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It’s almost 1/8 “ over the bridge :/
Gah!
Will the guitar move enough to compensate or do I just have to finish it out and string it up to really tell?
Let out a big sigh when I put that bridge on the top.




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It looks thin. If it’s not glued down why not just make a taller one?

It’s not glued down. At the highest point it is 9.47mm


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I see. The highest above I’ve ever gone is 1/16. Maybe someone who’s tried an 1/8 can help.

Tops generally will move "up" by about 1/64" to at most 1/32" upon first stringing and subsequent initial settling in. My experience with my own guitars is about 0.020" and I use that measurement to calculate neck angle. I personally like to have under string tension, a straightedge that has 0.040" of airspace between the top of the bridge. If I was building guitars for flat pickers that want high action, then I would lower that by 0.020 to 0.030". But most of my customers want fairly low, easy action.


Here's a page from my SOP about calculating the desired "airspace".

Minimum Airspace at Saddle Location
Fretboard + Frets + Minimum Airspace = Bridge Height
0.250" + 0.040" + 0.060" = 0.350"
Bridge Height -- 0.375" (0.350” after soundboard profiling to mate with top)
EVO Gold Crown Height -- 0.040"
Fretboard Height -- 0.250"

Compensation (0.060")
Soundboard rises approximately 0.020" under string tension
0.040" additional compensation (neck reset prevention)

Ideal Airspace = Minimum Airspace + Compensation = 0.120"
There should be 0.060" airspace above bridge without string tension and approximately 0.040" airspace above bridge with string tension.
Bridge location is 11" from 14th fret (25" scale).
Bridge location is 11.2" from 13th fret (24" Scale).




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The way I ensure I get a perfect neck angle is by placing a shim at the location of the bridge and then use a perfectly flat sanding block to sand the upper bout. The sanding block continually rests on the shim and flattens the region of the upper bout where the fretboard rests. I then set my neck angle so that the neck forms a perfect level surface with the upper bout. I use a 25' radius top and I have to sand very little off the upper bout to get that area flat. Lots of different ways to do this but that's my method. I've built quite a few guitars at this point -- the neck angle is always dead perfect - so this method does work well.

So how should i proceed?



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I like 1/8th inch over the bridge. 3/8th inch thick bridge, 1/8th inch saddle above the top of bridge gives me about 1/2 inch above the soundboard (a little less because of soundboard "pull up")
As the guitar ages it gives you a little bit of saddle adjustment before people start shaving the bridge and ultimately resetting the neck. Having the strings 1/2 inch above the soundboard is generally recommended and usually gives a better sound than much above or below that distance.

First of all are the frets installed on the FB??

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Think you've missed something Clay, looks like his FB plane is projecting 1/8" above a 3/8" bridge, that gives VERY low action.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

It seems as though we are discussing what the height of the saddle will be over the bridge, as well as string height above the top, rather than where the action might be set.

0.125" clearance over a 0.370" final thickness bridge should yield about 0.6" (or hair more) for string height over the top and a 0.250" or so tall saddle projection above the top of the bridge. That seems very high - certainly higher than a standard belly bridge will support, although a deep slot in a Gibson-style reverse belly or moving the saddle back closer to 1/4" from the front edge of the bridge might work with a thicker saddle.

Seems like it may be time to consider resetting the neck angle.

_________________
For the times they are a changin'

- Bob Dylan

here is my 2 cents
That line should be about 3/8 in off the top at the point of the saddle. Then make the bridge to about .350 in . Agree the top comes up and that depends on the bracing and RH. so how high are you off the top at the point of the saddle

_________________
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

To clear it up.
The line over the top of the frets (yes frets are installed) projects 1/8” over the saddle which is .373” in the middle

I’ve never adjusted the angle at this point.


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John
From the soundboard I’m just a TAD over 1/2” at the middle of the saddle


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Colin wrote:
"Think you've missed something Clay, looks like his FB plane is projecting 1/8" above a 3/8" bridge, that gives VERY low action."

You are right Colin. I was assuming the first picture was projecting the string path since no other information was given. If the straight edge is laying on a bare fingerboard the neck angle is tilted too far back.

The bridge looks a bit thin so my recommendation would be to just make a new one. If you want to use the bridge then you will need to reset the neck angle and then remeasure your bridge location for proper intonation.

No
The frets are installed I think I put that in the OP. Maybe I neglected it

With the frets installed the line is a TAD over 1/2” over the board.

This needs to be dropped
I’ve a plan of attack:)


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I didn’t make that clear.., sorry


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For a 25.34" scale length with a 0.070"/0.095" action, the low E (E2) will sit about 0.176" above the plane of the frets at the saddle with 0.004" relief, while the high E (E4) will sit about 0.150" above the plane. This means that you can add an average of 0.163" to your fret plane value to estimate the height of the strings above the top. I omitted the trigonometry, but I can draw that out for you if you prefer.

For your 0.370" bridge, you'll likely end up with 0.360" or so after flattening or radiusing and glue-up, so that 0.125" fret plane height over the roughed bridge will increase to 0.135", or a combined total of 0.505" fret plane height.

You'll lose about 0.060" of string height to body distortion for a lightly braced dreadnaught or larger body, and closer to 0.030" for a Size 2. Assuming this is a 000 or similar, 0.045" over the first year is realistic, so:

0.505" Fret plane at saddle:
+ 0.163" String plane to Fret plane difference at saddle:
- 0.045" Body distortion:
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= 0.623"String height over top:

So saddle height above the bridge will be 0.263" at the mid-point (0.623" string height at the center of the saddle - 0.360" bridge height) with moderate relief (0.004"-0.006") factored in.

Summary: The fret plane needs to come down by about 0.100-0.125" to get the string height under control and achieve a manageable saddle projection. We prefer to see about 0.550" initial string height on smaller-bodied instruments, but closer to 0.525" on dreadnaughts and larger, with the expectation that the remaining 0.015" to 0.030" body distortion will come as the guitar settles in.

_________________
For the times they are a changin'

- Bob Dylan

I would bring the angle forward...

This would be done by removing heel to body material from the front (fingerboard side) w a sharp chisel I assume



A very nice and generous member spoke w me on the phone about this.

I’ll be doing this and bringing the line (with neck in and frets on, to 3/8” over the soundboard at the saddle location from what I gleaned

The only part I’m concerned about is screwing up the joint or making it lean

Time to sharpen up the laser chisel (that’s my one blue spruce chisel) and do some marking:)


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I get to let this soak in and formulate the best path of action during the work day ha. It seems like a simple fix to the builders here probably, but for me it’s a new move, which hopefully will be successful


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I've had to do this a couple of times. Don't forget to take a little off the tenon length too, I've had it bottom out before I figured out what was going on.

I think I’m worrying more than I should
I’ve gone to a lot of precautions with this build to make it very sound... somehow this got through.... but I don’t want something like this to derail the “by FAR” best build I’ve had to date


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Yes, a sharp chisel is your pal in this. Setting it so that your fret plane kisses the top of your 3/8 bridge should be fine. Start by cutting about a half inch behind the FB, then an inch, then 1.5" etc, rather than trying to get the whole cut in one go. Hope that makes sense. Then floss as needed to clean up the joint. Try to be very careful about removing the same amount of wood off each side so your centreline stays good.

It is much easier to bring a neck back. For that reason, I always set my necks about 1mm forward at rough fit. Then, right before I glue the neck on, I floss it to the exact angle, both perfecting the joint and the angle at the same time.

Mind you, I use a bolt on neck. If you're using a dovetail and have to change the anlke, then you have to mess around with shims to get it right as well...