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Greetings from Montana. I am building my first guitar - a J185. I have previously built a baritone ukulele and an F5 mandolin both of which turned out better than should be expected.

I am nearing completion of this guitar but have stumbled into an issue of my own making.

The angle between the top of the body and the side at the neck is 88.5* - not a perfect 90*.

The angle between the side of the guitar and the plane of the neck/fretboard is also 88.5*. I cut the 1.5* into the heel stock before I measured the top/side angle. I know - I'm learning. So it seems I have inadvertently doubled the recommended body/neck angle.

When I measure at the bridge, the plane of the fretboard without frets is approximately 3/8" above the top. There is about 1/8" between this plane and top of the bridge. This is the part that is confusing me.

The bridge measurements seem close so changing the angle to reduce the top/neck angle will move the fretboard plane closer to the bridge. That doesn't seem right.

And this angle produces a fretboard extension that is about 1/8" or less above the top at the soundhole.

It would be tremendously helpful if I could get some feedback on what I have done and some possible options for moving forward.

Thanks much in advance.

Gary Davis

This confuses me too. Is your bridge only 1/4” tall? Most are 3/8”.
I also use the straight edge with frets installed. You gain some height there if you did.
A goal is for the plane of the straightedge at the bridge to be 1/2” above the top.
If you want to continue with want you have (bridge), put the frets installed and see where the straight edge lands. If it is 1/64 to 1/16” above the front edge of the bridge that is correct.
If not, work on the neck joint until it is. If you have excess fall away of the extension you can shim it or live with it.

And congratulations on the F5! Not easy.

What attachment style are you using? What stage is the neck and body at?

Gary,
For the sake of continuing the discussion, sounds like you might have answered your own question- you cut the neck block and heel cheeks incorrectly. A 1/8" FB to top gap is a lot and perhaps correlates with having cut your angle incorrectly. You could shim your FB extension or correct the angle on the neck cheeks, depending on your actual neck angle, which I cannot quite understand.

The projection over the bridge discussion could be simplified (at least for discussing in the thread) by adding a couple of frets and taping your bridge in the final position- then do the projection, and state the distance over the front edge of the bridge. Or do the math, but include the assumptions in the discussion (and/ or a sketch) for clarity. For me, the height of the projection of the straight edge over the top is a result of the design, and an indicator of implementation, (neck angle, fret height, bridge thickness) and not a target or specification.

Backing up a bit, after the top and back are glued on, a common "best practice" is to sand a flat plane on the top, from the sound hole to the neck mortise. I do that with a sanding stick that rests on a 2.5mm spacer in the (future) bridge saddle location. THere are other ways to this, whatever works for you. This flat sanding is done early on in the build, BEFORE the binding channel is cut. That simple flat sanding is probably the most important step in my builds to ensure a super flat and gap free fit of the FB to the top, that follows the neck angle.

You will likely be better off to recut the cheeks of your neck to arrive at the proper projection to the bridge. THis may correct your FB extension gap as well. You may have to shorten the tenon a wee bit as the top of it will move forward, toward the neck block if you have to bring the neck angle down. Totally recoverable, and similar to digging a ditch; not complicated, but a lot of work.

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Measure Twice,

Karl Borum

I think pictures would help here -

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

Thanks y'all. I'll do some more cogitating and get back with images if I can't solve my problem with your guidance.

Neck to body attachment is M&T.

Body is complete. Neck is work in progress.

If I must reshape the heel sides to eliminate the extra 1.5*, I would very much appreciate advice on how best to approach this to maintain the good fit I have now. I see the potential to screw up the neck heel and having to build a new neck. This is already neck #2.

Thanks much for the help. I shall return.

Gary

How about pictures from the side with the neck in place and a straightedge either riding on frets or atop a spacer that's fret height? A degree and a half too much neck angle gets the fretboard pointing to the stars.

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Peter Havriluk

It takes very little wood removal to get a 1.5* change in neck angle.

Here’s what I like to see. My bridges are 3/8” in height. My fingerboards start out at .270” flat which leaves .020” room for profiling. With the unprofiled fingerboard clipped to the neck blank, no frets, I want a straightedge to just kiss the top of the bridge.

It sounds like you are hitting that. Please tell us how tall your bridge is. You say there is a 1/8” gap between the fretboard plane and the top of your bridge, and that is confusing me too.

You say there is about 1/8” gap at the sound hole which is quite a bit of fall away, but that in itself is not terribly relevant and all sorts of different aspects of the geometry can affect that, so at this point I wouldn’t worry about it.

You’ve wisely chosen a non dovetail joint, so adjusting the neck angle after cutting the tenon is very simple and there’s no reason why you can’t keep the good fit you have, but before getting instructions on how to do so, let’s sort out if you actually need to first.

It’s hard to get two different guitarmakers to agree on anything, and yet for reasons not needed to go into here, we generally agree as a group that the string height over the soundboard measured on the D string at the bridge should be about 1/2” give or take a smidge.

This is where the 3/8” bridge height many of us use comes from. With that bridge height, that gives you about a 1/8” saddle height to get your 1/2” above the soundboard with good string action height at the 12th fret.

So please, tell us your bridge height before changing anything on your neck and we’ll go from there…

I took some images. I hope they help y'all propose a solution.

I put some wood shims under the fretboard to emulate frets. They could be a hair too tall but you get the point.

The finished bridge was given to me by a now deceased luthier. It is 5/16" tall. Should I scrap this bridge?

With the "frets" in, the fretboard is about 1/8" over the bridge. Height above the soundboard at the bridge with the "frets" in is a smidge over 1/2".

Untitled by Gary Davis, on Flickr

Untitled by Gary Davis, on Flickr

Untitled by Gary Davis, on Flickr

Looking at the last image, it appears that the thickness of the shim is about the same as the height of the fretboard, with "frets," above the bridge.

Now I'm really confused but I trust the fine people here will straighten me out in no time.

Thanks all - Gary

Buried in this conversation is the idea that the bridge will rise 'a bit' under string tension....

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Peter Havriluk

Those shims are way too thick. Fret height is only about 1/16". 5/16" isn't terrible for the bridge but if it were mine I'd get one that is a full 3/8" tall so I could get a 1/2" string clearance in front of the bridge without exposing too much saddle. Looks like you're doing nice work, keep at it and you'll get there.

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Steve Smith
"Music is what feelings sound like"

I wouldn’t necessarily scrap that bridge if it has sentimental value to you. 5/16 is workable. I would plan to have the string height 1/32 closer to the top, so I’d aim for the unfretted board to hover 1/32 above the bridge, and a 5/32 saddle. Basically split the difference.

It does sound like you’re overset backwards a bit.

The good news is that since you’ve chosen a M&T joint, you can change the neck angle without losing joint integrity quite easily, especially as the fretboard is not yet on.

1) with a nice sharp chisel, cut a relief channel all the way around the tenon. Cut until only 1/8-3/32 of the outside perimeter remains. The idea is to make it faster and simpler to floss the cheeks by making it so that you don’t need to sand the entire surface adjacent to the tenon, just the edges.

2) take some sandpaper (I like 150 grit for this) and put some packing tape on the back. A strip about 8” long and the width of the packing tape. The packing tape allows it to slide a little easier, and prevents the paper from ripping.

3) with the sound hole facing you, put the sandpaper between the neck and body with the tape side on the body. Pull the sandpaper towards you while applying a bit of pressure on the neck towards yourself. Pull it all the way through, put it back, pull it all the way through, repeat a few times. Count how many pulls you did, then do the same amount on the other side. Then recheck your neck angle. Don’t go crazy stripping as it takes very little wood removal to affect the change you’re after. Wash rinse repeat until your neck angle is where you want it. Check your centerline too as you go and if you need to take a few strokes extra on one side or the other, do so.

Hope that helps.

Addendum…don’t put the papers full length into the joint, only put it as deep as the heel cap. You don’t want to sand anything off the heel, only the edge directly under the FB, but in a perfectly straight line. Hope that makes sense…

I want to offer a little suggestion that might simplify this a bit. If you just leave off the fingerboard and bridge (for now), a great rule of thumb is that a straightedge sitting on the neck and extending over the saddle location should show a 0.1" gap between the bottom of the straightedge and the top of the guitar, at the saddle location.

I think there is a lot of room for error when you start measuring the thickness of the fingerboard, and the bridge, and shims, and whatever else is used to get this angle right. I personally feel it is better to strip all of that away and just shoot for the 0.1" gap.

Also, when you get to where you think you have the neck tilted and yawed correctly, and while the neck is still bolted to the body, you can give the upper bout a bit of a kiss with a flat board covered with sandpaper to make sure there is an uninterrupted flat plane under the fingerboard.

Make a 1/4”plexiglass surrogate fretboard that keys in the truss rod slot and cut slots for the sandpaper flossing strips. Makes it easier to decrease or increase the neck angle and the surrogate fretboard clamped on makes checking the angle easier. I usually clamp the guitar in the holding vise and tape the bridge on while fine tuning the neck set.

IMG_6125 by Terence Kennedy, on Flickr

IMG_6124 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.

Nice!

I agree with this...Once this is done everything else should fall into place assuming you are using a .250 thick fretboard.

I didn't read all the other posts but I think you are OK Gary.

What stood out to me was your number 88.5 and your statement that your sides are not 90 degrees to the top. They should not be 90 degrees to the top.

We shoot for a 1.5 degree neck angle. 90 minus 88.5 = 90. So this suggests you are pretty much right on the money.

Now the neck does have to be fitted and the neck angle refined and with a dovetail this is perhaps the most challenging part of building an acoustic guitar. You have a mortice and tenon but it still needs to have the neck angle dialed in.

I like to see the straight edge come into the bridge right about at the top of the bridge, not over it, not under it. If my neck is fretted I want to be over the bridge the height of the frets or slightly less.

Be absolutely sure to use the truss rod and straighten the neck as much as possible. The straight edge should be in direct contact with the neck for frets or fret positions 1 - 12 and then we see what we have over the bridge.

Lastly one off our magic numbers is 1/2" and that is a goal of what we want the string height to be at the face of the bridge. It's not required but higher than this increases torque on the bridge and lower leaves some power that could have been had on the table.

Gary I think you've done some great work here good going.

Thanks y'all again. I'll try to spend some time this weekend with your suggestions.

Gary

Just an additional remark. Straightedge clearance over the bridge unstrung is not an absolute number but depends on how much movement you expect under string tension and after settling in to a stable situation. You really can’t know this until you have observed an instrument for a year or so.

For my builds 1/16” clearance on an unfretted neck with no tension is about right. I think it is always better to error on being slightly underset as it is a lot easier to increase the neck angle down the road than to decrease it.

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

Thanks for that. For posterity sake, I checked the plans and it calls for a bridge thickness of 5/16". And I remeasured the thickness of my fretboard and it is just under 1/4" - like 0.22".

Yesterday was a day full of agony. This morning is starting out better so maybe I can make some progress today. My plan is to further refine the shape of the heel per the plan and then recheck my fit. I feel I'm so close its scary knowing I can fook it all up so easily at this stage.

Thanks all - Gary