Official Luthiers Forum!

Ok - of all the things I struggle with in a guitar build - it is getting the neck angle right from the very beginning. I guess what I am saying is that I must not be getting the angle on the rims, and thus the top, at the right starting point as I spend a LOT of time fitting my necks to the body when it is time.

I am wanting to start the entire process over and see where I am doing something wrong.

Here's some background info....

25' radius top
I sand my rims to this 25' dish to start
I then flat sand the rims in the area where the fingerboard will sit on the top. This flat area extends just to where the sound hole would start.
I flip my sanding dish over to it's flat side
I have a specific piece of wood that I use to "prop up" the lower bout to create what I want for this flat area rim angle for setting the neck angle.
It is at this point that I think I must be doing something wrong. I would expect things to be closer.
I would expect this angle to be VERY critical to the fit of the top and neck - and want to know how to do this BETTTER - MUCH BETTER!
What I am doing seems way to inexact for this critical fit.

My typical problem is that my neck angle creates a tendency for my fingerboards to slightly float above the top near the sound hole (I hope that makes sense.

FYI - My necks are built with a 1.5 degree angle - but I am having a new CNC prototype built for me and can adjust that angle if needed.
FYI2 - My tops have a flat transverse brace.


I'll take all the input I can get as I am really frustrated with this part of building guitars!

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P A U L B U R N E R
Burner Guitars

This is definitely a difficult step.
With a 25' radius for the top, if you do not sand a flat, you should get a gap at the body-neck joint if the neck angle is right. If you have a gap at the soundhole, this mean you sand too much trying to make this flat area and/or you need a smaller neck angle. Most people will sand the side with the dish, fit the top and then sand the top flat under the fingerboard (you need very little thickness) using a jig.
A Wilson jig is also usefull to get correct the neck angle for your particular construction.

Fwiw, I both expect and desire that gap under the FB, as long as it's not excessive.

For me, the angle of the neck changes from guitar to guitar. The string height above the top remains the same, but the actual angle between fretboard plane and cheeks is different from box to box, as there is often a little play in the neck block both side to side and front to back, by which I mean that the block might not be 100% square in all planes.

Alain, are you saying some flat sand the top in the fingerboard extension area a little AFTER it is attached to the rims?

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P A U L B U R N E R
Burner Guitars

Hesh has a good tute on this out there somewhere.

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James W Bolan
Nashville Tennessee

+1
25' radius top, I use a 60' Radius UTB, use a sanding block pivoting on the saddle position (raised 3mm above the soundboard) to dress off the FB extension area and fit the necks individually.
I use a sliding bevel to get the angle, transfer it to the neck, and cut my mortice and tenons by hand/bandsaw.
Quick'n easy.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I radius all top braces ACCEPT the middle 3" of the UTB. I do a 25' R on the top rims. I will sand the top under the FB extension if I need a little more drop off. I will sand a little more drop off into the top side of the extension if need be. I start with 1.5 degree in the neck but that will change somewhat of course. It's a good place to start. I have tried other approaches and this one works for me but it is less than perfect science. Some sets take minutes, some take hours. I still use a mortise and tenon but if a person was to do a butt joint and engineer an easily adjusted sanding jig ,for a spindle sander possibly, to do the neck angle, Bob would most likely be your uncle. If anyone does this I'd love to see a photo.

John Hall has a tut on it too.

http://www.luthiersforum.com/forum/viewtopic.php?f=10117&t=25931

You can use this method to flatten the upper bout with a very slight radius on the UTB (upper transverse brace) if you wish and some of the guitars that I build last year I used a 60' radius and it worked fine. You may have to ever so slightly hollow out the underside of the fret board extension if you radius the UTB ever so slightly too. For me this was about 10 swipes with a single edged razor blade used as a scraper and took a minute or two.

Conversely as with all things Lutherie there are lots of ways to do most things. One can also radius the UTB and then flatten the top itself very simply with a number of methods that I can recall. I did this too early on but I am not personally keen these days to reduce my top thickness in this region so I build in my angles instead.

A couple of things to know: Often builders, newer builders believe wrongly that doing all things correctly including setting the neck's angle for 1.5 degrees will get you where you want to go effortlessly.

Wrong....

In my experience you always have to fit a neck and you really want to fit the neck too to get that perfect, gapless neck joint which remains one of the important things that pros use to look at to evaluate the work of others. Some f*ctories... are known to use filler in the neck joint which is a pretty poor and sloppy practice IMO... Some even use glue to fill gaps as well also a poor practice not only in terms of poor craftsmanship but come neck reset time the repair Luthier will have to do unnatural acts to get the freaking thing loose. Fitting a neck well and with no gaps is a art however even a beginner with some guidance and patience can also get a gap free neck joint. I have not looked at these toots in a couple of years but if I recall correctly I think that I mention the concept of "reading the neck joint" which will tell you what you need to do.

There is another one of my toots (visions of French Bulldogs... ) in the toot section about fitting necks. This toot, flattening the upper bout and the neck fitting toot really go hand in hand. Just look for toots under my name a few pages back and you will find it, I just did.

As for me using these methods neck fitting is drama free (but you still have to do it.....) and the fret board extension lays perfectly flat as is AND I get the .010 - .015" fall-away that I want on my stuff with the fret board extension.

Hope this helps Paul! Happy Holidays to you, Kyle and yours as well my friend.

UPDATE: My neck fitting toot was a link to my now defunct web site that I took down in September.

When I get some time I will update the toot and repost here for all to read.

Every single time I prep the sides for installing the top by flattening the upper bout, I nod to Hesh's excellent tutorial on the subject. I am on 26 now, and have used his method every time, with excellent resulting neck angle geometry

This is a good topic. The obvious answer is use a supported extension but despite good intentions I have not re-tooled for that yet.

What kind of neck attachment system are you using?

I think the whole thing starts with how much your guitars settle in over the first year or two. Different neck attachment systems settle differently. A full Bourgeois/Mayes/Wells double tenon bolt on will settle more than a glued dovetail or a bolt on with a glued extension.

If you have your upper bout perfectly co-planar with the neck angle you may have a rising extension at one year which no one wants.

As I use a double tenon attachment I usually angle the upper bout to slightly less than the neck angle to create a little drop off which will hopefully be decreased to the proper amount by movement after string up.

After the top is on I flatten the area under the extension with a Fox paddle and also fine tune the upper bout angle with this going for a little drop off so the pivot point is less than expected bridge height.



Another thing that can make the end of the fretboard sit proud is that sometimes finish builds up over the upper end of the rosette where the pieces are gapped and creates a bump that will push the end up or the end of the fretboard can warp producing a convex surface.

if you are working around a fixed neck angle that could make things a little tougher too because as mentioned all headblocks do not wind up at exactly the same angle so every guitar may have small variations in the optimal neck angle.
It's nice to be able to deal with that by a good tenon cutting jig.

That said, I am almost up to 70 guitars and I still get surprised sometimes at how a guitar has settled in.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

I use a method similar to Martin factor although my top bracing is different than theirs (I too use 25' like OP). I sand the entire top rim flat, then sand in a coplanar angle/slope from the top of the sound hole forward to the neck block. Gives me an almost perfect angle every time.

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"I've been had again"
Tim Benware
Creedmoor, NC

Some very good advice here. I may have missed it here but, one thing I do is clamp the top down and put a straight edge on the fingerboard extension area and measure the distance at the saddle location. If it is not what I want I remove the top and make an adjustment to the rims before I glue the top on.

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Joe Beaver
Maker of Sawdust

That's right check it. I do the same but don't use my top. I use a piece of mdf just large enlighten to cover the "flat sanded ramp area above the sound hole". I have an arched piece of wood across the lower bout at the same spot as the bridge. This piece has a pencil mark at the desired spot. Straight edge to the bridge height mark.
You have to do math to figure the differences but since I started doing this about 10 gits ago my neck angle has been a breeze to fit and my necks are very straight throughout their length.


Sent from my iPhone using Tapatalk

this is my method

https://www.youtube.com/watch?v=FNcbA1P95KE

after the guitar is complete here is how I do the initial set up

https://www.youtube.com/watch?v=TXfyVb3L3G0

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

There are some complicated jigs being used -- IMO, way overkill for what is an incredibly easy task.

There are a few very important parts to this task

1) Be able to establish repeatable top geometry every time!!! Early on, I had trouble with perfect repeatability because attaching the back would sometimes change the top geometry (the back would want to flatten lengthwise). Attaching the top and back while the rims are in a mold does help with this issue. Also, make certain that your radius dishes are very stable. 1" mdf is flexible and will introduce problems with precision. I've glued my radius dishes together with a thick mdf layer in between. I've also sealed this dish with oil varnish -- it will last a lifetime.


2) Calculate the desired height at the bridge's leading edge that you want when laying a straightedge on the soundboard upper bout. Create a flat sanding board (with sandpaper at the end) and an appropriately sized shim. Place the shim at the bridge location and sand the soundboard region where the fretboard extension goes to achieve proper geometry. Be careful not to push down on the soundboard while sanding to introduce errors.

3) After ensuring perfect repeatability, over time I discovered that a 28' radius left me sanding a bit more than a 25' radius would require. I find that a 25' radius is almost perfect for the airspace at the saddle that I need. I usually end up sanding just a bit near the binding rather than closer to the soundhole. Not much top material is removed during this process.

4) I then use this perfectly created "slope" and fit the neck afterwards. Each neck is slightly different and you should be fitting each neck so that the fretboard is perfectly straight as it rests on the soundboard.

5) Some other things: the thickness of the sandpaper factors in when creating the shim. Also, I am for a neck angle with that hits the leading edge of the bridge at 1/16" proud. You must factor in top geometry changes after string tension as well. You do this be ensuring your process is perfectly repeatable. Then you build a guitar and make changes accordingly. My neck angles are identical from guitar to guitar in terms of airspace above the bridge.

Hope that helps. If you want more details, give me a call (386.690.2567)

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Simon

Another tip that has helped me with consistency. Once the side braces are glued in the rims go back in the mould and stay there until the box is closed. I have been bending a stick between the head and tail blocks but I think I'm going to start screwing them to the mould.

Hesh......there really aught to be Hesh book.. A Luthieric compendium , Hesh on this, and Hesh on that.
I think.