This video is from a Forrest sales representative:
In it, he says:
* Rip Cut: Raise the blade high. The carbide stays cooler and expands less during the cut.
* Crosscut Solid Wood: Raise the blade one inch above the top of the wood.
* Plywood: Set the blade height so that the bottom of the gullet is at the height of the plywood, to reduce or eliminate tearout. Cutting plywood is hard on blades and dulls them faster. If you have a Woodworker II blade, try to limit the amount of plywood that you cut or buy one of their plywood blades.
Here are my own thoughts about blade height:
High Blades (recommended for rip cuts):
* Fewest possible teeth in contact with the wood at any given time.
* Less friction, less heat. Less likely to burn the wood
* Less heat, less expansion of the carbide tips. The kerf remains more uniform.
* Less heat, lowers the chances of burning the wood.
* The carbide tips expand less, so there is a lower chance that a tip might grab the wood and cause a kickback.
* Lower effort to push wood through blade.
Low Blades at Bottom of Gullet (recommended for plywood cuts):
* Most teeth in contact with the wood at a given time.
* Most teeth per inch of cut means smoother cuts with less tearout.
* More friction, more heat, with associated issues. (Hotter blade, more carbide tip expansion, more effort to push wood through blade, etc.)
Blades Raised to One Inch Above Work (recommended for crosscuts):
* Probably a Forrest compromise to balance smoothness of cut and reduce tearout with keeping friction and heat to an acceptable level.
* Has a balance of pros and cons from both approaches above (high blade and low blade).