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I'd like to improve my methods to make this job go quicker and get desired results. I kind of do this in a hit or miss way. One area that I think I mess up is not checking the angle with it strung up and calculating the exact amount to remove before taking the strings off. Anything you can give me.

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Hutch

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

EDIT : this is what I used to be using. See my other post, a few down for the current formula I'm using now.

Try this, works for me.

https://www.liutaiomottola.com/formulae/Reset.htm

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Pierre Castonguay

Guitars distort under string tension...on a new guitar, the top will appear to 'rise' by less than 1/32" on a stiffer-braced small-body instrument to over 1/16" on a larger, lightly-braced guitar. To address this distortion between strung and unstrung geometry, our practice for repair students was to determine the desired change in neck angle (really, fret plane height over bridge) strung, then repeat the measurements with guitar unstrung for a day or two. We could then set the neck to the desired change, do a quick check with weights at the body fret, and glue up.

All that measurement business aside, the guys where I worked would use a shop-made tool that allowed a direct measurement of fret plane height versus top and get the set right to within 10 thousandths. Possibly magic, but more likely just lots of repetition to 'know' where the neck needed to be.

It's worth the effort to understand the geometry, as it frees you from relying on ROT or 3rd party tools. To that end, here is a graphic that covers the various planes used for neck set/reset work at the bridge, as well as visualization of the correction to be applied for body distortion under string tension. Determining the amount to be trimmed off the heel is pretty simple - just the product of the heel depth at body/distance from body edge to saddle ratio and the needed change in string height at the saddle for desired string height at saddle for given 12th fret action and relief.

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For the times they are a changin'

- Bob Dylan

This is the formula I’ve used for years. It works, but quite often (usually) one has to account for the extra height of a new saddle. Guitars requiring a neck reset invariably arrive with extremely short saddles. You simply add half the extra height of the new saddle to the desired change of 12th fret string height.


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Agreed!


Pierre
Guitares Torvisse

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Pierre Castonguay

I am trying to follow why he used the string length over the body in the calculation. I have always used the length from the nut to where the neck meets the body. For classical guitars there isn't much difference but for some instruments ( Greek bouzoukis?) there might be. I am also wondering why he doubles the difference of the change in height wanted (I know you double the saddle height (2X) when wanting to raise the strings at the 12th fret X amount).
I would use :
(Ai-At) * (Lh/Ln) where Ln is from the nut to where the neck meets the body. This has worked for me, but I am quite willing to be shown the errors of my ways.

Sorry about my previous post, THIS one is what I've been using for some time now. I did what Gerry suggests and plugged the formula into a spreadsheet. I just forgot where I got it from, and that’s from Gerry Hayes' website. Working from the top of the bridge removes the existing too-low saddle from the equation as you have to make a new one anyway.

https://hazeguitars.com/blog/neck-reset ... we-measure

The spreadsheet method has the added benefit of enabling you to keep track of all resets, before and after, by adding a new line for each guitar worked on. Makes tracking your fine-tuning experience a bit easier, at least for me as I don't do as much resets as bigger shops.


Pierre
Guitares Torvisse

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Pierre Castonguay

Sorry, Clay. The correct variable is indeed the distance from the neck-body joint to the saddle.


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How about stringing it up before gluing it in?

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Hutch

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

many do seem to take this job and make it harder than it is
a neck set while similar to a reset it harder than a reset.
I only did about 1200 of them so this is the easiest method I saw

on a reset lay a straight edge across the top behind the bridge and measure the distance off the rim
remove the strings and measure again.
subtract the 2nd measurement from the first one

this tells you how much the top moves under string load

Now adjust the neck so it is flat and measure where it is under string load
then measure without strings

subtract #2 from #1
now you know how much the neck moves under load.

pull neck and know that your top rises X add 1/16 to X that is how much you want to raise the neck plane

that should tell you enough to get you where you need to be. Every guitar is different there is no perfect formula
find what works for you and go with that

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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

For guitars without an adjustable truss rod, finding the change between strung and unstrung (the body distortion measurement) is a little more complex because neck relief cannot be zeroed out. Be sure to measure the relief strung up, then again unstrung...apply lead shot bags at the body/neck join (with neck supported at nut and body supported at tail block) to get the same relief as measured with strings at tension...then take your measurement (the body will not distort appreciably without string tension, so the measurement will be sufficiently accurate for reset purposes).

When resetting, we almost always went to 0.500" string height off top, but sometimes went either higher or lower due to final saddle height, health of the instrument, size and configuration (e.g., 0000 versus Size 5), and other factors.

Just one of the many things to consider is just how tall a saddle the guitar will handle. If the instrument is a Martin, it's likely to be equipped with four or more distinct bridge thicknesses between as little as about 0.300" and as much as 0.420" from the factory (yes - I was shocked as well when I learned that Martin had that little control over geometry...scandalous!). This is usually not that much of an issue with a well-fitted drop-in saddle of adequate depth, but through saddles can present a different sort of challenge. While a drop-in 1/8" thick saddle may happily support a 0.200" saddle height on a Gibson-style belly-up bridge, the average older Martin through saddle will likely be unhappy - read slot fracture on the treble side) with anything over 0.140" - 0.150" saddle height, and that assumes a perfect slot, well-fitted saddle, and hot hide glue allowed to thoroughly dry before stringing up.

Sadly, my somewhat limited experience was that it is not uncommon to see flawed execution of through-saddle bridges on both factory-made and custom guitars, so measure the thickness ahead of the slot on the treble side before committing to a desired saddle height. Anything under 0.125"-0.130" ahead of the saddle as measured along the first (i.e., E4) string line should warrant concern if considering a saddle height over 0.120"; if building new, 0.180" thickness ahead of the slot on the first string line guarantees a trouble-free saddle up to 0.180"-0.200" (with the later for lighter strings and moderate break angle).

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For the times they are a changin'

- Bob Dylan

The Martin bridge height variations don't surprise me - - - these are factory production-line instruments and by the time the bridge is up for installation, the neck's been installed (glued). I think that the time required to 'tune' a dovetail just isn't available, so pick the bridge that fits.

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Peter Havriluk

I'm not following this.

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Hutch

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

Hutch,
Maybe you're a visual guy like me.

I think John means this:

I hope your belly doesn't rise that much!

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Why be normal?

Ahh! That makes sense now. Thanks Ken

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Hutch

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

That seems like a balancing act though unless the bridge area is truly flat. I'll give it a try though.

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Hutch

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