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mortise tenon neck shim
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Author:  blindrobert [ Sun Feb 03, 2013 1:34 pm ]
Post subject:  mortise tenon neck shim
So - I routed the mortise for my neck joint about 3/32 off-center. I have widened the mortise and was planning to add shim to one side to center the tenon. My question is this:

Is it better to put shim on the side of the tenon or on the side of the mortise? It seems easier to work with a shim on the side of the tenon - easier to clamp when gluing, easier to sand for a good fit, easier to blend into the curve at the bottom of the joint.

Am I missing something?
Author:  B. Howard [ Sun Feb 03, 2013 2:16 pm ]
Post subject:  Re: mortise tenon neck shim
Which ever is easiest for you, functionally it does not matter.
Author:  Rob Flindall [ Sun Feb 03, 2013 2:23 pm ]
Post subject:  Re: mortise tenon neck shim
I did something a little bit different when I corrected a mortise alignment mistake. Instead of shimming either the mortise or tenon, I cut a piece of mahogany to fit exactly into the mortise and glued it in. After it dried, I recut my mortise where it should have been the first time. This, in essence, created the perfect sized/shaped shim inside the mortise with no muss, fuss or sanding in order to get the shim just the right thickness.

Rob
Author:  blindrobert [ Sun Feb 03, 2013 2:30 pm ]
Post subject:  Re: mortise tenon neck shim
I like that solution, Rob!

I had already decided to proceed in the opposite fashion of how I advocated in the original post. I formed a shim to go inside the mortise thinking that at least when it was apart everything looked centered and the tenon wouldn't look lopsided.

Rob's idea is the way I will go in the future. I need to figure out a better way of centering the mortise pattern on the neck jig I have. I got one of the Simpson jigs and it centers up the tenon nicely with a shim that goes into the truss rod slot, but you are on your own for centering/squaring the mortise pattern. Don't get me wrong, it's a fine jig - the mistake was mine.
Author:  Darrel Friesen [ Sun Feb 03, 2013 2:30 pm ]
Post subject:  Re: mortise tenon neck shim
Is it even necessary to shim it? Once the neck is centered and the fretboard glued down, isn't it essentially like a butt joint, albeit with a little airspace in the mortise? Just saying. Is it an effect on sound?
Author:  Rob Flindall [ Sun Feb 03, 2013 2:37 pm ]
Post subject:  Re: mortise tenon neck shim
Lol - I too am using the Simpson jig. The tenon cutting portion of the jig is pure magic. The mortise portion of the jig, however, is not. While cutting my mortise with that attachment, the jig tilted slightly, causing my mortise to not run down the centre line. I corrected the mortise using my outline above and when I was done, I fired that mortise jig attachment into the corner where it will sit for all eternity. The mortise attachment doesn't sit snugly onto the guitar, allowing it to move around. There's a reason why the big boys, like Martin, already have the mortise/dovetail cut into the headblock prior to gluing up the rim. Lesson learned for me. :)

Rob
Author:  Tom West [ Sun Feb 03, 2013 2:44 pm ]
Post subject:  Re: mortise tenon neck shim
I think I would have made the mortise 3/16" wider,plugged with Mahogany, recut mortise on center.No shims. That way it looks less obtrusive,some one won't take the neck off in the future and pass judgement on your work. Or at least they will be a bit more gentle. Thought about this a bit and not sure you will get my meaning. Make the mortice so there is equal wood on both sides when you repair.
Tom
Author:  crich [ Sun Feb 03, 2013 3:31 pm ]
Post subject:  Re: mortise tenon neck shim
You could glue a shim to the side of the tenon with a piece of hardwood with the grain perpendicular to the tenon. I do that anyways to strengthen the tenon. Clinton
Author:  jac68984 [ Sun Feb 03, 2013 3:56 pm ]
Post subject:  mortise tenon neck shim
Darrel Friesen wrote:
Is it even necessary to shim it? Once the neck is centered and the fretboard glued down, isn't it essentially like a butt joint, albeit with a little airspace in the mortise? Just saying. Is it an effect on sound?


What he said.
Author:  Rob Flindall [ Sun Feb 03, 2013 6:10 pm ]
Post subject:  Re: mortise tenon neck shim
Todd - that's a significantly improved mortise/dovetail cutting jig. I like it. I might try making one up. Thanks for posting the pic.

Rob
Author:  blindrobert [ Sun Feb 03, 2013 7:04 pm ]
Post subject:  Re: mortise tenon neck shim
Jag wrote:
Todd - that's a significantly improved mortise/dovetail cutting jig. I like it. I might try making one up. Thanks for posting the pic.

Rob


Agree. That jig looks great. As to the earlier posts asking whether the shim is even necessary - probably not. But it looks a little cleaner to me and I'm trying to be in the habit of making my work look as clean as possible, even when fixing a mistake.
Author:  Chris Pile [ Sun Feb 03, 2013 11:55 pm ]
Post subject:  Re: mortise tenon neck shim
I don't think a little air pocket will matter. I've reglued a bunch of necks on Gibsons over the years that had yawning chasms instead of modest gaps.
Author:  AnthonyE [ Mon Feb 04, 2013 5:56 am ]
Post subject:  Re: mortise tenon neck shim
This is another area in which Im questioning on my first build. Should I prepare my headblock with a mortise to fit my neck before gluing the headblock in or should I route out the mortise after the box is closed up. I am not building a cutaway. Most of my build is Cumpiano methodology therefore he shows preparing the headblock before gluing in place, but this is done on his old version of the pinned mortise and tenon. If I was to cut the mortise after closing the box then I would need to build a jig for routing.
Author:  theguitarwhisperer [ Mon Feb 04, 2013 11:09 am ]
Post subject:  Re: mortise tenon neck shim
AnthonyE wrote:
This is another area in which Im questioning on my first build. Should I prepare my headblock with a mortise to fit my neck before gluing the headblock in or should I route out the mortise after the box is closed up. I am not building a cutaway. Most of my build is Cumpiano methodology therefore he shows preparing the headblock before gluing in place, but this is done on his old version of the pinned mortise and tenon. If I was to cut the mortise after closing the box then I would need to build a jig for routing.


The hardware based M/T he now uses also has a pre-prepared neck block.
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