I have a Pro Mark 210 chipper that has two cutting edge blades. One side was dull so I wanted to flip them over to the sharp side. I pulled the side covers and chute off to see the bed knife and was a little shocked at what I saw, there was almost 1/2'' clearance between knife and bed. The service book says to set clearance at .020 to .030. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.