This is a little out of season, but we're doing a lot of planter work before customers put them in the shed for storage, so it's fresh on my mind. Maybe you'll remember it next spring when you're working on your own planter.
When removing disk openers for replacement or adjustment, the individual disks often wedge onto their spindles and refuse to come off after the nut has been removed from the spindle shaft. It's because spring tension, created by the contact area where the leading edges of the disks press together, "locks" them onto the spindles.
I've beat on them with my hand, flailed at both sides with a hammer, and tried to pry them loose with a pry bar. But that spring tension creates a locking force that makes simple removal into a briefly annoying challenge.
An air driven impact wrench or a battery-powered impact wrench is the answer. Removing a disk's nut with an impact wrench creates enough vibration to briefly release the spring tension so that once the nut is off, the disks slide easily off their spindles. If you've used a hand-wrench to remove disk openers and wrestled with getting the disks loose, buzzing off the nuts with an impact wrench is like magic, the way it loosens the disks so they slip off their spindle.
Just remember that while the right disk opener spindle and nut are normal thread (righty-tighty, lefty-loosey), the left disk opener spindle and nut are reverse-threaded on many planters.