To make a long story short, what started out as a knife change on my G0490 yesterday resulted in a reset of the infeed and outfeed tables to be coplanar as well. I've had this jointer for five years now and I initially setup the tables to be coplanar but some minor adjustments were required yesterday. Not a very exciting afternoon as I spent about five hours total to get back up and running.
I started milling up some rough sawn material that was in bad shape to begin with, i.e. twisted and bowed, so I first thought that the odd results were from the material. Out of curiosity, I switched to some fairly flat and straight rough sawn poplar about 5' in length and the results were the same. The problem is that the boards are concave up along their lengths, meaning the boards are thicker at the mid-span than at the ends so it rocks on the midpoint. After several passes, it's very visible sighting down the face of each board that a hump exists at the middle. I've run hundreds of board feet through this jointer so I'm very aware of stock orientation, consistent pressure across the length of the board on the outfeed side, etc. so I'm puzzled as to the problem.
I did speak with Grizzly's customer service but their only suggestion was about consistent pressure so no new revelations there.
What's causing this?
Thanks in advance!