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Can someone direct me to posts or tutorials on how to properly set a neck angle during the build. I MUST be doing something wrong as I end up spending HOURS trying to get the angle correct after the box is closed and I have the slot cut for my bolt-on necks.

I am wondering if somehow I am torquing my rims out of shape in my mold which is throwing off my neck angle - or sanding my rims out of angle in some way.

I either have my necks/fingerboards having a gap down by the soundhole (ramping up too high), or I have the angle off the opposite way and have to fight to get things to fit.

Neck blocks are ordered at 1.5 degree angle I am thinking from memory.

I am sanding the rims on my 25' radius dish and then sand the area where the fingerboard extension sits to almost flat as I was taught with a pre-determined angle which might be where I am making my mistake.

Before I start my next batch of guitars after about a 3-year break, I'd like to figure this out.

Thanks!

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

At which stage are you setting your neck angle?

I set my necks after the box is closed, bound, and pretty close to final sanded.

IMO, that's the time to do it. It doesn't matter what micro shifts have happened to the neck block in relationship to everything else, as you can account for it once the box is a closed unit.

If you're expecting a premade block/neck relationship to stay constant throughout the many, many opportunities for it to shift while assembling the body, I think that's expecting an awful lot...the precision required to keep that relationship constant would be pretty onerous...

Right before I put on the top I do the sanding of the rims to the 25' radius and also the flattening of the area pretty much across where the transverse brace sits.

I am attempting to sand the proper angle into the rims at this point and am evidently missing a step or a way to calculate the angle without the top on the guitar.

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

Well you're doing it the hard way. While it's important to build the correct geometry into the rims, it's IMO more sensible to fashion the neck's geometry to account for subtle shifts in the set of the neck block rather than to hope the neck block will match what the neck already is, if that makes sense.

Paul, I do it the same way but use 30’ rad tops. I have my body/neckblock/rim geo correct because when it’s all done my fb ext sits flat and inline with the neck and proper height at the saddle. But I also have to do a lot of trimming on the neck to get the neck to body join just right. I have just accepted it. If you find a solution I’m all ears.

Are you using a jig at all? The lmii jig is pretty cheap when you consider what it accomplishes imo.
I build the box. Set a shim where the saddle
Will go at a certain height, adjust the jig and cut the neck angle.


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I use the Simpson jig that i acquired here I believe way back when. Works well for me.

It's definitely good that you want to figure this out once and for all before you start building again because it's so important. I build on an open work board so it's different from building in a mold and I won't bother explaining My method because of that. But what I did was sit down and spend a couple hours figuring this out with pencil and paper and came up with a plan that works.

But ultimately what it comes down to is the proper height at the bridge. Most of luthiers aim for the string height over the soundboard at the bridge to be about a half an inch. Once you have the sound box closed and the neck made attach the neck, dry of course, and with a straight edge dead center on the fret board measure the airspace over the soundboard where the saddle is. You should have about 1/32nd of an inch of aerospace over whatever thickness bridge you choose, typically 3/8th. This measurement is taken with a fretted fretboard if you do not have the fret board fretted then just do the math.

So for a 3/8 thick bridge you would want the airspace to be about 3/8 plus 1/32nd of an inch above that. That way with the action set properly and the string tension pulling the top up a little bit you will have about 1/8 in saddle sticking above the 3/8th inch bridge and a string height of about 1/2 of an inch over the soundboard.

If you don't get it quite right then you simply adjust the heel of the neck till you get the angle correct. If you have airspace over the fret board extension then you would need to shim it. Not an ideal situation but it works. It's best to try and get that geometry of the top perfect. But really that's about it

Expanding a bit on what JF said—

Forget about neck angle, in terms of trying to shoot for a specific angle. The degree differences between right and wrong are too small to measure. Focus instead on the amount of gap (airspace, height, whatever terminology you use) at the saddle location. That’s what you want to get right, and you do it by flossing the neck heel until you get the right amount of gap.

I personally find that there is more fitting work to be done at the fingerboard extension area of the top if you use a 25’ radius for the top. Larger radii (28’-30’) make that process easier, and tend to make a “looser” top, which I like. Just something to consider.

I sand the upper bout angle into the rimset with a jig so I will be pretty close after the box is closed.

With the box closed I put a bridge of the average thickness I use in the proper location, make sure the rims are block sanded flat in the area where the neck attaches and use a long protractor to measure the angle that gives me the clearance over the bridge that I want. I tape a 1/4” shim to the edge of the top to represent the fretboard and the protractor rests on that.

I transfer that angle to the adjustable tenon routing jig. It gets me pretty close.

I think it is critical that you know how much your guitars will settle under tension. Different neck attachment systems and upper bout anatomy and bracing may settle in differently. That will determine how much bridge clearance you need.

Final upper bout angle is fine tuned with the Fox paddle. I actually try to put a very slight drop off in the upper bout which tends to go almost level with string tension. I like a very slight final drop off under tension.

If your upper bout is curved like mine with a tapered heel there is still a fair amount final fitting/flossing to do so I still tend to spend at least a couple of hours with final fit and angle even after getting it close off the jig.

Just one way, looking forward to reading different approaches.

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

this is a 2 part process
here are my videos on this the first to show setting up the rim the 2nd setting the neck the 3rd is the initial set up to show how this works out
in the end
https://www.youtube.com/watch?v=LrgRKKsxL-M

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

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

So Ed, how are you doing the setting of your necks to make sure the fingerboard lays nice and flat to your top and gives you the angle you want AFTER putting the top on?

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

Thanks Terence - but what is a Fox paddle???

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

JF - thanks for this. I seem to be getting the angle for the string height at the saddle set just fine and am doing a similar setup. There always seems to be some sanding to get the angle tweaked just right - but I get close. My problem is that I am having gaps under my fingerboard (mostly ramping up at the very end) which makes me think I am not getting the geometry set properly so that it will lay nice and flat. That is what I am trying to figure out where I am going wrong.

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

Okay right I hear you. So what you need to do is come up with a jig or a method of getting that angle right. Sometimes a sanding dish alone is just not good enough and what you might have to do is use a flat sanding board to put an angle in the body of the guitar starting from about the top of the sound hole to the Head block and sand that angle in. I have that angle built into my work board.

So so when you close the sound box the top will be canted from The sound hole to the neck lock. So if you laid a straight edge going down the center seam of the top from the neck block to the back of the guitar The straight edge should ramp up and have airspace where the bridge is located. You just have to do the math and figure out those numbers and make it a part of your building process.

This video shows what I mean by using a sanding board. This is the back of the guitar but it's the same thing.

https://vm.tiktok.com/ZMebo8Mna/

For one, I like fallaway in my FB. So when it hits the body, it slopes down gently just a bit.

I use a 28' radius, but clamp it to rims that are flat on top. This ends up with the geometry I want in the body. Then I adjust the angle of the neck itself by sanding in the correct angle back and forth and side to side, to account for whatever the body actually is.

Your OP made it sound to me like you're buying premade parts, and hoping that after assembly, the relationship will still be right.

Are you making your necks from scratch?

The OLF has lots of great information. One such piece was something Woodie G posted about how they do this at Greenridge Guitars. I tried it on my last guitar, and liked it, so I am using it going forward.

The top-facing edges of the sides and all braces on the top are profiled for a 28' radius dome. One exception is the upper transverse brace, which receives a 60' radius (which is darn near flat, but not quite). This gives a flatter (but not completely flat) area under the fingerboard extension, but you don't have to do any special flattening of the upper bout of the sides.

This fits into my way of building very well, it doesn't take a lot of time, and the geometry all does what I want it to do.

+1 for flat or near flat upper-transverse.

Also, here is a good document from Jeff Jewitt that summarizes the tutorial that Hesh first shared here plus more - https://drive.google.com/file/d/1zfPpM8 ... iwpKm/view

You're getting good advice here from these other folks that represent a ton of experience.

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Hesh's tut here, viewtopic.php?f=10117&t=25931

Two thought that I do not think I saw in the responses. Maybe... One John Hall screws the neck block in the mold to make sure it stays square. Leave it screwed in until the top and back are glued on. That way the block is less likely to shift. I do not do this but I do have a lateral length of spruce that I use like a go bar rod between the neck block and the tail that I leave installed until the box is closed. A 1° shift in the block while gluing on the top will effect your neck angle a lot.

The second thing I do is to clamp on the top before I glue it on and check that the neck angle is right by projecting a straight edge along the fretboard extension area of the top and measure the projection at the saddle. I use 2.5 mm but that will very based on the guitar you are building. If it is off, I will adjust the sides either taking off the waist side or the neck block side using a flat sanding bar.

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http://www.Harvestmoonguitars.com

After 45 years , I think I finally have it figured out for the way I build guitars.....
First of all, I build with a flat (not domed) top like Olson and Hoffman.
I find that once the string tension is applied the top gets a slight belly in it.
My method is actually very simple.

After attaching the back to the sides, I sand the entire top surface of the rims dead flat, I do this by sanding them on a flat piece of plywood with coarse grit paper glued to it, just like sanding the dome for the back, but instead of going in circles it is rubbed back and forth on the paper.

Then I put a piece of wood under the guitar at the bridge location the thickness of the amount I want the space at the bridge to be and sand the headblock and sides up to the soundhole point to this angle.

Then I glue the lining on and re-sand them flush to the sides with the same method.
Then I temporarily clamp the top to the sides and check the angle.

If it checks out I glue the top to the boat, if not, I adjust the angle again by more sanding.

The end of the neck is then cut to the angle of the sides so the plane of the neck follows the angle of the top .

I know we're all getting to the same place but by different routes. So I made these 3 piece sticks that help me see how much to sand using a 25' radius dish on the lower bout and a "flat" one for the upper. I'll try to get these pics in here showing a straightedge that is held flat on the neck block and rides across the "stick" at the place of the sound hole and is "floating" above the place for the saddle by my amount (.100"). I tried to take the pic and hold everything at once , oh well.

Paul here is how I do the rims, kind of the same principal as Brad. A spacer that replicates the bridge located properly and a sanding board with a piece of 1/4" acrylic to mimic the fretboard. I make the spacer the same height as the bridge. That seems to work for my guitars. I use that arrangement to sand a flat angle onto the upper bout of the rimset and use basically a flat top brace. The pictures are really old, I use a different headblock now with an integral extension but the sander takes care of that too. I also wait to cut the mortise in the headbock until the box is closed now.

IMG_2428 by Terence Kennedy, on Flickr

IMG_2429 by Terence Kennedy, on Flickr

IMG_2430 by Terence Kennedy, on Flickr

The Fox paddle I learned about when I took his course back in the day. It fine tunes the upper bout angle and flattens the area under the fretboard. The spacer for me is the height of the bridge. The sanding board is 1/4" acrylic to mimic the fretboard. I mark the area of the fretboard extension and sand until the marks are gone. If you get your rimset angled properly you don't remove much,

IMG_2431 by Terence Kennedy, on Flickr

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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 build with completely flat top rims. The UTB is 3/8" wide and has a 50' radius glued with a matching caul. The X brace has a 25' radius, also glued with radiused cauls. I use a dovetail and the neck block is cut on a table saw before installation. After the box is assembled and bound, the neck tenon is cut on a table saw and the neck is fitted without the fretboard. I'm looking for a 3/32" gap at the saddle location.

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