Official Luthiers Forum!

I made a jig to locate the bridge over the weekend. I just temporarily positioned the bridge on my 000 to check the neck set. I had previously rough set the neck so I didn't expect it to be way off. I had the bolt-on neck in place and tightened completly and layed a straight edge over the frets on the neck. I was surprised how high the straight edge was over the pyramid bridge. Wow, sure didn't look right.

As a double check, I layed my 1/2" thick small square in front of the bridge and the straight edge was about the right height (just a shade high). So I measured the thickness of the pyramid bridge and it's only 5/16" high. So if I want 1/2" height at the saddle, the saddle will stick up 3/16" above the bridge. This seems odd to me......does that sound right or am I missing something?

Another question. My fretboard extension has a slight drop in it (likely the fret tangs causing the bow). I reverse bowed the fretboard and it was laying flat before glueing to the neck but that was a couple months back. Anyhow, when I mount it to the guitar and tighten the screw nearest the fretboard extension, the bow is easily pulled out of the fretboard extension and there seems to be a good fit to the soundboard. However, if I need to sand the portion of the heel in contact with the guitar body to change the neck angle, the fretboard extension droop holds the front of the neck off the body so only the bottom of the heel is in contact with the body. I can't sand in that position or I will be increasing the neck angle rather than decreasing it. Do I just man up and push till the fretboard extension gives and the heel rests flat on the body? Not sure if I could pull the sandpaper with that much pressure. Any suggestions?

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Formerly known as Adaboy.......

Don't do it! I squeezed a gap out of my first one's neck, and it made the 14th and 15th frets unplayable (frets after them effectively up too high then). I managed to get it straightened back out, and just left the gap there. Mine's problem is that the upper bout surface is slightly curved, so there's no way for the fingerboard to lay flat unless I scrape a matching curve into the bottom of it (wish I'd noticed before finishing and I could have just sanded that area of the top flat).

On the bright side, it sounds like you got the upper bout geometry right for string height of 1/2" But I don't know about traditional pyramid bridge guitars... did you make the bridge yourself, or buy it pre-made? It looks like LMI's pyramid bridges are 3/8" thick, so if you bought it somewhere else, maybe it was designed for a lower string height? Or maybe you shaved off too much while matching to the radius of the top?

If I were you, I'd just let the saddle be tall, unless it seems like it will crack the bridge from the torque. Gives you more room before needing a neck reset anyway Otherwise, shave some off the bottom of the fingerboard extension so it can lay flat with the adjusted angle, or pull the bridge and make/buy a new one 3/8" tall.

Has your top shrank & sunk down some also?

I'm building my number 2 & the top has sunk a lot with the low humidity from running the furnace.

Kevin Looker

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I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

Ok, I'll add a little more info. The bridge is flossed with a 28' radius. I marked the bottom of the bridge with pencil and sanded just enough to make the pencil marks disappeared on the bottom of the wings. So this lowered the bridge height a little. The bridge is bought (I didn't make it)......but it sounds like it was roughly 3/8" high originally (I didn't measure it) and I've removed most of 1/16" of bridge height in the middle it appears.

I leveled the bottom of the fretboard, with sandpaper on granite, before I fretted. Of course the frets introduced a back bow.......which I countered best I could by clamping the fretboard in the opposite bow for a couple of days (adjusting the position of the clamps at times to counteract where the board was bowed). It laid flat for roughly 1 day before I glued it to the neck with epoxy. So the back of the board is flat and I didn't know at the time to sand any fall off in the fretboard extension. I glued the fingerboard a couple months back. Currently, the fretboard extension is again curled caused by the fret tangs.....so this gets in the way just enough that the heel of the guitar doesn't sit flat on the body when the neck is placed on the body.

My straight edge is very near 1/2" high at the saddle.......so using Todd's recommendations (.350"-.375"), I'm a little too high so I need to lower the neck angle. The only method I've seen to lower the neck angle is to "floss" under the heel. So here is the issue.......I need to floss the area of the heel near the fretboard extension to reduce the neck angle; however, this part of the heel isn't making contact with the body due to the small curve in the fretboard extension holding this portion of the heel proud of the body. (hopefully that makes sense......I'm not very good at describing this) I can pressure the neck down into the mortise and the fretboard extension flexes back into a fairly straight position and it looks fairly good (once the neck angle is lowered a bit it will look great I think). However, it's enough pressure that I can't floss the heel (can't pull the sandpaper out) without relieving some of the pressure.......and then I'm sanding the rear of the heel increasing the neck angle instead of decreasing it.

So what is the best way to address this? If the fretboard extension weren't curving down into the soundboard, it would be fairly simple to correct the neck angle by flossing. Hope this makes sense and I sure appreciate the suggestions!

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Formerly known as Adaboy.......

Darryl,

You might consider pulling some of the frets on the extension, and replacing them with frets with a narrower tang. The tang on your present fretwire can be flattened. The fit in the FB would then be looser, so they might need to be glued in. That should take care of the FB extension keeping you from getting to the top end of the neck cheeks.

I do a fair amount of neck angle adjustments with a sanding board, which I have several of in various shapes. The one I use for neck cheeks looks like a thick tongue depressor with 120 grit stuck on one side. The sides are angled a bit so it can get right into inside corners.

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

Darryl,

I think you are mistaken about your saddle height measurement unless I am not reading it correctly. If your straight edge is just a shade high on the 1/2 inch block then that means your saddle will need to be about 6/16ths high or more on the pyramid bridge, way too high. I aim for a flush fit with the straight edge to the bridge before fretting and typically set up the saddle to about 1/8th in height over the bridge.

Also fwiw I widen the fret slots over the tongue and set the neck in before fretting. I glue the frets in over the extension and it helps eliminate that hump.

Just curious. Does anyone ever try gluing the fingerboard on last or after setting the neck, rather than doing the whole thing with a fretboard glued on already? Seems you might have a way to pare down that 14th fret bump more easily and not have to install frets on a guitar body. In other words install fretted board after neck is set and glued in.

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"Preoccupation with an effect gives it power and enhances the error"
from "Your Owner's Manual" by Burt Hotchkiss.

Pat's suggestion of pulling a few frets on the neck extension to reduce the back bow was a good one and got me thinking. I ended up placing my neck on a granite block, supporting the fretboard right where the fingerboard extends past the heel and used clamps to induce a bow in the opposite direction. To aid the flexing the other direction, I dampened it a couple of times last evening with water to expand that side of the board. I left it clamped overnight and just now at lunch removed the fingerboard from the clamps and placed it on the guitar. It had a slight back bow the opposite direction! Success! Now I can sand the heel.

I resanded 10 strokes or so on each side to remove some finish that was on the heel in spots and then bolted the neck in place. The angle looked better after just removing these finish spots.

I measured with my dial caliper and here is where I'm at. The bridge is 0.320" above the top (low for a standard sized bridge due to sanding a radius in the bottom I guess) and the straight edge is 0.155" over the bridge. So the straight edge is 0.475" above the top at the saddle location. I was originally shooting for 1/2" saddle height above the top. Using Todd's numbers of 0.30" - 0.60" saddle height loss due to neck relief, top rise, etc., I'm setting at 0.445" - 0.415" height at the saddle. Where should I be at? It gets a little confusing since the bridge is a little low and not a standard 3/8" height.

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Formerly known as Adaboy.......

I find it easiest to set the neck angle before the fingerboard has been installed, otherwise it is just in the way. I do install the fingerboard just after setting the neck angle though but no frets until it is glued to the guitar after finishing. Then I can level the fingerboard fret it and not have to worry about anything moving.

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Tickle your guitar daily, and it'll tickle you back.

Thanks for that explanation Todd.......very helpful. You're right, I shouldn't have said "height at the saddle".......I meant the current height of the straight edge at the saddle.

It will be interesting taking that much off this end of the fretboard.......with the fretboard in place! <smile>

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Formerly known as Adaboy.......

a 60' or even a flat UTB, or wedging the body from top of soundhole to neck should allow an untapered extention.

would you elaborate on how you do this???

thanks

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MK5acoustics.com