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Help!! Dovetail issues....
Author
Post
Paul

Total Topics: 3
Total Posts: 5
Ok, I know this is everone's favorite topic. I started to work on fitting the neck tonight (this is a martin d18 kit) and thought I had read/researched, fretted etc over this step to the point where I couldn't mess it up(yeah right). But I think I did. Basically the neck was sitting about 3/8" up out of the neckblock as the instructions/other sources indicated it should (Note: This joint was not tight to my limited knowledge at this point --and no work had been done on it yet).

So I proceeded to remove material from the sides of the tenon as instructed to drop the tenon in the dovetail mortise. I worked slowly and got it dropped part of the way down after an hour or so (still sits about 1/8" proud of the body) but the whole works seems really loose to me. I fear I may have really screwed it up. Is this reversible...can I glue shims to the sides of the tenon and start over? I made one good decision --I stopped on it until I get some help!

I'm embarassed to show these pictures but I need help so....

I can move it from here:


To here:


...with ease. Please don't laugh at me too much (well you can if you want). It's funny how building a guitar can make a grown man feel like an idiot!! For some reason I don't want to throw away the 8.7 billion man-hours I have invested in the little wooden torture device known as a guitar kit just yet. Thanks in advance for any comments, advice, etc.
Paul

Nov 13, 06 | 6:19 pm
billm

Total Topics: 32
Total Posts: 145
Hi Paul -

If I understand the problem you're describing - it's an expected development according to the Stewmac kit instructions. After all the material removed to get the neck aligned correctly, it's going to be loose. So, you guessed it, the next step is to make a shim.

Cut an appropriately sized piece of wood, file it down until the neck fits tightly in the correct position with the shim in place. When you glue the neck on, the shim is part of that step.

- BillM

Nov 13, 06 | 8:43 pm
Bill Cory

Total Topics: 158
Total Posts: 3584
Paul -- If I were in your situation with this, I would email John Hall and ask him to come and look at your pictures then prescribe a fix. He's probably seen this before and will know exactly what to do. I imagine a shim might be necessary like Bill says but you'll want to avoid the same predicament after shimming.

Bill

Nov 14, 06 | 5:50 am
Paul

Total Topics: 3
Total Posts: 5
Thanks Bill and BillM. It seems to me like shims would be the way to get a mulligan on this. I have some very thin walnut veneer that might work. It seems to me that If I could use the shims to get back to close to square one that I could then take material off the sides of the neck dovetail (more carefully--with chalk, carbon paper) to get a better fit. This stuff sure ain't easy the first time around --hopefully I will look back on this and laugh.

Do you have John Hall's e-mail or know where I could get it??

Paul

Nov 14, 06 | 6:58 am
Bill Cory

Total Topics: 158
Total Posts: 3584
John Hall owns Blues Creek Guitars -- his ad is on the front page of the forum. Or just click any "Blues Creek Guitars" post and that'll get you to his profile and email link through the forum's email system. Good luck with this --
Bilk

Nov 14, 06 | 7:12 am
blues creek guitars Authorized Martin Repair Ctr

Total Topics: 52
Total Posts: 1011
This isn't that bad, What I think may behappening is that you may have changed the angle of the necks dovetaile.
First get some CHALK and make a sanding stick with 100 grit sandpaper. I use the PSA ( pressure sensitive material ) . The stick should be about 1 inch wide with 45 degree angles on both side so you can work into the corners. Make it about 6 inches long.
Note you need to round off or break the sharp corners to all inside mate surfaces to avoid the joint holding off.

You will need to make up some shims to build up your neck again. A good shapr plane will make nice shims and you can iron them flat. You need to build up the neck's doevtail and not the block.
If you need shim material let me know

Okay assuming we have the neck back above the top. All inside corners are broken ( rounded off ) chalk up the neck block and push the neck into the neck.
REMEMBER YOU ARE GOING TO ADJUST CENTER PARALLEL TO TOP SIDE TO SIDE AND ACTION HEIGHT
You also want to hollow the heel so the heel isn't tight agains the body. You don't want to pop that off
Okay with the chalk on the necks dovetail just remove the chalk. You want to have the lower part of the joint grabiing to pull the neck tight to the body.
Remover the chalk pop back into the neck block , measure the center , the sadlle height postion and the fretboard parallel where it would lay on the top.
Take your time as a small amount or wood removal makes a big difference. I like to do a dry fit and keep the neck just above the top until the finishing process is complete as I do the neck and body separate.
You know you are doing right when you can feel the neck bite and stay on teh body. IF the neck won't do that you are flattening the angle. The neck can have more of an angle than the block . You can tell you are on when you see more chalk near the lower part of the cheek that sits against the side of the block.
Allways twist the neck , is the heel wiggles then you need to remove the upper part of the tail near the top. The top wiggles , you need to close the heel.
take you time. If you need to call me and I can help over the phone
john hall
blues creek guitars

Nov 14, 06 | 8:20 am
Freeman

Total Topics: 27
Total Posts: 668
There happens to be a thread on UMGF right now about shimming a sloppy dovetail - John ("Tippie") has been a contributor there.

The other thing to consider (along with the shims) is to drill into the heel of the neck and put a 1/4-20 insert, then measure and drill a slightly oversized hole thru the neck block. Yes, you are going to make it a bolt-on, well, not actually, the bolt will help hold it in perfect alignment but your shims and glue will give it the strenght. This is exactly what Martin does with their MT joint. My triple ought has a stainless steel round head 1/4-20 bolt in its neck joint and the 12 string that I am currently working on will also (even tho the fit of the dovetail is pretty darn good).

If you decide to do this be very careful installing the insert in the neck - you can split that very easily. I drilled the hole one size larger that recommended in the instructions and epoxied the insert in place. If you want to be a purist you can always remove the bolt after the glue sets (think of it as a clamp <g>), but in my opinion it doesn't hurt anything to leave it (and in the 12 string I want all the strenght I can get).

I can send you a pic if you want to see what I did.

Nov 14, 06 | 8:30 am
blues creek guitars Authorized Martin Repair Ctr

Total Topics: 52
Total Posts: 1011
This isn;t something I like to see as if you change the geometery of the necks dovetail the bolt actuall pulls the joint apart. The wedge effect needs to come from the wedge. The bolt will help but it isn't the best.
I hope to soon have this covered on my sebsite
john

Nov 14, 06 | 9:01 am
Freeman

Total Topics: 27
Total Posts: 668
Yes, I agree with John, but when I built my six string there was just the tiniest bit of wobble and I used the bolt to hold everything in alignement while the glue set. It is a bit difficult to build a clamping caul to fit around the sharp point of the heel and use a long bar clamp to pull the joint tight into the body (but you see pictures of this in the StewMac, Kincade and Martin books). I figure the bolt does the same thing.

Mine was nowhere as bad as the pictures and that one certainly needs some shims and basically starting over, but I still feel that the bolt is a viable way to help a less than perfect dovetail fit. I purposely drilled the hole thru the head block oversized so it is not determining the neck set. When I glued up I used one clamp to press the neck down into the block, two for the extension on the top, and the bolt.

Ideally you get the dovetail perfect, and now that I'm building my fourth I think I'm pretty close. On my mando the side angle is just a hair off which means the bridge isn't exactly centered. Maybe by number ten.....

Nov 14, 06 | 9:58 am
blues creek guitars Authorized Martin Repair Ctr

Total Topics: 52
Total Posts: 1011
Once you master the dovetail you will appritate the joint.

Nov 14, 06 | 11:45 am
Ken Cierp

Total Topics: 58
Total Posts: 2262
I am just going to be a "fly on the wall" here. I like the conversation. However, in my humble opinion, the Stew Mac instructions are horrible and frankly unfair -- they assume the builder is going to make mistakes and therefore go right into the “repair mode”. Now that you are trying to fit the neck they tell how you are going to have problems because certain aspects of construction were not performed correctly --- isn’t a little late to warn folks that they must not let the neck block tilt?? The instructions should have fail-safe methods of preventing this from happening. Anyway, I hope to learn something new. I respect those who like to put in the time and effort on a dovetail --- I no longer have the patience or inclination.

Ken

www.kennethmichaelguitars.com

Nov 14, 06 | 12:08 pm
Paul

Total Topics: 3
Total Posts: 5
I really appreciate the discussion and great help here. I now at least feel more confident that I will be able to back up and have another go at it. Hopefully I will have learned something and will not screw it up as bad next time.
Paul

Nov 14, 06 | 12:27 pm
Ken Cierp

Total Topics: 58
Total Posts: 2262
This is a great link for the "whys" and "what fors?" of changing the neck angle lots of photos. Some good tips in how to spot and remove interferences when trimming things up. May be of some help in resolving the above situation.

http://www.guitarspecialist.com/neck.htm

Ken

Nov 14, 06 | 12:58 pm
blues creek guitars Authorized Martin Repair Ctr

Total Topics: 52
Total Posts: 1011
Ken brings up some good points. I am familiar with Stew Macs kit but never used one or saw the instructions other than what is posted on the site.
I am in the process of showning this process and will have photos of this and other procedures that builders can make use of. THere is alot more info available now than when I started. I was lucky to have had training at CF Martin and schooled at CUSTOM PEARL in Malone.
If anyone is near me and wants to stop by I am available to help if I can
john hall

Nov 14, 06 | 1:05 pm
mbbransc

Total Topics: 13
Total Posts: 71
That guitar specialist article was REALLY good!! Ideally, when building a guitar and the bridge/saddle are not mounted, what should the height of the straight edge be over the top? I just finished setting my neck last night and it is TIGHT and straight. I just assumed I'd sand the saddle down to match where it needs to be, but now I'm curious if I'm actually finished setting the neck.

thx
Brandon

Nov 15, 06 | 8:06 am
Ken Cierp

Total Topics: 58
Total Posts: 2262
On my stuff I take the measurement with the fingerboard on (and frets installed) it should be the thickness of the bridge plus .04 +/- a few thousands.

My primer shows how this looks.

http://www.kennethmichaelguitars.com/neckangle.html

Ken

Nov 15, 06 | 8:50 am
Freeman

Total Topics: 27
Total Posts: 668
All good stuff. John suggested his chalk/carbon paper trick after I did a poor job on my first one - that has really helped on the third. Rather than trying to chisel and use straight sanding blocks I made some ten degree blocks on my band saw and did ALL the fitting with sand paper and chalk - much slower but much more accurate.

I think it is a shame that we have to screw up a few guitars learning how to do this and I've suggested that someone like StewMac make a practice kit (look at how many other operations like binding routing or finishing you practice on scrap - but you first neck set is on a nearly finshed guitar).

All of this helps me understand why a good tech gets $3 or 400 for a dovetail neck reset, and why Taylor invented the engineering marvel of the NT neck. And if you think the StewMac instructions are bad, the Martin booklet suggests that if you totally screw up the joint you just fill it with epoxy.

Nov 15, 06 | 9:37 am
blues creek guitars Authorized Martin Repair Ctr

Total Topics: 52
Total Posts: 1011
I am doing a photo documentation. If I hope to have it ready soon. If you want to use it on the site here get in touch and I can let you have a copy. Seeing is alot better than reading
john hall

Nov 15, 06 | 8:06 pm



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