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Thanks Clay, very much appreciated my friend!

I have to disagree. I have measured purchased and pre-slotted boards and they were off. I cut them by hand and don't have problems with intonation.

Even factories get it wrong too.

Gang saws wear, or gets knocked out of alignment for whatever reason. Pretty much not many are going to use CNC, it will either be done by hand using a table saw with guides, or gang saws.

And if you buy the pre slotted board from Aliexpress, who knows if they're done right or not.

You really only need to be accurate to about .3mm with fret spacing, and that is completely doable using a ruler with fine divisions. String gauge will change intonation far more than that.

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

And I'll disagree with you JF. We have in our database precise measurements of the fret spacing of nearly 500 instruments some common, some iconic and very valuable in an over ten year study of fret spacing. Dave wrote software to drive the study as well that does of the math of the rule of 18 and other fret spacing methods used by the usual suspects over the years.

We have defined errors in spacing that are audible and noticeable and in our study we can visually back up what people like John are saying that they can hear. Our measurements are done with long calipers that have been calibrated and checked and the study will likely be published in the future, Dave just needs to finish it up and it's been asked for by one of the publications.

We see the very worst fret spacing of all on small Luthier built instruments with fret spacing errors that create all manner of issues for the players of which some players have even brought us the guitar wondering if their frets were off.

The very best and most precise fret boards we have ever measured were the CNC boards that I used by Watkins and later on after I was no longer building the CNC boards by Birko that our business has used for repair work. On both of these examples the error rate was nearly nonexistent. Andy's boards are available right now and are IME the most precise fret spaced and generally well made fret boards available today. So much so that if I were building again I would be using Andy's boards and feel fortunate to have them.

Yep and our study shows this. We can tell which gang saw was used back in the day at g*bson and we can see the template that they used wearing over time with the errors expanding due to template wear in a specific direction.

Then all of a sudden everything gets tightened up as if they deployed new tooling or made a new template.

I don't know what is charged today for a quality CNC board but when I was building they were cheap and a huge upgrade.

Back when I started out (when we had to fight the big triceritops for the best tree ferns for top wood) there were no pre-slotted boards. We learned to do them by hand and get them 'good enough' (which means, IMO, +/- .2 mm or better). While I buy pre-slotted boards these days, I also still make some, since it's the only way I know to get them in woods like persimmon or hornbeam when you don't have a table saw. It's not impossible, but its not easy either.

All you need is a miter box and a Japanese hand saw, and you can cut fret slots all day.

I think I will use my mill DRO to establish the spacing though.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com