Great price on those knives wood. Here's some of what I ran across.
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After the jointer knives have been sharpened and reset, it is wise to
joint the knives so they are exactly the same height. Cover all but
about one-fourth the length of a large abrasive stone with wax paper.
Place the stone on the rear table with the exposed section over the
knives. Clamp a wooden stop block to the front table to help guide
the stone. Lower the table until the stone barely touches the knives.
[reference to illustration]
Turn on the poser. 
When the cutterhead is revolving, move the stone slowly from one side to the other. A true cutting circle will result. Be sure to joint the entire length of the
knives. The joint or land (sometimes called the heel) should not be
wider than 1/32". After jointing, replace the fence and guard.