Hollow Grind - Blade Geometry
Flat Grind Info
A flat grind, sometimes called a full flat grind if the grind reaches all the way up to the spine, is where the primary bevel spans nearly the entire distance from the spine to the edge of the blade. It is basically like a sabre grind that starts much closer to the spine of the blade.
Though the flat grind resembles a sabre grind, the characteristics are different. The Flat grind is more work than a hollow or sabre grind because more material needs to be ground away in the process, but it leaves you with a blade that is stronger than a hollow grind, and a better cutter than a sabre grind. Kind of a jack of all trades, if you will.
Like a hollow ground blade, a flat ground blade will almost always have a secondary bevel. Without the secondary bevel the edge woudl be very fragile.
Though the flat grind is stronger than a hollow grind, it isn't quite as thin right at the edge, and it also isn't as strong as a sabre grind. Most kitchen knives are flat ground, and Spyderco has an affinity for full flat grinds with their Calypso and Military line of folders.