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I have been pondering intonation on an acoustic. After the neck is set and the bridge is located, How do you correct for intonation on your guitar. I'm not even close to getting my first build done with today being close to 100 degrees. So you can imagine the humidity with the ocean so close. So I'm researching this. Thanks in advance for your comments and time.
Jerry

I measure from the nut to the 12th fret. Then whatever that is measure from the 12th fret to the center of the saddle slot. Measure how much space you have from the edge of the bridge to the slot. Then mark that on the guitar. I draw a centerline on the bridge and just use the middle joint of the top to line up squarely.

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Jason Moe
LaCrosse WI 54601

Don't just use the nut to 12th and then double and mark. Be sure to add in compensation. About .110 extra on the low E, and about .035 extra on the high e as a starting point. You can carve the break point of the addle to fine tune that point. About every .012-.015 = 1 cent.

So if you're using a 25.5" scale the distance from the leading edge of the nut to the center of the saddle would be 25.610 as a starting point. Likewise 25.535 to the high E. If you get that right you can carve your saddle appropriately.

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John Mayes
http://www.mayesluthier.com

hi,
John do you agree with this measure for 650mm scale
regards

The variables to this are going to be , action height , and string gauge. I use a .100 saddle slot but it is not uncommon to see them from 3/32 to 1/8. I use 2 different compensation length , one for a guitar in light gauge short scale ( .100") and long scale. The measure point is to the front of the saddle of the saddle . I also measure this along the string line itself and I can get a 12 th fret intonation dead on with this using a 3 2 action height. I will have to compensate the saddle but with the .100 thick saddle I can get things dialed in very well.
So along the line of the 1st string I want to be double the scale length plus .100. along the 6th string I will add .225 so the compensated length is 1/8 " longer on the bass side than the treble. In my perfect setup I want to see the string height at the saddle and bridge 1/2 inch off the top in front of the bridge. I like to see a neck relief of .004 to .007 and action height at the 12th fret of 2/32 on the 1st and 3/32 on the 6th.

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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

Seems about right to me. You need to be prepared to devise your own method/measurement too as the intonation can change based on action, relief, string gauge ect.

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John Mayes
http://www.mayesluthier.com

Interesting E-mail this morning too. I got a note from a guy named Alex Stratford. Here is the body of the e-mail. It, conveniently enough, coincided perfectly with this thread.

"Hi John. Long time fan of yours. I'm building my second guitar and I was hoping for some clarification. I was curious if you could give me a ball park figure for compensation. When I place my saddle I normally take the nut to 12th distance, double that, and then add .100 at the low E. does that sound about right? I'm using a .125 saddle thickness and last time my strings came in 5 cents sharp at the 12th. I asked Mike Doolin about it as well and here was his reply:

Hi Alex,

That is just a tiny bit short. Here are the starting compensation factors I use for each string:

E 0.031
B 0.109
G 0.047
D 0.078
A 0.109
E 0.109

I use a .1875" wide saddle to leave plenty of bone under the strings behind the ramps (see http://www.DoolinGuitars.com/pinless.html). Remember that one cent is .015", so that makes it pretty easy to file strings back and forth to fine tune the compensation.

Mike


Is this similar to what you do? Thanks!

-Alex

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John Mayes
http://www.mayesluthier.com

Also I should note I messed up the wording in my first reply. Actually could have a serious difference when measuring, although the OP's picture seemed to miss my mis-wording anyway.

I meant to say double the measurement, and add the compensation I mentioned to the front of the saddle not center. I was thinking of different carving points in my head...yeah things rattle around up there.

I have a jig that references off the front of my fretboard and drills hols in the body that place the bridge (pre-cut saddle slot). I just re-measured my jig too for further clarification and the numbers I got are almost identical to Mike Doolin's, Mine might be an extra .020 or so, but that is probably explained away because mike uses a wider saddle. So my numbers, using Mike D.'s style of posting them would be:

E 0.051
B 0.130
G 0.067
D 0.100
A 0.130
E 0.135

So your drawing, assuming a .125 saddle slot, would be 1.3mm on the High E, and 3.4 on the low E added to the scale length to the leading edge of the saddle.

Also I compensate the nut in essence by shortening the distance from the 1st fret to the nut by .030 and then backing up the break point of a few strings, so in essence if you do not do that it would add on another .030 in length because my jig is already compensated for that.

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John Mayes
http://www.mayesluthier.com

Well Jerry,
who asks how do I set my intonation...

Ok...since you asked...
I slid my bridge around till it seems to be in the right position.

I then start to shave a bit here and a bit there on the fulcrum of the bridge till, the sucker sounds right.

But then you see Jerry, I don't build flat tops.

Now arn't you glad you asked?

and no I don't use a tunner, only my ear of which I have two of. One for each side of me head.

Got any other questions?


blessings
be
Padma

PS: please forgive any attitude in this here post, It 110 here and we ain't got no ocean breeze by like you do.

.

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.

Audiences and dispensations on Thursdays ~ by appointment only.


.

Seems like this is the most stressful part of the build. You can have everything else perfect but if you can't play it in tune, it is just a wooden box.

I measured, remeasured, remeasured again. Used several different methods of measuring. Read numerous threads on bridge and saddle positioning. From the time the guitar was ready for the bridge placement to the actual decision was probably 3 weeks because I was being paranoid. Ended up building this jig to locate the correct position. Built out of a bar clamp, based off of the saddlematic that Stewmac sells. Must have gotten lucky and got it right because I strung it up last night and everything is fine.

I am working on a new idea right now that would let you string up the guitar and play it, before installing the saddle, to find the ideal position. I'll let you know if it works out.

Tim

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Tim

Here is the way I do it.

The diagonal line is the mathematical measurement for placing the saddle.
The verticle lines are the width the saddle
needs to be plus an 1/8"on either side.


The locating jig with strings loaded in the trapeze tailpiece. The dowell is a 3/16" Note the block of
wood with a screw in it.


The jig just resting on the lower bout.The hole is centered to receive the block of wood with the screw in it. The slotted piece has the trapeze tailpiece mounted on it. The wing nuts allow it to be adjusted for thicker sides or thinner sides.

The block of wood with the screw tightened
to prevent the jig from moving.
3/16" dowel taped along the saddle line.


Strings installed and tuned to pitch.
Note the top nut has been notched for
correct spacing not finalized to depth.
Next will be to strobe tune the saddle
to place it exactly where it needs to
be by moving the entire bridge and saddle.
before taping underneath the contoured
bridge (that I have yet to do) and drilling
the bridge pin holes for the two "E"
strings. These two holes will guarantee
perfect alignment both left and right and
up and down. Also near perfect intonation
when it's time to glue it down permanently./16" dowel taped along the saddle line.

It's about ready to disassemble
and seal and start shooting nitrocellulose.

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"Try to be the person your dog thinks you are."

http://sites.google.com/site/bertsguitarshop/

One thing which needs to be emphasised is that if you are setting your saddle position by testing using a tailpiece or with the stemac inotator, your string height needs to be at final playing height. Too high and you will end up with excess compensation and your saddle too far back for the final setup.

Jeff I use different diameter dowels. This one took a 3/16" on others I've used 1/8" even tooth picks to get the action set at final playing height. I correct the bridge height based on what thickness dowel I use.

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"Try to be the person your dog thinks you are."

http://sites.google.com/site/bertsguitarshop/

What a great thread!! A LOT of really useful information here.....thanks for sharing guys!

Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

Thanks for all the Input here. You guy's are a great bunch and very informative.

I just hope to get back out in the shop.... been hot hot hot here.....