My new jointer planer has 5 rows of 15mm x 15mm x 2.5mm square four-sided convex edge carbide knives for a total of 80 knives. When an edge of a knife gets dull or damaged you simply remove the locking screw and rotate the knife to a new edge. The helical arrangement of the blades results in a smoother cut and less tear-out on difficult grain. I spent some time doing the final tuning of the infeed and outfeed tables today as well as sealing all the joints on my dust collection system.