Shane: Read the other thread on engraving; there's no reason to ever model fret slots in a model for cutting. At best, they'll get in the way of your CAM software when you're trying to machine the radius. Use projected curves, just like I showed you on the dishes.
The only time one would want to model fret slots is on a model to be rendered, and in that case you'll probably have frets covering them anyhow! Modeling a dressed, rounded, beveled, and tang-nipped fret is a good exercise BTW
But...booleans are useful for other stuff, so here's the video and the e-mail that accompanied it. If you can't see in the video, the original file was a radiused fretboard polysurface with a bunch of little 'fretslot negative' objects intersecting it.
http://www.youtube.com/watch?v=dl3U4TiviOo
Hi Chris,
Glad to help. I figured it was a lot faster than typing out what I did, and I showed you almost the exact process I went
through in figuring out the problem (exploding objects, looking for dupes and interior walls).
You did use good procedure in making the intersection objects 'overlap' the base object instead of being flush with it.
The most common boolean error is trying to subtract an object that's flush inside or union an object that's flush outside
another: often they're ever so slightly different at their boundary and it won't work.