything aligned along the center line first by dealing with the mortise and tenon, and make sure the roll is OK in this process, and deal with the pitch last, as it will be much easier if all the other issues are already dealt with.

[Alan Carruth]

What Micheal said: do one thing at a time.