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Neck Reset - Martin Simple Dovetail
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Author:  dradlin [ Tue Jun 06, 2017 11:56 am ]
Post subject:  Neck Reset - Martin Simple Dovetail
I'm working on a neck reset on a Martin with the latest machine set and cut simple dovetail joint. I can say I'm not at all a fan of this design.

First, the face of the body is machined to create a profiled pocket about .02" to .03" deep into which the neck heel inserts.

Image

The logic is surely to true the mounting face as the foundation for setting the neck geometry.

The first problem is that neither the pocket nor the heel mounting face are flat.

The second problem is that the pocket profile doesn't fit the heel well, it's tight (even too small) in spots, and gaps in other spots.

The third and greatest problem is that the presence of the pocket prevents one from flossing the neck heal as is normal to the process to fine tune the neck set angle and precisely match the heel to the mounting face.

So I've got some head scratching to do... has anyone tackled one of these? If you haven't tread with caution.


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Author:  Pat Foster [ Tue Jun 06, 2017 10:35 pm ]
Post subject:  Re: Neck Reset - Martin Simple Dovetail
Dang. What a PITA for a repairer doing a reset. Having worked on and designed manufacturing equipment, I'd guess that the neck angle was set by machine, cutting the area on the body where the cheeks make contact, rather than cutting the cheeks on the neck. That would eliminate having to cut the cheeks in the angle between the cheeks and the fretboard extension. Simpler for the machine. Just my two cents.

Pat
Author:  dradlin [ Wed Jun 07, 2017 7:58 am ]
Post subject:  Re: Neck Reset - Martin Simple Dovetail
Agreed Pat... the design is definitely completely biased towards automating manufacture, no regards for serviceability.

Precisely fitting a simple (parallel) dovetail without being able to spot the fit with chalk or carbon paper may prove to be an impractical process.

I'm beginning to think that converting to a bolt-on (adding another bolt) warrants consideration... but not yet.


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Author:  Pat Foster [ Wed Jun 07, 2017 8:45 am ]
Post subject:  Re: Neck Reset - Martin Simple Dovetail
Good plan.

Looking at the pic again, it looks like the relief is deeper at the heel end.

You could floss it by making a thin shim of constant thickness that would fit into the recess, bringing the sandpaper up above the surface of the sides, held in place by Contact shelving liner (which I use to protect finishes when building-it's low tack). But you probably thought of that.

Pat
edit: I should have mentioned: The shim would be used only for flossing, then would be removed.
Author:  dradlin [ Wed Jun 07, 2017 3:04 pm ]
Post subject:  Re: Neck Reset - Martin Simple Dovetail
Yes, deeper at the heel end... I understand that the pocket at the shoulder and pocket in the top under the extension are milled to setup the neck angle.

Some success paring the cheeks with a chisel and spotting with adhesive paper in the heel pocket.


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Author:  mountain whimsy [ Wed Jun 07, 2017 5:06 pm ]
Post subject:  Re: Neck Reset - Martin Simple Dovetail
Rather than dealing with the neck and worrying about flossing, could you work the heel pocket to set the new angle? You'd have to shim the dovetail too, but I believe you'd have to do that regardless.
Author:  dradlin [ Tue Jun 13, 2017 8:08 am ]
Post subject:  Re: Neck Reset - Martin Simple Dovetail
mountain whimsy wrote:
Rather than dealing with the neck and worrying about flossing, could you work the heel pocket to set the new angle? You'd have to shim the dovetail too, but I believe you'd have to do that regardless.


I completed this one by painstakingly paring the heel to set the neck angle instead of flossing. Working the heel pocket is certainly an option, though I chose working the heel as it being more familiar.


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Author:  dradlin [ Tue Jun 13, 2017 8:19 am ]
Post subject:  Re: Neck Reset - Martin Simple Dovetail
What is illogical about this neck joint design... a neck bolt is only used in manufacture to draw in the heel during glue-up of the neck to body, but that causes a gap in the fit of the sliding dovetail. The glue therefore behaves to a large extent like a gap filler with some adhesive properties.


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