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these is a lot of discussion on this topic and I would like other experts to chime in

Through the years we seen changes on the saddle angle. Martin in the early days of steel used a flatter angle and now its about a 3 degree , and gibson was a touch more.

So how can you determine the proper angle for your guitar? Remember that the compensation for intonation is based on scale length. The string to string intonation is based off string gauge .

I like to think first of the Variables we face.

A The action height
some player like higher action than others so the higher the action the longer the compensation length
Neck relief , A the neck curves again this requires more length
Top bow this is a guess to a degree as RH will also have something to say on how the top reacts and again
higher sharp lower flat
Bridge twist as the bridge loads the saddle will roll forward and again this creates a sharp condition
Players style some are aggressive and play with a tight fretting hand
Age of strings work hardening will change the strings characteristics


so now , how can we control all this?
The key is how you set the saddle on initial set up. Know that in the end all of these variables create a sharp condition. How much is as individual as the player. So I have been using a .100 inch wide saddle and I know some go as much as 1/8 inch , so with a 3 degree slot on the bridge you have some room for working the length of each string to dial in the compensation. I also shoot for .150 to .180 saddle height off the top of the saddle. Know that in the summer , the top may rise and drop in winter so a lighter braced guitar may need a winter and summer saddle.

I make my bridges .400 in high to start. When I set a neck I am looking at .375 in height at the top , on the line of the saddle. So when I set the bridge I shoot for this height. Now I can assume ( I know this is dangerous ) the top rise may be about 1/16 of an inch. So that will take us to a .325 height on the saddle for the initial set up.. This can change a bit so if you get close just remember to be about 1/16 off the bridge. Too much and you have too high a saddle and too low not enough.

Once you get the saddle height and set up allow a few days for the guitar to settle in. It is not uncommon to see changes in 3 to 14 days. The top will come up and bridge will roll a bit. I like to see a few cents flat on initial set up because I know things will go sharp during settle in. Don't touch the saddle yet but after settle in time you can now address the saddle for final intonation adjustment by tweaking the saddle on each string.

there is nothing magical , its all physics. Learning these skills are part of the trade. The better you can set up the more work you get. I am sure you noticed that in the end , its always just how long does each string need to me. All the variables have a tendency to make stings play sharp so learning how to dial that in is very important.

_________________
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

Thanks John. I don’t claim to be an expert but I will say that for many of the guitars that come through my shop I note a saddle angle that allows compensation to be set accurately for strings 1, 2, 3 and in some cases 4, but without sufficient length from the nut to intonate strings 5 & 6 better than about five or six cents sharp @ the 12th fret - that is, the bass side of the saddle is not far enough back. Generally another mm or so (.040) would help. For many, especially those who don’t venture up the neck, close enough is good enough. Some customers do have me remill their saddle slots to a little over 1/8th of an inch which gives the needed space - but undersaddle pickups, bridge pin location etc can rule it out for some brands of guitar.

That all relates to fettling existing instruments - on a new build you have the opportunity to get it right from the jump and one of the easiest ways to build some adaptivity into your design is to plan to mill your slot once the bridge is glued and you’ve had a chance to string the guitar (with a temporary floating saddle) and let it settle as John describes. When designing your bridge you can take this into account and come up with a design with space for the saddle to be a little further forward or back as the instrument requires.

Gore spent a lot of time in his books on intonation, and talked about different ways of determining the 'correct' offsets for the saddle and nut. For those of us who are not so mathematically inclined he showed a simple monochord setup that will enable you to find the correct offsets by trial for any string and setup. 'Perfect' intonation is probably not possible, but you can get 'arbitrarily close' with a rig like that.

Do you all take the fact that the bridge will roll and settle in over time into consideration and adjust the bridge slightly further from where it would otherwise be. The reason I ask, and keep in mind that I have only completed one, but I used the Stewmac fret calculator for 24.75" (Gibson) scale length and centered the saddle on that line thinking that I would have half the thickness of the saddle to play with but I ended up about 5-6 cents shy after moving the peak to the back of the saddle so I compensated at the nut to make up the difference. The top is on the light side which probably allowed for slightly more roll.

Would it be wise to do so?

_________________
Ron Riggs

I have been Bitten....by the Guitar building bug!
Not sure there is any cure for my condition
at least I hope not!

yes I , mentioned that in my post

_________________
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

yes that was mentioned in the original post

_________________
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

I’ve made good use of the calculator on RM Mottola’s site - https://www.liutaiomottola.com/formulae ... sation.htm

Lots of other goodies there too if you aren’t familiar.

I calculated the compensation for each string based on a set of light gauge strings and then made a story stick to repeatably place the bridge at the target location.







Brad


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there is an issue here
not all suppliers are the exact same scale length so always check the numbers
nut to 12th fret times 2 plus.1

_________________
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

Is that a plus point 1 (.1) or plus (1), John ?

_________________
Ron Riggs

I have been Bitten....by the Guitar building bug!
Not sure there is any cure for my condition
at least I hope not!

RM’s calculator is a great tool if you really want to get accurate and take string gauge etc into account. I have used it to relocate the saddle slot on poorly-compensated ABGs with great success. If you read this, thanks RM!

Hey Brad!

You read my mind. Thats on my list to make! I like that. I have seen the jig that takes you to the 12th fret (half way) and then move to the 12th fret to determine the saddle. But i like the one shot deal like yours it seems like it would better remove any cumulative errors by going half way and then half way again to get to the bridge.

I'll be needing it soon as I am about ready to close up the body on #2.

Also I went to RMMottola's web site an plugged in the numbers....looks good!

Thanks

_________________
Ron Riggs

I have been Bitten....by the Guitar building bug!
Not sure there is any cure for my condition
at least I hope not!

I like using the math to pinpoint where I would like the saddle to be, which helps me place the bridge, but I also like to leave the bridge unslotted until it is glued onto the guitar, I have strung up the guitar with something simulating a saddle on top of the bridge, and the guitar has had a few days to get used to the string tension. Then I can slot the bridge where I know the intonation will be good.

I don't think that method takes bridge rotation into account.

_________________
Hutch

Get the heck off the couch and go build a guitar!!!!

John, if that’s directed at me, no issue, I am the supplier!


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no the point is this different suppliers may not match different jig makers.
A martin 24.9 scale isn't 24.9
so use the jigs to get you close but use measurements to be sure.
So if you get a jig from company A and a fret board from Company B do not assume they match.

_________________
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

That’s my point, it’s ALL from me.

I make my own fretboards on the CNC using the same layout used for the jig. It’s all good.

I learned my lesson a long time ago about templates and jigs. One time I bought bending forms, templates and molds all from the same supplier and got three different shapes!

I make everything myself on the CNC these days. Total control over the whole process.


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Thanks John great thinking and thanks for sharing.

What has not been brought up here and should be from someone who sets intonation on about 10 - 15 guitars a week is the player. I can pull a note at least 3 - 4 cents sharp or flat by the pressure I apply when fretting. This makes player technique a variable that in combination with other factors can skew the math and results.

Action height also can result in excessive string stretch which throws intonation off.

And as you would have guessed nut slot height can skew intonation in the first several fret positions by over 4 cents which is detectable by most people hearing wise.

So there is physics here, science for sure. There is also "art" and the art of knowing both how a guitar should be set-up properly to be a proper tool for a musician and also knowing how we humans skew intonation by how we play at times.

So with all this said you can do the math (and you should like John says) and measure away but we also have to allow for humans and how we play as well.

Some more food for thought for those interested: On electrics pick-up height can also skew intonation, if they are too high the magnetic pull can and does change intonation and that's why pick-up that are too high is not a good idea.

I have a Rikenbacker 360 12 in my shop downstairs right now so be nice to me.... this guitar is one of the likely worst intonation nightmares ever produced. Shared saddles on a 12.... not a good idea for intonation snobs. But you spend a day cutting the nut slots.... (exaggerating of course) lower the action to "12 string some rattle permitted" levels and do the best you can with the discrepancy between the two strings on some of the shared saddles.

Hesh brings up some good points. While I was talking about acoustics electrics are a different animal

My point was that you have to know and understand the variables that cause intonations going sharp.

If you set up a guitar today for perfect intonation I an tell you , that guitar will be sharp in 2 weeks.

For those of us doing this daily and for years , we learned a few tricks. For those of you just starting , we want to share what we learned to pay
it forward.

I go to martin often and early on I saw a device they had to figure out intonation and compensation .
https://www.youtube.com/watch?v=JDKlmVkHDAU

_________________
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

I've always used "medium" fret wire, what about using a "medium/high" ? Would that be an intonation changer? The guitar I'm building is a Gypsy Jazz "Petite Bouche", the one with the small oval soundhole. the scale is 26.4"

good question
fret high , and play technique are part of the variables , the higher the fret , the more you are bending the strings sharp.

Play technique , is one thing I want to see the player use his guitar so I can set up the guitar for his style.

If he is a Fister and I mean plays with a heavy fretting hand you need to compensate for that

In the end , if you get up the guitar a tad flat , you will be better than dead true. There is a big difference in how you fret when you are tuning and how you are playing.

All of us that do this for a living rely on a method we develop. I use harmonics and 12th fret

So if I am finishing up the guitar. I want to tune it and check harmonics and 12th fret, One thing I didn't mention but others did is using the nut also in compensation. My manipulated the strings starting points and ending point you can tweak intonation to a players style . After all a set up for a 1st position player would be a lot different than that for an electric lead player. Master this and you will be in demand for set up work.

_________________
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

John, I Always like your videos. Thank You.

I'm glad you mention the player, I've always felt that they play a big roll in how a guitar is set up.

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Say what you do, Do what you say.

Higher fret wire has greater potential to be more of an intonation problem because there is more opportunity to stretch the string over a higher fret.

However.... not all players mash a string into the fret board and a player with a medium to light touch should be pretty OK with most fret wire regardless of height. The ham handed sorts will be stretching strings more with taller frets though so there is that potential.

Good question.