Neck block mortise

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Michael Thoner
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Joined: Fri Apr 15, 2016 11:22 am

Neck block mortise

Post by Michael Thoner »

When I was cutting the sides to uncover the dovetail mortise, I accidentally shaved a little from the top front edge of the neck block. The dovetail won't fit tight now, and I think I need to put in shims. All I have for wood is a little scrap rosewood from the sides, which is a hair over 1/16". Only about 10 - 20% of the mortise is affected. Is it a good idea to glue the rosewood to the sides of the mortise, and shave the neck tenion to fit?
MaineGeezer
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Re: Neck block mortise

Post by MaineGeezer »

No -- adjust the shims as required. Don't take anything off the mortise or tenon. You can use just about anything for shims. If you really have no wood, get some birch veneer edge banding, if you can find some that is not pre-glued, and use that. Or whatever.

The luthier I took "lessons" from shims all his necks. He never fits them tight. When we cut the mortise and tenon for my 2nd guitar, it came out even looser than he normally makes his joints, so I had to use a lot of shims. Not a problem.

If you have a loose joint, you have to establish the neck angle angle up/down and left/right and seating depth of the joint as you fit it. This is done by adjusting shim thickness and also by shaving the faces of the neck where it pulls up against the body. It doesn't take much to make large difference, so proceed cautiously. It took me days of cautious sanding and shaving and trying, mostly because it was only the 2nd one I've ever done. Carter (my instructor) can fit one in a couple of hours.

...at least that's my fairly inexperienced view of things.
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Michael Thoner
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Re: Neck block mortise

Post by Michael Thoner »

Do you mean to shape the shims to perfection before installing?
johnnparchem
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Re: Neck block mortise

Post by johnnparchem »

Michael Thoner wrote:Do you mean to shape the shims to perfection before installing?
Have you view John Hall's Videos on setting a dovetail? They are worth viewing. I never muck with the mortise so I will shim the tenon. After the shim is glued on the tenon\shim will be shaped as part of fitting the dovetail joint.
Michael Thoner
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Re: Neck block mortise

Post by Michael Thoner »

While I was dremeling out the sides to reveal the mortise, I accidentally got a little into the top outside edge of said mortise leaving an uneven edge in the top 1/4. After watching some neck joint repair videos, I was led to believe that the norm is to shim the mortise (for like a neck reset). The tenion is still pristine. But shims in the mortise would give me that perfectly flat edge in there to make a tight fit. Is there any reason eir would not work for said shims, or do I need to spend days and money for a little mahogany?
johnnparchem
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Re: Neck block mortise

Post by johnnparchem »

Michael Thoner wrote:While I was dremeling out the sides to reveal the mortise, I accidentally got a little into the top outside edge of said mortise leaving an uneven edge in the top 1/4. After watching some neck joint repair videos, I was led to believe that the norm is to shim the mortise (for like a neck reset). The tenion is still pristine. But shims in the mortise would give me that perfectly flat edge in there to make a tight fit. Is there any reason eir would not work for said shims, or do I need to spend days and money for a little mahogany?
I would need to see pictures to make further suggestions as you are looking to fix to damage. To me it seems even if the top of the mortise was mucked up you can still get a good fit. Also I shim the tenon on a neck reset. After the shims are on I shave back the shims with a chisel (some sand) until the dovetail can go in all the way tight with good contact. Lot easier to fit a tenon to a mortise than a mortise to a tenon.

Shim with any wood you have.

I do not disagree with Maine, When I do a dove tail I also start with a loose joint, set the necks and angles and shim the joint to fit. I like gluing them to the tenon after the angles are set and shaving them back to fit the joint. It both mine and Maine's descriptions we are only working with the shim.
Michael Thoner
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Re: Neck block mortise

Post by Michael Thoner »

Here's a few pics
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Michael Thoner
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Re: Neck block mortise

Post by Michael Thoner »

Other side
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Michael Thoner
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Re: Neck block mortise

Post by Michael Thoner »

I put chalk on the mortise and you can see where we lose contact. It's the top 3/4 inch.
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johnnparchem
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Re: Neck block mortise

Post by johnnparchem »

It would not hurt to put a small shim in the damaged area and shaped it back. Otherwise it looks like you have a good fit. It looks like you would only need a short shim. It would be close enough to the top where it would be easy to shape flat.
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