The straight talk on planer knives, according to the folks at Powermatic, is that straight knives are soooo last century. On their planers and jointers, from the 22 ” 201HH to the 6″ 54HH, you’ll instead find helical cutterheads: four-sided indexable carbide knife inserts.
Why does this matter to you? Because in addition to reducing tear out when planning or jointing curly stock, it greatly reduces the amount of time woodworkers need to spend sharpening and readjusting the knives in their planers and jointers. Take a knife out, sharpen it, re-insert it and readjust it and all its neighbors? That’s not the way things work in the neighborhood of the helical heads. (The “Byrd” system at Powermatic.)
Instead, if one of your knives gets nicked, give it a quarter turn: you’ll have moved to one of the other four super sharp sides. Tighten it back down. You’re done. Each of the knife inserts locks into its own pocket on the cutterhead and doesn’t affect its neighbors. (How many inserts and pockets there are depends on which product you’re looking at.)
Does smoother stock and reduced sharpening down-time sound intriguing to you? You can find out more at http://www.powermatic.com. (Prices vary on the Powermatic planers and jointers; from around $800 for the 6″ jointer to around $2,000 for the 15″ or 20″ models).