If cutter has knives already installed locate top dead center, (straight edge on out feed side) rotate cutter head so knife travels to 12:00. If knife doesn't touch straight edge try all 2 or 3 to find one , if none then lower out feed side a smidge until knife touches straight edge. Mark cutter head to frame for later reference. Do this for all knives, (even if it means adjusting out feed table again).
Not sure about all Jointers, (some may or may not have loading springs or jack screws), mine has 2 loading springs per knife. If it were my planer, (jack screws) but then I'd use my dial indicators. I lost a spring once and replaced both with old ink pen springs, remember knife orientation before removing, (don't put in backwards).
I used to use round microwave magnets, they grabbed the table and held the knives in place, but one or both my kids made off with them, now I use a 5X5X1/4" slice of mahogany that I weigh down with a dumbbell plate or magnetic feather board.
I suggest gently wedging the cutter head still to maintain TDC. Orient and set a knife in a slot, (my jointer has 4 locking screws) I turn the 2 outside then the 2 inside nut head screws until I feel slight resistance, e.g., (1,4,2,3 ... 4,1,3,2) a smidge each time. This can minimize knife warp and rise. Do the same thing for each knife.
When done remove all the junk and test with a straight edge and hand rotation, you should barely hear a scrape as each knife hits TDC. If one or more sound much louder or not at all reset said knife.
Never bite the hand that looks dirty!
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