Fitting neck to acoustic guitar...is there a layout product like Dykem for metal that can be used on wood?

[beginner]

Hello, I hope you can help me.

I'm struggling a bit fitting the neck to the guitar body. I've gone slow, watched a bunch of videos. It's so close but I'm missing something...I don't want to keep blindly attacking the project in the hope that i'll magically file or sand the last offending area.

I believe "conceptually" that I understand the process i.e. leaving a rim at the outermost parts of the cheeks, removing wood in an angled fashion medially, removing from the heel to raise the angle of the fretboard to just a bit above the plane of the bridge vs removing from the cheek to lower the angle of the fretboard.....and finally drawing a piece of sandpaper to co-apt the neck to body contour. I've tried for the most part to respect these concepts.

When i did some metal work in the past we used to use a layout dye solution called Dykem....you would paint it onto the interfacing surfaces and when they were joined or rubbed together it would remove a bit of dye from whichever area was abutting or interfering.

I tried rubbing a pencil mark on the adjoining wood surfaces but it didn't really show up or help.

Curious if there is something similar for wood working? appreciate your thoughts, suggestions and help.

appreciate your help.

[Kevin Sjostrand]

Commonly chalk is used for fitting. Apply it to the cheeks and put in place.....move it slightly and the high spots will show up where the chalk is rubbed off.

[beginner]

thank you for responding...i think i have some chalk that I used for metal files. I'll try that.

[BlindBo]

Neck joints are difficult to learn for many of us non-professionals. Many use these three steps for fitting a neck.
ACE:
A- Angle for getting the neck plane correct as you described relative to the bridge.
c - Centerline. Controlled by removing material from the neck cheeks, “flossing” with sandpaper as you also described.
E - Elevation to get the top of the neck plane level with the plane of the top. This is adjusted differently depending on whether you are using a dove tail or a bolt-on.
I find it works best for me to focus on each operation separately. I. E, complete one operation before moving to the next. If you start working then all at the same time, things start getting confusing very quickly.

It might help us help you if you can give us little more info.
What type of joint? Dove Tail or bolt-on?
Where is (or are) your issues?
Have you successfully accomplished any of the above three steps yet?
Take care.

[beginner]

thank you. it is a dovetail joint, no bolts.
please note: the perspective is looking at the front of the guitar with the neck pointing up.


the most significant errors/deficiencies i identify are as follows:
the neck alignment to the center line of the guitar is biased to the left (will need to be rotated anti-clockwise to correct).
the fingerboard is not flush with the front face of the guitar with slightly more show on the right side (apx 2mm and 1.5 mm off the face of the guitar)
the angle with which the frets intersect with the bridge are such that this plane is too low

[BlindBo]

If I did my conversion correctly, it looks like your center line is off by approx 1/8” at the tail end of the top. In my book, anything less than an 1/8” is acceptable and anything less than a 1/16” is a good. You should be able to fix that fairly easy by flossing the left heel cheek (bass side for right handed guitar).
This solves the C in ACE.

Neck joint. It appears the fret board is already in place. For future reference, I think it’s a lot easier the “rough” fit the neck before gluing the fret board in place. It allows you to do your flossing from both the top and the bottom and it allows you to true the neck plane (where the fret board glues on) to the guitar top before the fret board is in place.
I couldn’t tell how far out or low you are from the photos, but, if it’s low to the bridge, you’ll need to remove some material at the top of each cheek. Depending on how much is required, you can do this with a sanding block. If a large amount, use a sharp chisel.
Caution:
1. Try to remove the same amount from each side.
2. As you remove material at the top, occasionally take a full stroke on the heal so that your fit against the body doesn’t get too wonky.
3. Be sure to account for your fret height.
This solves the A in ACE.

Elevation
This requires almost as much skill as the angle adjustment. You really want this to be a good, flush fit to the top. This will require carefully adjusting the neck tenons to drop the heel height.
Dove tail tenons are typically machined at approx 10 degrees. Make yourself some sanding blocks with at 10 degree angle on one face, apply some 180 grit sandpaper using double sticky back carpet tape to this surface and trim any paper overhangs off with a razor knife or blade. Secure the neck to a rigid fixture to hold the neck stable while you sand the tenons. I either clamp a 4x4 to my workbench or use the French on my table saw. Carefully sand off a small amount of material from each side of the tenon. Work very slowly and make sure your sanding block is true to the tenon. You DO NOT want to do anything to change the angle on the tenon at this point. It should begin to fall in the joint after a limited number of sanding strokes. Just take your time and measure often.
That solves the E in ACE.

There is a lot more to getting a really good neck set, but, this should keep you busy for a while. And please remember, I’m fairly new at this too and others may have completely different advice.
Good luck!

[BlindBo]

I think I gave you bad advice. If your neck plane is too low, you need to remove material at the BOTTOM of the cheeks. Sorry, had a brain lapse there!

[beginner]

Thank you so very much for taking the time to help. Your post helped me to better understand the process.

In retrospect I didn't quite understand or appreciate the fact that I was focusing too much effort on tailoring the cheeks....but neglected to consider or modify the central tenon. I believe that i'm using the correct terminology (the central prominent wood that is shaped like a dove's tail I'm calling the tenon....and the outermost sides of the neck that will make contact with the body of the guitar I'm calling the cheeks).

It should have been obvious but I missed it.

It takes me a lot longer to do physical things with my medical situation....maybe that's good as i do things in baby steps.

I will work on the guitar today and follow up.

It's a fun learning experience and if/when i attempt another build I'll glue the fretboard on later on in the process as you've recommended. It makes a lot of sense.

[BlindBo]

Yes, you have your terminology correct. The tenon relationship to the mortise in the neck block is critical. When sanding on the tenon, be very careful about the angle and remove the absolute minimum amount required to get the elevation you need.
John Hall has good videos on the whole process.

As you are doing, most folks recommend getting the neck set done before finishing. You may have to tweek it after finishing, but, usually very little. This lets you set the neck w/o the fret board in place. Once you sand the neck plane to the top plane, you can glue the fret board on, true up the edges to the neck, and proceed to finishing the neck. Again, many folks add the frets after the neck is on the guitar. This allows you to sand the fret board true to the neck before fretting.

Be sure to note in John’s videos that all the neck ACE adjustments are evaluated with the neck clamped tightly in the joint, not just a loose, hand fit.

I’m familiar with medical issues. I am 85-90% blind and it takes me several months to complete a project. A lot of that time involves correcting issues I’ve created and didn’t see at the time. I refer to most of my projects as “tar babies”.
Good luck and keep at it.

[MaineGeezer]

It ain't easy. A couple of points.
Do the fitting in a logical sequence; fix one direction (up/down, left/right, etc.) at a time, otherwise it's easy to end up chasing your tail and not getting anywhere.
I''ve always fitted necks with the fretboard attached,because that's the way the luthier who taught me does it. Not to say it''s better or worse, just that different people do things differently.
It's perfectly okay to use shims, if the joint ends up loose. Seems as though I always use shims because I never cut the dovetail and tenon exactly correct. The only fault I find with shims is I need three hands to keep them in place while sliding the joint together.