Hi All, With Glenn Reithers permission I am reposting his thoughts on fret calculation (from a facebook conversation) here so more people can get benefit from it.
The Readers Digest Version: Use the ExMi online fret calculator. It has a stretch compensation option that is perfect for high actions. I always use it. And yes, stepped bridges solve a lot of issues.
The reasoning behind it: When I say high I mean higher than what you find on a Strat, not lap steel high. My answer to your question is that it makes it more slide-friendly while still being finger friendly. And most people are building with larger tolerances than what Fender or Gibson are - it's a rustic instrument after all - so a higher action means their frets are less likely to buzz. And because cbg's aren't as loud as a big body acoustic, you tend to dig in more with the strumming hand and that might mean fret buzz especially on lighter gauge strings. Even a low action will have a stretch factor its intonation. I'd love a calculator that has an action height component. My low action action would be 2mm at the 17th fret, but that was on a double neck that had a a slide twin on a very high action so I could assume you wouldn't play slide on the low action fretted neck. The highest playable and in tune action I've done was 5.5mm at the 17th fret. Yeah, it's very high. But with the stretch compensated fretting it plays in tune nicely.
"even though you play slide, you still want to play up and down the fingerboard fretting notes and chords too" Exactly. That's why I use the ExMi calculator with stretch compensation. You want an action that is high enough to play slide without clacking on frets all the time, but not so high that that the act of clamping down on a string alters the string tension so much that it plays sharp. With a stretch compensation factor in your fret scaling you can set the action quite high and still be in tune.
By the way, I didn't use stretch compensation on the aforementioned low action neck. The stretch compensation would have made some notes flat.
An interesting side note to this. The difference between the normal fret scale and the stretch compensated one is up to 1.5mm, which would be a huge error when cutting fret slots. That taught me to not obsess about fret scales that go to 3 decimal point. I just round to the nearest 0.5mm now.
Thanks for sharing
It was too good not too. I'm not sure if this will work but here is a PDF of his guide to Fretting.
Funny and informative.
Wow, thanks again! You are awesome.
Hey I'm just the messenger it is all Glenn Reithers work. He is on this site and I believe posted it before..