Surface planning bits are used primarily to prepare and surface the MDF sheet used as a spoil board on your CNC. The spoil board must be flat to ensure even suction.
The surface planning bit has replaceable knives held on by screws. These knives have 4 usable sides, simply rotate the knife when one side becomes blunt and replace the knife when all sides are blunt.
Cutterhead takes 12 x 12 x 1.5 Four Edge TOKs. Knives sold separately.