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Test Fitting the Neck: Tenon is too Long
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=28535		 Page 1 of 1
Author:  Darryl Young [ Sat Aug 07, 2010 5:14 pm ]
Post subject:  Test Fitting the Neck: Tenon is too Long
Well I have another learning opportunity [clap] . Seems I've had my share lately, ha.

I trimmed the sides where they covered the neck mortise and test fitted my neck. Wouldn't you know it, the tenon bottoms out in the mortise before the surface of the neck (where the fretboard mounts) is level with the top of the guitar. It stands proud about 0.080" above the surface of the soundboard. The depth of the body at the neck block is 3.334" (measured with my dial calipers)......not sure if that is narrower than normal or not. If it makes a difference, I sanded a 1 1/2 deg angle in the rim from the top of the soundhole forward before gluing the soundboard on. Possibly this created a drop in the top leaving the neck proud (or at least contributed). This is a 000 with a bolt-on neck from Hanneli-Moon that is built fairly close to Martin specs (a custom kit from John).

Anyhow, appreciate your input on the best way to correct this. My guess is I need to trim the bottom of the tenon where the neck can slide further down. In the pics below you can see the portion of the tenon that needs trimming is rounded over corresponding to a rounded area in the mortise.

So if this is the proper fix (please tell me if there is a better way), then a few questions.

1) After trimming the tenon, do I need to round it over to match the mortise in the neck block. If so, what is the best way to do that? (doesn't look simple)

2) I assume I will need to redrill the holes in the neck block to align with the threads in the neck dropped down 80 thou. Any suggestions on how to locate and drill these new holes accurately? I doubt I will be outside the original holes so the bit may want to walk over in alignment with the old holes. This may be the most difficult part of correcting the problem.......align the new holes on the centerline, spaced the correct distance apart to match the neck holes, and moved down about 0.080" - 0.085" (assuming the holes are a little oversized).

Appreciate your thoughts. Here are the pictures. You can see the binding I put on the top (with the extra B/W strip inside and outside the herringbone) on some of the pictures (first binding attempts are fun learning experiences [:Y:] ). I posted this on the KitGuitarForum but wanted to post here for quick feedback. A couple of pictures in the following post as well.

The first shot of my guitar with the neck in place:
Attachment:
Guitar.JPG


Side View:
Attachment:
SideView.JPG
Author:  Darryl Young [ Sat Aug 07, 2010 5:16 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
And here is a top view:
Attachment:
TopView.JPG


And finally, here is a pic of the tenon. Note that it is rounded in the area I need to trim. Do I need to round over this area similarly after trimming?
Attachment:
NeckTenon.JPG
Author:  Tom West [ Sat Aug 07, 2010 5:32 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
Darryl: Try a thin neck...!!! laughing6-hehe I would trim either the tenon or mortise or both. Plug the holes you have in the block. Put two headless bolts with sharpened points where the heads were into your inserts,leaving the points proud and use that to mark your new hole locations. Drill your holes from the outside and you never had a problem.
Tom
Author:  Darryl Young [ Sat Aug 07, 2010 5:47 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
Yeah......that's it, a thin neck and use nylon strings......who will notice? bliss

The bolts with sharpened points is a good idea......assuming I fill the old holes first so they don't poke into the old hole.
Author:  Tom West [ Sat Aug 07, 2010 6:36 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
Roger Roger Darryl ...fill the holes to give your self a chance. If you mark your spots lightly a brad point should do or a bit deeper and a regular bit. As far as the fit for the bottom of the tenon is concerned,I just use that to set for depth to level the fingerboard and the top of the box. Have fun and good luck.
Tom
Author:  Hesh [ Sat Aug 07, 2010 7:18 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
What my buddy Tom said. :D

Darrly bro when you get to fitting the neck in earnest or even just to the gutiar body.... laughing6-hehe :? :roll: there is a "fitting a neck" toot on my site, link in signature.
Author:  Darryl Young [ Sat Aug 07, 2010 8:19 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
Do you think I can drill the new hole straight enough with a hand drill or do I need to somehow set the neck up in my drill press?
Author:  Darryl Young [ Sat Aug 07, 2010 8:39 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
Nice tute Hesh, thanks!
Author:  Tom West [ Sat Aug 07, 2010 8:51 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
Darryl: I would do it with a hand drill. If you care careful with alignment all should be well. You'll have to gauge for yourself as to how comfortable you are doing it that way.If you have a press big enough maybe that's the way to go for you.
Tom
Author:  Daniel Minard [ Sat Aug 07, 2010 11:14 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
Easier than setting up to drill the new holes on your drill press, just make a snug fitting hardwood block to fit in the mortise & drill that with your drill press at the proper locations & hey presto. You got yourself a jig.
I drilled quite a few freehand, & found it was pretty easy to eyeball if you use a long drill bit... Not so much with a standard length one.
A simple drilling fixture makes the job easier & more accurate, though.
Author:  Jody [ Sun Aug 08, 2010 6:40 am ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
I just had this problem, my neck block was sufficient enough I was able to use a router and a mill end to deepen the channel of the mortise, it took all of about two minutes running the router freehand . Jody
Author:  Terence Kennedy [ Sun Aug 08, 2010 7:36 am ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
Same idea on lengthening the mortise. You could take a smidgen off the tenon too without compromising the lower insert. Plug the holes and use the sharpened bolts to remark and drill. Thinning the neck means you have to deepen the truss rod slot too. Lots of work.
Author:  Darryl Young [ Sun Aug 08, 2010 2:39 pm ]
Post subject:  Test Fitting the Neck: Tenon is too Long
I'm curious, what is the minimum distance you would leave between the end of the mortise and the back of the guitar? (or bottom of the neck block)
Author:  Howard Klepper [ Sun Aug 08, 2010 3:25 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
Why don't you ask the builder of your kit? They're the ones who got it wrong.
Author:  Terence Kennedy [ Sun Aug 08, 2010 4:28 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
Darryl Young wrote:
I'm curious, what is the minimum distance you would leave between the end of the mortise and the back of the guitar? (or bottom of the neck block)


I'd probably be OK with just above the edge of the binding. 5/16" or thereabout.
Author:  Darryl Young [ Sun Aug 08, 2010 4:43 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
Howard Klepper wrote:
Why don't you ask the builder of your kit? They're the ones who got it wrong.


The neck and neck block is from Hannalei-Moon. I can't assume it was done wrong.......I may not have paid attention to this detail when positioning the neck block while glueing to the rim.
Author:  Darryl Young [ Sun Aug 08, 2010 7:07 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
I have it fixed! bliss

I used my Veritas dovetail to trim the tenon, a flat washer of the correct size to draw the correct shape, a chisel to trim close to the line, and sandpaper to smooth everything out.

Attachment:
TenonRepair.JPG


On bolt-on necks, the holes are often oversized to have a little adjustment......so since it was only 0.085", I used a rattail file to elongate the bolt holes in the neck block. Now everything fits. But that isn't the best news, the fretboard extension and the nek angle came out very nice!!! bliss Take a look:

Attachment:
FlatFBExtension.JPG


Attachment:
NeckAngle.JPG


Now I need to trim the heel to the proper length. This is a Martin style guitar.......so the heel with heel cap in place should be short of the edge of the back....how far short?

Now debating if I should I use this pre-shaped, pyramid bridge.......or make my own from one of the Braz. bridge blanks I got from Lars???

Attachment:
BrazBridgeMat.JPG
Author:  bluescreek [ Sun Aug 08, 2010 8:11 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
glad to see you got it taken care of . this is how you learn , one step at a time
Author:  woody b [ Sun Aug 08, 2010 8:28 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
Nice job. For the heel, I like to make the neck stop and the heel cap start even with the binding. Sometimes I'll use a thicker heel cap and make it flush with the body. It looked better after the neck in the picture was shaped. I don't know what Martin does. Do it your way instead of making a clone. Martin doesn't use nice laminated necks like you're using.
Author:  Darryl Young [ Sun Aug 08, 2010 9:05 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
Woody, is your heel cut perpendicular to the face of the heel? The face of the heel on mine isn't exactly 90deg to the surface of the neck.......so I'm trying to figure out which surface to use as a reference when I trim the heel.

Thaks for your idea of trimming level with the binding.
Author:  Terence Kennedy [ Sun Aug 08, 2010 9:32 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
There was a recent thread on that. Various approaches.

viewtopic.php?f=10101&t=27467&p=368735&hilit=heel+angle#p368735
Author:  Darryl Young [ Mon Aug 09, 2010 10:19 pm ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
Thanks for that link Terrence.
Author:  Miketobey [ Tue Aug 10, 2010 7:18 am ]
Post subject:  Re: Test Fitting the Neck: Tenon is too Long
I did some measuring on my Hana-lei Moon neck and block. It is my understanding the the neck sits just proud of the top of the block for top thickness. Thus, when you fit, the bottom of the block is your adjustment point for the height of your body at the headblock(which you also selected). Also, remember that Chris builds in the 1.5* neck angle in your assembly-unless you knew your build plan to a professional level where you selected another angle.

He does assume a moderate top radius when he fits up the combo. Therefore, if you set the block properly to the back of the rim assembly, it can handle , say a 15 foot radius, and your top of the headblock will either accept the 25 or 28 foot radius, or flat(see Hesh's tutorial) and the fretboard ends up tight to the top for gluing, at the right angle for a traditional bridge thickness range and you are good to go.

Some who know me may recall I had a STM event in connection with positioning my headblock to get my design thickness at the tail and headblock( this was with my H-M beautiful neck/block combo in hand). That is when I figured out that I needed to set the headblock on the sides in my mold with a small amount of back-of-the-ribs- material "overhanging" and some, but less sitting proud of the top of the headblock for planing and/or dish sanding to final desired height I had already chosen in my order. You have to be a "minimalist" when shaping at the top so that the pre-planned neck angle and chosen total height are not compromised.

I will say that this is something Chris should add to his buyer information to avoid confusion like this-not all of his customers are experienced enough to understand that they are making critical choices on those specifications- one has to build "to" those specs. I kind of wandered my way(by dumb luck) down the logic trail to sort out this component- required construction step. BUT- when Chris and I talked on the phone for my order he did make the point that the heel cap took care of adjustment and blend at the back of the guitar as needed-the pre-sized is close enough so that no exaggerated cap thickness is needed and there is room for choices for aesthetic requirements.

Because Chris gets these so close, your modification did not change the built in neck angle-thus your excellent contact relationship with top and fretboard extension. What you did was a "mid-build" very gentle neck reset-and done well, but needed because of what I describe above. Had you not chosen bolt-on, the "issue" would not have come up-you would have just worked your dovetail fit until the fretboard extension laid nicely on the upper bout and the built-in neck angle would have still given you the proper relationship of the FB to bridge thickness plane.
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