Neck Block Alingnment

[David L]

How do you guys center up the neck block for gluing? the dovetail cut out prevents me from making a centerline on the block for alignment. I got the tail block glued in place, that was easy.

Thanks,
David L

[Tony_in_NYC]

You can make a centerline on your workboard and center the body against that, then using the inside of the block, make a centerline, and go from there.
Or, barring that, use tape across the dovetail cutout, mark your centerline on the tape, and Bob's your uncle!!

[David L]

I'm working with the body top side up so that I can position the top of the neck block just a wee bit proud of flush (I believe that it's supposed to be proud). I'm not using a workboard as the radius on the back of the rim would make that difficult. I'm using an outside mold (from John) and have the mold positioned in the center of the body. The tape method sounds good. BTW Who's Bob? Thanks Tony!

David L

[Tony_in_NYC]

I'm working with the body top side up so that I can position the top of the neck block just a wee bit proud of flush (I believe that it's supposed to be proud). I'm not using a workboard as the radius on the back of the rim would make that difficult. I'm using an outside mold (from John) and have the mold positioned in the center of the body. The tape method sounds good. BTW Who's Bob? Thanks Tony!

David L

Bob is going to be your uncle. Maybe. http://en.wikipedia.org/wiki/Bob's_your_uncle
However, and I might be wrong, not if you install the neck block the way you want to. I would double check this with your kit manufacturer, but this is my experience:
The neck block does not need to be installed proud of the rim on the top side. Back side, yes. The rim on the top of the guitar gets sanded almost perfectly flat. Then, you sand in a little bit of a slope from the waist (approximately, this depends on the model you are building) to make the top of the guitar have a complementary angle to the neck. Generally speaking, Martin style guitars have a 1.5 degree neck set angle. Meaning, the neck tilts back from the body by 1.5 degrees where it meets the neck block. Thus, if your top plate is completely flat from tail to neck block, you will have issues with your action and the neck set, and so on. I dont know where you purchased your kit, so I am not going to tell you the method I use will definitely work for you. My kits have all come from Ken Cierp at KMG and he uses a 1.5 degree back set on his necks similar to Martin. On my first and second kits, I did not measure the neck angle with a gauge. I blindly followed the instructions he provides online. Both came out with nearly perfect angles, action, playability, etc.
The neck and tail block need to be proud of the back edge of the rim to be able to properly contour them to the radius of the back plate.
I hope what I wrote makes sense when you read it. I have been known to be a poor teacher.
So, you want the neck, from the where the nut would be, right up to the sound hole to be a straight line with no gaps over the body when you are done.
Keep in mind, I use bolt on necks, so what I am about to say might be wrong, but I dont think it is. If you install the neck block proud of the top, when you make it flush, that will cut down on the depth of the dovetail mortise. That could cause issues when you do install the tenon part of it as you might not have enough depth left to get it to sit flush to the top plate of the guitar. Then you will be trimming the dovetail and trying to keep the geometry correct while fitting it and that is not fun.
Just to reiterate, I am not a professional, I have completed 2 guitars and have 3 in the works now. Please contact your kit maker to get help. If you bought from John Hall or Ken Cierp, I know you will get good service. If you bought it elsewhere, I do not know what type of customer service you will get. However, I am sure one of the pros here who has worked with dovetails will chime in tomorrow and give you guidance.
Where did you get the kit by the way? What body style did you go with? Wood choices? We all need to know these things!!

I apologize for my rudeness earlier. I forgot to say, Welcome to the forum David L!! You will definitely find helpful and friendly people here. Myself excluded. ;o)

[David L]

Hey Tony,
Thanks for welcoming me to the forum. Although I am a newbie to the forum, this is my fourth post, or should I say "cry out for help" (that description would be more accurate). I purchased my kit from John and have a couple of things coming from Ken. I will only buy from someone else if niether one of them don't have what I need (notice I didn't misspell the word "want" N.E.E.D) and this eary in my lutherie adventures I have not run into that problem yet. Thier support to this forum (as well as others) is immeasurable. My kit is an HD28 Dread E.I.R b/s. I sure am glad you chimed in because I see now that I was more than likely to make a big boo-boo. The two things you said that really make sense is coming up too shallow on my dovetail, not allowing the neck to seat properly and your right, I want to do as little as possible to the dovetail joint. I now see (thanks to you) that I need the meat at the back of the rim to accomodate the radius. By the time I would have figured that out I would be scratching my head saying "AH S..T". So I should draw a centerline down a workboard, slide the mold to the top of the rim, mount the mold to the workboard centering the body on the centerline, does this sound somewhere close to being right?

Thanks ,
David L

[tippie53]

One thing I will tell you is that do not assume the block center is the center for the mortise. I place the neck into the block and with a square mark the center of the neck onto the block. Use that for the center line. That way if the neck block center is off to the mortise center , you are good.
In most manufacturing , the blocks have a datum point of zero , and if the block is longer that the actual designed blanks the machine don't care it just knows where the zero point is . Martin blocks are notorious for this flaw . Just something to think about.

[kencierp]

I totally agree with John Hall regarding the center line of the neck block. Its the machined area center (matters not DT or MT) not the sides of the block that is the concern. Here's some pictures of the tape and work board method Tony mentioned
http://www.kennethmichaelguitars.com/KM ... embly.html
BTW 100's perhaps 1000's of Martin kits have been assembled using the KMG instruction manual -- the neck set principles are exactly the same.

[Tony_in_NYC]

One more thing, if you use a work board, put the top of the rim face down and use your work board to make sure everything is flat against it. Then put the neck block in and it is automatically flush with the rim. Make sure the block is facing the right way! I.e. top of D.T. opening down on the workboard.

[David L]

OK, so here's what I did (is that a collective uh-oh I hear?). I located the center of the neck by applying two layers of masking tape across the neck at the nut end and the heel end and marked the center at both locations. I inserted the neck into the neck block. I lined an eighteen inch scale up on the two center locations on the neck and marked that location on the tape that I put across truss rod access cutout of the neck block. This mark was less than 1/32" off of the center of truss rod access cut out. I then drew a centerline on a work board, slid the mold down even with the "top" of the rim, flipped the body/mold over (top side down) and located it to the centerline of the work board and screwed it in place. I first did a dry-run clamp-up to make sure everything lined up and then glued and clamped it in place. I'm still not totally convinced that I have it lined up good enough. It seemed like taking these measurements was not cut and dried, working off the angle of the neck, drawing lines on less than rigid tape, left me scratching my head (and some other body parts that I won't mention) wondering just how close I really am. I tried to make other measurements to bumb against each other to reinforce my "center" mark and I think that I am close. Hopefully I am within the tolerances of what "normal" neck adjustments will take care of. I'm not real good at a whole lot of things, but one of the few things that I excel at is over-thinking and over-complicating things and hopefully this is the case here. I just hate having to wait til further on in the build to find out how well I did (or how well I didn't do).

Thanks,
David L

[Tony_in_NYC]

Next time, mark the line on the tape before you stick it on the block. You can get a cleaner line that way.
Also, if the center of the DT was only 1/32 off of the center of the block, you could have sanded down the block to make the DT center in the block and then problem solved sir...or Bob's your uncle, as it were.
1/32nd is pretty small...I doubt you would have ever noticed it if you had not centered it correctly anyway!
When I glue the bridge on my second, I forgot to add the locating pins and the bridge slipped ever so slightly from where it should be. You cant see that it is wrong if you just look at it, but if I were to tell you, you might. It affected the intonation a bit so that even with a compensated saddle, I cant get the intonation perfect at the 12th fret. This is not a problem since my brother does not play above the 7th fret anyway! Should he or I ever really learn to play, I would fix the bridge for him. For now, it stays as it is.
You will be fine.