Fitting fretboard to body

ChuckBarnett

Well-known member
Joined
Mar 3, 2017
Messages
492
Reaction score
3
Location
Arlington, WA U.S.A.
I am building a bolt-on tenor uke. When I set the fretboard onto the bolted on neck I'm seeing a 0.007" (feeler gauge) gap between the underside of the fretboard and the top, just north of the soundhole. That gap tightens up as you slide the gauge closer to the neck. As a noob, I think I need to get that gap to pretty much zero so that the fretboard lies flat against the top.

Complicating this is that I've done a radiussed top (I know, I know...)

I'm also concerned that if the angle of the top of the fretboard and the ukukele top isn't open enough, there may not be much height for the strings over the saddle. (I could slip a laminate layer between the neck and fretboard...)

I have yet to install frets and hesitate to go further until I solve this question.

Any help for the boy??
 
How bad is the gap right at the neck joint? Does it seem to go away when the fretboard is pressed down near the soundhole? It seems like you have a slight case of drop-off, which many builders consider as desirable. Place a straight edge on the first 12-14 fret slots and measure the gap where the bridge/saddle will sit. Or just slide your bridge under there. It shouldn't quite fit.

I keep a faux fingerboard on hand with frets 1 and 12 in position, rather than using a fretless board as you are doing. When clamped to the mounted neck the straight edge should just sit on top of the positioned bridge. You seem to have a bit of back set in the neck, which might require a saddle too high to be attractive. I hope I'm not misreading your problem.
 
Thanks, for your help!

There is no Gap at that spot. It's quite tight. If you can make sense of the photo, the heel of the neck is at the left with a straight edge extending over the ukulele. If you look closely you can see a gap starting at 11 on the rule going to nearly 14 at the sound hole end. Measuring underneath the fretboard at that spot I get .007". I will check out over the bridge location for height.
View attachment 128207

How bad is the gap right at the neck joint? Does it seem to go away when the fretboard is pressed down near the soundhole? It seems like you have a slight case of drop-off, which many builders consider as desirable. Place a straight edge on the first 12-14 fret slots and measure the gap where the bridge/saddle will sit. Or just slide your bridge under there. It shouldn't quite fit.

I keep a faux fingerboard on hand with frets 1 and 12 in position, rather than using a fretless board as you are doing. When clamped to the mounted neck the straight edge should just sit on top of the positioned bridge. You seem to have a bit of back set in the neck, which might require a saddle too high to be attractive. I hope I'm not misreading your problem.
 
In my first build I found the opposite problem: a gap at the neck end of the fretboard extension. So I stuck coarse sandpaper to the heel surface of the body and carefully slid the neck heel back and forth over that with greater pressure on the heel cap end. Eventually I got the fretboard to lay flat as I could against the radiused top.

I guess the same trick can work this time and if there's too little height over the bridge, I will need to shim the fretboard. What am I missing here?

Thanks, all!

Chuck B
 
If it makes you feel any better, I've had this same problem and it ain't good. I finally traced it back to faulty radiused neck blocks which were slightly out of square due to worn bearings in my spindle sander. It was an example of how small errors can compound.

What can result is having to make your saddle too high which is not good. It effects playability (action to high), serious intonation issues and loss of volume... The good news is that you have not attached the neck yet and your idea to sand the neck heel to get things square is correct.
 
In an ideal world, your neck is pitched back too far. You over-compensated for the radius in the top. Let's say that you will have an 8mm gap after fretting. Your bridge will have to be approx. .320" to fill the gap and your saddle .180" to give you a perfect .090" of string clearance over the 12th fret. That's a big lump of wood to stick on a uke top. I usually go for a bridge .250" thick, in which case your saddle would be sticking way up in the air. The .320" bridge is cosmetically a better choice. In this fictional world you should correct the neck pitch and set everything back to normal specs.

In this world, I would clamp and glue the fingerboard extension (a .007" gap is nothing and bending the board that much will not be important), then make a suitable bridge out of a light-weight wood to have a normal saddle height. Remember that string tension can often mess up the most carefully laid-out plans and be ready to adapt.

A couple random things to think about ('cause I don't know where else to put them):
Every player says that tone is their most important consideration in an instrument. Every experienced builder knows that players don't really believe that.

People are quick to point out that the bridge is a brace. Why would anyone want a big-ass lump of a brace right in the middle of their top if they could help it?

Some luthiers knock themselves out on a feature that makes a 2% sonic difference that no one notices, even if they appreciate the idea. If you can find five simple changes that make a 2% difference most people will hear the improvement. So don't force yourself on an instrument except to experiment. Those five changes aren't hard to find and most experienced builders already know them.

Most musicians (and many luthiers) are no more open-minded than the rest of the world where their instruments are concerned. But those that are open-minded are the most fun to work for.
 
If it makes you feel any better, I've had this same problem and it ain't good. I finally traced it back to faulty radiused neck blocks which were slightly out of square due to worn bearings in my spindle sander. It was an example of how small errors can compound.

What can result is having to make your saddle too high which is not good. It effects playability (action to high), serious intonation issues and loss of volume... The good news is that you have not attached the neck yet and your idea to sand the neck heel to get things square is correct.

What do you mean by radiused neck blocks? fretboard radiusing blocks?
 
No, the block that goes inside the body which must be radiused to fit the curve of the sides and the curve of the neck heel. It glues to the seam of the sides and to the top and the back. It goes opposite to the tail block which is also radiused.

Picture of a neck block on an uke that I'm replacing the top. neck block.jpg
 
I'm not grasping the problem, Sequoia. Do you mean that the neck joint area was out of square with the plane of the top? How did your sander make that happen?
 
Well I make my neck blocks on big drill press with a spindle sander using a radius template underneath the block. As I pushed the block against the spindle there was play in the bearings which put the spindle out of the true 90 degrees making the block slightly off by about a degree or two. After glue-up, the side was then slightly out of square with the plane of the top causing the above mentioned problem. I compensated by setting the spindle out of true by a degree or two which then made the block square 90 degrees to the deck. I think these are the sorts of real world problems us wood workers deal with all the time.

Bottom Line Lesson: Drill presses were not designed to take lateral pressure on their bearings and thus the abnormal bearing wear.
 
In an ideal world, your neck is pitched back too far. You over-compensated for the radius in the top. Let's say that you will have an 8mm gap after fretting. Your bridge will have to be approx. .320" to fill the gap and your saddle .180" to give you a perfect .090" of string clearance over the 12th fret. That's a big lump of wood to stick on a uke top. I usually go for a bridge .250" thick, in which case your saddle would be sticking way up in the air. The .320" bridge is cosmetically a better choice. In this fictional world you should correct the neck pitch and set everything back to normal specs.

In this world, I would clamp and glue the fingerboard extension (a .007" gap is nothing and bending the board that much will not be important), then make a suitable bridge out of a light-weight wood to have a normal saddle height. Remember that string tension can often mess up the most carefully laid-out plans and be ready to adapt.

A couple random things to think about ('cause I don't know where else to put them):
Every player says that tone is their most important consideration in an instrument. Every experienced builder knows that players don't really believe that.

People are quick to point out that the bridge is a brace. Why would anyone want a big-ass lump of a brace right in the middle of their top if they could help it?

Some luthiers knock themselves out on a feature that makes a 2% sonic difference that no one notices, even if they appreciate the idea. If you can find five simple changes that make a 2% difference most people will hear the improvement. So don't force yourself on an instrument except to experiment. Those five changes aren't hard to find and most experienced builders already know them.

Most musicians (and many luthiers) are no more open-minded than the rest of the world where their instruments are concerned. But those that are open-minded are the most fun to work for.

Thanks for the info-packed response! Still learning, so I now have some questions:

1. The fretboard doesn't really need to be flat?? Do some folks attach fretboard and neck to the body and then flatten the fretboard? Not sure how I would go about that. (I stuck sandpaper to a flat counter top slab and ran the f/b back and forth.)

2. I didn't realize that bridge size/mass was important. This, being a tenor, are ther specs that I should shoot for? I was hoping to continue the Ebony theme I have for the fretboard and headstock veneer into the bridge.

3. "string tension can often mess up the most carefully laid-out plans... be ready to adapt" I've no clue...

Thanks, again!

Chuck B
 
In an ideal world, your neck is pitched back too far. You over-compensated for the radius in the top.

One more question: Not sure I would characterize what I did as "overcompensating..." simply because I didn't realize that would be much of a problem or that there was any way to address the problem before the point I'm at now. I simply shot for about an 88.5 degree angle (after my first build showed the opposite problem -the gap was where the heel hits the body rather than near the soundhole.)
 
1) The fretboard does not have to be flat, it is the neck bed that has to be perfectly flat. Sometimes I get a slight bow to my fretboards after fretting because the fret tangs force the wood apart. Who cares? Once the fretboard is glued down it will be flat. If there is slight curl of the tongue over the body, I just glue and clamp it down with a clamp through the sound hole.

2) I don't worry to much about bridge mass although some do and I suppose it could be important. To me it is just the thingy that holds the saddle. Mine are just scaled down classical guitar bridges made out of rosewood and they function just fine.

3) Another thing I don't think about much because it doesn't seem to present a problem although it could. Maybe the poster could expand on that idea.
 
Would it be rude of me to jump into this thread with my own "issue"? It's something I've been meaning to bring up and aligns with this thread, so why start another?

I have been radiusing the tops of my ukes. My current method has resulted in tall saddles, and it's something I thought I'd want to remedy, though mostly because I thought it looks a little weird.

It doesn't, however, seem to affect tone, intonation, or volume, or playability. This is the loudest uke I own. It has a cedar top and a lot of punch. My ears can be really sensitive to pitch, and intonation is very good. The action is not high, just high enough.

So, besides looks, what is a compelling reason to change this? (not that I wasn't going to try) What will I actually gain?IMG_20200709_083514429.jpg
 
Some measurements would be nice Brett for comparison purposes.

- height of bridge
- height of saddle
- total height of bridge with saddle
- overall thickness of fretboard to top of frets
- height of the string over fret at the 12th fret
- height of the string over the first fret

That the uke plays and sounds good to your ear is the important thing and if it all works, well fine. From the picture it looks like the bridge is low which would make the saddle look high, but it all comes out the same in the end.
 
Action at the first fret .55mm (my little steel ruler) and at 12th a little more than 2mm. The playability is great on this uke. I can strum and play pretty hard without buzzing. Also, this one has a higher tension string set up.

Fretboard+frets 6mm, Bridge height 6mm. Saddle another 6mm higher.

I have since started rough cutting bridge blanks thicker than fingerboards, but in this case I must have just used a piece from the same FB blank.
 
All those measurements are good except the bridge height which is kinda high. But if it gives you that action height which is nice and low, it all works so you are good to go.
 
Top Bottom