Powermatic 20" planer problem

[Mark Angle]

I've got a Powermatic 208 20 inch planer. Having problems with "dishing" as the rep. calls it. Most of the time I get waves in the boards and usually not the full length of the board. They are 3/8" ridge to ridge. Appears to be worse on the left side and has even happened on just the left side of the board with the right side smooth. Even turned the board around and still on the left side. Have checked infeed, chip beaker, pressure bar, and outfeed and all are to specs. Table to cutterhead is off only about 0.001" from side to side. Called PM and they said raise the pressure bar from .008 to .003 below the cutter head. For 2 boards it was fine then started showing up again. AND the dishing isn't the same amout all the time, sometimes less, sometimes more. Have run SYP and red oak, does it on both. Have used backer board (wide board clamped to feed table) to rule out bottom rollers, got same result. I also lock the table each time. ANY IDEAS AT ALL????

[Kirk (KC) Constable]

If they gave you a suggestion that worked for awhile once, I think I'd see what else they had to say. They can't possibly want this info to get too much publicity...


KC

[J.R. Rutter]

"Have checked infeed, chip beaker, pressure bar, and outfeed and all are to specs. Table to cutterhead is off only about 0.001" from side to side. "
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Have you checked/reset the knives? A high knife can unbalance the cutterhead and set up strange harmonic vibrations. I have the 20" Shop Fox planer and get uneven patterns from time-to-time. It was much worse out of the box than it is now. When setting knife height, it is best to start with all knives installed so that tension in the head is balanced. I found that right out of the box, the knives were progressively higher from #1 to #4. Starting with an empty head and setting all knives equal will cause this. The marks that I get show up more in soft wood, but snad out easily...
-JR

[Mark Angle]

JR, Thanks will check that for sure. The harmonic vibration problem could be the problem. You can almost tell every time it's cutting the waves because of a "harmonic" pitch to the sound of the planer running. You can hear the tone of the planer going up and down.